Adaptive PID Controller for Idle Mode of an SI Engine

The indices in idle-speed control for SI engine are smoothness and low emission. To maintain the crankshaft speed within a given range in the presence of load changes, ECU (Engine Control Unit) needs to detect speed change and adjust the quantity of combustible mixture as quickly as possible. At the same time, emission should be controlled by air-fuel ratio controller. Because the intake step motor has dynamic positional error, the intake air volume can't be controlled accurately. Map-based injection, oxygen feedback and adaptive PID controller are combined to form a quick and low-cost air-fuel ratio control system, by which a low steady Idle-speed of 650rpm(±20rpm) is realized on a 3-cylinder gasoline engine.