Engine misfire, knock of roughness detection method and apparatus

A method for detecting an abnormal combustion event, such as misfire, knock or roughness, in an internal combustion engine which produces a series of combustion events and which transmits power through a power transmitting member, said method comprising the steps of:

• obtaining a first set of signals related to the torsional stress in the member produced by a first series of combustion events;
• obtaining a second signal related to the torsional stress in the member produced by a second combustion event;
• calculating an expected value of the second signal from the first set of signals;
• calculating a difference between the expected value of the second signal and the second signal;
• calculating an expected value of a moving standard deviation;
• dividing the difference between the expected value of the second signal and the second signal by the expected value of the moving standard deviation to obtain a ratio;
• and
• comparing the ratio to a threshold to detect an abnormal combustion event.

A method for detecting torque variation in a power transmitting member which experiences torque variation, said method comprising the steps of:

• obtaining a first set of signals related to the torsional stress in the power transmitting member during a first time period;
• obtaining a second signal related to the torsional stress in the power transmitting member during a second time period;
• calculating an expected value of the second signal from the first set of signals;
• calculating a difference between the expected value of the second signal and the second signal;
• calculating an expected value of a moving standard deviation;
• dividing the difference between the expected value of the second signal and the second signal by the expected value of the moving standard deviation to obtain a ratio;
• and
• comparing the ratio to a threshold to detect torque variation in the power transmitting member.

A method for detecting an abnormal combustion event, such as misfire, knock or roughness, in an internal combustion engine which produces a series of combustion events and which transmits power through a power transmitting member said method comprising the steps of:

• obtaining a first set of signals related to torsional stress in the power transmitting member produced by a first series of combustion events during a first time period;
• calculating an expected value for a third signal selected from the first set of signals, the third signal occurring prior to a second signal where in said second signal is related to torsional stress in the power transmitting member during a second time period;
• weighting each of the third signal and the expected value of the third signal with respective weighting coefficients;
• and
• summing the weighted third signal and the weighted expected value of the third signal to produce an expected value of the second signal;
• obtaining the second signal;
• and
• calculating a ratio of the second signal and the expected value of the second signal to determine abnormal combustion.