Master Cylinder Pressure Estimation of the Electro-Hydraulic Brake System Based on Modeling and Fusion of the Friction Character and the Pressure-Position Character

To estimate the master cylinder pressure of the electro-hydraulic brake system (EHB) accurately and robustly, this paper proposes a master cylinder pressure estimation method (MCPE) based on modeling and fusion of the friction character and the pressure-position character of EHB. First, the kinetic equation of EHB is established based on Newton's Law. Second, the sliding friction in EHB is theoretically analyzed and tested under multi conditions (e.g., rack speed, individual difference, wear and temperature). Test results show that the sliding friction is stable except for conditions below −25 °C. The static friction in EHB is derived from EHB's kinetic equation. Based on the above, a novel robust Karnopp friction model is established. Third, the pressure-position relationship of EHB is tested under multi conditions (e.g., rack speed, brake circuit, parking brake state, brake pair wear and temperature). Test results show that the pressure-position relationship is susceptible to all the tested conditions. The influence of rack speed on pressure-position relationship is further analyzed and a novel dynamic pressure-position model is established, which incorporates a static term and a dynamic term. Vehicle test verifies the superiority of the dynamic pressure-position model in terms of response speed and accuracy. Furthermore, a robust MCPE is proposed by combining the kinetic equation of EHB, which incorporates the proposed novel friction model, and the dynamic pressure-position model based on recursive least square algorithm with a forgetting factor. Finally, the accuracy and robustness of the proposed MCPE is demonstrated by vehicle test under multi braking conditions.