| The crankshaft angular vibration (CAV) signal of ICE gains extensive application in both torsional vibration analysis and fault diagnosis for its advantages of simple measurement and abundant information. This paper presents effective signal preprocessing methods and misfiring dignosis method accordingly directing towards the key problem existing on the crankshaft angular vibration signal measurement and multiple misfiring diagnosis methods of ICE. The research efforts enriches and develops the correlative theories, and have engineering application values in crankshaft angular vibration measurement and analysis, operating state monitoring and fault diagnosis for each cylinders, and automatic control etc.Firstly, launching on the measurement and preprocessing technique of angular vibration signal, it analyzed the reasons for the phenomena of losing points (teeth) in instantaneous rotate speed curve, and presented and contrasted two methods of dealing with losing points: adding points (teeth) and combining points (teeth), and also expatiated on the principle of combining points. Secondly it analyzed the effect of interference signal in original voltage pulsing signal and put forward that using band-pass filter could smooth the interference signal of narrow (low) frequency. Then, through analysis on the effect of different kinds of distorted point, it further improved the distorted point replace (DPR) method, which was validated using experimental data. Thirdly it analyzed the effect of sampling frequency on A/D sampling fitting method precision, through frequency division in order to get the lower frequeny sampled data by using high frequency sampled data, came to the conclusion that sampling frequency is at least as nine times as the pulse fundamental frequency. Finally, through analyzing the calculating precision of the two curve fitting methods under different conditions contrastively, it indicated that the linear interpolation method could reach the same precision as the least squares fitting method at high sampling frequency, and the later is more stable at low sampling frequency.Through theoretical derivation, the mathematical relationship between the gear teeth number and CAV measuring accuracy was analyzed quantitatively in this paper; the simulational signal was also analyzed. The minimum number of sampling points in every cycle was then determined when a single harmonic amplitude accuracy met the requirements of precision, meanwhile, the effective harmonic frequency orders could be obtained when the teeth number was constant. Through the experimental research on a 6135 diesel engine, after the treatment of combining points, the harmonic amplitude over teeth changes were compared and the correctness of the conclusion was further verified. In the meantime, the TV signal could be modified exactly and effectively with the use of modificatory formula presented in this paper.Based upon the studies in depth on the single order quasi-rigid body model and single order quasi-trapezia model, it develops the general formula and a new multiple misfire detection method of ICE by ultilizing multi-single orders synthetically. The simulation and experiment researches verify the usefulnees of the method.Be based upon the above research efforts, the CAV measurement and analysis system PTVM was upgraded to PTVM2007, and a kind of CAV measurement and analysis system PTVMAD07 was developed, both systems could measure and analyze the angular vibration signal. Another system software of operating state monitoring and fault diagnosis of ICE (PTVM-FDS) is also developed. The reseaches on the experimental signal indicated that the system could monitor the operating state and diagnose misfiring cylinder of ICE with 4 or 6 cylinders.
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