Active Hydro-pneumatic Suspension Active Disturbance Rejection Sliding Mode Control to Improve Vehicle Stability

Hydro-pneumatic suspension is widely used because of its desirable nonlinear stiffness and damping characteristics. However, the presence of parameter uncertainty and high nonlinearity in the system, lead to unsatisfactory control performance of the traditional controller in practical applications. Therefore, A novel stability control method for active hydro-pneumatic suspension (AHPS) is proposed. Firstly, a nonlinear mathematical model of the hydro-pneumatic suspension considering the seal friction is established based on the hydraulic principle and the knowledge of hydrodynamics. On the basis of the established hydro-pneumatic suspension nonlinear model, a vehicle dynamics model is established. Secondly, an active disturbance rejection sliding mode controller (ADRSMC) is designed for the vertical, roll, and pitch motions of the sprung mass. The extended state observer (ESO) is used to estimate the lumped disturbance caused by the nonlinearity and uncertainty of the model, which is then incorporated into the sliding mode control law. This allows the control law to adapt to the working state of the suspension system in real-time, which can effectively address the impact of uncertainty and nonlinearity on the system. Finally, simulation verification is carried out on the bump and random roads, two typical working conditions. The results show that compared with traditional passive hydro-pneumatic suspension (Passive), the proposed ADRSMC can reduce the amplitude of vehicle acceleration by more than 50%, and the optimization effect is better than active disturbance rejection control (ADRC), which significantly improves the stability of the vehicle. This study provides a certain reference for the design of an active hydro-pneumatic suspension control strategy.