Control Strategy for All-Wheel Cooperative Steering of Multi-Axle Vehicle

Applications in commercial and military fields created high demands on the steering performance of multi-axle vehicle. With the characteristic of more degrees of freedom (DOF), all-wheel cooperative steering is more conducive to improve the steering performance of multi-axle vehicle. This paper studies multi-axle vehicle assembled with steer-by-wire system, and proposes a control strategy to achieve all-wheel cooperative steering to improve the low-speed steering flexibility and high-speed steering stability of multi-axle vehicle. Based on the ideal steering performance at low-speed and high-speed, the steady-state gain of multi-axle vehicles at different speeds is reshaped. Also, the corresponding vehicle reference model is constructed to provide the ideal vehicle state as a reference. The precision of the vehicle reference model is verified by an all-wheel independent steering platform. Accordingly, the state feedback control module which contains a sliding mode controller and a disturbance observer is designed to make the actual state of the vehicle track the designed idea state, which is verified under a variety of path tracking conditions in the simulation environment. Simulation results show that the control strategy proposed for multi-axle vehicle can achieve all-wheel cooperative steering, improving the low-speed steering flexibility and high-speed steering stability of multi-axle vehicle.