Coordinated control of the steering system and the distributed motors for comprehensive optimization of the dynamics performance and the energy consumption of an electric vehicle

This paper presents a coordinated control algorithm for comprehensive optimization of the vehicle dynamics performance and the energy consumption for a full drive-by-wire electric vehicle, which is driven by a four-in-wheel-motor actuated system and steered by a steer-by-wire system. In order to coordinate the four-in-wheel-motor actuated system and the steer-by-wire system, first, the mechanisms influencing the vehicle dynamics control performance and the energy consumption of the two systems are derived on the basis of quantitative analyses of a typical vehicle motion control process and, then, the control algorithms for each subsystem are developed. For the steer-by-wire system, a triple-step control technique is implemented to decouple the yaw rate and the side-slip angle controls, which makes it easier to tune the control parameters. The control algorithm of the four-in-wheel-motor actuated system is designed with a hierarchical control scheme, which is able not only to satisfy the yaw rate and side-slip angle tracking demands but also to deal with the actuation redundancy and the constraints. Finally, based on the mechanisms influencing the control performances of the two subsystems, coordinated control is proposed to obtain comprehensive optimization of the vehicle dynamics control performance and the energy consumption. The coordinated control developed is convenient for implementation as the structures and the control algorithms of the subsystems remain unchanged. In this way, the control algorithms of the subsystems can be developed independently. Simulations are carried out with a CarSim software full-vehicle model for three typical driving scenarios and with different road conditions. The results show the effectiveness of the coordinated control algorithm developed.