Abstract: An internal combustion engine idle air control system including an idle air control actuator coupled to an idle air control valve for varying the position of the valve within an engine intake air passage for engine inlet air control under idle operating conditions adjusts the time rate of change in position of the idle air control valve in response to change in barometric pressure to account for change in air density passing across the valve and to account for change in torque load acting against the valve to precisely respond to torque load changes during idle operations without violating idle air control actuator stability margins.

Abstract: Engine speed control through variation in ignition timing of an air-fuel mixture in engine cylinders to vary engine output torque in response to current and predicted future engine speed error includes a proportional-derivative control strategy for damping engine speed oscillations, includes an additive combustion timing offset determined as a function of accessory load status for simplified calibration, and includes control gains determined as a function of a predicted future engine intake manifold absolute air pressure to better predict and compensate engine load changes and determined as a function of predicted future engine speed to stabilize combustion timing.

Abstract: Control and functional isolation of an actuator applied to an internal combustion engine through an interface module which is interposed between the actuator and a controller having a control function, with state of the actuator estimated, converted to standard units of measure, and corrected in the interface module in response to an estimate of a parameter influenced by the actuator state, the parameter expressed in the standard units of measure, and the corrected state applied as feedback to the controller which, through application of the control function, issues to the module a desired state. The desired state is restored by removing a correction value from the desired state, is converted to actuator position units, and is applied to control actuator position.

Abstract: Engine torque control as a function of a steady state and a transient torque control command to drive engine speed toward a target engine speed provides for a correction to the steady state torque control command to account for unmodelled effects of such slowly changing parameters as ambient temperature and pressure and engine coolant temperature, by determining a difference between an expected and an actual engine control parameter as function of the current engine operating level, translating such difference to an engine torque requirement deviation caused by unmodelled effects, and providing a torque correction therefor so that compensation may be provided in an appropriate manner for the unmodelled effects. The torque correction may further be stored as a function of the current value of the slowly changing parameters to develop a stored model which may be accessed, once developed, to provide the compensation with minimum on-line computation.