Dynamic response and robustness of electro-hydraulic servo-driven vehicle active suspension under impact loads

To address the nonlinear dynamic characteristics, parameter uncertainties, and external disturbances of an electro-hydraulic servo-driven vehicle active suspension system subjected to complex road excitations, a control method based on feedback linearization sliding mode control (FLSMC) is proposed. A nonlinear mathematical model of the valve-controlled cylinder electro-hydraulic position servo system is established, and a composite controller that combines input–output feedback linearization with sliding-mode variable-structure control is designed. First, feedback linearization is employed to compensate the nonlinear dynamics of the hydraulic actuator, including nonlinear friction and flow–pressure coupling effects. Second, sliding mode control (SMC) is introduced to compensate system parameter perturbations and road disturbances, thereby enhancing the robustness of the system. Third, the global stability of the closed-loop system is proven based on Lyapunov stability theory. A co-simulation model, consisting of a quarter-vehicle suspension model and the electro-hydraulic servo drive, is constructed on the Matlab/Simulink platform, and the control performances of PID, SMC, and FLSMC under sudden impact road loads are comparatively analyzed. The results show that, under the FLSMC strategy, the root-mean-square (RMS) tracking error of the suspension dynamic deflection is reduced by 96.74% and 89.84%, and the RMS value of the vehicle body vertical displacement is reduced by 89.41% and 71.87%, compared with the PID and SMC controllers, respectively. This result verifies the superior performance of FLSMC in improving tracking accuracy and enhancing the suspension travel compensation capability. Meanwhile, the proposed method can effectively suppress the inherent chattering phenomenon of sliding mode control. The research results significantly improve vehicle ride comfort and body attitude stability under impact road loads, and provide a theoretical basis for the optimal design of high-precision hydraulic active suspension control systems.