Development Of Data Acquisition And Processing System For I.C. Engine Fault Diagnosis

The internal combustion engines as the travelling or stationary devices had the great effect on industry production and human society. Because it worked in the foul operating conditions, the possibility of breakdown was very high. If the fault developed, it would give a serious impact on the whole mechanical system and bring the huge damage directly and indirectly. So it was very important to ensure the I.C. engines in a good operation condition. Because of its complicated configuration, high impactive interference and non-stationary operation characteristic, I.C. engines were one of the most difficult diagnosis devices. Also because the signal-noise separation, data processing and the adaptability of diagnosis criterion had critical requirement, the signal of I.C. engines should be processed by special software. Based on previous research, this thesis developed a data acquisition and processing system which suited for non-stationary signal and had the time-frequency joint analysis function.The signal generated by I.C. engines was typical non-stationary signal. The system that developed for non-stationary signal included two parts, signal acquisition and processing system. The signal acquisition system involved two kinds of A/D converter, type USB2080 and type UDAQ20612. These two kinds of A/D converter were purchased from the market. The acquisition programme of USB2080 was programmed by author, the acquisition programme of UDAQ20612 was provided by supplier. Considering the data format of UDAQ20612, the data transform programme was programmed by author and had been integrated into whole system. The signal processing system had many functions, such as FFT analysis function, PSD analysis function and filtering function. For non-stationary signal, the STFT analysis function, CWT and DWT analysis function could be utilized to analyze. The system was compiled in Borland C++ Builder, Matlab and achieved the designing principle and method of human-computer interface. The interface designed for system was powerful, beautiful and use-friendly.For validating the signal processing system, the A.E. data of plain bearing in S195-2 diesel combustion engine that from professor Qinping of Southwest Jiaotong University had been used to prove the signal processing system function. For testing the signal acquisition system, the A/D converter and the software had been applied to sample the non-stationary signal of railway station. By sampling the different length signal, shot length shock vibration data and long length noise data, the software and the signal acquisition system had been proved the feasibility and practicability. Also, the signal processing system had perfectly diagnosed the occurrence and development fault of plain bearing in S195-2 diesel combustion engine. So the signal acquisition and processing system was concluded to be credible and feasible.