Model-Based Throttle Control using Static Compensators and IMC based PID-Design

In modern spark ignited engines the throttle is controlled by the electronic control unit (ECU) which gives the ECU direct control of the air flow and thereby the engine torque. This puts high demands on the speed and accuracy of the controller that positions the throttle plate. The throttle control problem is complicated by two strong nonlinear effects, friction and limphome torque. This paper proposes the use of two, simultaneously active, static compensators to counter these effects and approximately linearize the system. A PID controller is designed for the linearized system, where IMC design is applied to design the PD controller and a gain scheduled I-part is added for robustness against model errors. A systematic procedure for generating compensator and controller parameters from open loop experiments is also developed. The controller performance is evaluated both in simulation, on a TC-benchmark problem, and experimentally. A robustness investigation pointed out that the limp-home position is an important parameter for the controller performance, this is emphasized by the deviations found in experiments. The proposed method for parameter identification achieves the desired accuracy.