Hierarchical control of vehicle active suspension system with uncertain sprung mass and time-varying disturbance

A hierarchical control strategy is proposed for nonlinear uncertain active suspension systems. To provide the target force needed for the suspension, the top controller is built with a sliding mode controller that is based on a nonlinear disturbance observer. To precisely follow the goal force, the bottom controller is made in the style of a backstepping adaptive controller. Coordinated control of the suspension dynamic displacement and sprung mass acceleration of the nonlinear uncertain suspension system is realized by the controller. Firstly, a nonlinear filter is incorporated to maintain the vehicle body’s vertical motion stability while meeting the suspension’s mechanical structural limitations. Secondly, the nonlinear disturbance observer is used to compensate the influence of uncertain sprung mass, mechanical structure nonlinearity and external disturbance. Thirdly, a coordinated adaptive backstepping tracking controller to estimate the uncertain parameters resulting from the physical characteristic change of the electro-hydraulic actuator is designed using backstepping technology and Lyapunov stability theory. This allows the control object to precisely track the goal force generated by the upper controller and guarantee the body’s stability. Finally, the effectiveness of the hierarchical controller is analyzed under random road, bumpy road conditions.