Displacement characteristics hierarchical control of electro-hydraulic compound steering for commercial vehicle

The electro-hydraulic compound steering combines the function of electric power steering and hydraulic power steering, which can reduce the energy consumption of steering, ensure the stability of vehicles, and meet the steering demand under unmanned driving. In order to fully coordinate the steering stability and path tracking requirements in the unmanned steering process, this paper proposes a hierarchical control strategy of displacement characteristics for commercial vehicle electro-hydraulic compound steering. The mixed H₂/H_∞ controller for the vehicle stability is designed in the upper layer, which takes the vehicle yaw rate as the control variable. Based on the motor model and sliding-mode control theory, the sliding-mode variable structure controller of motor angle is designed in the lower layer, and the hydraulic power distribution is completed by estimating the steering resistance torque. Simulation results show that the designed controller can effectively track the yaw rate on the premise of ensuring path tracking effect. Combined with steering torque estimation and hydraulic power distribution rules, it can effectively realize the coordinated control of hydraulic power and motor rotation angle.