Research on Steering Control Strategy of Four-Wheel-Steer-by-Wire System

To control automobile's steady slip angle and keep constant steering gain at the same time,rear wheel steering control strategy and front wheel steering control strategy are researched.Firstly,full vehicle two degree of freedom models of Four-Wheel-Steer-by-Wire are built.Then two types of Rear-Wheel angle control strategies based on zero steady slip angle are achieved,i.e.proportional with Front-Wheel angle type and yaw rate feedback type,of which the former doesn't change system poles while the latter does.Then their front wheels steering ratio formulas are acquired based on steering gain not changing with velocity.Simulations show that the Front-Wheel steering control strategy can keep constant steering gain and decrease driver workload and improve the handling,and the Rear-Wheel steering control strategy can achieve zero steady slip angle and control vehicle attitude,thus improving the handling and stabilities.