Study on Composite Control Strategy of Transient Air-Fuel Ratio for Gasoline Engine Based on Model

Abstract

The control accuracy of transient air-fuel ratio of gasoline engine is a difficult problem in the current engine control system. To achieve effective control of transient air-fuel ratio for gasoline engines, a composite control method is proposed, which consists of inverse model feedforward based on least squares support vector machine(LS-SVM)and feedback control with model-free adaptive control(MFAC).Feedforward control can accurately estimate the intake air volume in the cylinder. Neither feedforward or feedback control can achieve better control results. A composite control strategy based on feedforward + feedback is proposed. The feedforward model is used to perform dynamic feedforward compensation of the intake air amount in the transient air-fuel ratio, and in combination with feedback control, the air-fuel ratio is feedback-controlled by modifying the fuel injection amount, and system disturbances and errors are corrected. In this paper, two composite control strategies are designed for the air-fuel ratio of the engine under transient conditions. The results show that the inverse model based on LS-SVM can accurately approximate the air fuel ratio transient process, and this method has stronger robustness and anti-interference combined the MFAC feedback control. Therefore, the composite control strategy has good control performances and can improve the control precision of air-fuel ratio in transient conditions.