| Automobile suspension device not only is the import assembly that assurance ride comfort, but also is the import assembly which promises the car operational stability, the car brake and the car active safety. While automobile move more quickly now, it's drive smoothly and safety performance relate with the quality of suspension device. Along with the road transport condition improve, the drive speed of car is continuously raising, therefore, in order to keep the suspension device in good function, discover suspension device existent problem in time, we should periodically process necessary suspension performance test.Automobile suspension performance test can divide into three types: the first type is the whole car test on road, the second type is the whole car test at experiment field, the third type is the whole car test on indoor test equipment. The first two type cost a long time and a great deal of manpower, material resources, financial power. Indoor experiment can extensively change experiment condition, in the meantime can promise the stability of experiment condition. We can measure automobile suspension dynamic performance and vibration system parameter under the circumstance of various vibration form. The experiment condition is divided into free vibration experiment, the sine regulation vibration experiment, the unit rank jump experiment and random experiment.Dynamic vibration experiment research is extensively used the sine regulation vibration experiment method, because it is in general use, and gets more information under simple necessary equipments. The main purpose of sine regulation vibration experiment is to measure frequency characteristic of the vibration system. Therefore, by improving the existing machine type, the thesis designed a new suspension performance tester with the function of adjust frequency and amplitude. The content mainly includes a few aspects as follows:1,According to the request of the performance that drive smoothly and safely, and the possibility of the vibration system signal can collect, the thesis built up car body acceleration, tire opposite dynamic load and suspension dynamic flexvity as the evaluation method of suspension performance experiment. This evaluation method can reflect all automobile suspension performance, better then the one parameter evaluation method.2,The thesis process a necessary simplification to the car vibration system, built up 1/4 car two-degrees dynamics model and mathematics model via LAPLACE transformation of the mathematics model, thesis gets the transfer function, frequency response function and amplitude frequency characteristic of car body displacement, the car wheel displacement, and car body acceleration, car wheel opposite dynamic load and suspension dynamic flexvity to speed inspirit. Use M program in Matlab, made the curve of amplitude frequency characteristic of the above-mentioned vibration response variable, drawn the influence curve of suspension shock absorber damping coefficient, tire pressure and load towards suspension performance, provide theory model for the simulation analysis in chapter Five.3,The thesis carried on a reformation on the existing mechanical automobile suspension performance tester and increased adjust frequency and amplitude function, pass protect device, and designed electric control system for the new device. The new tester can provide reliable sin inspirit for simulating all level road, provide the hardware foundation for the automobile suspension evaluation method, satisfied the request of suspension performance deep analysis and fault diagnoses.4,Under the Windows environment used VC++ and Matlab programs to develop the experiment system test software. Use the strong GUI function in Matlab made the curve of car body acceleration, tire opposite dynamic load and suspension dynamic flexvity visible, can check the abnormal frequency and amplitude at the frequency. Based on these curve we can make sure the range of frequency, make sure the amplitude and energy of all frequency, so we can diagnose the fault of suspension system by the curve.5,Built up sine excitation signal and 1/4 car two-freedom-degrees suspension vibration imitate model under the Simulink in Matlab. According to the parameter, which were given, of line sine frequency conversion excitation and automobile suspension, thesis completed the time domain imitate analysis of car body and car wheel's move, speed, acceleration. Designed M program in Matlab to transform time domain imitate data use Fourier transformation, drown the simulation curve of car body acceleration, tire opposite dynamic load and suspension dynamic flexvity in the frequency domain, under the condition of varies shock absorber damping and tire stiffness. The frequency domain curve came out of simulation model completely fit to theories analytical, verified the possibility of suspension performance experiment and analyse under the frequency changed linear sine excitation signal.Experiment system works safety and credibility, experiment process reasonable, fast, accurate, and the data is in good repeat. Experiment system satisfied the request that the suspension performance research, according to the time domain and frequency domain analysis, it can drown the curve under various excitation, provide an experiment system for optimize suspension design parameter and automobile suspension performance test.
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