机械毕业设计英文外文翻译247基于制动试验台的虚拟仪器与变频技术
机械毕业设计英文翻译
Design, Invention, CreativityThese are all familiar terms but may mean different things to different people. These terms can encompass a wide range of activities from styling the newest look in clothing, to creating impressive architecture, to engineering a machine for the manufacture of facial tissues. Engineering design, which we are concerned with here, embodies all three of these activities as well as many others. The word design is derived from the Latin designate, which means “to designate, or mark out.” Webster's gives several definitions, the most applicable being “to outline, plot, or plan, as action or work..., to conceive, invent - contrive.” Engineering design has been defined as “... the process of applying the various techniques and scientific principles for the purpose of defining a device, a process or a system in sufficient detail to permit its realization... Design may be simple or enormously complex, easy or difficult, mathematical or nonmathematical; it may involve a trivial problem or on e of great importance.” Design is a universal constituent of engineering practice. But the complexity of engineering subjects usually requires that the student be served with a collection of structured, set-piece problems designed to elucidate a particular concept or concepts related to the particular topic. These textbook problems typically take the form of “given A, B, C, and D find E.” Unfortunately, real-life engineering problems are almost never so structured. Real design problems more often take the form of "What we need is a frame to stuff this widget into that hole within the time allocated to the transfer of this other gizmo.” The new engineering graduate will search in vain among his or her textbooks for much guidance to solve such a problem. This unstructured problem statement usually leads to what is commonly called “blank paper syndrome.” Engineers often find themselves staring at a blank sheet of paper pondering how to begin solving such an ill-defined problem.Much of engineering education deals with topics of analysis, which means to decompose, to take apart, to resolve into its constituent parts. This is quite necessary. The engineer must know how to analyze systems of various types, mechanical, electrical, thermal, or fluid. Analysis requires a thorough understanding of both theappropriate mathematical techniques and the fundamental physics of the system's function. But, before any system can be analyzed, it must exist, and a blank sheet of paper provides little substance for analysis. Thus the first step in any engineering design exercise is that of synthesis, which mean~ putting together.The design engineer, in practice, regardless of discipline, continuously faces the challenge of structuring the unstructured problem. Inevitably, the problem as posed to the engineer is ill-defined and incomplete. Before any attempt can be made to analyze the situation he or she must first carefully define the problem, using an engineering approach, to ensure that any proposed solution will solve the right problem. Many examples exist of excellent engineering solutions which were ultimately rejected because they solved the wrong problem, i.e., a different one than the client really had.Much research has been devoted to the definition of various “design processes” in tended to provide means to structure the unstructured problem and lead to a viable solution. Some of these processes present dozens of steps, others only a few. The one presented in Table 1-1 contains 10 steps and has, in the author's experience, proven successful in over 30 years of practice in engineering design.Table 1-1 A design processITERATION Before discussing each of these steps in detail it is necessary topoint out that this is not a process in which one proceeds from step one through ten in a linear fashion. Rather it is, by its nature, an iterative process in which progress is made haltingly, two steps forward and one step back. It is inherently circular. To iterate means to repeat, to return to a previous state. If, for example, your apparently great idea, upon analysis, turns out to violate the second law of thermodynamics, you can return to the ideation step and get a better idea! Or, if necessary, you can return to an earlier step in the process, perhaps the background research, and learn more about the problem.Mechanical System1) AxleThe structure appearance of the axle depends on the axle erection site and form on the case body mainly, axle part decorate and fix way , receive strength situation and processing technology ,etc..Structure designing requirement of the axle : ①The part should have accurate , firm job positions on the axle and axle; ②The part is installed and dismantled, adjusted conveniently on the axle; ③The axle should have good manufacturing engineering ,etc. . ④Try one's best to prevent the stress from being centralized2) Worm transmissionThe sport transmission interlocking among the axles for the implementation space, generally interlock in the angle. Characteristic its structure compactness, than heavy, transmission steady, apt lock since transmission. The shortcoming rubs and is worn and torn largely, the caloric value is big, ηis low, ∴suitable for the transmission of the power of centre.3) Rolling bearingBecause rolling bearing is the rolling friction, ∴it is small to rub obstruction, the caloric value is small , with high efficiency, start sensitively, safeguard it conveniently, and already standardization, easy to select for use and change, it is very extensive so use.The invalid form of the rolling bearing and calculation criterion:Main invalid form:(1) Lose a bit more tiredly --Installation lubricates and safeguards the normal invalid form under the good situation--Basis of calculating in main invalid form and life-span of bearing(2)Plasticity is out of shape --The rotational speed is very low and doing the main invalid form when the intermittence is swung--Cause the vibration , noise , rub the moment to increase, operate the precision to reduce(3) Wearing and tearing --Under lubricating badly and sealing the situation not tight, or the main invalid form of bearing working under many dust condition.Wear and tear the consequence: The bearing swims in the crack and strengthens, the precision of movement is reduced, vibration and noise increase.Calculate criterion : The general bearing ①carry on fatigue life and calculate (to clicking losing ); ②The quiet intensity is checked.Low-speed bearing: Only go on ②(quiet intensity is checked) .High-speed bearing: ①Calculate fatigue life ; ②Rotational speed of check-up limit.。
机械类毕业设计外文翻译
机械类毕业设计外文翻译外文原文Options for micro-holemakingAs in the macroscale-machining world, holemaking is one of the most— if not the most—frequently performed operations for micromachining. Many options exist for how those holes are created. Each has its advantages and limitations, depending on the required hole diameter and depth, workpiece material and equipment requirements. This article covers holemaking with through-coolant drills and those without coolant holes, plunge milling, microdrilling using sinker EDMs and laser drilling.Helpful HolesGetting coolant to the drill tip while the tool is cutting helps reduce the amount of heat at the tool/workpiece interface and evacuate chips regardless of hole diameter. But through-coolant capability is especially helpful when deep-hole microdrilling because the tools are delicate and prone to failure when experiencing recutting of chips, chip packing and too much exposure to carbide’s worst enemy—heat.When applying flood coolant, the drill itself blocks access to the cutting action. “Somewhere about 3 to 5 diam eters deep, the coolant has trouble getting down to the tip,” said Jeff Davis, vice president of engineering for Harvey Tool Co., Rowley, Mass. “It becomes wise to use a coolant-fed drill at that point.”In addition, flood coolant can cause more harm than good when microholemaking. “The pressure from the flood coolant can sometimes snap fragile drills as they enter the part,” Davis said.The toolmaker offers a line of through-coolant drills with diameters from 0.039" to 0.125" that are able to produce holes up to 12 diameters deep, as well as microdrills without coolant holes from 0.002" to 0.020".Having through-coolant capacity isn’t enough, though. Coolant needs to flow at a rate that enables it to clear the chips out of the hole. Davis recommends, at a minimum, 600 to 800 psi of coolant pressure. “It works much better if you have higher pressure than that,” he added.To prevent those tiny coolant holes from becoming clogged with debris, Davis also recommends a 5μm or finer coolant filter.Another recommendation is to machine a pilot, or guide, hole to prevent the tool from wandering on top of the workpiece and aid in producing a straight hole. When applying a pilot drill, it’s important to select one with an included angle on its point that’s equal t o or larger than the included angle on the through-coolant drill that follows.The pilot drill’s diameter should also be slightly larger. For example, if the pilot drill has a 120° included angle and a smaller diameter than a through-coolant drill with a 140°included angle, “then you’re catching the coolant-fed drill’s corners and knocking those corners off,” Davis said, which damages the drill.Although not mandatory, pecking is a good practice when microdrilling deep holes. Davis suggests a pecking cycle that is 30 to 50 percent of the diameter per peck depth, depending on the workpiece material. This clears the chips, preventing them from packing in the flute valleys.Lubricious ChillTo further aid chip evacuation, Davis recommends applying an oil-based metalworking fluid instead of a waterbased coolant because oil provides greater lubricity. But if a shop prefers using coolant, the fluid should include EP (extreme pressure) additives to increase lubricity and minimize foaming. “If you’ve got a lot of foam,” Davis noted, “the chips aren’t being pulled out the way they are supposed to be.”He added that another way to enhance a tool’s slipperiness while extending its life is with a coating, such as titanium aluminum nitride. TiAlN has a high hardness and is an effective coating for reducing heat’s impact when drilling difficult-to-machine materials, like stainless steel.David Burton, general manager of Performance Micro Tool, Janesville, Wis., disagrees with the idea of coating microtools on the smaller end of the spectrum. “Coatings on tools below 0.020" typically have a negative effect on every machining aspect, from the quality of the initial cut to tool life,” he said. That’s because coatings are not thin enough and negatively alter the rake and relief angles when applied to tiny tools.However, work continues on the development of thinner coatings, and Burton indicated that Performance Micro Tool, which produces microendmills and microrouters and resells microdrills, is working on a project with others to create a submicron-thickness coating. “We’re probably 6 months to 1 year from testing it in the market,” Burton said.The microdrills Performance offers are basically circuit-board drills, which are also effective for cutting metal. All the tools are without through-coolant capability. “I had a customer drill a 0.004"-dia. hole in stainless steel, and he was amazed he could do it with a circuit-board drill,” Burton noted, adding that pecking and running at a high spindle speed increase the d rill’s effectiveness.The requirements for how fast microtools should rotate depend on the type of CNCmachines a shop uses and the tool diameter, with higher speeds needed as the diameter decreases. (Note: The equation for cutting speed is sfm = tool diameter × 0.26 × spindle speed.)Although relatively low, 5,000 rpm has been used successfully by Burton’s customers. “We recommend that our customers find the highest rpm at the lowest possible vibration—the sweet spot,” he said.In addition to minimizing vibration, a constant and adequate chip load is required to penetrate the workpiece while exerting low cutting forces and to allow the rake to remove the appropriate amount of material. If the drill takes too light of a chip load, the rake face wears quickly, becoming negative, and tool life suffers. This approach is often tempting when drilling with delicate tools.“If the customer decides he wants to baby the tool, he takes a lighter chip load,” Burton said, “and, typically, the cutting edge wears much quicker and creates a radius where the land of that radius is wider than the chip being cut. He ends up using it as a grinding tool, trying to bump material away.” For tools larger than 0.001", Burton considers a chip load under 0.0001" to be “babying.” If the drill doesn’t snap, premature wear can result in abysmal tool life.Too much runout can also be destructive, but how much is debatable. Burton pointed out that Performance purposely designed a machine to have 0.0003" TIR to conduct in-house, worst-case milling scenarios, adding that the company is still able to mill a 0.004"-wide slot “day in and day out.”He added: “You would think with 0.0003" runout and a chip load a third that, say, 0.0001" to 0.00015", the tool would break immediately because one flute would be taking the entire load and then the back end of the flute would be rubbing.When drilling, he indicated that up to 0.0003" TIR should be acceptable because once the drill is inside the hole, the cutting edges on the end of the drill continue cutting while the noncutting lands on the OD guide the tool in the same direction. Minimizing run out becomes more critical as the depth-to-diameter ratio increases. This is because the flutes are not able to absorb as much deflection as they become more engaged in the workpiece. Ultimately, too much runout causes the tool shank to orbit around the tool’s center while the tool tip is held steady, creating a stress point where the tool will eventually break.Taking a PlungeAlthough standard micro drills aren’t generally available below 0.002", microendmills that can be used to “plunge” a hole are. “When people want to drillsmaller than that, they use our endmills and are pretty successful,” Burton said. However, the holes can’t be very deep because the tools don’t have long aspect, or depth-to-diameter, ratios. Therefore, a 0.001"-dia. endmill might be able to only make a hole up to 0.020" deep whereas a drill of the same size can go deeper because it’s designed to place the load on its tip when drilling. This transfers the pressure into the shank, which absorbs it.Performance offers endmills as small as 5 microns (0.0002") but isn’t keen on increasing that line’s sales. “When people try to buy them, I very seriously try to talk them out of it bec ause we don’t like making them,” Burton said. Part of the problem with tools that small is the carbide grains not only need to be submicron in size but the size also needs to be consistent, in part because such a tool is comprised of fewer grains. “The 5-m icron endmill probably has 10 grains holding the core together,” Burton noted.He added that he has seen carbide powder containing 0.2-micron grains, which is about half the size of what’s commercially available, but it also contained grains measuring 0.5 and 0.6 microns. “It just doesn’t help to have small grains if they’re not uniform.”MicrovaporizationElectrical discharge machining using a sinker EDM is another micro-holemaking option. Unlike , which create small holes for threading wire through the workpiece when wire EDMing, EDMs for producing microholes are considerably more sophisticated, accurate and, of course, expensive.For producing deep microholes, a tube is applied as the electrode. For EDMing smaller but shallower holes, a solid electrode wire, or rod, is needed. “We try to use tubes as much as possible,” said Jeff Kiszonas, EDM product manager for Makino Inc., Auburn Hills, Mich. “But at some point, nobody can make a tube below a certain diameter.” He added that some suppliers offer tubes down to 0.003" in diameter for making holes as small as 0.0038". The tube’s flushing hole enables creating a hole with a high depth-to-diameter ratio and helps to evacuate debris from the bottom of the hole during machining.One such sinker EDM for produc ing holes as small as 0.00044" (11μm) is Makino’s Edge2 sinker EDM with fine-hole option. In Japan, the machine tool builder recently produced eight such holes in 2 minutes and 40 seconds through 0.0010"-thick tungsten carbide at the hole locations. The electrode was a silver-tungsten rod 0.00020" smaller than the hole being produced, to account for spark activity in the gap.When producing holes of that size, the rod, while rotating, is dressed with acharged EDM wire. The fine-hole option includes a W-axis attachment, which holds a die that guides the electrode, as well as a middle guide that prevents the electrode from bending or wobbling as it spins. With the option, the machine is appropriate for drilling hole diameters less than 0.005".Another sinker EDM for micro-holemaking is the Mitsubishi VA10 with afine-hole jig attachment to chuck and guide the fine wire applied to erode the material. “It’s a standard EDM, but with that attachment fixed to the machine, we can do microhole drilling,” said Dennis Powderly, sinker EDM product manager for MC Machinery Systems Inc., Wood Dale, Ill. He added that the EDM is also able to create holes down to 0.0004" using a wire that rotates at up to 2,000 rpm.Turn to TungstenEDMing is typically a slow process, and that holds true when it is used for microdrilling. “It’s very slow, and the finer the details, the slower it is,” said , president and owner of Optimation Inc. The Midvale, Utah, company builds Profile 24 Piezo EDMs for micromachining and also performs microEDMing on a contract-machining basis.Optimation produces tungsten electrodes using a reverse-polarity process and machines and ring-laps them to as small as 10μm in diameter with 0.000020" roundness. Applying a 10μm-dia. electrode produces a hole about 10.5μm to 11μm in diameter, and blind-holes are possible with the company’s EDM. The workpiece thickness for the smallest holes is up to 0.002", and the thickness can be up to 0.04" for 50μm holes.After working with lasers and then with a former EDM builder to find a better way to produce precise microholes, Jorgensen decided the best approach was DIY. “We literally started with a clean sheet of paper and did all the electronics, all the software and the whole machine from scratch,” he said. Including the software, the machine costs in the neighborhood of $180,000 to $200,000.Much of the company’s contract work, which is provided at a shop rate of $100 per hour, involves microEDMing exotic metals, such as gold and platinum for X-ray apertures, stainless steel for optical applications and tantalum and tungsten for the electron-beam industry. Jorgensen said the process is also appropriate for EDMing partially electrically conductive materials, such as PCD.“The customer normally doesn’t care too much about the cost,” he said. “We’ve done parts where there’s $20,000 [in time and material] involved, and you can put the whole job underneath a fingernail. We do everything under a microscope.”Light CuttingBesides carbide and tungsten, light is an a ppropriate “tool material” formicro-holemaking. Although most laser drilling is performed in the infrared spectrum, the SuperPulse technology from The Ex One Co., Irwin, Pa., uses a green laser beam, said Randy Gilmore, the company’s director of laser tec hnologies. Unlike the femtosecond variety, Super- Pulse is a nanosecond laser, and its green light operates at the 532-nanometer wavelength. The technology provides laser pulses of 4 to 5 nanoseconds in duration, and those pulses are sent in pairs with a delay of 50 to 100 nanoseconds between individual pulses. The benefits of this approach are twofold. “It greatly enhances material removal compared to other nanosecond lasers,” Gilmore said, “and greatly reduces the amount of thermal damage done to the workpiece material” because of the pulses’ short duration.The minimum diameter produced with the SuperPulse laser is 45 microns, but one of the most common applications is for producing 90μm to 110μm holes in diesel injector nozzles made of 1mm-thick H series steel. Gilmore noted that those holes will need to be in the 50μm to 70μm range as emission standards tighten because smaller holes in injector nozzles atomize diesel fuel better for more efficient burning.In addition, the technology can produce negatively tapered holes, with a smaller entrance than exit diameter, to promote better fuel flow.Another common application is drilling holes in aircraft turbine blades for cooling. Although the turbine material might only be 1.5mm to 2mm thick, Gilmore explained that the holes are drilled at a 25° entry angle so the air, as it comes out of the holes, hugs the airfoil surface and drags the heat away. That means the hole traverses up to 5mm of material. “Temperature is everything in a turbine” he said, “because in an aircraft engine, the hotter you can run the turbine, the better the fuel economy and the more thrust you get.”To further enhance the technology’s competitiveness, Ex One developed apatent-pending material that is injected into a hollow-body component to block the laser beam and prevent back-wall strikes after it creates the needed hole. After laser machining, the end user removes the material without leaving remnants.“One of the bugaboos in getting lasers accepted in the diesel injector community is that light has a nasty habit of continuing to travel until it meets another object,” Gilmore said. “In a diesel injector nozzle, that damages the interior surface of the opposite wall.”Although the $650,000 to $800,000 price for a Super- Pulse laser is higher than a micro-holemaking EDM, Gilmore noted that laser drilling doesn’t require electrodes. “A laser system is using light to make holes,” he said, “so it doesn’t have a consumable.”Depending on the application, mechanical drilling and plunge milling, EDMing and laser machining all have their place in the expanding micromachining universe. “People want more packed into smaller spaces,” said Makino’s Kiszonas.中文翻译微孔的加工方法正如宏观加工一样，在微观加工中孔的加工也许也是最常用的加工之一。
机械类毕业设计英文翻译
襄樊学院毕业设计(论文)英文翻译题目超声波简介及其应用专业机械设计制造及其自动化班级机制0712姓名刘康学号07116201指导教师职称李梅副教授2011年5月25日Introduction and application of ultrasonic Ultrasonic is a mechanical waves which frequency above 20,000 Hz. Ultrasonic inspection commonly used in the frequency of 0. 5~5 MHz. The mechanical waves in the material spread in a certain speed and directions, acoustic impedance different heterogeneous interfaces such as defect is encountered or the bottom surface of the object being tested, will reflections. This reflection phenomenon can be used to ultrasonic testing , most common is pulse echo testing method testing , pulse oscillator issued of voltage plus in probe with pressure electric ceramic or quartz chip made of detection components , probe issued of ultrasonic pulse by sound coupled media such as oil or water , entered material and in which spread , encountered defects , part reflection energy along original way returns probe , probe will change it in electric pulse , by instrument zoom and display in oscilloscope tubes of screen . Depending on where the flaw echo on the screen and amplitude of reflection wave with artificial defects in a reference block rate compared to defect location and approximate dimensions. Apart from Echo method, and use another probe to the other side of the workpiece to accept signal penetration method. When use ultrasonic detection the physical properties of materials, also often take advantage of ultrasonic in sound velocity, attenuation and resonance characteristics of workpiece.Ultrasonic characteristics: 1, ultrasonic beam to focus on a specific direction, along the straight lines in the media, has a good point. 2, ultrasonic wave propagation in the media, attenuation and scattering occurs. 3, ultrasonic wave on the interface of heterogeneous media will make reflection, refraction and mode conversion. Using these features, you can get the defective interface from reflected reflection, so as to achieve the purpose of detecting defects. 4, ultrasonic energy is power than sonic. 5, the ultrasonic loss is very small in solid transmission , probe depth, as occurs in the hetero - interface by ultrasonic phenomena such as reflection, refraction, especially not by gas - solid interface. If the metal air holes, flaws and layer defects such as defects in a gas or a mixture, when defects at the interface of ultrasonic propagation to the metal and on all or part of the reflection. Reflected ultrasonic probe received, handled through circuits inside the instrument, on the screen of the instrument will show a different height and have a certain pitch waveform.Based on waveform characteristics of determine defect depth, location, and shape of the workpiece.Non - destructive testing is not damaged parts or raw materials subject to the status of the work, a means of detection of surface and internal quality checks, Nondestructive Testing abbreviations short for NDT. Ultrasonic testing is also called ultrasonic, ultrasonic flaw detector, is a type of non - destructive testing. UT is on industrial ultrasonic testing non - destructive testing methods. Ultrasonic enters objects when a defect is encountered, some sound waves produce reflection, transmit and receive an analysis of the reflected wave, exception can accurately gauge the flaws. And is able to display the location and size of internal defects, determination of material thickness.Advantages of ultrasonic inspection is to detect thickness, high sensitivity, high speed, low cost, is harmless to human body, can be positioned and quantitative defects.Display of ultrasonic detection on defects are not intuitive, testing of technical difficulty, vulnerable to subjective and objective factors, and inspection results are not easy to hold, ultrasonic testing requirements on the work surface smooth, requiring experienced inspectors to identify defects types, suitable for the part of considerable thickness inspection, ultrasonic inspection has its limitations.Variety of ultrasonic flaw detector, but most widely application of pulse - echo ultrasonic flaw detector. In general, in uniform material, presence of defect will create material discontinuity,this often acoustic impedance of the discontinuity is inconsistent , by the reflection theorem we know that, in two different acoustic impedance by ultrasonic reflection on the interface of media occurs. Size and interface on both sides of the reflected energy media differences in acoustic impedance and orientation, relative to the size of the interface. Pulse - echo ultrasonic flaw detector is designed according to this principle. Most of pulse - echo ultrasonic flaw detector is a scan, the so-called A-scan display is the way the display of ultrasonic detection in materials is the horizontal coordinate of transmission time or distance, the ordinate is the amplitude of ultrasonic reflected wave. Such as , in a workpiece in the exists a defects , because defects of exists , between defects and material formed a different media junction surface, interface of sound impedance different , when launch of ultrasonic encountered this interface will occurs reflection , reflection back of energy and probe received it, in monitor screen in the horizontal of must of location on will display out a reflection wave of waveform , horizontal of this location is defects wave in was detection material in the of depth . The reflected wave height and shape of different because of different defects, reflecting the nature of the defectNow is usually on the measured object, human launch industrial materials such as ultrasound, and then use its reflection, Doppler effect, transmission to get the formation of internal information and processing of measured object image. Ultrasonic flaw detector which more general Doppler effect method is using ultrasonic in encountered movement of object Shi occurs of more general Doppler frequency moved effect to came the object of movement direction and speed , characteristics ; transmission rule is by analysis ultrasonic penetrating had was measuring object of changes and came object of internal characteristics of , its application currently also is development stage ; ultrasonic flaw detector here main describes of is currently application up to of by reflection method to gets object internal characteristics information of method. Reflection method is based on ultrasonic in by different sound impedance organization interface will occurs strong reflection of principle work of , as we all know , When sonic from a media spread to another media in the interface will occurs reflection , and media of differences more large reflection will more large , so we can launch out penetrating force strong , and to line spread of ultrasonic to a object , and on reflection back of ultrasonic for received and under these reflection back of ultrasonic , and range , situation on can judgment out this organization in the contains of various media of size , and distribution situation and various media of comparison differences degree , information which reflection back of ultrasonic of has can reflect out reflection interface away fromdetection surface of distance , range can reflect out media of size , and comparison differences degree , characteristics , ultrasonic flaw detector to judgment out the was measuring object is has exception . In this process involves many aspects of content, including produce, receive, ultrasonic signal conversion and processing. One method is through the circuit of ultrasonic excitation signals to crystals such as quartz, lithium sulfate, with the piezoelectric effect, making it resulting in ultrasonic vibration ; receives the reflected ultrasonic waves when the piezoelectric crystals, there will be pressure from the reflected sound waves and electrical signals and transferred to the signal processing circuit for a series of processing, observation of ultrasonic flaw detector resulting images for people to judge.Types of image processing can be divided into A type display display, M and B type show, C-type display, such as F-type display. Which A type display is will received to of ultrasonic signal processing into waveform image , under waveform of shape can see was measuring object inside is has exception and defects in there , and has more large , ultrasonic flaw detector main for industrial detection ; M type display is will a section after fai of processing of detection information by time order expand formation a dimension of " space more points movement timing figure " , for observation internal is movement state of object , ultrasonic flaw detector as movement of organ , and artery vascular; B type display is will side - by - side many section after fai of processing of detection information group synthesis of second dimension of , and reflect out was measuring object internal fault section of " Anatomy image " hospital in using of B Super is with this principle do out of , ultrasonic flaw detector for observation internal is static of object ; and c type display , and F type display now with was comparison less . Detection of ultrasonic flaw detector can be very accurate, and more convenient, fast compared to other testing methods, nor harmful to detect objects and actions, so welcomed by the people more and more popular, has a very broad prospects for development. With the further development of electronic technology and software technology, digital ultrasonic flaw detector there are broad development prospects. Believe in the near future, more advanced new generation of digital intelligent ultrasonic flaw detector will gradually replace traditional analog detector, mainly for image display detector will be widely used in industrial inspection.Ultrasonic characterization of defects is always a difficult problem, still mainly relies on experience and analysis of inspection personnel, and poor accuracy. Development of the modern discipline of artificial intelligence for the realization of instrument automatic defect characterization offers the potential. Application of pattern recognition technology and expert systems, various characteristics of a large number of known defects input sample library, to accept the equipment people experience, and after studying with automatic defect characterization capabilities.超声波简介及其应用超声波是频率高于20千赫的机械波。
机械类毕业设计外文翻译范文
机械类毕业设计外文翻译、毕业设计（论文）外译文题目：轴承的摩擦与润滑10 月 15 日外文文献原文：Friction , Lubrication of BearingIn many of the problem thus far , the student has been asked to disregard or neglect friction . Actually , friction is present to some degree whenever two parts are in contact and move on each other. The term friction refers to the resistance of two or more parts to movement.Friction is harmful or valuable depending upon where it occurs. friction is necessary for fastening devices such as screws and rivets which depend upon friction to hold the fastener andthe parts together. Belt drivers, brakes, and tires are additional applications where friction is necessary.The friction of moving parts in a machine is harmful because it reduces the mechanical advantage of the device. The heat produced by friction is lost energy because no work takes place. Also , greater power is required to overcome the increased friction. Heat is destructive in that it causes expansion. Expansion may cause a bearing or sliding surface to fit tighter. If a great enough pressure builds up because made from low temperature materials may melt.There are three types of friction which must be overcome in moving parts: (1)starting, (2)sliding, and(3)rolling. Starting friction is the friction between two solids that tend to resist movement. When two parts are at a state of rest, the surface irregularities of both parts tend to interlock and form a wedging action. T o produce motion in these parts, the wedge-shaped peaks and valleys of the stationary surfaces must be made to slide out and over each other. The rougher the two surfaces, the greater is starting friction resulting from their movement .Since there is usually no fixed pattern between the peaks and valleys of two mating parts, the irregularities do not interlock once the parts are in motion but slide over each other. The friction of the two surfaces is known as sliding friction. As shown in figure ,starting friction is always greater than sliding friction .Rolling friction occurs when roller devces are subjected to tremendous stress which cause the parts to change shape or deform. Under these conditions, the material in front of a roller tends to pile up and forces the object to roll slightly uphill. This changing of shape , known as deformation, causes a movement of molecules. As a result ,heat is produced from the addedenergy required to keep the parts turning and overcome friction.The friction caused by the wedging action of surface irregularities can be overcome partly by the precision machining of the surfaces. However, even these smooth surfaces may require the use of a substance between them to reduce the friction still more. This substance is usually a lubricant which provides a fine, thin oil film. The film keeps the surfaces apart and prevents the cohesive forces of the surfaces from coming in close contact and producing heat .Another way to reduce friction is to use different materials for the bearing surfaces and rotating parts. This explains why bronze bearings, soft alloys, and copper and tin iolite bearings are used with both soft and hardened steel shaft. The iolite bearing is porous. Thus, when the bearing is dipped in oil, capillary action carries the oil through the spaces of the bearing. This type of bearing carries its own lubricant to the points where the pressures are the greatest.Moving parts are lubricated to reduce friction, wear, and heat. The most commonly used lubricants are oils, greases, and graphite compounds. Each lubricant serves a different purpose. The conditions under which two moving surfaces are to work determine the type of lubricant to be used and the system selected for distributing the lubricant.On slow moving parts with a minimum of pressure, an oil groove is usually sufficient to distribute the required quantity of lubricant to the surfaces moving on each other .A second common method of lubrication is the splash system in which parts moving in a reservoir of lubricant pick up sufficient oil which is then distributed to all moving parts during each cycle. This system is used in the crankcase of lawn-mower engines to lubricate the crankshaft, connecting rod ,and parts of the piston.A lubrication system commonly used in industrial plants is the pressure system. In this system, a pump on a machine carries the lubricant to all of the bearing surfaces at a constant rate and quantity.There are numerous other systems of lubrication and a considerable number of lubricants available for any given set of operating conditions. Modern industry pays greater attention to the use of the proper lubricants than at previous time because of the increased speeds, pressures, and operating demands placed on equipment and devices.Although one of the main purposes of lubrication is reduce friction, any substance-liquid , solid , or gaseous-capable of controlling friction and wear between sliding surfaces can be classed as a lubricant.V arieties of lubricationUnlubricated sliding. Metals that have been carefully treated to remove all foreign materials seize and weld to one another when slid together. In the absence of such a high degree of cleanliness, adsorbed gases, water vapor ,oxides, and contaminants reduce frictio9n and the tendency to seize but usually result in severe wear; this is called “unlubricated ”or dry sliding.Fluid-film lubrication. Interposing a fluid film that completely separates the sliding surfaces results in fluid-film lubrication. The fluid may be introduced intentionally as the oil in the main bearing of an automobile, or unintentionally, as in the case of water between a smooth tuber tire and a wet pavement. Although the fluid is usually a liquid such as oil, water, and a wide。
(完整版)机械毕业设计外文翻译7243268
Introduciton of MachiningHave a shape as a processing method, all machining process for the production of the most commonly used and most important method. Machining process is a process generated shape, in this process, Drivers device on the workpiece material to be in the form of chip removal. Although in some occasions, the workpiece under no circumstances, the use of mobile equipment to the processing, However, the majority of the machining is not only supporting the workpiece also supporting tools and equipment to complete.Machining know the process . For casting, forging and machining pressure, every production of a specific shape of the workpiece, even a spare parts, almost the shape of the structure, to a large extent, depend on effective in the form of raw materials. In general, through the use of expensive equipment and without special processing conditions, can be almost any type of raw materials, mechanical processing to convert the raw materials processed into the arbitrary shape of the structure, as long as the external dimensions large enough, it is possible. Because of a production of spare parts, even when the parts and structure of the production batch sizes are suitable for the original casting, Forging or pressure processing to produce, but usually prefer machining.Strict precision and good surface finish, Machining the second purpose is the establishment of the and surface finish possible on the basis of. Many parts, if any other means of production belonging to the large-scale production, Well Machining is a low-tolerance and can meet the requirements of small batch production. Besides, many parts on the production and processing of coarse process to improve its generalshape of the surface. It is only necessary precision and choose only the surface machining. For instance, thread, in addition to mechanical processing, almost no other processing method for processing. Another example is the blacksmith pieces keyhole processing, as well as training to be conducted immediately after the mechanical completion of the processing.Primary Cutting ParametersCutting the work piece and tool based on the basic relationship between the following four elements to fully describe : the tool geometry, cutting speed, feed rate, depth and penetration of a cutting tool.Cutting Tools must be of a suitable material to manufacture, it must be strong, tough, order to effectively processing, and cutting speed must adapt to the level of specific parts -- with knives. Generally, the more the work piece or tool for reciprocating movement and feed rate on each trip through the measurement of inches. Generally, in other conditions, feed rate and cutting speed is inversely proportional to。
机械专业毕业设计相关翻译外文文献
A PSoC-based parallel inductor connection driverof ultrasonic motorHongzhan Wang 1,Huafeng Li 21Department of Technical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China2Precision Driving Laboratory, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, ChinaAbstract — Schemes for drive and control of the traveling-wave ultrasonic motor (TRUM) is proposed in the paper and then the hardware circuit structure and the software designing of relevant functions for the driver is expounded in detail. The developed system includes two feedback loops; voltage control loop and resonant frequency tracking loop. Comparing to traditional driver of TRUM, this device has greatly improved the controllability of TRUM. What’s more, the motor’s velocity can be kept steady in different value.I. I NTRODUCTIONPiezoelectric ultrasonic motor (USM) is a new type of motor developed since the 1970s. The advantages of USM, such as high torque /volume ratio, noiseless operation, no electromagnetic induction interference and high holding forces without an energy supply, make them attractive in many applications like space, MEMS, high accuracy system, automatic, and camera and so on.The common ways to control the USM are amplitude modulation, frequency modulation and phase difference modulation.Amplitude modulation adjusts the USM speed by modulating the driving voltage amplitude, which advantages are good linearity, simple circuit and smooth velocity change. But the speed range is narrow and the dead zone is big. The torque is small at low speed. Frequency modulation changes the USM speed bymodulating the driving frequency, which has the advantages likegood dynamics, easily start at low speed, and simple circuit. As the resonant point of USM is variable due to variable temperature and non-linearity exists, the stability of this way is not good enough. Phase difference modulation regulates the USM speed by modulating the phase difference of two driving signals between -90° and +90°. The direction and magnitude of speed change smoothly in this way. However, dead zone exits when the phase difference is almost zero and increases when the load torque enlarges. In recent years, many kind of driving circuits have been studied by researchers. A driving circuit with energy feedback, consisting of a push-pull converter and a current-source two-phase parallel resonant inverter, is presented by Lin [1]. It adjusts the duty ratio of the driving signal to control theamplitude of the output voltage. Bal et al. [2] propose a drive system including PWM, PFM and hybrid control techniques. Furthermore, Several driving circuits for TRUM, using special chips, such as DSP and CPLD/FPGA, are also presented. Paper [3] presents a PWM method for speed control of the TRUM using DSP in the control system. It adjusts the duty ratio of the driving signal to control the USM, same as [1]. Paper [4] proposes a DSP controlled drive system of the TRUM. The driving frequency is selected as control input both for the speed and position control loop. Paper [5] studies a drive system using programmable on-chip voltage reference module of microcontroller to generate the input signal, and paper [6] uses CPLD/FPGA in USM servo drive system.Generally, the driving system of USM generates the needed square wave by voltage-controlled oscillator (VCO) first, and then it is power-amplified to drive the motor. By changing the voltage of VCO, the driving frequency is modulated and thespeed is changed finally. As inductance and USM is in serial in the matching circuit, the driving amplitude and frequency are coupled in frequency modulation, which means the drivingamplitude is changed too when the frequency is changed. This makes the speed control difficult. In order to overcome the problem, a new type of driving system based on PsoC (Programmable System-on-Chip) is presented. The driving voltage and frequency can be adjusted separately and the amplitude is stable under variable load. II. D ESIGN OF THE SYSTEM In this design, a 28-pin chip, PSoC CY8C29466, is used to control the driving system, which integrates a microcontroller and general-purpose analog and digital components. With the help of PSoC, the circuit is dynamic reconstruction and the number of components is decreased, which makes the driving circuit and system easy. The USM is driven by sine wave which amplitude and frequency are adjustable. A matching circuit by inductance and USM in parallel is designed to increase the efficiency of circuit. A manual encoder is used to adjust the working parameters. The hardware circuit consists of power part and feedback part, shown in Fig.1, and the power part is composed of boost part and inverter part.Fig. 1. the drive system of the TRUMIII. H ARDWARE CIRCUIT AND SYSTEM BASED PS O CAs stated above, the whole drive system consists of power part and feedback part. The power part is realized by DC/DC and DC/AC circuit. The feedback part contains a monitor-electrode feedback circuit and DC power voltage feedback circuit.A. Power circuit Fig.2 shows the power circuit. As the peak to peak of the TUSM driving voltage is above 100V and the power supple is low voltage DC source, a boost circuit is needed. There are many type of boost circuit like push-pull, half-bridge and full-bridge. The pull-push DC/DC converter has the advantages of no isolate drive, low input voltage, high efficiency of transformer and the inputs of switch tube is common ground, so pull-push DC/DC converter is used here. A full-bridge rectifieris applied after the transformer. L1, L2, C1 and C2 composefilter circuit. The drive circuit is a half-bridge inverter circuit, where C1 and C2 are DC voltage-dividing capacitors. Each bridge leg is used to drive one phase of USM. With specialcontrol sequence of four switching tubes, the high voltage square waves A and B with phase difference of 90° are obtained. When the driving signals’ duty ratio of tube M1 and M2 are changed, the DC amplitude is changed. The driving frequency of USM are modulated by the switching frequency of Q1~Q4. All the above driving signals of switch tubes are generalized by PSoC. La and Lb, which are in parallel with USM, are the matching inductance of USM. As a result, the amplitude and frequency of USM can be adjusted separately. The specifications of driver are listed as follows:Output voltage:200～350V pp , frequency range: 20~50 kHzFig. 2. Power circuitB. Feedback circuitAs the resonant frequency of the USM is variable due to temperature change, closed-loop control is necessary. A piezoelectric ceramic piece is pasted on the stator as a sensor called monitor-electrode, which produces an AC voltage by piezoelectric effect. The AC voltage amplitude is proportional to the speed of USM. In this system, the voltage of the monitor -electrode is divided by the resistors first, and then be rectified through a single-phase bridge and filtered by capacitor. TO get good dynamic character, the capacitor couldn’t be too large. The above circuit is shown is Fig.3. As shown in Fig.2, the potentialof the USM ground, which keeps floating all the time, is higher than the ground of the source. If the voltage divided by thecapacitor is ignored, the ground potential of USM is half the output voltage of half-bridge. As the feedback voltage is much smaller than the working voltage of USM, the feedback will be failed if the ground potential of source is taken as reference ground for the feedback circuit. To overcome the problem, a 3-terminal adjustable reference TL431 and a linear optical coupler PC817 are used.C. Design of control system The control strategy will be described in detail in this section. Fig.4 and Fig.5 show the system structure based on PSoC and the flowchart of the software program.Fig. 4. diagram of the systemWhere:dcf V : Feedback voltage of push-pull converterdc V : Output voltage of push- pull converters V : Feedback voltage of monitor-electrode,A B f f : Frequency of PWM to phase A and phase Bω: Rotational speed of USMInput: signal of manual encoderWhen the USM works for the first time, the amplitude andfrequency of diving voltage are adjusted by a manual encoder. Then the desired parameters are stored in the EEPROM of PSoC and set as the initial values when the USM works next time. The USM works with the driving voltage and monitor-electrode voltage both in closed loop. As the working time increases, the electrical parameters of USM will change, which will cause the amplitude of working voltage changed. In order to keep the amplitude of working voltage stable, thedcV is measured and then the pulse width of PWM1 is adjusted to keep the working voltage equaling to the desired value. As for the tracking of resonant frequency, the voltage of monitor-electrodesV is measured and then the frequency of PWM2 and PWM3 are adjusted to stabilizesV to desired value. By these means, the amplitude and frequency of the working voltage can be regulated separately, which increases the controllability ofFig. 5. Flowchart of the software program D.Deign of the PSocThe main components of CY8C29466 include a M8C Harvard microprocessor, one 24MHz or two 16MHz timer source, 16 digital modules and 12 analog modules. It can be designed as timer, PWM, SPI and amplifier, ADC, DAC, filter and comparator etc.Three 16-bit double-output PWM modules are used to generate the driving signals for push-pull converter and half-bridge inverter respectively. The frequency, duty cycle and dead time can be set as follows1ClockfPeriod=+(1)11PulseWidthDutyCyclePweiod+=+(2)1DeadTimeDTimeClock+= (3) where:Clock: Clock of the PWM modulePeriod: Data in Period RegisterPulseWidth: Date in Pulse Width RegisterDeadTime: Date in Dead Time RegisterA 48MHz clock, twice the frequency of PSoC’s CPU, is applied to improve the accuracy of PWM module.The 8-bit AD module is used to transfer the monitor-electrode voltage and the working voltage to PSoC. The source voltage is taken as reference, and the digital value of voltage is at the range of 0 and 256. Furthermore, a 16-bit timer is used to generate interrupt.IV.E XPERIMENTAL RESULTIn this section, A TRUM with diameter of 45mm is used to verify the developed PSoC controlled USM drive system.To improve the voltage waveform of motor, two small inductors (0.125mH in this case) are connected with the motor in series. Since the value of inductor is very small, the change of output voltage is very small when the frequency changes. Fig.5 (a) and (b) show the voltage wave of drive system with the series inductors or not. With series inductors, the voltage waveform is not very steep.Fig.6 shows the no-load revolving speed of USM at different frequency under different voltage of 200V, 250, 300V and 350V. The frequency and amplitude of the voltage are adjusted separately during the motor running.(a)(b)Fig. 6. Voltage wave (200Vpp): (a) no series inductor, and (b) with seriesinductor.Fig. 6. Revolving speed versus driving frequency (no load) under voltage 200V,250, 300V and 350VV.In this paper, a new type of drive system of TRUM based on PSoc is investigated. The principal of the system is presented. Experiments are carried out with a 45mm diameter TRUM. Experimental results show that the frequency and amplitude of the output voltage is easily controlled with the help of PSoC, which increases the controllability of TRUM.A CKNOWLEDGMENTThe project is supported by National Natural Science Foundation of China (NSFC) (50407004 and 50735002). REFERENCES[1] F.J. Lin, R.Y. Duan, J.C. Yu, “An ultrasonic motor driveusing a current source-parallel-resonant inverter withenergy feedback,” IEEE Trans. Power Electron, 14 (1)1999, pp.31–42.[2]G.Bal, E. Bekiroglu, “A highly effective load adaptiveservo drive system for traveling wave ultrasonic motor,”IEEE Trans. Power Electron, 20(5) 2005, pp.1143–1149.[3]S.W. Chung, K.T. Chau, “Servo speed control oftraveling wave ultrasonic motors using pulse widthmodulation,” Electric Power Components and Systems,29,2001, pp.707–722.[4]G.Bal, E. Bekiroglu, “A PWM technique for DSPcontrolled ultrasonic motor drive system,” ElectricPower Components and Systems, 33 (1) 2005, pp.21–38.[5]Bekiroglu, “Microcontroller-based full control ofultrasonic motor with frequency and voltage adjusting”Sensors and Actuators A, Phys, 2008, pp.151–159.[6]Jian-Shiang Chen and In-Dar Lin, “Toward theimplementation of an ultrasonic motor servo drive usingCPLD/FPGA” Proceedings of the IEEE InternationalSymposium onⅡ. V.2, pp. 903 – 908, 1999。
机械设计制造及自动化毕业设计英文翻译资料
A NOVEL INTEGRATED SYSTEM FOR RAPID PRODUCT DEVELOPMENTThis paper presents a novel integrated system of rapid product development for reducing the time and cost of product development. The system is composed of four building blocks —digital prototype, virtual prototype, physical prototype and rapid tooling manufacturing system. It can aid effectively in product design, analysis, prototype, mould, and manufacturing process development by integrating closely the various advanced manufacturing technologies which involve the 3D CAD, CAE, reverse engineering, rapid prototyping and rapid tooling. Furthermore, two actual examples are provided to illustrate the application of this integrated system. The results indicate that the system has a high potential to reduce further the cycle and cost of product development.Keywords: Rapid product development; rapid prototyping; integrated system.1. IntroductionDue to the pressure of international competition and market globalization in the 21st century, there continues to be strong driving forces in industry to compete effectively by reducing manufacturing times and costs while assuring high quality products and services. Current industries are facing the new challenges: quick response to business opportunity has been considered as one of the most important factors to ensure company competitiveness; manufacturing industry is evolving toward digitalization, network and globalization. Therefore, new products must be more quickly and cheaply developed, manufactured and introduced to the market. In order to meet the demand of rapid product development, the various new technologies such as reverse engineering (RE), 3D CAD, rapid prototyping (RP), and rapid tooling (RT) have emerged and are regarded as key enabling tools with the ability to shorten the product development and manufacturing time. For example, it has been claimed that RP can cut new product development costs by up to 70% and the time to market by 90%.1 In the form of a better design, more design possibilities, a 3D CAD model can be shown to the customer for approval and prevents misunderstandings. A virtual prototyping is employed to guide in optimizationof the product design and manufacturing process planning, which may result in the accurate determination of the process parameters, and reduce the number of costly physical prototype iterations. Rapid tooling technique offers a fast and low cost method to produce moulds, and shows a high potential for faster response to market demands. When properly integrated among 3D CAD, CAE, RE, RP and RT, these technologies will play a much more important role to reduce further the development cycle and cost of the product production. On the basis of above technologies, a novel integrated system of rapid product development is to be founded so as to meet the requirement of rapid product development.2. Architecture of the Integrated Development SystemThe development process from initial conceptual design to commercial product is an iterative process which includes: product design; analysis of performance, safety and reliability; product prototyping for experimental evaluation; and design modification. Therefore, any step of the new product development process has a direct and strong influence on time-to-market in short order. A good product development system must enable designers or design teams to consider all aspects of product design, manufacturing, selling and recycling at the early stage of the design cycle. So that design iteration and changes can be made easily and effectively. The more fluent the feedback is the higher possibility of success the system has. Design for manufacturing (DFM) and concurrent engineering (CE) necessitate that product and process design be developed simultaneously rather than sequentially.The integrated system of rapid product development is composed of four modules: digital prototype, virtual prototype, physical prototype and rapid tooling.The product development starts from the creation of a 3D CAD model using a CAD software package. At that stage, the product geometry is defined and its aesthetic and dimensional characteristics are verified. The main function of digital prototype is to perform 3D CAD modelling. The CAD model is regarded as a central component of the whole system or project information base which means that in all design, analysis and manufacturing activities the same data is utilized. The product and its components are directly designed on a 3D CAD system (e.g.Pro/Engineer, Unigraphics, CATIA, IDEAS, etc.) during the creative design. If a physical partis ready, the model can be constructed by the reverse engineering technique. RE is a methodology for constructing CAD models of physical parts by digitizing an existing part, creating a digital model and then using it to manufacture components. RE can reduce the development cycle when redesigns become necessary for improved product quality. Preexisting parts with features for improved performance can be readily incorporated into the desired part design. Therefore, it is very useful in creating the CAD model of an existing part when the engineering design is lost or has gone through many design changes. When a designer creates a new design using mock-up, it is also necessary to construct the CAD model of the mock-up for further use of the design data in analysis and manufacturing. The three primary steps in RE process are part digitization, features extraction, and CAD modelling. Part digitization is accomplished by a variety of contact or non-contact digitizers. There are various commercial systems available for part digitization. These systems range from coordinate measuring machine (CMM), laser scanners to ultrasonic digitizers. They can be classified into two broad categories: contact and non-contact. Laser triangulation scanner (LTS), magnetic resonance images (MRI), and computer tomography (CT) are commonly used as non-contact devices. Contact digitizers mainly have CMM and cross-sectional imaging measurement (CIM). Feature extraction is normally achieved by segmenting the digitized data and capturing surface features such as edges. Part modelling is fulfiled through fitting a variety of surfaces to the segmented data points.In order to reduce the iterations of design-prototype-test cycles, increase the product process and manufacturing reliability, it is necessary to guide in optimizing the product design and manufacturing process through virtual prototype (VP). VP is a process of using 3D CAD model, in lieu of a physical prototype, for testing and evaluation of specific characteristics of a product or a manufacturing process. It is often carried out by CAE and virtual manufacturing system. Computer aided engineering (CAE) analysis is an integral part of time-compression technologies. Various software tools available (i.e. ANSYS, MARC, I-DEAS, AUTOFORM, DYNAFORM, etc.) can speed up the development of new products by initiating design optimization before physical prototypes are built. The CAD models can be transferred to a CAE environment for an analysis of the product functional performance and of the manufacturing processes for producing the product’s components. It has also proven to be ofgreat value in the design optimization of part geometry, to determine its dimensions and to control warpage and shrinkage while minimizing process-induced residual stresses and deformations. Virtual manufacturing system (VM) is the natural extension of CAE. It simulates the product functionality and the processes for producing it prior to the development of physical prototypes. VM enables a designer to visualize and optimize a product process with a set of process parameters. The visualization of a virtually simulated part prior to physical fabrication helps to reduce unwanted prototype iterations. Therefore, a product virtual manufacturing system may result in accurate determination of the process parameters, and reduce the number of costly physical prototype iterations. 3D CAD model and VP allow most problems with unfitting to become obvious early in the product development process. Assemblies can be verified for interference as VP can be exercised through a range of tasks. Structure and thermal analysis can be performed on the same model employing CAE applications as well as simulating down-stream manufacturing processes. It is clear that VP increases process and product reliability. Although VP is intended to ensure that unsuitable designs are rejected or modified, in many cases, a visual and physical evaluation of the real component is needed. This often requires physical prototype to be produced. Hence, once the VP is finished, the model may often be sent directly to physical fabrication.The CAD model can be directly converted to the physical prototype using a RP technique or high-speed machining (HSM) process. The 3D CAD model is to be exported not only in the STL format which is considered the de facto standard for interfacing CAD and RP systems, but also in the NC coding which can be used by HSM. HSM has a potential for rapid producing plaster or wooden pattern for RT. RP is a new forming process which fabricates physical parts layer by layer under computer control directly from 3D CAD models in a very short time. In contrast to traditional machining methods, the majority of rapid prototyping systems tend to fabricate parts based on additive manufacturing process, rather than subtraction or removal of material. Therefore, this type of fabrication is unconstrained by the limitations attributed to conventional machining approaches. The application of RP technique as a useful tool can provide benefits throughout the process of developing new products. Specifically, there are serious benefits that RP can bring in the areas of market research, sales support, promotionalmaterial, and the ever-important product launch. Physical RP can also become a powerful communications tool to ensure that everyone involved in the development process fully understands and appreciates the product being developed. Hence, it can help to reduce substantially the inevitable risks in the route from product concept to commercial success, and help shorten time-to-market, improve quality and reduce cost. Over the last 20 years, RP machines have been widely used in industry. The RP methods commercially available include Stereolithgraphy (SLA), Selective Laser Sintering (SLS), Fused Deposition Manufacturing (FDM), Laminated Object Manufacturing (LOM), Ballistic Particle Manufacturing (BMP), and Three-Dimensional Printing (3D printing), etc.Once the design has been accepted, the realization of the production line represents a major task with a long lead time before any product can be put to the market. In particular, the preparation of complex tooling is usually in the critical path of a project and has therefore a direct and strong influence on time-to-market. In order to reduce the product development time and cost, the new technique of RT has been developed. RT is a technique that can transform the RP patterns into functional parts, especially metal parts. It offers a fast and low cost method to produce moulds and functional parts. Furthermore, the integration of both RP and RT in development strategy promotes the implementation of concurrent engineering in companies. Numerous processes have been developed for producing dies from RP system. The RT methods can generally be divided into direct and indirect tooling categories, and also soft (firm) and hard tooling subgroups. Indirect RT requires some kinds of master patterns, which can be made by conventional methods (e.g. HSM), or more commonly by an RP process such as SLA or SLS. Direct RT, as the name suggests, involves the manufacturing of a tool cavity directly on a RP system, hence eliminating the intermediate step of generating a pattern. Soft tooling can be obtained via replication from a positive pattern or master. Soft tooling is associated with low costs; used for low volume production and uses materials that have low hardness levels such as silicones, epoxies, low melting point alloys, etc. RTV silicone rubber moulds, epoxy moulds, metal spraying moulds, etc. are some of these typical soft moldings. Hard tooling is associated with higher volume of production, and the use of materials of greater hardness. Keltool process, Quickcast process, and the ExpressTool process are some of these hard toolings. Electrical discharge machining (EDM) seemsto be an interesting area in which rapid tooling finds a potential application. Some methods of making EDM electrodes based on RP technique have developed, such as abrading process, copper electroforming and net shape casting, etc. On the basis of the above techniques, a novel integrated system of rapid product development is to be proposed. Its overall architecture is shown in Fig. 1.3. Case Studies3.1. Case study 1: ImpellerA total of thirty plastic impellers, with a relatively complex geometry, were required by acustomer within fifteen working days from the receipt of a 2D CAD model. There were many factors to be considered in deciding the most appropriate route for producing the impellers. These factors mainly involved cost, lead-time, the number of parts required, the final material for the parts, and the part geometry. In order to maximize the benefits in terms of time and cost reduction for the parts, it was decided to use silicon rubber mould and the parts were eventually produced by vacuum casting process. Silicon rubber mould is an easy, relatively inexpensive and fast way to fabricate prototype or pre-production tools. It can be utilized for moulding parts in wax, polyurethane, ABS, and a few epoxy materials. The process is best suited for projects where form, fit, or functional testing can be done with a material which mimics the characteristics of the production material. The casting parts with fine details and very thin walls can be easily and rapidly produced. The whole process flow involved the 3D CAD modelling, producing master pattern (RP prototype), silicon rubber mould, and casting green parts. The time sequence for the fabrication of impellers was described as follows. Due to the complexity of the impeller, the task of generating the 3D CAD model using Pro/Engineer software package took almost 3 calendar days. The master pattern for this project was built on a SPS 600 machine in 2 calendar days. SL process was chosen because it was cost effective and the surface finish was good. The next step involved creating a roomtemperature vulcanized (RTV) silicone rubber mold which was completed within an additional 3 calendar days. Finally, the ABS materials were cast into silicon rubber mould under the vacuum casting condition, and the green parts were achieved in 4 calendar days. The required 30 components were produced successfully and completed in 12 calendar days. The primary process stages are illustrated in Fig. 2. These impellers only cost about 5 thousand RMB and took 12 working days. Consequently, in contrast to the traditional development mode, the impellers developed using the integrated system can cut cost by up to 50% and the time-to-market by 75%. When evaluated against satisfying urgent requirement with respect to time, the procedure is clearly worth pursuing, as indicated by the case study described above. Gong from a 3D CAD solid modeling to fully functional production impellers in less than 12 working days is certainly extraordinary.With proper implementation of the process by qualified personnel, working within the scope of the constraints noted, the acceptance and advancement of the integrated manufacturing methodis likely to grow.3.2. Case study 2: MannequinTen plastic mannequins were required by a client in three months from the receipt of the plaster model of the emulational body. This component was an ideal candidate for using integrated system to development, with a very complex surface and a requirement for only 10 parts. In order to produce the plastic mannequin, the various technologies including reverse engineering, 3D CAD, rapid prototyping and rapid tooling were used to complete model measuring, surfaces reconstructing, 3D CAD modelling, prototype and mould building. The whole development work was presented below. The first step of the project was to construct a CAD model of the emulational body by RE process. ATOS measuring equipment made in GOM Inc. which has a high scanning (10,000 points/sec) and can measure models in a wide range from 500mm to 10mm, was employed to capture the digitized data of the plaster mold. Figure 3(a) shows the point clouds of the body model. The subsequent process was to perform surfaces reconstructing. To speed this process, a special reverse engineering program, called CopyCAD (DelcamInc.), was used to create quickly and easily the CAD surfaces from the digitized data. After surfaces reconstructing, many errors in the original model and the joints must be modified by PowerShape software package (another software of Delcam Inc.). The surfaces model of the body is represented in Fig. 3(b). To fabricate easily, the surface model was divided into 11 individual components which included the head, body, upper arms, forearms, tights, shanks and feet using Pro/Engineer software package. Subsequently, every surface model was converted to a solid model, and many holes and slots needed to be designed for fixing joints such as shoulder, knees, etc. Then, the solid parts and joints were assembled to form the solid model of the emulational body. Figure 3(c) illustrates the completed CAD solid model. The RP prototypes of these components were built on a LPS 600 machine. The assembly RP body model is shown in Fig. 3(d). In addition, silicon rubber moulds of these components were fabricated for producing the green parts. Finally, the required 10 plastic mannequins were produced successfully and the project was completed in about 12 weeks. Figures 3(e) and (f) describe respectively the silicon rubber mould of half head and the green product. The case indicates the rapid development of large product and complex surfaces can be realized quickly following the integrated development mode.4. ConclusionIn this paper, we have presented an integrated system based on RP for rapid product developing. The system consists of four modules: digital prototype, virtual prototype, physical prototype and rapid tooling. It employs fully and integrates closely the various advanced manufacturing technologies which involve the 3D CAD, RE, CAE, RP, and RT. In this system, the procedure of development from design to end product is worked step by step: design, analysis, rapid prototype and tooling. By evaluating the whole process and its various components, and comparing them with traditional process, it has been clear that one can reap benefits in various ways. The system can effectively compress the design and manufacturing cycle time and reduce the development cost, which is an important factor in competition. Using this integrated system to develop new product shows a high potential for faster response to market and customers’ demands. As a result, it will play a more and more important role to reduce the manufacturing cycle and cost of product development in the future. AcknowledgementsThis research was supported by The National High Technology Research and Development Program (863 Program) under the project “The integrated manufacturing technology and equipments of rapid tooling for rapid product development”(No.2023AA421270), and “Tenth Five-Year” National Key T echnologies R&D Program of China under the project “Research and demonstrator of rapid manufacturing integrated system based on rapid prototyping” (No. 2023BA205B10- CMTT1001).。
外文翻译：基于制动试验台的虚拟仪器与变频技术
附录VIRTUAL INSTRUMENT AND FREQUENCY CONVERSION TECHNOLOGY-BASED BRAKE TEST SYSTEM Brake is widely useful and very important safety assuring equipment. The aim of Brake test system，which is based on visual instrument and frequency changing technology，is to integrative measure and analyze the performance and quality of the brake.This paper mainly introduces the principle，composing，function and features of the brake test system. And from the point of view of the principle of Visual Instrument （VI）technology，a test system，based on the VI and frequency changing technologies and consist of frequency changing drive and control sub-system and measuring sub-one，is constructed. With the test system the performances and braking course could be auto controlled and measured to the brakes which includes disc and drum ones. And the measuring and control software is programmed with the LabVIEW published by American NI Corporation，USA.Then data real time acquisition，processing，displaying and recording will be realized. The test system also has the functions of voltage adjusting，rotating speed control，load regulating，JC value setting，temperature measuring，and braking route and time memorizing and analyzing. It will be very important for meaning and exciting boosting effect to advance quality and capabilities of the brakes and the security of equipments and system which have adopt the brakes.1 Operating principlesAccording to the principle of work and power，the change of kinetic energy in the moving of objects equals to the full power of the force act on the object in that process.The energy obtained by brake to be tested：Therefore，it is feasible to use combined inertial flywheels to simulate rotating inertia of crane hoist and its transmission components to test the performance and quality of the brake. According to the moment of momentum theorem：T b·t =J i·ω （1）When T b is fixed，t b can be controlled through combinations between Ji and ω differently. Brake drum or plate，which will be measured，and combined inertial flywheels for loadingon are driven to rotate by AC frequency conversion motor （or DC one，which will not be dealt with in this article carefully）. According to the principles shown in the formula （1），we can simulate actual processes of brakes fitted on lifting and transport machineries，engineering ones，mining ones and construction ones by changing the technical specification duty JC，the flywheel's inertial moment Ji and motor's rotational speedni.When detected brakes work in simulation cycle and brake repeated，infrared thermoscopes and torque sensors，and other sensors will record braking shown in the heat，braking torque，braking time and brake speed parameters.2The composition and structure of the brake test systemThis test system is intended to achieve the performances of drum and disc brakes and has following functions：（1）Brake replacementAccording to different type of brakes the corresponding base will be chosen and brake position could be adjusted using electric slide test-bed；（2）Multi-level loadingWe can simulate the actual loading on brakes in a crane with different combined flywheels. The test system adopts manual hydraulic system composed by a three-position four-way hand-operated direction valve，a relief one and their accessories，and it is operation saving and convenient to replace flywheels.（3）Regulation the rotational speed n （or ω）It can be realized by changing frequency supplied to the AC motor. When braking torque is very large，such as 10000Nm，it should be appropriate for regulating initial brake speed upward 1000r/min to minimize rotating inertia possibly.（4）Braking frequency adjustmentBased on actual needs braking frequency can be confined in a range of 1~4 times per minute.（5）Braking torque measurementThere are three methods：a）Direct measurement via torque sensors：Rotational speed and torque sensor will be installed between the detected brake drum or plate and inertial flywheel plates.Dynamic braking torque of detected brake will be directly measured，shown in Fig.1 and Fig.2. According to the scope of braking torque of detected brakes，two or three rotational speedand torque sensors should be prepared for testing torque to meet the accuracy requirements；b）Indirect parameter measurement：Based on the rotating inertia and braking time we can get brake torque using mathematical relationship between these parameters，as shown in Fig. 2.c）Indirect measurement by pedestal-force：The pressure sensors are installed under the base where detected brake are fixed to feel the forces given by brake，and then to obtain brake torque.The second approach has small investment，simple structure and no torque sensors which mean not considering related troubles of changing torque sensors. But the procedure to calculate torque is complex，and accumulating total errors would be larger and then the result accuracy will be low.The third way has the advantage of the replacement of sensors is easier and no special requirements for sensors installing precision. It is still an indirect measurement but the procedure is less than that in the second method and that means the cumulative errors relatively is smaller. And visible shortcoming is poor dynamic response.（6）Automatic controlExcept to manual operation test system is also programmed control.（7）MonitoringBraking frequency，initial braking speed，the aggregate braking number，moment，time and so on will be shown automatically.（8）Automatically data acquisition and processingThe curve describing braking torque，time and speed could be drawn automatically by means of computer software while detected brake is measured in dutycycle operation. Therefore，in response to the way to test braking torque the system can be divided into three ones of that with torque sensor such as Fig.1 and 2 above，that without torque sensor such as shown in Fig.3 and that of pedestal-power measurement without torque sensor，as shown in Fig.4. The test system is mainly composed of AC frequency conversion transmission system，flywheels loading system，rotational speed and torque sensors，base which to fix drum or plate brakes，adjustable DC power supply，detected brakes and test and control system.In addition to the above functions，the system could test following performances of the brakes：a）Release performance：This is tested under the conditions of 85%Ve and rated load，adjusting voltage via booster devices；b）Close performance：This is tested under the conditions of rated voltage Ve and 50% of rated loading；Otherwise，the following performances could also be tested：1）Structural performances：a）Ability of brake shoe's position following drum；b）Assembly for keeping gaps between drum and shoes equalling；c）Lubricating.2）Other items：a）Contact area；b）Spring testing；c）Braking linings and shoes gap；d）Pin's hardness.3 AC frequency conversion adjusting speed systemCompared with DC motor，the AC motor has simple and compact structure，little maintenance workload，high efficiency，small rotating inertia and quick dynamic response，and it could be made of high-voltage，large capacity and high speed. Currently，AC motor has trend to replace DC one in the field of adjusting speed transmission.Generally speaking，there are many kinds of motors which could be applied to diverse types of converter-driven，and which are roughly divided into ordinary AC motor，special one and dedicated one. The frequency conversion adjusting speeding system is composed of frequency converter anddedicated lift motor.To the ordinary asynchronous motor，the following factors should be considered while to determine their capacity：（1）Chosen motor capability should be greater than the power load needed；（2）Compared with needed load pull-in torque the greatest torque that motor exports should have sufficiently surplus volume；（3）Even supply voltage is lower 10% than rated value，motors can export needed torque also；（4）Considering the life length of motor it should running in the specified temperature scope；（5）Because of transmission rate of the transmission system，efficiency and load fluctuation，the motor power should have enough surplus volume；（6）Against load nature，it is necessary to choice a suitablemotors operating modes such as continuous service system，short-term operation and duplication system.In the AC adjusting speed control system with frequency converter motor's slowdown is achieved by reducing the output frequency of the converter. When motors need slow down faster than the rate of free deceleration，underspeed of converter output frequency might be ran-up and the speed which is corresponding to that frequency is lower than the actual rotational speed of motor，and motor will be regenerative braking. In such cases，asynchronous motor will be an asynchronous generator，and load mechanical energy will be converted to electrical energy and then feedback to the converter. However，when the back feed is overload，overvoltage protection circuit of converter will work to cut converter's output and motors will be freely slowdown instead a rapid speed-down. To avoid above phenomenon，that is，to consume the energy in other parts of the DC circuit without causing voltage rise in the voltage-fed converter，regenerating braking circuits （braking resistors）are normally used and the energy fed back to the DC circuit will consumed in the form of heat. For the test system，it is apparently that braking resistances are not necessary because of the usage of brake for braking deceleration. It is necessary to define surplus capacity of motor or converter on the basis of practical situation. And on the case of ensuring to meet requirements of driving system performance，energy consumption or economic factors should be considered，and overall system has a smaller investment and maximum benefits.基于制动试验台的虚拟仪器与变频技术制动器是广泛有益的和非常重要的安全保障设备。
机械类毕业设计外文翻译_New
机械类毕业设计外文翻译外文原文Options for micro-holemakingAs in the macroscale-machining world, holemaking is one of the most— if not the most—frequently performed operations for micromachining. Many options exist for how those holes are created. Each has its advantages and limitations, depending on the required hole diameter and depth, workpiece material and equipment requirements. This article covers holemaking with through-coolant drills and those without coolant holes, plunge milling, microdrilling using sinker EDMs and laser drilling.Helpful HolesGetting coolant to the drill tip while the tool is cutting helps reduce the amount of heat at the tool/workpiece interface and evacuate chips regardless of hole diameter. But through-coolant capability is especially helpful when deep-hole microdrilling because the tools are delicate and prone to failure when experiencing recutting of chips, chip packing and too much exposure to carbide’s worst enemy—heat.When applying flood coolant, the drill itself blocks access to the cutting action. “Somewhere about 3 to 5 diam eters deep, the coolant has trouble getting down to the tip,” said Jeff Davis, vice president of engineering for Harvey Tool Co., Rowley, Mass. “It becomes wise to use a coolant-fed drill at that point.”In addition, flood coolant can cause more harm than good when microholemaking. “The pressure from the flood coolant can sometimes snap fragile drills as they enter the part,” Davis said.The toolmaker offers a line of through-coolant drills with diameters from 0.039" to 0.125" that are able to produce holes up to 12 diameters deep, as well as microdrills without coolant holes from 0.002" to 0.020".Having through-coolant capacity isn’t enough, though. Coolant needs to flow at a rate that enables it to clear the chips out of the hole. Davis recommends, at a minimum, 600 to 800 psi of coolant pressure. “It works much better if you have higher pressure than that,” he added.To prevent those tiny coolant holes from becoming clogged with debris, Davis also recommends a 5μm or finer coolant filter.Another recommendation is to machine a pilot, or guide, hole to prevent the tool from wandering on top of the workpiece and aid in producing a straight hole. When applying a pilot drill, it’s important to select one with an included angle on its point that’s equal t o or larger than the included angle on the through-coolant drill that follows.The pilot drill’s diameter should also be slightly larger. For example, if the pilot drill has a 120° included angle and a smaller diameter than a through-coolant drill with a 140°included angle, “then you’re catching the coolant-fed drill’s corners and knocking those corners off,” Davis said, which damages the drill.Although not mandatory, pecking is a good practice when microdrilling deep holes. Davis suggests a pecking cycle that is 30 to 50 percent of the diameter per peck depth, depending on the workpiece material. This clears the chips, preventing them from packing in the flute valleys.Lubricious ChillTo further aid chip evacuation, Davis recommends applying an oil-based metalworking fluid instead of a waterbased coolant because oil provides greater lubricity. But if a shop prefers using coolant, the fluid should include EP (extreme pressure) additives to increase lubricity and minimize foaming. “If you’ve got a lot of foam,” Davis noted, “the chips aren’t being pulled out the way they are supposed to be.”He added that another way to enhance a tool’s slipperiness while extending its life is with a coating, such as titanium aluminum nitride. TiAlN has a high hardness and is an effective coating for reducing heat’s impact when drilling difficult-to-machine materials, like stainless steel.David Burton, general manager of Performance Micro Tool, Janesville, Wis., disagrees with the idea of coating microtools on the smaller end of the spectrum. “Coatings on tools below 0.020" typically have a negative effect on every machining aspect, from the quality of the initial cut to tool life,” he said. That’s becaus e coatings are not thin enough and negatively alter the rake and relief angles when applied to tiny tools.However, work continues on the development of thinner coatings, and Burton indicated that Performance Micro Tool, which produces microendmills and microrouters and resells microdrills, is working on a project with others to create a submicron-thickness coating. “We’re probably 6 months to 1 year from testing it in the market,” Burton said.The microdrills Performance offers are basically circuit-board drills, which are also effective for cutting metal. All the tools are without through-coolant capability. “I had a customer drill a 0.004"-dia. hole in stainless steel, and he was amazed he could do it with a circuit-board drill,” Burton noted, adding th at pecking and running at a high spindle speed increase the drill’s effectiveness.The requirements for how fast microtools should rotate depend on the type ofCNCcharged EDM wire. The fine-hole option includes a W-axis attachment, which holds a die that guides the electrode, as well as a middle guide that prevents the electrode from bending or wobbling as it spins. With the option, the machine is appropriate for drilling hole diameters less than 0.005".Another sinker EDM for micro-holemaking is the Mitsubishi VA10 with afine-hole jig attachment to chuck and guide the fine wire applied to erode the material. “It’s a standard EDM, but with that attachment fixed to the machine, we can do microhole drilling,” said Dennis Powderly, sinker EDM product manager for MC Machinery Systems Inc., Wood Dale, Ill. He added that the EDM is also able to create holes down to 0.0004" using a wire that rotates at up to 2,000 rpm.Turn to TungstenEDMing is typically a slow process, and that holds true when it is used for microdrilling. “It’s very slow, and the finer the details, the slower it is,” said , president and owner of Optimation Inc. The Midvale, Utah, company builds Profile 24 Piezo EDMs for micromachining and also performs microEDMing on a contract-machining basis.Optimation produces tungsten electrodes using a reverse-polarity process and machines and ring-laps them to as small as 10μm in diameter with 0.000020" roundness. Applying a 10μm-dia. electrode produces a hole about 10.5μm to 11μm in diameter, and blind-holes are possible with th e company’s EDM. The workpiece thickness for the smallest holes is up to 0.002", and the thickness can be up to 0.04" for 50μm holes.After working with lasers and then with a former EDM builder to find a better way to produce precise microholes, Jorgense n decided the best approach was DIY. “We literally started with a clean sheet of paper and did all the electronics, all the software and the whole machine from scratch,” he said. Including the software, the machine costs in the neighborhood of $180,000 to $200,000.Much of the company’s contract work, which is provided at a shop rate of $100 per hour, involves microEDMing exotic metals, such as gold and platinum for X-ray apertures, stainless steel for optical applications and tantalum and tungsten for the electron-beam industry. Jorgensen said the process is also appropriate for EDMing partially electrically conductive materials, such as PCD.“The customer normally doesn’t care too much about the cost,” he said. “We’ve done parts where there’s $20,000 [in time and material] involved, and you can put the whole job underneath a fingernail. We do everything under a microscope.”Light CuttingBesides carbide and tungsten, light is an appropriate “tool material” formicro-holemaking. Although most laser drilling is performed in the infrared spectrum, the SuperPulse technology from The Ex One Co., Irwin, Pa., uses a green laser beam, said Randy Gilmore, the company’s director of laser technologies. Unlike the femtosecond variety, Super- Pulse is a nanosecond laser, and its green light operates at the 532-nanometer wavelength. The technology provides laser pulses of 4 to 5 nanoseconds in duration, and those pulses are sent in pairs with a delay of 50 to 100 nanoseconds between individual pulses. The benefits of this approach are twofold. “It greatly enhances material removal compared to other nanosecond lasers,” Gilmore said, “and greatly reduces the amount of thermal damage done to the workpiece material” because of the pulses’ short duration.The minimum diameter produced with the SuperPulse laser is 45 microns, but one of the most common applications is for producing 90μm to 110μm holes in diesel injector nozzles made of 1mm-thick H series steel. Gilmore noted that those holes will need to be in the 50μm to 70μm ra nge as emission standards tighten because smaller holes in injector nozzles atomize diesel fuel better for more efficient burning.In addition, the technology can produce negatively tapered holes, with a smaller entrance than exit diameter, to promote better fuel flow.Another common application is drilling holes in aircraft turbine blades for cooling. Although the turbine material might only be 1.5mm to 2mm thick, Gilmore explained that the holes are drilled at a 25° entry angle so the air, as it comes out of the holes, hugs the airfoil surface and drags the heat away. That means the hole traverses up to 5mm of material. “Temperature is everything in a turbine” he said, “because in an aircraft engine, the hotter you can run the turbine, the better the fuel economy and the more thrust you get.”To further enhance the technology’s competitiveness, Ex One developed apatent-pending material that is injected into a hollow-body component to block the laser beam and prevent back-wall strikes after it creates the needed hole. After laser machining, the end user removes the material without leaving remnants.“One of the bugaboos in getting lasers accepted in the diesel injector community is that light has a nasty habit of continuing to travel until it meets anothe r object,” Gilmore said. “In a diesel injector nozzle, that damages the interior surface of the opposite wall.”Although the $650,000 to $800,000 price for a Super- Pulse laser is higher than a micro-holemaking EDM, Gilmore noted that laser drilling doesn’t require electrodes. “A laser system is using light to make holes,” he said, “so it doesn’t have a consumable.”Depending on the application, mechanical drilling and plunge milling, EDMing and laser machining all have their place in the expanding microm achining universe. “People want more packed into smaller spaces,” said Makino’s Kiszonas.中文翻译微孔的加工方法正如宏观加工一样，在微观加工中孔的加工也许也是最常用的加工之一。
机械毕设外文翻译
Switched Reluctance Motors Drive for the Electrical Traction in Shearer Abstract—the paper presented the double Switched Reluctance motors parallel drive system for the electrical traction in shearer. The system components, such as the Switched Reluctance motor, the main circuit of the power converter and the controller, were described. The control strategies of the closed-loop rotor speed control with PI algorithm and balancing the distribution of the loads with fuzzy logic algorithm were given. The tests results were also presented. It is shown that the relative deviation of the average DC supplied current of the power converter in the Switched Reluctance motor 1 and in the Switched Reluctance motor 2 is within 10%.Keywords- switched reluctance; motor control; shearer; coalmine; electrical drive.I. INTRODUCTIONThe underground surroundings of the coal mines are very execrable. One side, it is the moist, high dust and inflammable surroundings. On the other side, the space of roadway is limited since it is necessary to save the investment of exploiting coal mines so that it is difficult to maintain the equipments. In the modern coal mines, the automatization equipments could be used widely. The faults of the automatization equipments could affect the production and the benefit of the coal mines. The shearer is the mining equipment that coal could be cut from the coal wall. The traditional shearer was driven by the hydrostatic transmission system. The fault ratio of the hydrostatic transmission system is high since the fluid in hydrostatic transmission system could be polluted easily. The faults of the hydrostatic transmission system could affect the production and the benefit of the coal mines directly. The fault ratio of the motor drive system is lower than that of the hydrostatic transmission system, but it is difficult to cool the motor drive system in coal mines since the motor drive system should be installed within the flameproof enclosure for safety protection. The motor drive system is also one of the pivotal parts in the automatization equipments. The development of the novel types of the motor drive system had been attached importance to by the coal mines. The Switched Reluctance motor drive could become the main equipments for adjustable speed electrical drive system in coal mines [1],because it has the high operational reliability and the fault tolerant ability [2]. The Switched Reluctance motor drive made up of the double-salient pole Switched Reluctance motor, the unipolar power converter and the controller is firm in the motor and in the power converter. There is no brush structure in the motor and no fault of am bipolar power converter in the power converter [3][4]. The Switched Reluctance motor drive could be operated at the condition of lacked phases fault depended on the independence of each phase in the motor and the power converter [5]. There is no winding in the rotor so that there is no copper loss in the loss and there is only little iron loss in the rotor. It is easy to cool the motor since it is not necessary to cool the rotor. The shearer driven by theSwitched Reluctance motor drive had been developed. The paper presented the developed prototype.II. SYSTEM COMPONENTSThe developed SwitchedReluctance motors drive for the electrical traction in shearer is a type of the double Switched Reluctance motors parallel drive system. The system is made up of two Switched Reluctance motors; a control box installed the power converter and the controller. The adopted two Switched Reluctance motors are all three-phase 12/8 structure Switched Reluctance motor, which were shown in Figure 1. Figure1. Photograph of the two three-phase .12/8 structure Switched Reluctance motorThe two Switched Reluctance motors were packing by the explosion-proof enclosure, respectively. The rated output power of one motor is 40 KW at the rotor speed 1155 r/min, and the adjustable speed range is from 100 r/min to 1500r/min.The power converter consists of two three-phase asymmetric bridge power converter in parallel. The IGBTs were used as the main switches. Three-phase 380V AC power source was certificated and supplied to the power converter. The maincircuit of the power converter was shown in Figure 2.In the controller, there were the rotor position detection circuit, the commutation circuit, the current and voltage protection circuit, the main switches’ gate driver circuit and the digital controller for rotor speed closed-loop and balancing the distribution of the loads.III. CONTROL STRATEGYThe two Switched Reluctance motor could all drive the shearer by the transmission outfit in the same traction guide way so that the rotor speed of the two Switched Reluctance motors could be synchronized.The closed-loop rotor speed control of the double Switched Reluctance motors parallel drive system could be implemented by PI algorithm. In the Switched Reluctance motor 1, the triggered signals of the main switches in the power converter are modulated by PWM signal, the comparison of the given rotor speed and the practical rotor speed are made and the duty ratio of PWM signal are regulated as follows,1()11()1(1)1()e=()g fk i k p k k k k k n n D k e K e e D D D ---∆=+-=+∆where, ng is the given rotor speed, nf is the practical rotorspeed, e is the difference of the rotor speed, 1()k D ∆is the increment of the dutyratio of PWM signal of the Switched Reluctance motor 1 at k time, Ki is the integral coefficient, Kp is the proportion coefficient, ek is the difference of the rotor speed at k time, ek-1 is the difference of the rotor speed at k-1 time, D1(k) is the duty ratio of PWM signal of the Switched Reluctance motor 1 at k time, and D1(k-1) is the duty ratio of PWM signal of the Switched Reluctance motor 1 at k-1 time.The output power of the Switched Reluctance motordrive system is approximately in proportion to theaverage DC supplied current of the power converter asfollows, 2in p I ∝ where, P2 is the output power of the Switched Reluctance motor drive system, Iin is the average DC supplied current of the power converter.In the Switched Reluctance motor 2, the triggered signals of the main switches in the power converter are also modulated by PWM signal. The balancing the distribution of the loads between the two Switched Reluctance motors could be implemented by fuzzy logic algorithm. In the fuzzy logic regulator, there are two input control parameters, one is the deviation of the average DC supplied current of the power converter between the two Switched Reluctance motors, and the other is the variation of the deviation of the average DC supplied current of the power converter between the two Switched Reluctance motors. The output control parameter is the increment of the duty ratio of the PWM signal of the Switched Reluctance motor 2. The block diagram of the double Switched Reluctance motors parallel drive system for the electrical traction in shearer was shown in Figure 3.The deviation of the average DC supplied current ofthe power converter between the two Switched Reluctance motors at the moment of ti is12i in in e I I =-:.1i i i e e e -=- where, ei-1 is the deviation of the average DC suppliedcurrent of the power converter between the two SwitchedReluctance motors at the moment of ti-1. The duty ratio of the PWM signal of the Switched Reluctance motor 2 at the moment of ti is2()2(1)2()i i i D D D -=+∆where, 2()i D ∆ is the increment of the duty ratio of the PWM signal of theSwitched Reluctance motor 2 at the moment of ti and D2(i-1) is the duty ratio of the PWM signal of the Switched Reluctance motor 2 at the moment of ti-1.The fuzzy logic algorithm could be expressed asfollows,if ~~if E i E = and ~~EC j E C = then U~ ~~U U U =i = 1,2,…, m, j = 1,2, …,nwhere, E~ is the fuzzy set of the deviation of the average DC supplied current of the power converter between the two Switched Reluctance motors, E~C is the fuzzy set of the variation of the deviation of the average DC supplied current of the power converter between the two Switched Reluctance motors, and U~ is the fuzzy set of the increment of the duty ratio of the PWM signal of the Switched Reluctance motor 2.The continuous deviation of the average DC supplied current of the powerconverter between the two Switched Reluctance motors could be changed into the discrete amount at the interval [-5, +5], based on the equations as follows,[]10220e i e e INT K e K ==The discrete increment of the duty ratio of PWM signal of the Switched Reluctance motor 2 at the interval [-5, +5] could be changed into the continuous amount at the interval [-1.0%, +1.0%], based on the equations as follows,12()[]100.02i D D D INT K D K -==There is a decision forms of the fuzzy logic algorithm based on the above principles, which was stored in the programme storage cell of the controller.While the difference of the distribution of the loads between the two Switched Reluctance motors could be got, the duty ratio of PWM signal of the Switched Reluctance motor 2 will be regulated based on the decision forms of the fuzzy logic algorithm and the distribution of the loads between the two Switched Reluctance motors could be balanced.IV. TESTED RESULTSThe developed double Switched Reluctance motors parallel drive system prototype had been tested experimentally. Table I gives the tests results, where 1σis the relative deviation of the average DC supplied current of the power converter in the Switched Reluctance motor 1, 2σis the relative deviation of the average DC supplied current of the power converter in the Switched Reluctance motor 2, and,1211122100%2in in in in in I I I I I σ+-=⨯+ 1222122100%2in in in in in I I I σ+-=⨯It is shown that the relative deviation of the average DC supplied current of the power converter in the SwitchedReluctance motor 1 and in the Switched Reluctance motor2 is within 10%V. CONCLUSIONThe paper presented the double Switched Reluctance motors parallel drive system for the electrical traction in shearer. The novel type of the shearer in coal mines driven by the Switched Reluctance motors drive system contributes to reduce the fault ratio of the shearer, enhance the operational reliability of the shearer and increase the benefit of the coal mines directly. The drive type of the double Switched Reluctance motors parallel drive system could also contribute to enhance the operational reliability compared with the drive type of the single Switched Reluctance motor drive system.中文翻译：关磁阻电动机驱动电牵引采煤机摘要-本文介绍了双开关磁阻电动机并联传动系统控制驱动电牵引采煤机。
工业机器人毕业设计外文翻译
外文资料：INDUSTRIAL ROBOTSMechatronicsThe success of industries in manufacturing and selling goods in a world market increasingly depends upon an ability to integrate electronics and computing technologies into a wide range of primarily mechanical products and processes. The performance of many current products-cars, washing machines, robots or machine tools-and their manufacture depend on the capacity of industry to exploit developments in technology and to introduce them at the design stag into both products and manufacturing processes. The results so that the whole industrial system to produce a cheaper and easier than in the past, more reliable, more powerful manufacturing technology, this intense competition, leading to the original electronic engineering and mechanical engineering have been gradually difference among the various disciplines with engineering design replaced with the mutual penetration, resulting in a mechanical and electrical integration, or mechatronics.In this competitive environment, the success of products and technologies are those that effectively combine the electronic and mechanical products, but not the main reason is the absence of a successful application of electronic technology. General product innovation in machine-building industry, often starting from the mechanical hardware design, but in order to achieve vision, from the initial stages of the design process must take full account of electronic technology, control engineering and computer technology. Research from the machinery and electronics to engineering design, the key is through the mechanics and electronics hidden boundaries, put them together, it is understood today the key to this transformation took place.To be successful, early in the design of the study need to establish the concept of mechatronics, when the specific program has not yet formed, so there is choice. In this way, design engineers, especially mechanical design engineers will be able to make a decision too quickly to avoid falling into the stereotypes and reduce productivity.Fully study the market trend, we will find electromechanical integration with a design, will lead to a revival of the field, such as high-speed textile machines, measurement and measurement systems, and automatic test equipment, integrated circuits Xiang kind of special equipment. In many cases sub ah, the emerging field of production and recovery are often formed by the embedded microprocessor electronics and basic mechanical system caused by the integrated and enhanced processing capacity.Flexibility of the manufacturing process the request resulted in the production of flexible operating system concepts in this system, many components such as computer numerical control machine tools, robots and automatic guided vehicles, etc. associated with joint production, exchange of information between them through Local Area Network.The products so far, most do not realize the design of electromechanical integration of diversity for the engineering sudden opportunity. The final product sold to customers is the essence of our revenue sources, which may begin the application is the date the new mechatronic products and provide enhanced functionality important difference between traditional products.The following examples may illustrate that the traditional products: Automatic transmission control engine and automatic control of the development of engines and transmissions tend to reduce the radiation, save fuel and time by preventing excessive speed and the use of the fuel flow can be adjusted to avoid false-driven gear and so on.Power-driven tools of modern power-driven tools, such as drill bits you can provide a variety of functions, including speed and torque control, reverse action and acceleration control.The new examples of mechatronic products are as follows:Standard components assembled a traditional industrial robot because of structural problems often many restrictions. Using a number of structural parts and drive, coupled with the central processor can be made by the standard components to assemble the robot system, so users can assemble to meet their own needs various robots.Video and CD player, video and CD player laser head is equipped with sophisticated, you can read the digital information on the disk. Withmicroprocessor control system can provide multi-track selection, scan preview and many other features.The above examples show that the purpose of the use of machinery is the continuous improvement of electronic consumer goods, not to keep consumer prices lower. Machinery and electronics products provide solutions to specific problems of the ideal way to use a low-cost element or standards.The personal computer controller and programmable logic controllerEarly machine tools and robots in the controller's function is to store and perform some simple procedures for the implementation of the tool or device with a predetermined speed to generate the required movement. Since 1981, IBM's first since the emergence of personal computers, many manufacturers produce microprocessors based on its so-called. Through the main memory and secondary storage devices exchange data, which allows users to use than the system microprocessor to provide the actual storage space for more storage space programming. It is this processing power and storage efficiency had a dramatic impact, making more and more industrial sectors to PC, for data acquisition and control applications. In addition to handling capabilities, PC machine control applications as a key component of many other advantages. These advantages are:(1) choice of application software more than a dedicated controller.(2) Select the tools to improve application efficiency and room for more.(3) The PC is available in a variety of forms ranging from a single card, a portable,a desktop and ruggedized industrial version for use on the factory floor.(4) bus architecture with multiple expansion slots, digital and analog input / output cards can be produced by several manufacturers.(5) special machine or a small computer than a more flexible, depending on the application can be very convenient for a variety of configurationsPC, data acquisition and control device may be an additional external and interest rates through, or it may be a plug-in board. Typically add a separate external rack, the internal packaging has to provide power to the host through the serial or parallel data communications cable. A variety of standard format modules can be inserted in the rack as needed.PC, data acquisition There are basically two ways. The first use of analog /digital conversion card connected directly with the host backplane. Conversion cards generally do port address can be any support for input / output command driven programming language. Usually connected to the card, select the base address. This allows a different card or card number the same host in the same PC connection and operation. The second method is to use the interface circuit board with a digital voltage meter and frequency meter and other equipment to control the PC, to receive data. The Common Criteria is an international Association of Electrical and Electronics Engineers IEEE-488 standard parallel communication link. Comparison of fast, easy and economical is the first approach, using the input / output port address the card to the PC, the output of the measurement data or control signals received from the PC machine. These cards are versatile, easy to obtain, and has the following characteristics:(1) multi-channel digital input / Shucu interface with optical isolation and Darlington driver settings.(2) pulse timing and counting facilities.(3) multi-channel programmable A / D conversion.(4) D / A conversion.(5) thermocouple input.PC machine control applications including the latest developments in data acquisition and control software, can provide the user with a drop-down menus and mouse-driven windows environment.Before the invention of the computer control system main relay logic circuit with electrical or pneumatic logic circuits to automate. The late 20th century invention of 60 programmable logic controllers (PLC) directly instead of the relay controller. It should be noted, in the United States, also known as programmable logic controller PLC, abbreviated as PC. Do it with a personal computer PC or IBM-PC to be confused.Programmable logic controllers and micro-computer composed of the same, there are microprocessors, memory and input / output devices. Processor performs memory control process according to input instructions, defined by the logic control program to provide output. Every step during the implementation period, the program is quickly scanned to record all of the input state, then the program logic to determine output. Controller scan each of these steps are repeated.Some small, dedicated to the sequential control of the programmable logic controller usually has 12 input ports and eight output ports are extended to both pinch the 128 input / output circuit. Input interface connected to these lines, the process of receiving input signals from the control, and these signals into a form suitable for processing. Similarly, the programmable logic controller output interface with a variety of process hardware, such as lights, motors, relays and spiral coil.Using a handheld programming keyboard, or with the corresponding software development kit with a personal computer connected to the programmable controller command input random access memory, the random access memory with battery backup power supply generally. If the programmer to establish procedures for using the symbol key, and some programming console LCD display can also display some of the graphics, using ladder logic diagram shows the format process. After a debugging program, the control method through simulation testing, you can put code into erasable programmable read-only memory chips, mounted on the programmable logic controller.Many manufacturers are in the manufacture of programmable logic controller. Although some manufacturers use their own proprietary software language, but most are still using ladder logic diagrams. Invention of this language is intended to be more acceptable to some customers, these customers are interested in is how to shift from hard-line programmable logic controller, relay control. In addition to input / output devices, the programmable logic controller also includes timers, counters, and other special function devices.Communication with other control devices exchange the traditional programmable logic controller is not the strengths of the network. Many industrial controllers are equipped with RS232 serial port, and other digital control equipment systems to exchange information.The robotIndustrial robot is a tool to improve manufacturing productivity. He can assume that humans may have dangerous jobs. The first industrial robot in nuclear power plants had to be replaced and the fuel rods. Industrial robots can work on the assembly line, such as the installation of electronic components, printed circuitboard. In this way, people can escape the monotony of the work stand out. Robots can also remove the bomb, as the disabled person services for our community to do all kinds of work.Robot is a re-programming, multi-agency work can be pre-programmed positions in all moving parts, materials, tools or other special equipment, complete a variety of different jobs.The location is pre-programmed robot to complete the work must follow the path. In some pre-programmed location, the robot will stop some operations, such as installing parts, painting or welding. These pre-programmed location is stored in the robot's memory to recall at any time of continuous operation. If the job requirements changed, the location of these pre-programmed data, together with other programming can be changed. These characteristics make industrial robot programming and computer are very similar.Robot system can control the robot's work unit. Robot work cell robots perform tasks in the work environment. Unit of work, including the robot manipulator, controller, working platforms, safety equipment and gear. In addition, the robot should be able to communicate with the outside world signals.Robot manipulator to complete the specific work of the robot system, which consists of two parts: the mechanical parts and ancillary parts. Subsidiary part of the installed robot base. Several fixed on the floor at the job site. But sometimes the base is able to move, in this case, the base placed in orbit for the robot from one location to another location should be.Subsidiary part of the robot arm. It may be a straight arm can move, it may be a hinged arm, the robot work to provide multiple axes. Articulated arm that is connected to the relevant section of the arm. End of the arm with a wrist. Wrist mounted on another shaft and fitted with flange root. In the flange also can be connected to different tools to complete different tasks. Mechanical axis allows the robot hand in a specific area to work. This area is called the robot unit of work, it depends on the size of the robot. If the robot the size of the increase will increase the size of the unit of work.Manipulator movement control drive or drive system. They drive the state work unit in the rotation. Drive system can make the electrical, hydraulic, it can be pneumatic. Drive power generated by the various institutions converted intomechanical energy, all kinds of drive system is connected by mechanical transmission. Those from the chain, gears and ball screw driven mechanical transmission device composed of the axis of the robot.Used to control the robot to control its movement and the work unit of the external device. Handheld keyboard by hanging the movement of the robot controller program input. The data stored in the controller's memory for future calls.Controllers also work in the unit with an external device to communicate. For example, the controller has an input line. Completion of processing input lines connected, high-speed controller for robot pick in the specified location processed parts. Mechanical hand a new part into the machine, the controller send a signal to start processing.Some of the drum controller is composed by a mechanical operation, the internal implementation of the input sequence of events. The controller is generally used very simple robot system. Most of the robot controller in your system much more complex, reflecting the latest developments in electronic technology. They are controlled by the microprocessor, the operation more flexible.The controller can transmit signals in the communications line. This mechanical hand and two-way communication between the controllers continuously update the location and operation of the system. The controller also includes a computer with different devices to communicate. This communication link to the robot as part of computer-aided manufacturing systems. Microprocessor system uses solid-state storage devices. These storage devices may be magnetic guns, random access memory, floppy disks and tapes.Controller and the robot powered by a power source supply. Robotic systems typically use two kinds of power: a controller may provide alternating current; the other power source used to drive each axis manipulator. For example, if the robot is controlled by a hydraulic or pneumatic drive, these devices will receive the control signal, a robot in motion.The robot sensorAlthough the robot has great ability, but often than not with a little practice, but the workers. For example, workers can find parts that fell on the ground or no parts feeder. But not the sensor, the robot will not get this information. Even the mostsophisticated sensor system, the robot is smaller than an experienced worker. Therefore, a good robot system design requires many sensor and robot controller using the phase to make it operate as close as possible the perception of workers. The most frequently used robotics sensors into contact with the non-contact. Contact sensors can be further divided into tactile sensors, force and torque sensors. Tactile or contact sensors can be measured by the drive-side and the actual contact between other objects, micro-switch is a simple tactile sensor. When the robot by the drive-side contact with other objects, the robot stop motion sensors to avoid collisions between objects to tell the robot has reached the goal; or detection to measure the size of the object. Force and torque sensors in the robot's gripper and wrist joint between the last, or the load on the robot parts, measuring reaction force and torque. Force and torque sensors and piezoelectric sensors are mounted on flexible parts of the strain gauges.Non-contact sensors include proximity sensors, vision sensors, sound detectors, sensitive components and scope. Proximity sensors detect objects near the sensor and the label. For example, eddy current sensor can accurately maintain a fixed distance between the plates. Most cheap robot proximity sensors including a light-emitting diode and a photodiode receiver transmitter, receiver reflector closer to the reflection of light. The main disadvantage of this sensor is closer to the object reflectance of light will affect the received signal. Other proximity sensors using capacitance and inductance associated with the principle.Visual sensing system is very complex, based on the TV camera or laser scanner works. Video signal by hardware pretreatment to 30-60 per second input into the computer. Computer analysis of the data and extract the required information, such as the existence of objects and object features, location, direction of operation, or assembly of components and product testing is complete.Sound sensitive devices used to sense and interpret sound waves. To detect sound waves from the basic continuous speech word for word recognition that people, all kinds of sound ranging from the complexity of sensitive components. In addition to human verbal communication, the robot can use voice control of sensitive components arc welding, I heard the voice of the collision or the collapse of the movement of the robot when the organization to predict the mechanical damage will occur and the detection of objects within the defects.There is also a non-contact systems for projector and imaging the surface of the object surface shape information or distance information.Static detection and closed-loop sensor probe used in two ways. When the detection and operation of the robot system moves alternately, it is usually necessary to use the sensor. That probe is a robot is not operating, the operation has nothing to do with the sensors, this method is called static detection. In this way, vision sensors are looking for is to capture the position and direction of the object, then the robot moves straight to the site.In contrast, closed-loop operation of motion detection robot, always under the control of the sensor. Most sensors are closed loop mode, they can always detect the actual location of the robot and the deviation between the ideal position, and drive the robot fix this error. In the closed-loop detection, even if the object in motion, for example, the conveyor belt, the robot can grasp it and sent it to the desired location.However, in the early 20th century, 80, a number of factors hindered the development of closed-loop detection. The most important reason is the image map for too long, almost equal to the robot move from one place to another time. For practical, for the robot arm motion, image analysis time by reducing down time should be able to accept and explain a few frames.In the use of force and tactile sensor control movement, reaction time to visual sensor that is no longer a problem, because very little information when the sensor transmission. In other words, we can placed on the wrist force and torque sensor 6, or place a finger on the low-resolution binary sensor array. Since the sensor more complex, we can expect delivery by the sensor data can be more of information.中文翻译：工业机器人机电一体化在国际市场中，制造业和工业产品德销售业绩取得的成绩，越来越依靠电子技术和计算机技术与传统机械制造和机械产品的广泛结合。
机械毕业设计外文翻译
A Comparison of Drive Starting Mechanisms forAggregate Belt ConveyorsAbstractThe purpose of this paper is to describe the torque/speed characteristics，during starting conditions，of the most common drives used on belt conveyors today. Requirements of a Belt Conveyor DriveA belt conveyor is considered to be a constant torque device. In other words，the required driving torque is approximately constant at varying speeds (see figure l).other applications，such as a pump drive，have variable torque requirements(see figure2).However，to increase the speed of a conveyor additional torque must be added untilthe desired speed is obtained. Newton’s Second Law of Motion governs this relationship.∑F m a=The most straightforward example would be a constant acceleration torque(see figure3).In reality the acceleration torque is rarely constant. However，static calculation models as outlined in the Conveyor Equipment Manufacturers Association handbook (CEMA) make this assumption. When using static models the average acceleration torque is estimated over the entire acceleration time and assumed to be linear. Dynamic models，which are beyond the scope of this paper，allow acceleration torque values to vary in magnitude during the acceleration(or deceleration)Period.It should be noted that，given a constant load，a larger acceleration torque results in a faster acceleration time and also higher Peak belt tensions. Conversely，a smaller acceleration torque results in a longer start time and smaller Peak belt tensions. Across-The-Line AC Motor StartTechnically this is the simplest type of drive used on a belt conveyor. In this drive type an AC squirrel cage induction motor is started by simply throwing the contactor and energizing the motor. The resulting output torque，assuming that rated voltage is maintained，is strictly a function of the motor design. NEMA has Provided design standards that define the output torque characteristics of the most commonly used 3 Phase motors up to approximately 250 hp(figure4).In sizes larger than 250 hp manufacturers generally use the NEMA design codes in a relative manner(i.e.，NEMA C has a greater locked rotor torque than a NEMA B motor).The most critical locations on the AC motor speed/torque curve have been named for definition purposes. These common names are provided in figure 5.The most rigorous method of determining average acceleration torque，for static calculations，is to break the curve into several vertical sections，then sum the individual areas under the curve and finally divide by the number of sections.The more common way is to apply the following simplified equation:These static approximation methods work for most belt conveyors but can get the designer into trouble from time to time，especially on long and/or steep and/or fastconveyors. One item that needs to be examined is breakaway torque. Just because the drive provides enough average torque to accelerate the load doesn’t mean that it provides enough torque to break it away from zero speed and get it moving.CEMA defines breakaway torque as twice the torque required to overcome the total friction plus the torque required to lift the load vertically. Locked rotor torque (LRT) needs to be greater than breakaway torque! A good static Program makes this check.In addition to examining the effect that average torque has on the conveyor components the belt designer needs to determine the effect of peak torque. It is not uncommon for the breakdown torque (BDT) of a NEMA C motor to be greater than2.5 times full load torque (FLT).Generally the belting and Pulley manufacturers allowa transient overload of 1.5 times full load operating load. An across-the-line start can easily cause tensions to exceed these maximums. These higher than normal loads can be designed into the conveyor if they are known up front.Considering only average starting torque can cause the conveyor designer to undersize the take-up weight. It is not uncommon for conveyors with across-the-line starters to experience intermittent drive slip. This generally happens when Peak torque (BDT) is input by the drive and the take-up has been sized for average torque but not peak torque. The result can be devastating. When the drive pulley slips during this condition，the tension on the Tl and T2 sides (high and low)of the drive Pulley tries to equalize. This can subject a low tension bend or take-up pulley，just behind the drive pulley，to tensions that approach Tl tension. These Pulleys are rarely，if ever，designed for this load condition and the result is low tension Pulley failure. This condition is easily demonstrated with dynamic analysis.Another common Problem with across-the-line starts is caused by voltage dips during starting. If the power distribution system is not stiff enough to handle the huge inrush currents of an across-the-1ine start，the starting torque of the motors can be reduced to a Point that the conveyor will not start. This is due to the fact that the output torque ofan AC squirrel cage induction motor is reduced by the square of the applied voltage. In other words，a voltage drop of 10%would equate to a torque reduction of 19%. Reduced Voltage StartingThe reduced voltage starting of an AC squirrel cage induction motor is done for two basic reasons:1 .To reduce the inrush current that naturally occurs when a motor is Startedacross-the-1ine. A typical current/speed graph is shown in figure 6.It is not uncommon for the inrush current to be 6 times or more than it is at full load torque. As stated above high inrush currents cause the voltage in a power distribution system to sag. The cost of electrical power distribution equipment can become very high if it needs to be designed to handle the high inrush currents.2 . To reduce Peak motor torque during starting conditions，which subsequentlyincreases acceleration time. By reducing the Peak torques the conveyor components can be designed for lower tension loads. This primarily includes belting，Pulleys and external support structure. This can result in significant cost savings.Two common types of reduced voltage starters are the Current Limiting and the Constant Torque devices.Graphs are included above(figures 7 through 8) that depict the same motor/conveyor application with an Across-The-Line，a limitd Curren, and a constant Torque start. After studying the graphs it becomes apparent that the best use of the limited torque start is to protect the power distribution system from high inrush currents. The constant torque start reduces the high torque Peaks and Protects the conveyor’s mechanical components. In both cases the Start time is increased because the over all magnitude of accelerating torque is reduced. However，neither method will make it easier to start a“hard-to-start conveyor.”Correcting a hard starting conveyor is not areason to use a reduced voltage starter!翻译带式输送机驱动方式比较摘要本文的目的是描述最常见的机用输送皮带起动时的扭矩/转速特性。
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附录VIRTUAL INSTRUMENT AND FREQUENCY CONVERSIONTECHNOLOGY-BASED BRAKE TEST SYSTEMBrake is widely useful and very important safety assuring equipment. The aim of Brake test system，which is based on visual instrument and frequency changing technology，is to integrative measure and analyze the performance and quality of the brake.This paper mainly introduces the principle，composing，function and features of the brake test system. And from the point of view of the principle of Visual Instrument （VI）technology，a test system，based on the VI and frequency changing technologies and consist of frequency changing drive and control sub-system and measuring sub-one，is constructed. With the test system the performances and braking course could be auto controlled and measured to the brakes which includes disc and drum ones. And the measuring and control software is programmed with the LabVIEW published by American NI Corporation，USA.Then data real time acquisition，processing，displaying and recording will be realized. The test system also has the functions of voltage adjusting，rotating speed control，load regulating，JC value setting，temperature- 1 -measuring，and braking route and time memorizing and analyzing. It will be very important for meaning and exciting boosting effect to advance quality and capabilities of the brakes and the security of equipments and system which have adopt the brakes.1 Operating principlesAccording to the principle of work and power，the change of kinetic energy in the moving of objects equals to the full power of the force act on the object in that process.The energy obtained by brake to be tested：Therefore，it is feasible to use combined inertial flywheels to simulate rotating inertia of crane hoist and its transmission components to test the performance and quality of the brake. According to the moment of momentum theorem：T b·t =J i·ω （1）When T b is fixed，t b can be controlled through combinations between Ji and ω differently. Brake drum or plate，which will be measured，and combined inertial flywheels for loading on are driven to rotate by AC frequency conversion motor （or DC one，which will not bedealt with in this article carefully）. According to the principles- 2 -shown in the formula （1），we can simulate actual processes of brakes fitted on lifting and transport machineries，engineering ones，mining ones and construction ones by changing the technical specification duty JC，the flywheel's inertial moment Ji and motor's rotational speed ni.When detected brakes work in simulation cycle and brake repeated，infrared thermoscopes and torque sensors，and other sensors will record braking shown in the heat，braking torque，braking time and brake speed parameters.2The composition and structure of the brake test systemThis test system is intended to achieve the performances of drum and disc brakes and has following functions：（1）Brake replacementAccording to different type of brakes the corresponding base will be chosen and brake position could be adjusted using electric slide test-bed；（2）Multi-level loadingWe can simulate the actual loading on brakes in a crane with different combined flywheels. The test system adopts manual hydraulic system composed by a three-position four-way- 3 -hand-operated direction valve，a relief one and their accessories，and it is operation saving and convenient to replace flywheels. （3）Regulation the rotational speed n （or ω）It can be realized by changing frequency supplied to the AC motor. When braking torque is very large，such as 10000Nm，it should be appropriate for regulating initial brake speed upward 1000r/min to minimize rotating inertia possibly.（4）Braking frequency adjustmentBased on actual needs braking frequency can be confined in a range of 1~4 times per minute.（5）Braking torque measurementThere are three methods：a）Direct measurement via torque sensors：Rotational speed and torque sensor will be installed between the detected brake drum or plate and inertial flywheel plates.Dynamic braking torque of detected brake will be directly measured，shown in Fig.1 and Fig.2. According to the scope of braking torque of detected brakes，two or three rotational speed and torque sensors should be prepared for testing torque to meet the accuracy requirements；b）Indirect parameter measurement：- 4 -Based on the rotating inertia and braking time we can get brake torque using mathematical relationship between these parameters，as shown in Fig. 2.c）Indirect measurement by pedestal-force：The pressure sensors are installed under the base where detected brake are fixed to feel the forces given by brake，and then to obtain brake torque.The second approach has small investment，simple structure and no torque sensors which mean not considering related troubles of changing torque sensors. But the procedure tocalculate torque is complex，and accumulating total errors would be larger and then the result accuracy will be low.The third way has the advantage of the replacement of sensors is easier and no special requirements for sensors installing precision.It is still an indirect measurement but the procedure is less thanthat in the second method and that means the cumulative errors relatively is smaller. And visible shortcoming is poor dynamic response.（6）Automatic controlExcept to manual operation test system is also programmed- 5 -control.（7）MonitoringBraking frequency，initial braking speed，the aggregate braking number，moment，time and so on will be shown automatically. （8）Automatically data acquisition and processingThe curve describing braking torque，time and speed could be drawn automatically by means of computer software while detected brake is measured in dutycycle operation. Therefore，in response to the way to test braking torque the system can be divided into three ones of that with torque sensor such as Fig.1 and 2 above，that without torque sensor such as shown in Fig.3 and that of pedestal-power measurement without torque sensor，as shown in Fig.4. The test system is mainly composed of AC frequency conversion transmission system，flywheels loading system，rotational speed and torque sensors，base which to fix drum or plate brakes，adjustable DC power supply，detected brakes and test and control system.- 6 -基于制动试验台的虚拟仪器与变频技术制动器是广泛有益的和非常重要的安全保障设备。