Adaptive pressure control for electro-hydraulic brake system considering nonlinearity and uncertainty

To address pressure control inaccuracy caused by nonlinearity (master cylinder piston position-pressure relationship) and uncertainty disturbances (temperature-induced changes in system parameters and brake pad wear) in an electro-hydraulic brake system (EHB), this paper suggests a cascaded adaptive control strategy consisting of a pressure outer loop and a position inner loop to improve pressure control performance. Firstly, the master cylinder pressure tracking adaptive control technology is used in the pressure outer loop. This technology uses the master cylinder piston position-pressure nonlinear relationship as the pressure feed-forward and combines fuzzy PI feedback control to enhance the dynamic compensation ability of feedback control for position-pressure relationship, improving the pressure tracking accuracy of the EHB system. Then, for the position inner loop, a linear active disturbance rejection controller (LADRC) is designed based on the EHB dynamic model. This controller has the capability of observing and compensating for uncertain disturbances, thereby guaranteeing the robustness of pressure control. Finally, sinusoidal and step pressure tracking experiments are performed on a hardware-in-the-loop bench. The results indicate that the proposed control strategy can significantly improve the steady-state accuracy and dynamic response characteristics of pressure tracking.