An observer-based controller design method for improving air/fuel characteristics of spark ignition engines

The wide operating range, the inherent nonlinearities of the induction process and the large modeling uncertainties make the design of the fuel-injection controller very difficult. Even though a sliding mode fuel-injection control method is in good agreement with the characteristics of the system, the unavoidable large time-delay between control action and measurement causes the problem of chattering. In this paper, an observer-based fuel-injection control algorithm is suggested for fast response and small amplitude chattering of the air-to-fuel ratio. The characteristics of the proposed controller are compared with those of other controllers. The proposed controller is simple enough for online computation and is implemented on an automotive engine using a PC-386. The simulation and the experimental results show that this algorithm reduces the chattering magnitude considerably while speeding up the transient response and is robust to modeling errors.