Abstract: Disclosed are a method and apparatus for minimizing or eliminating the effect of air gap variation on the output signal of a magnetostrictive stress/torque signal. An RLC drive circuit is utilized by choosing appropriate circuit parameters and drive frequency such that the flux reducing effect from increasing air gap due to increase in magnetic reluctance is offset by a flux increasing effect from a concomitant reduction in eddy currents. The invention is particularly suited to cross design magnetostrictive sensors and to automotive engine diagnostics applications such as misfire, knock, and roughness detection.

Abstract: A method and apparatus for comparing torsional stress/strain states of a power transmitting member of an internal combustion engine to detect an abnormal combustion condition, including misfire, knock or roughness. Statistical processing steps may be used to detect an abnormal combustion event including: calculating a mean and standard deviation for a set of signals related to the torsional stress induced in the power transmitting member, calculating a difference between a later signal and the mean, calculating a ratio of the difference to the standard deviation, and comparing the ratio to a threshold. The ratio so obtained from a given cylinder may further be compared with one or more other such ratios from other cylinders. In other words, the autocorrelation and/or cross-correlation techniques may be used. A magnetostrictive sensor may preferably be used to obtain the signals relating to the torsional stress in the power transmitting member, such as the engine crankshaft.

Abstract: Disclosed are a method and apparatus for comparing torsional stress/strain states of a power transmitting member of an internal combustion engine to detect an abnormal combustion condition, including misfire, knock or roughness. Statistical processing steps may be used to detect an abnormal combustion event including: calculating a mean and standard deviation for a set of signals related to the torsional stress induced in the power transmitting member, calculating a difference between a later signal and the mean, calculating a ratio of the difference to the standard deviation, and comparing the ratio to a threshold. The ratio so obtained from a given cylinder may further be compared with one or more other such ratios from other cylinders. A magnetostrictive sensor may preferably be used to obtain the signals relating to the torsional stress in the power transmitting member, such as the engine crankshaft.