Active Rear Wheel Steering Control for Four-Wheel Independent Steering Vehicle with Optimal Variable Transmission Ratio

With the rapid development of steer-by-wire technology, the four-wheel independent steering vehicle has attracted more and more attention due to their advantages in active safety and maneuverability. In order to improve driver comfort and vehicle stability, in this paper, an active rear-wheel steering control method for four-wheel independent steering vehicle with optimal variable transmission ratio is proposed. Firstly, considering the impact of the transmission ratio coefficient from the steering wheel to the steering actuator on driver burden and vehicle dynamics, the optimal variable transmission ratio coefficient is designed based on the comprehensive objective evaluation index and the steering response characteristic index. Since the front tire force is more likely to operate in the nonlinear region, an active rear-wheel steering control method based on yaw rate and steering angle is developed to improve vehicle handling stability. In order to reduce tire wear, the obtained front and rear axle steering angle is distributed to the four wheels according to the Ackermann steering principle. Finally, the effectiveness and superiority of the proposed method are verified by hardware-in-the-loop experiments.