Closed-loop design for decoupling control of a four-wheel steering vehicle

In this paper, a four–wheel–steering (4WS) system with multiple inputs is introduced. This multiple–input 4WS system provides the driver with the ability to control the sideslip motion and yaw motion of the vehicle simultaneously and independently. The decoupling control of these two independent motions is accomplished by a steering controller which translates the steering commands into the steer angles of the front and rear wheels. A method to find the inverse transfer matrix of the vehicle in a simple symbolic form is introduced to design the steering controller. By the design method introduced in this paper, the decoupling control of the sideslip and yaw motion can be achieved by three types of controllers for a stable vehicle plant without any signal fed back. The performance of the system under the variations of the vehicle parameters is also investigated via computer simulation.