Abstract:

To enhance the steering ability of multi?wheel distributed electric drive vehicles in a complex maneuvering environment， a dual?steering system based on direct yaw moment control is designed. The control system adopts a hierarchical structure， with the yaw moment decision layer as the upper layer and driving force distribution layer as the lower layer. In the upper layer of the control system， the road surface is identified based on unscented Kalman filter and recursive least square algorithm. The slip steering ratio is adaptively adjusted according to the vehicle state information and road conditions. Then the dual?steering reference model is determined by the vehicle dynamics model and slip steering ratio. For the control signal jitter caused by the discontinuous characteristics near the sliding surface， the sliding mode control algorithm is improved and the sliding mode conditional integral controller is designed to make the actual yaw rate track the desired yaw rate calculated by the dual steering reference model. In the lower layer of the control system， on the premise of ensuring the vehicle’s total driving force， the generalized target control force demand of the upper layer is allocated to each actuator according to the control allocation rules. The hardware?in?the?loop real?time simulation platform is used to verify the control strategy. The results show that the hierarchical control system can achieve the function of road recognition and vehicle dual?steering well. It can control the vehicle effectively according to different road conditions， reduce the turning radius of the vehicle in the narrow curve area， restrain the chatter and jitter of the vehicle state parameters and motor torque， and improve the steering mobility and high?speed driving stability of the vehicle in small radius driving.

Key words: hub motor, road identification, direct yaw moment control, sliding mode control with conditional integrator, dual?steering control