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英文资料Lab VIEW for Measurement and Data AnalysisLab V I E W i s the tool of choice due to i t s unparalleled connectivity to instruments, powerful data acquisition capabilities, natural dataflow-based graphical programming interface, scalability, and overall function completeness.IntroductionUsers generally s t a r t their work by acquiring data into an application or program, because their tasks typically require interaction with physical processes. In order to extract valuable information from that dala, make decisions on lhe process, and obtain r e sults, the data needs to be manipulated and analyzed. Unfortunately, combining analysis with data acquisition and data presentation i s not always a straightforward process. Application software packages typically address one component of the application, but seldom address a l l aspects and needs to get to a complete solution. L a b V r E W was designed to address lhe requirements for a start-lo-llnish, fully-integrated solution, so that customers can seamlessly integrate a l l phases of their application i n a single environment.|Total Band Power |1»»01|Acquire Waveform 1|Third-Octave Analysis! lWeiqhtingTiitACQUIRE ANALYZE PRESENTFigure 1. Lab VIEW Virtual Instrument Block DiagramWhile there are many tools that independently address each of the requirements, only Lab V I E W combines a l l of them with the power of graphical programming and stale-of-the-art data acquisition hardware，using the power of your PC. I t i s thecombination of data acquisition, data analysis, and presentation of results, that truly maximizes the power of Virtual Instrumentation. A virtual instrument consists of an industry-slandard computer or workstalion equipped with powerful application software, cost-effective hardware such as plug-in boards, and driver software, which together perform the functions of traditional instruments. This i s why applications and programs built with Lab V I E W are referred to as VI (virtual instrumenls).As an engineering-focused tool, Lab V I E W makes hundreds of analysis functions available for researchers, scientists，and engineers, as well as students and professors. They can build these functions right into their applications to make intelligent measurements and obtain results f a s t e r.Choosing the Correct Method forAnalysisUsers incorporate analysis into their applications and programs in different ways. There are certain considerations that help determine the way in which analysis should be performed.Inline v s. Offline analvsisInline analysis implies that the data i s analyzed within the same application where i t i s acquired. This i s generally the case when dealing wilh applications where decisions have to be inade during nin time and the results have direct consequences on the process, typically through the changing of parameters or executing of actions. This i s typically lhe case i n control applications. W h e n dealing wilh inline analysis, i t i s important to consider the amount of data acquired and the particular analysis routines that are performed on that data. A proper balance must be found because they could easily become computationally intensive and have an adverse effect on the performance of the application.Other examples for inline analysis are applications where the parameters of the measurement need to be adaptecl to the characteristics o l"the measured signal. One case i s where one or more signals need to be logged, but these change very slowly except for sudden bursts of high-speed a c t i v i t y. In order to reduce the amount of data logged, the application would have to quickly recognize the need for a highersampling r a t e, and reduce i t when the burst i s over. By measuring and analyzing certain aspects of the signals the application can adapt to the circumstances and enable the appropriate execution parameters. Although t h i s i s only one example, there are thousands of applications where a certain degree of intelligence - the ability to make decisions based on various conditions -and adaptability are required, which can only be provided by adding analysis algorithms to the application.Decisions based on acquired data are not always made i n an automated manner. Very frequently, those involved with the process need to monitor the execution and determine whether i t i s performing as expected or i f one or more variables need to be adjusted. Although i t i s not uncommon for users to log data, extract i t from a f i l e or database and then analyze i t offline to modify the process, many times the changes need to happen during run time. In these cases, the application must handle the data coming from the process, and then manipulate, simplify, format, and present the data in a way that i t i s most useful to the user. Lab V I E W users can then take advantage of the many visualization objects to present that data in the most concise and useful manner.Lab V I E W offers analysis and mathematical roulines that natively work together with data acquisition functions and display capabilities, so that they can be easily built into any application. In addition, Lab V^W offers analysis routines for point-by-point execution; these routines are designed specifically to meet the needs of inline analysis in real-time applications. Users should consider certain aspects when deciding whether point-by-point routines are appropriate.Point-by-point analysis i s essential when dealing wilh control processes where high-speed, deterministic, point-by-point data acquisition i s present. Any time resources are dedicated to real-time data acquisition, point-by-point analysis becomes a necessity as acquisition rales and conlrol loops are increased by orders of magiiilude. The point-by-point approach simplifies the design, implementation, and testing process, because the flow of the application closely matches the natural flow of the real-world processes lhat the application i s monitoring and conlrolling.<°)NextArray___H M _n —k- - -........-j --------------------Array-based AnalysisAcquircd Currant Acquis4ion 1_画圖腿1圓^^丨*Point-by-Poinl AnalysisFigure 2. Array-based Analysis vs. Point-by-Point AnalysisReal-time data acquisition and analysis continue to demand more streamlined and stable applications. Point-by-point analysis i s streamlined and stable, because i t t i e s directly into lhe acquisition and analysis process. With streamlined, stable point-by-point analysis，the acquisition and analysis process can move closer to the point of control in F P G A (field programmable gate array) chips, D S P chips, embedded conirollers, dedicated CPUs, and Asics.To better understand the advantages of point-by-point analysis routines, National Instruments suggests reading the document t i t l e d "Getting Started with L a b V I E W Point-By-Point VIs^This clocument describes how to use the VI and includes a case study that shows a complete application buill i n Lab VIEW. The application demonstrates the simplicity and flexibility of point-by-point analysis.B y adding these powerful algorithms and routines into applications, users eliminate the guess work and create intelligent processes that can analyze results during run time, improving efficiency and iteratively correlating input variables to experiment or process performance.Ol'lline applicalions don’l typically have the deinand for resulls to be obtained i n real-time fashion in order to make decisions on the process. Offline analysis applications require only that sufficient computational resources are available. The main inlem of such applications i s to identily cause and effecl of variables alTecting a■ RswSiflMl■ Currtnt Acquoition■Acquirtd 0»taProcessed Data<°)process by correlating multiple data s e t s.These applications generally require importing data from custom binary or ASCII f i l e s and commercial databases such as Oracle, Access, and other QL/ODBC-enabled databases. Once the data i s imported into Lab VIEW, users perform several or hundreds of available analysis routines, manipulate the data, and arrange i t in a specific format for reporting purposes. Lab V T E W provides functions to access any type of l'i l e foi*mal and dalabase, seamlessly connect to powerful reporting tools such as NI Diadem and the Report Generation Toolkit for Microsoft Office, and execute the l a t e s t data-sharing technologies such as X M L,Web-enabled data presentalion, and ActiveX.Programmatic vs. Interactive AnalvsisAs Lab V I E W users, scientists and engineers are very familiar with the many ways i n which they can acquire data tVom hundreds of devices. They build intelligence into their applications to perform inline analysis and present results while the applications are running. In addition, they are aware that acquiring data and processing i t for the sake of online visualization i s not enough. Users typically store hundreds or thousands of megabytes of data i n hard drives and data bases. After anywhere from one to hundreds of runs of lhe applicalion, users proceed lo extract informalion i n order lo make decisions, compare r e sults, and make appropriate changes to the process, until the desired results are achieved, oI t i s relatively easy to acquire amounts of data so large that i t rapidly becomes unmanageable. In f a c t,with a fast D A Q board and enough channels, i t may only take a few milliseconds to compile thousands of values. I t i s not a t r i v i a l task to make sense out o i'a l l lhai data. Engineers and scientists are typically expected lo presenl reports, create graphs, and ultimately corroborate any assessments and conclusions with empirical data. Without the right tools, this can easily become a daunting task, resulting i n l o s t productivity.In order to simplify the process of analyzing measurements, Lab V I E W programmers create applications that provide dialogs and interfaces that others can use so that depending on their input, specific analysis routines are perfonned on any given daia<°)s e t. By building this type of application, users build a certain degree of interactivity into their applications. For this to be efficient, the programmer inust have extensive knowledge about the information and the types of analysis in which the user i s interested.ANfvatoVdB^}J f5T f l T~P k^t94M n S0M d K M $^n &_c*>d f t<f c U n M DcWwlHweP^| D^mdU^*N'•■«T".^tf^^ **^*l g;a c n(||@sas»JLW^BtfMM^2Umt^\M7V i AFigure 3. Time Domain Reflection VI Based on Joint Time-Frequency Analysis FunctionsWith Lab V T E W，users can easily perform significant data reduction and formatting belore sloring i t to disk, so that when the stored data i s retrieved for further analysis, i l i s easier to handle. Lab V I E W also provides hundreds of functions for generating reports based on the results and information obtained from the acquired data.National Tnstaiments offers additional tools thal are highly integrated with Lab V T E W and are designed to enhance collaborative engineering. NI Diadem i s one such tool; i t provides an easy-to-use environment for interactive, post acquisition analysis and report generation, with powerful technical data inanagemeni capabilities.Which Analysis Tools are Available for Lab VIEW?NI Lab V I E W already includes a powerful set of tools for analysis. These tools encompass a built-in set of libraries and functions designed specifically for analysis, with which users can address a wide range of applications.Lab V r e W analysis tools cover a broad range of applications. Advanced analysis functions can measure such signal characteristics as t o t a l harmonic distortion, impulse response, frequency response, and cross-power spectrum. Scientists and engineers canalso incorporate mathematics or numerical analysis into their applications tor purposes such as solving differential equations, optimization, root finding, and other mathematical problems.Although users can develop these functions themselves, built-in functions make i t easy to work quickly on the problem instead of the tools. The advantage of using these functions also eliminates the need to understand the underlying theory required to build such algorithms.□s.H t a u MFigure 4. Sound Level Meter Application based on the Sound and Vibration Analysis ToolsetAdd-On Tools forAnalysisIn addition to the built-in analysis libraries，users rely on add-on toolsets and modules to reduce development time for specialized application needs. B y incorporating toolset components into custom applications, users reduce the need for particular expertise commonly associated with development more vertical applications such as advanced digital signal processing, sound and vibration measurements, order analysis, image processing, PID control, and simulation.Advanced Signal ProcessingThe Sienal Processing Toolset provides functions designed specifically lor advanced<■?digital signal processing (DSP). The included functions are divided into three categories: Joint Time-Frequency Analysis，Wavelet Analysis, and Super resolution Spectral Analysis. In addition, the toolset provides a graphical u t i l i t y with which users can interactively design digital f i l t e r s.Joint Time-Frequency AnalvsisUnlike conventional analysis technologies, the JTFA ^oint time-frequency analysis) routines examine signals in both the time and frequency domains simultaneously. JTFA can be applied i n almost a l l applications in which the FFT i s used, such as biomedical signals, radar image processing, vibration analysis, machine testing, and dynamic signal analysis. However, with JTFA you get more information by analyzing the time and frequency domains simultaneously.Like the classical Fourier analysis, the JTFA consists of lwo major methods - linear and quadratic. The linear algorithms include short time Fourier transform (STFT) and Gabor expansion (inverse short-time Fourier transform.) Lab V I E W u s e i\s can take advantage of these linear transfonns, to transfer a signal from the time domain into the joint tiine-frequency domain and vice versa. These routines are extremely powerful for noise reduction purposes. The quadratic methods contain adaptive spectrogram, Choi-Willianis distribution, cone-shaped distribution, Gabor expansion-based spectrogram (also known as Gabor spectrogram), STFT-based spectrogram, and Winger-Ville distribulion. Users can apply lhe quadratic transfoiTiis, lo easily see how the power spectrum of a signal evolves over time. The Gabor spectrogram results i n the best compromise between high resolution and cross-term interference.WaveletsWavelets are a relatively new signal processing method. A wavelet transform i s almost always implemented as a bank of f i l t e r s that decompose a signal into multiple signal bands. I t separates and retains lhe signal features in one or a few of lhese sub bands. Thus, one of the biggest advantages of using the wavelet transform i s that signal features can be easily extracted. In many cases, a wavelet transform outperforms the convenlional FFT when i l comes to fealure exiraction and noise reduction. Because乂.7the wavelet transform can extract signal features，wavelet transfonns find many applications i n data compression, echo detection, pattern recognition, edge detection，cancellation, speech recognition, texture analysis, and image compression.Super resolution Spectral AnalysisA primary tool for spectral analysis i s the Fast Fourier Transform (FFT). For high-resolution spectra, FFT-based methods need a large number of samples. However, in many cases the data set i s limited because of a genuine lack of data or because users need to ensure that the spectral characteristics of the signal do not change over the duration of the dala record. For cases where the number of dala samples i s limited, Lab V I E W users can use model-based analysis to determine spectral characteristics. Using this technique, users assume a suitable signal model and determine the coelTicients of the model. Based on this model, lhe application can ihen predict the missing points i n the given f i n i t e data set to achieve high-resolution spectra. In addition, model-based methods can also be used for estimating the amplitude, phase，damping factor, and frequency of dainpcd sinusoids. Super resolution spectral analysis can be used in diverse applications including biomedical research, economics, geophysics, noise, vibration and speech analysis.Sound and Vibration AnalysisThe Lab V I E W Sound and Vibration Toolset extends Lab V I E W with functions and visualization tools for handling engineering units, calibralion, frequency analysis, transient analysis，sound-level measurements, and fractional-octave analysis. This toolset provides advanced tools to effortlessly create custom applications for sound and vibration analysis.Functions include f u l l,1/3，1/6,I/I2 and 1/24 octave; user-defined sampling frequency; user-defined number of bands; A, B, C weighting in time domain; standards compliance; exponeniial averaging (Slow, Fasl, and Custom time constant); cross-power spectrum; frequency response (H 1，H2, and H3); coherence; and coherent output power. Tn addition, the toolset provides additional visualization tools such as waterlall graph, color map graph, octave bar graph, and octave line graph thai can beeasily built into the front panels of Lab V I E W applications.Order AnalysisThe Lab V T E W Order Analysis Toolset provides libraries to build cuslom Lab VIEW-based measurement and automation applications with order analysis capabilities for order tracking, order extraction, and tachometer signal processing. The toolset employs Gabor Order Tracking, a palented algorithm based on the ideas of joint time-frequency analysis.With the Gabor Order Tracking algorithm, Lab V T E W users can analyze sound, vibration, and other dynamic signals l*rom mechanical systems with rolating or reciprocating components. I t offers flexible order energy selection in the joint time-frequency domain. Additional tools include plotting individual order(s) versus time or rpm, order extraction tools to separate order-specific signal components lrom the acquired signal, automatic order selection tools to find and specify the most significant orders, and user-specified order selection for analysis.Vision/Image ProcessingWith I M A Q Vision for Lab VIEW, engineers and scientists can create and prototype machine vision applications that use color paltem matching. Color paltem matching quickly locates known reference patterns i n a color image and overcomes roadblocks presented by traditional monochrome cameras that have difficulty discerning color images. In addition, I M A Q Vision software adds high-level machine vision and image processing to Lab VIEW. You can use I M A Q Vision in machines as well as factory and laboratory automation operations that require extremely reliable high-speed vision systems.Lab V I E W users can take advantage of the National Instruments Vision Development Module for developing machine vision and scientific imaging applications. The module includes I M A Q Vision Builder, an interactive environment used to quickly prototype vision applications without programming, and I M A Q Vision, a library of powerful functions for image processing. I M A Q Vision Builder and I M A Q Vision are tightly integrated to simplify vision software development. I M A Q Vision Builder canautomatically generate an I M A Q Vision Lab V I E W bkx:k diagram that contains the same functionality as the series of operations prototyped i n I M A Q Vision Builder. Users can integrate the diagram inlo aulomation or production t e s t application, which may include motion control, instrument control, and data acquisition.PTD ControlThe Lab V T E W PTD Control Toolset adds sophisticated control algorithms to control applications. By combining the PlD and fuzzy logic control functions in t h i s toolset with analysis functions in LabVIEW, users can quickly develop programs for automated control. In addition, by integrating these control tools with NI data acquisition hardware, users can create powerful, robust control systems. These Lab V T E W control application can then be combined with the Lab V I E W Real-Time Module for real-time control applications.SimulationThe National Instruments Lab V I E W Simulation Interface Toolkit gives control design engineers a seamless link between Lab V I E W and The Math Works Simulink software. With these integrated tools, engineers can effortlessly take an idea from a software concepl lo real-world prototyping. The toolkii includes Lab VTEW-based user interface components that plug into the simulink environment as well as tools that work with The Math Works Real-Time Workshop® to import control models into Lab VTEW. Engineers can lhen take these models and integrate them with a wide variety of I/O.Lab V I E W users can also take advantage of the Lab VffiW System Simulation and Design Toolsel, which provides tools to design, simulate, analyze, and opliniize linear and nonlinear control systems. With these tools, users can accelerate system design by using VI modeled after control engineering symbols, such as H(s) for transfer function, l/s\'or integration, / for delay, and more. After verifying lhe system design, users can quickly integrate Lab VffiW analysis functions and D A Q hardware to implement a real-world system.ConclusionWith the power and flexibility of today’s computers, engineers and scientists have an unprecedented ability to efficiently measure, control, monitor, diagnose, automate, t e s t,and characterize any process. This however i s not possible, without the ability to look a t data and extract useful information.National Instruments Lab V I E W and lhe integrated analysis functions i t provides, make up a powerful graphical application development environment designed specifically for engineers and s c i entists. Lab V I E W provides solutions regardless of industry or area of focus within the engineering process, from design and validation to production.Tn addition, Lab V I E W offers unparalleled connectivity to plug-in D A Q devices and stand-alone instruments for acquiring data. Lab V E E W provides powerful analysis l i b r a r i e s, routines, and algorithms that range from basic malh to advanced signal processing, for both general-purpose applications as well as more vertical needs，which can be seamlessly integrated with a l l other functions in Lab VIEW. These liinctions, i n conjunction with powerful data visualization capabilities, make Lab V r e W the ideal tool for any application.。