Investigation about backstepping method and adaptive feedforward mechanism application for air fuel ratio control in transient state

Abstract

Recently, in order to improve the fuel consumption of a gasoline engine, a condition of mixed intake gas was varied to improve combustion efficiency. Besides, a transient state was increased in the test-mode of regulation. In order to purify the exhaust gas efficiently with a three-way catalyst, the AFR should be controlled within the window around a stoichiometric ratio. Therefore, a precise control system was required to control AFR to the target value under any intake gas condition. For a fast-response and highly robust control system, both a feed-forward(FF) controller and a feed back(FB) controller were required. And those controller were desirable to equip with a robustness or an adaptability. From this point of view, in order to add an adaptability to the model based FF controller, the error value was used to adjust the compensation value. And the feedback controller was designed using the backstepping method that was well known as a nonlinear adaptive controller. And both controller was operated as if those were fused in one-controller, then, a precise AFR control results were obtained. Then, Two sets of parameters in each controller were provided and an investigation was carried out as to which combination is superior for robustness regarding several initial starting engine speeds.

Keywords

• gasoline engine
• air fuel ratio
• adaptive control
• feed forward control
• backstepping method