Research Of Analog Signal Generation For Engine's Torsional Vibration

Automobile engine shaft's torsional vibration will cause vibration and produce noise of the engine, transmission system and frame. For the research of torsional vibration, in order to verificate the stability and measuring precision of the torsional vibration device and instrumentations, it often needs the engine's torsional vibration signals under various working conditions, especially for some theoretical study. To find out the law, it needs a lot of real torsional vibration signals as the foundation. If there is a kind of special torsional vibration analog signal source, then it can provide great convenient for the design and research.Therefore, the research of the automobile engine's torsional vibration analog signal generator is of great significance.This dissertation based on the engine crankshaft's torsional vibration signal of a type of SUV automobile matching VM diesel, mainly includes 4 aspects:(1) torsional vibration signal's extraction; (2) torsional vibration signa's demodulation; (3) analog modulation of torsional vibration PPM;(4) hardware implementation of torsional vibration PPM.Firstly, the paper introduced the research of the signal processing technology of the crankshaft's torsional vibration of automobile's engine at home and abroad.Especially for the development of the vibration signal's testing of the crankshaft, and the development of modulation and demodulation technology for torsional vibration. And then the study's content and its significance were illustrated.Secondly, this paper introduced basic theory of torsional vibration, torsional vibration phenomenon and sources, and described it deeply. It mainly introduced the principle of phase modulation, analysised the phenomenon of pulse position modulation and demodulation of the torsional vibration signal, and described its modulation process and demodulation methods. Meanwhile, it briefly introduced the experimental section of the engine's torsional vibration.Thirdly, according to the theory of torsional vibration, the paper demodulated the signal from two ideas of Hilbert transformation and Equal Angle measurement, included processing data with MATLAB and simulating the demodulation process in SIMULINK. It made a comparative analysis of the results of the two demodulation methods. Fourthly, it obtained a modulation method of torsional vibration PPM from the idea of circuit modulation, got the modulation result in MATLAB and SIMULINK, and analysed the feasibility of the method. In search of the modulation rule of the PPM signal through the modulation results, it analysed the relationship between the analog signal's sampling value and the time migration of the PPM. Then established a mathematical model for the PPM modulation that digital modulation algorithm, thus realized the torsional vibration PPM signal's real recovery.Finally, with EasyARM2131 development board and related hardware facilities, in the plateform of KEIL uvision4, through software development, the paper realized the main function of the torsional vibration analog signal generator in KEIL uvision4 through programming, and tested the PPM wave in the oscilloscope.