Individual cylinder controller for three-cylinder engine

A method of detecting and correcting air delivery imbalances to the individual cylinders of a three-cylinder group of an engine for a vehicle comprising said engine, valve actuators for delivering air to said cylinders, an air-fuel ratio (A/F) sensor or O2 sensor for detecting an engine output responsive to the amount of air delivered to said cylinders, and an engine control module comprising a computer, the functions of said module including valve timing and lift for air deliveries of said valve actuators, said method being executed by said computer and comprising

• collecting a time sequential series of signals from a said sensor over at least one engine cycle at the current engine speed and load,
• converting said series of signals by discrete Fourier transform to a vector of A/F imbalances, in the frequency domain, related to said air delivery imbalances, said vector having a determined magnitude and phase angle,
• retrieving two air imbalance reference vectors of known magnitude and phase corresponding to the discrete Fourier transform of two nominal air imbalance patterns obtained during engine calibration and stored in the memory of said computer for the current engine speed and load,
• projecting said vector of A/F imbalances onto said two air imbalance reference vectors,
• determining the contributions in said A/F imbalance vector attributable to the two nominal air imbalance reference patterns, and
• applying, in each cylinder of the engine, air quantities of opposite magnitude to each of the contributions so determined to correct the air imbalance.

A method of detecting and correcting air, fuel or spark delivery imbalances to the individual cylinders of a three-cylinder group of an engine for a vehicle comprising said engine, valve actuators system for delivering air, fuel injectors system for delivering fuel and spark ignition system for delivery of engine ignition, to said cylinders, a crankshaft torque sensor for detecting an engine output responsive to the amount of air, fuel and spark delivered to said cylinders, and an engine control module comprising a computer, the functions of said module including valve timing and lift for air deliveries of said valve actuators, fuel injection timing and duration for fuel delivery and spark timing control for engine ignition, said method being executed by said computer and comprising

• collecting a time sequential series of signals from said torque sensor over at least one engine cycle at current engine speed and load,
• converting said series of signals by discrete Fourier transform to a vector of torque imbalances, in the frequency domain, related to said air, fuel or spark delivery imbalances, said torque imbalance vector having a determined magnitude and phase angle,
• retrieving two air, fuel or spark delivery imbalance reference vectors of known magnitude and phase corresponding to the discrete Fourier transform of two nominal air, fuel or spark delivery imbalance patterns obtained during engine calibration and stored in the memory of said computer for the current engine speed and load,
• projecting said vector of torque imbalances onto said two air, fuel or spark imbalance reference vectors,
• determining the contributions in said torque imbalance vector attributable to the two nominal air, fuel or spark delivery imbalance reference patterns, and
• applying, in each cylinder of the engine, air, fuel or spark quantities of opposite magnitude to each of the contributions so determined to correct the torque imbalance.