A Comparative Study on ESC Drive and Brake Control Based on Hierarchical Structure for Four-Wheel Hub-Motor-Driven Vehicle 2019-01-5051
Electronic Stability Control (ESC) is an important measure to proactively guarantee vehicle safety. In this paper, the method of four-wheel hub-motor torque control is compared with the traditional single-wheel hydraulic brake control in ESC system. The control strategy adopts the hierarchical structure. In upper controller, the stability of the vehicle is identified by threshold method, the additional yaw moment control uses a way to get the moment including feedforward and feedback parts based on the linear quadratic regulator (LQR). The medium controller is tire slip rate control, in order to get the optimal target slip rate from the upper additional yaw moment, a method of quadratic programming to optimize the longitudinal force is proposed for each wheel. The inputs of tire state for the magic tire model is introduced so as to calculate the target slip rate from the target longitudinal force. The lower controller is wheel cylinder pressure control and motor torque control which is realized by Carsim ideal control. Finally, through Co-simulation of Carsim/Simulink in the condition of open steering wheel loop for Sine with Dwell Waveform and closed driver loop for Double Lane Change, the results show that, at high speed and with large and frequent steering wheel angle, restricted by the motor torque, the method of motor torque control is not as effective as hydraulic brake control, but have the same effects and better driver seating comfort and handing stability at middle or low speed. If the control torque range of motor at high speed can be improved or the AFS and SBW can be applied to the field of ESC in the future, the drive motor control can be further developed in the application of the hub-motor-driven vehicle.