Towards constrained optimal control of spark-ignition engines

In this paper, the torque control problem for spark-ignition engines is considered. The objective is to provide good output torque tracking with minimum fuel consumption, while avoiding engine knock and misfire. To this end, three control strategies are proposed: a feed-forward controller with recalibrated engine maps, a PI control scheme and a model predictive controller. For the model predictive control strategy, a simplified air-path engine model is developed based on the Wiener model structure. The proposed controllers are shown to provide safe engine operation by avoiding engine knock and misfire. The performance of each control strategy is evaluated over a specific driving cycle and compared with a baseline control strategy. Simulation results show up to 40% performance improvement for the model predictive control strategy as compared to the baseline strategy.