The torque estimation of combustion engines is important for detection of abnormal combustion and misfiring in cylinders. If pressure sensors were available for pressure measurement at each cylinder, the torque estimation would be easier, but those sensors, however, cannot be used generally from cost and spacial viewpoints. Hence this paper considers a torque estimation method using the crank-shaft angle information, which can be used even for commercial cars, instead of pressure sensors. A problem caused by the crankshaft angle is that unexpected vibrations contaminating the angle information, whose frequencies are relatively close to the combustion period, deteriorate the torque-estimation accuracy especially in high engine speed case. This paper focuses on improvement of the estimation accuracy by paying attention to differentiation of the angle with such vibration.
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