Integrated Pressure Estimation and Control for Electro-hydraulic Brake Systems of Electric Vehicles Considering Actuator Characteristics and Vehicle Longitudinal Dynamics

In the automotive field, electro-hydraulic brake systems (EHB) has been developed to take place of the vacuum booster, having the advantage of faster pressure built-up and continuously pressure regulation. Pressure control, one of the most crucial issues to be solved for EHB, is influenced by the system nonlinearities (e.g., pressure-position, friction). Recently, there are a series of studies that focus on this issue. However, the pressure control based on pressure estimation is rarely investigated in the previous literatures. In order to achieve cost-effective and highly integrated, the pressure is regulated without any add-in sensors, making it very difficult to achieve a satisfactory performance. A pressure control system based on pressure joint estimation is developed in this article according to a requirement-oriented model. The pressure joint estimation is designed considering actuator characteristics and vehicle dynamics. The wheel speed feedback is used for modification via a proportional-integral observer. A pressure control combining feedforward, torque-adaptive friction compensation with feedback controller is employed to improve the pressure-tracking performance. The constraint of feedback gain of controller is derived based on the small-gain theorem to remain the input-output stability of the overall control system. Superior to the estimation method based on actuator characteristics, the joint estimation method improves the accuracy by more than 10%. The pressure-tracking performance and robustness of system are validated by vehicle experiments under the typical common braking situations.