RBF network feedforward compensation of load disturbance in idle speed control

Automotive engine idle speed control is a disturbance rejection problem. An engine at idle is typically well away from its most favorable region of operation and exhibits significant nonlinearities. Control of such a system is complicated by delays of both physical (time between induction and power strokes) and computational origin. In the model used, there are two control variables, and these differ in both their range of effectiveness and their temporal characteristics: spark advance is fast-acting but limited in its effect, while throttle has a large range but a slower effect which results both from the dynamics of filling the intake manifold and from the induction-power delay. The spark variable also has a maximum effective value, i.e., a value beyond which it has an effect opposite to that expected. This article describes a nonlinear adaptive feedforward controller for compensation of external load disturbances in the idle speed control of an automotive engine. The controller is based on a radial basis function (RBF) network approximation of certain input-output mappings describing the system. An underlying assumption used in the controller design is that the external engine load is known to the controller. In particular, that might be achieved by putting an appropriate torque sensor in the powertrain or using other available information.