Investigation of Vibration Signal Processing using Short Time Fourier Transform for Internal Combustion Engine

Abstract

The methods of short-time Fourier transform (STFT) signal processing have been used to enhance the condition monitoring of machines. It can be better to use in reciprocating machines such as internal combustion engines, as the signal is non-stationary. The FFT usage wouldn’t be beneficial in this case as it treats stationary signals such as those captured from rotating machines. The vibration of machines became challenging, as for the engine, pack up, faults in such complex systems can lead to frequency alternation and amplitude. In the present study, the vibration signal was acquired from the engine at the vicinity of the piston 2 and 3 to get acceptable signal intensity. The normal state is measured at idle speed condition and two other speeds 2000 and 3000 rpm. Three faults are investigated namely; misfire of one cylinder, two cylinder misfire and ignition timing. Then, the signal processed using STFT was used to distinguish and detect fault using vibration signal. The output signals were exported to MATLAB for further analysis. The experimental results revealed that the normal condition had more vibration than one cylinder misfire than two cylinder misfire due to the damping effect. In addition, the vibration levels at ignition timing (3 BTDC), (3 ATDC), (6 BTDC) and (6 ATDC) were recorded as maximum when compared to normal condition at 5 BTDC.