外文资料翻译---伺服阀试验台计算机辅助测试系统的研制

Study on Computer Assistant Test System of ServoValve Test-bed Abstract：According to the need of the static and dynamic characteristics of the test on servo valve , firstly this article introduces the necessary part of the system-the pump station. Next, it designs the corresponding hydraulic an d computer-aided test system and given the composition of software and har dware of the test system and the design process of software.In the end,we a pply the designed system to actual production to prove that it achieve the r equirements of the test on servo valve.Key words：servo valve, test rig, CAT, dynamic and static characteristics1. IntroductionElectro-hydraulic servo valve is the frequently-used control component in measurement and control system. Due to the wide use of electro-hydraulic servo system in metallurgy, engineering machinery, and chemical industry, a large number of servo valves are also be applied in these industries.Affect by the facters of environmental，abrasion,aging and so on,servo valve will malfunction inevitably and need repairs after using a certain time.After maintenance and repair,we must detect the servo valve through some certain testing methods of dynamic and static to decide whether its various properties meet the stipulated requirements or not. Thus,large enterprises establish independent servo valve test-bed according to the own needs.What is described below is a servo valve test-bed developed jointly by our unit and a university and the test-bed is based on computer-aided testing.2.Hydraulic pump stationHydraulic pump station also known as the pump station is an independent hydraulic device. It offers oil according to the requirements gradually and controlls the direction, pressure and flow rate of hydraulic oil, applied to the mainframe and hydraulic devices separability of hydraulic machinery. After the purchase users just connect hydraulic station and host of implementing agencies (motor oil or fuel tanks) with tubing, and hydraulic machinery can be realize these movements and the work cycle.Hydraulic pump station consists of pump device, block or valve, tanks, a combination of electrical boxes.The function of each components are as follows:(1)Pump device is equipped with motors and pumps, is the source of power of the hydraulic station. It changes mechanical energy into hydraulic oil pressure energy.(2)Integration block is assembled by hydraulic valve and channel body. It can adjust the direction, pressure and flow of the hydraulic oil.(3)Valve portfolio plate valve is installed in the board and channels connect with each other after the board witch is the same as integration valve.(4)Tank plate is a welding semi-closed container, and also located with oil filtering network and air filters used for oil, oil filters and cooling.(5)Electrical boxes have two patterns. One designs external fuse terminal plate; The other installs a full range of electrical control.Hydraulic station principle: motor driven pump rotation, and pump absorbsoil from the oil tank and changes mechanical energy into hydraulic pressure energy of the station. Hydraulic oil through manifold (or valve combinations) realizes the adjusting of direction, pressure, flow .Then through external pipe to the cylinder hydraulic machinery or motor, so as to realize the changing of the direction , the size of the force and the velocity, to promote the machinery working of all kinds.3. Hydraulic testing system and testing methodsTest-bed can complete the test on static and dynamic characteristics of servo valve.Static characteristics of the test includes characteristics of unloaded flow, characteristics of pressure-gain, characteristics of flow-pressure and characteristics of leakage; dynamic characteristics are mainly the test on frequency characteristics of servo valve. The above testing results of characteristics need to be drawn out in the way of graph. Figure 1 is a schematic diagram of hydraulic test system.3456811121920211.percolator 2.hydraulic pump 3.overflowvalve 4.energy accumulator 516.turbineflowmeter6-91718.on-off valve 10.statictesting position of valve11.dynamic testingposition of valve 12-15.pressuretransducer19.dynamic cylinder 20.velocitytransducer21.displacementtrancducer22.proportional overflow valve23.check valve unit2716151417232218913AB P A B P10OFig.1 static and dynamic testing systemof electro-hydraulic servo valve 1OAccording to the testing tems ,we install the valve to be tested on the static and dynamic testing board respectively.When we execute a static test, we should close the switching valve 8, and open the valve 6 .On the contrary, turn on valve 8 , and turn down valve 6 when we do a dynamic test.3.1 Testing method of characteristics of unloaded flowOperations are as follows,when we test the characteristics of unloaded flow.First,close switch valve 18 and 7, and open valve 17 and 9.We should make sure the pressure difference between the two output ports A and B of the electro-hydraulic servo valve △PL=0. And then input triangle-wave current signal with the frequency of 0.01Hz into the valve being tested. The size of the current signal vary in accordance with the following rule: changes from 0 to +i max, then from +i max to 0, then to +i max , and back to 0.Turbine flow meter 16 detects the flow in the process of the varying current and input the computer with the measured flow and corresponding current.The computer can draw the curve of the flow varing with the current,namely the curve of the unloaded flow characteristics ± q = f (±i) △pL= 0. And according to the measured data ,we can calculate valve flow-gain, symmetry, zero-drift and hysteresis and other important properties of the valve.3.2 Test method of load-flow characteristicsThe operations of the test on load-flow characteristics are as follows: First, open switch valve 18 and 9, close the valves 17 and 7, make sure the oil of port A and B flows through the one-way valve 23 and proportional relief valve 22. Proportional relief valve (minimum moderating pressure <0.5MPa) can change the load pressure during the test,and the turbine flowmeter 16 can measure the flow under a variety of load operating conditions. To start the test,we should adjust the relief valve 3, make sure the pressure of the system is the same as the rated pressure of the electro-hydraulic servo valve to be tested.Then input the valve coilbeing tested with a triangle-wave current signal of 0.01Hz,and then control theproportional relief valve 22 to make the load pressure change gradually from zero to the rated pressure by a certain increment and measure the flow under each increment and input into the computer at the same time. And then change the amplitude of the input current (frequency unchanged), repeat the above process,we can measure curves of more groups.This is the characteristic curve of the load flow of electro-hydraulic servo valve ± q = f (±△ PL) i = Cont.3.3 Test method of pressure characteristicsBefore the test, closed switch valve 17,18 and 7 and open the valve 9, make sure the output flow of the valve to be tested is zero.Then adjust the pressure relief valve 3 so that the pressure of the system equals to the rated pressure and return oil pressure (measured by pressure sensor 13) . Then input the valve coil to be tested with a triangular wave current signal of 0.1Hz.The computer reads the value of pressure transducer 14 and 15,so we can detect the pressure difference of the two out port of the servo valve.Change the input current signal amplitude,and we can measure pressure value under different current amplitudes.Pressure-gain curves can be sketched out,according to the value of current and pressure difference ±△=f (± i) q =0.PL3.4 Testing method of leakage featuresClose switch valve 17,18 and 9,and open valve 7,then adjust the relief valve 3 to make the pressure of the system is the same as the rated pressure of the valve tobe tested.Then input the valve coil with exciting current and measure the flow by flow transducer 5,and input the computer with the leak signal and rated exciting current signal after sampling. Leckage curves can be sketched out by the testing system q r = f (± i) .3.5 Test of dynamic characteristicsAccording to the international standard , test of dynamic characteristics of current servo valve mainly refers to width of amplitude frequency when characteristic curve of amplitude frequency is -3dB and phase-frequency width when characteristic curve of phase-frequency is -90°.We should use 10 sinusoidal signals of different frequiencies for exciting signals of the valve coil to be tested ,then measure the output flow signal in turn and filter out the signals different with the exciting signal of the flow signal and serve it as the response signals of the servo valve to be tested . The two signals are entered into the computer by turns after sampling , and epuate the auto-spectral spectrum of the exciting signals G XX(f) and cross-power spectrum of exciting signals and responding signals G XY(f) . By this method we can get the frequency response H (f) = G XX (f) / G XY (f) .When we do the test of the dynamic characteristics , close switch valve 6 and open valve 8 . An independent signal generator produces scaning sinusoidal signal . The signal is entered into the servo amplifier after amplification and drive the dynamic cylinder to move . With the help of the speed sensor installed on the dynamic cylinder ,we can equate the output flow of the servo valve being tested .And the shift sensor installed on the other side can be used for preventing the dynamic cylinder from deviating from the central position .4. Current circuit of the test systemThe signals need to be collected during the static characteristics test of the testing system signals include Current signals of the servo valve coil to be tested, Pressure of inlet oil port , Pressure signal of load port A and B , Pressure signal of leaking mouth , Flow signal of load port A and B , Flow signal of leaking mouth . The signals need to be collected during the dynamic characteristics test include current signals of valve coil to be tested ,V oltage signal outputed by speed sensor 20.Control signals outputed by the testing system include setting value of pressure of the proportional relief valve , Stimulating signals of valve coil to be tested produced by signal generator .The amplify signals of the servo valve to be tested in the above signals are current signals and the others are voltage signal . As these signals detected by the sensor usually contain noise or through modulation . So the signals should go through corresponding treatment before being inputed into the computer , then converted into digital signals by A/D converter for further use .Separate digital signal generator is used during the test ,and the signal generator use single chip microcomputer16as its core and can produce triangle waves, sine waves, square waves, linear sweep sine wave signals with the frequency of 0～800H Z and so on for servo valve testing . Signal generator communicate with the main computer by RS232 . During the test , the maincomputer tell signal generator the parameters such as generative type of waveform , amplitude and frequency of waveform . Signal generator produce stipulated type of waveform and input it into the servo amplifier of the valve to be tested . During the test of dynamic characteristics , transport the produced waveform data into the mian computer at the same time for calculating dynamic characteristics . Circuit structure of the system is shown in Figure 2.current signal i ofvalve to be testedpressure signal 12,13,14,15flow signal 16 leakage flow signal 5 sinusoidal current signal of valve to be testedvelocity transducer 20signalinputchammelandconditioningdatecollectcardtestingsystemdigital signal generatorservo amplifier of valveto be testedsignaloutputchannelpressure settingdraw dynamiccharacteristics curvetest result documentand date conservation Fig.1 current signal of testing system5. Software of testing systemThe main function of the software system is to complete the disposition of measured data and draw the testing curve . So the system can be divided into signal processing module , data communication module , interface management moduleand auxiliary function modules responsible for test document processing and data storage . These modules also contain a number of sub-module respectively , and then sub-module call the function of basic library functions to complete their respective functions.Signal processing module is the most important module of the test system and its sub-modules include digital filtering, curve fitting , the difference, frequency response calculation and error compensation. Algorithms can be used by digital filtering conclude median filtering , correlation filtering , limited convergence filtering and so on . We can choose the appropriate filtering method according to field interfere circumstance . Least-squares principle is usually used in curve fitting to make error sum squares of curve points the minimum . Frequency response calculation includes the calculation of auto-correlation and cross-correlation calculation . The relevant calculation uses the fast Fourier transform and inverse transform to achieve fast correlation algorithm .Functions of communication module include read and write input/output data buffer, modules of communicate with each other of digital signal generator. Before the test , operator put needed pressure , channel of flow signal and waveform parameters of signal generator into the system .The system will call the buffer zone to establish the function and communicating functions to establish data buffering area of each channel and send parameters to the signal generator and start the D / A and A / D data conversion at the same time . Each channel using interrupt mode to write data into the buffer zone . CPU reads the data of each buffer zone at intervalsof 1s and call interface processing management module to refresh the output interface after date diaposition .Interface management module is mainly responsible for the drawing of static and dynamic characteristic curves.The process is completed by esch sub-module through calling Plot（）function . Auxiliary function modules includes test data formatted output to a file, and test documents and data printing .The entire test system was developed under Microsoft VC6.0 , and its overall operation process is shown in Figure 3.PreparationMain InterfaceStatic DynamicStatic or dynamictest ?Choose static itemChoose test onpressure/flow/current Set paramater or pressure of signal generatorInput wrong ?Start D/ABuild buffer zoneDelay for 2sStart A/DRead dateDate filteringCurve fittingand differenceOver ?Stop date collect ,draw curveSave dateOverChoose current andspeed input channelSet scaning signalparamaterInput wrong ?Start D/ABuild buffer zoneDelay for 2sStart A/DRead dateDate filteringCalculateauto-correlationCalculate crosscorrelationCalculate frequencyresponse functionCurve fittingand differenceOver ?NoSave date ?NoYesNoYesYesYes Fig.3 testing software flow chat6. Examples for the testTable 1 is a experimental report generated by D072-386 servo valve produced by MOOG after repair . The main pilot project results and standard specifies were list in the report . Relate curves of the testing results are not enumerate here .Product 60L/min 12.5(mA)GB20233-882008/05/13MOD-D072-386S/N21321MPaA+，B- add 18mA biasing ：C+，D-signal（2008） Servo check word No.（0001）±Table 1 electro-hudraulic servo valve test bed name electro-hydraulic servo valve Rated flow Rated input experiment dateTest standard Model and specification number components Rated pressure deliver sample unit maintenance unite connection modeXX thermal power plant XX hydraulic center01020304M L/min%Between A and B Between A and B200±8200>5010%>30±±81991995057.638OK OK OK OK OKTest resultsTest itemCoil impedanceInsulation Rated flow Pressure gain Measurementposition and unitDesignated valve After repair ,the measued value ConclusionRemarks7.ConclusionThe test system anlehnungs design methods of virtual instrument and bring function of software in the test into full play . The operation of the testing work is even more simple and intuitive with the maximum reduction in the use of hardware and save the cost of servo valve test-bed .伺服阀试验台计算机辅助测试系统的研制摘要：根据伺服阀的动静特性的测试要求，首先介绍了系统所需要的油源部分—液压泵站，然后设计了相应的液压测试系统和计算机辅助测试系统，说明了测试系统软硬件的组成和软件的设计流程，最后将设计出的系统应用到实际生产中，证明可以达到伺服阀的测试要求。