Abstract
In this paper, we propose an adaptive steering controller for four wheel steering vehicles. In conventional steering controllers, the tire lateral force saturation characteristic has been ignored. Moreover, it has been required that vehicle parameters are constant and known. However, the tire lateral force saturation and vehicle parameter variations easily cause vehicle instability. To overcome these problems, we develop an adaptive steering controller based on actual vehicle model with the lateral tire force saturation. As a first step to utilize the model reference adaptive control (MRAC) strategy, a nonlinear ideal vehicle model with the acceleration saturation is proposed. Compared with the actual vehicles, the nonlinear ideal vehicle model has good steering performance. Next, an adaptive steering controller is developed so that the behavior of the actual vehicle can track the nonlinear ideal vehicle model. For the adaptive steering vehicle system, the stability condition is derived theoretically. At last, to show the effectiveness of the proposed adaptive steering vehicle system, numerical simulations are carried out.
