Combustion torque estimation from mass-produced crank angle sensor

The output power variation in individual cylinders must be detected to suppress combustion variation. We thus developed a method to estimate the coefficient of variation of combustion (COV) and the crank angle position of peak combustion torque from mass-produced crank angle sensor signals, which have insufficient resolution of tooth pitch and tooth pitch variation caused by manufacturing error. In this paper, we use the method to estimate COV and θTmax from mass-produced crank angle sensor information and evaluate its accuracy. First, to compensate for the shortage of the tooth pitch, a filter was developed to trigonometrically approximate crank rotation speed. Second, another filter was developed to correct the tooth pitch variation resulting from manufacturing error. This pitch error correction filter extracts the characteristic quantity of pitch error from the rotation speed measurement results at the fuel cut state and corrects the pitch error at a combustion state. In an actual vehicle measurement, the proposed combustion torque estimation method achieved a COV detection error of 2.6% and θTmax detection accuracy of 3.0 deg at a 1200-rpm engine speed.