Research On Virtual Instrument System For Testing Performance Of The Automobile Chassis Parts

In recent years, the automobile trade developed rapidly in our country, andthe consumer market of the automobile has become the field with very fastacceleration rate and having a bright future in the consumer market of our country.As the important component of trade of the automobile, the part trade of theautomobile has also obtained fast development, and has entered the internationalmarket earlier than the completed car. Among them chassis parts have bettercompetitiveness than electronic units. As a whole, domestic automobile parts havea great gap with foreign countries in many ways, for examples, less variety andquantity, poor technology, weak research and development ability, rigid supplymode, and so on. There are also test criteria to meet when entering internationalmarket. It is the primary choice to develop and use the advanced test technologyand equipments.Virtual instrument (VI) technology is the result that technology of the moderninstrument and computer technology combine together. It gives full play to dataoperation, data storing and data processing of the computer. VI has offered faster,simpler, more convenient, more flexible, high-efficient technological choice whiledeveloping the system of testing to engineers and technicians. The test systemdeveloped based on VI has high performance advantage, can be maintained andexpanded easily, and can fully utilize the modern network. The concept of VI haspassed the push and support of a lot of known enterprises in world since puttingforward for the first time by U.S.A. NI Company in 1984. VI has well-organizedsystematic alliances, has set up complete systematic norm. Virtual instrumentsystem is gradually becoming the mainstream of the third generation of test system.Developing test system for automobile chassis part based on virtual instrumenttechnology, we can give full play to advantage of VI, shorten development period.By design of module, the test system can be convenient to maintain and expand,and have strong flexibility.The method of testing performance of the automobile chassis parts mainlyincludes static test of structure and dynamic test of structure. To different parts,content and method of performance testing are also different. In simple test weexert certain excited signal to the test bench, then gather a certain signal of thesystem through the sensor and data acquisition card (DAQ), such as theacceleration or force , and control or analyze the signal, then get the performanceparameters of the part which is examined. This kind of test procedure mostlybelongs to open loop test. The excited signal is created in advance, and not variesduring testing procedure. In other tests, it is necessary to detect the system whichis composed of test bench and the part to be tested. After getting the systematicparameters, we generate the corresponding control signal, and then accomplish thetask of testing using this signal as the excited signal. The resonance testing for theparts in electromagnetic resonance test stand is this kind of test. The excited signalis sine signal whose frequency is the systematic resonance frequency. So it isnecessary to get the systematic resonance frequency by sweeping frequency test atthe beginning of the test. We should choose the suitable sweep signal and good testmethod to improve the precision and accuracy of frequency. Some automobilechassis parts need random vibration test. Because of the behavior of randomvibration, the control parameter usually is the power spectrum which is theparameter in frequency domain. This kind of test belongs to close loop test. Thestability and accuracy of controlling are mainly involved in control algorithm,generation of the excited signal in time domain and estimation of power spectrum.This paper carries on deep research to them, and introduces the method ofgenerating time sequence with phase discretization and the method of estimatingpower spectrum with AR model especially. This paper concentrates on research of virtual instrument testsystem of PC-DAQ mode. The DAQ finishes the conversion of the physicssignal and digital signal, and the computer is responsible for display,analysis, and storage of the tested data, and so on. The performance ofDAQ influences and determines range of application, precision and accuracy oftest system directly. It is the important content to configure and use DAQ correctly...