Design and Evaluation of Active Front Wheel Steering System Model and Controller

摘要

In this study, a model of Active Front wheel Steer (AFS) system are developed and tested. In addition, an Integrated Dynamics Control with Front steer (IDCF) controller is also designed to investigate the performance of AFS system when it is integrated with a brake system. The IDCF system composed of an AFS system and a DYC (Direct Yaw moment Control) system of rear wheels. The AFS controller and IDCF controller are compared under several driving and road conditions with and without braking input and steering input. A 8 degree of freedom vehicle model is also employed to test the controllers. The results show that the model of AFS system shows good kinematic steering assistance function. Steering ratio varies depends on vehicle velocity between 12 and 24. Kinematic stabilization function also shows good performance because yaw rate of AFS vehicle tracks the reference yaw rate. IDCF shows improved responses compared to AFS because body side slip angle is also reduced regardless of road condition, steer input and brake input. These results represent that IDCF enhances lateral stability and steerability. Results also prove that AFS system shows satisfactory result when it is integrated with another chassis system. On a split-μ road, two controllers forced the vehicle to proceed straight ahead.