State observer based adaptive sliding mode control for semi-active suspension systems

In order to improve ride comfort and handling stability of a vehicle, this paper will present an adaptive sliding mode control algorithm for semi-active suspension systems. A hybrid reference model is proposed which combines virtues of sky-hook and ground-hook control logics, and chooses a more suitable compromise for a given application. The stability of the adaptive sliding mode control strategy is analyzed by means of Lypunov function approach taking into account the nonlinear damper characteristics and sprung mass variation of the vehicle. A state observer is designed based on unscented Kalman filter to estimate the suspension states in real-time for the realization of the controller, which improves the robustness of the control strategy and is adaptive to different types of road profiles. Finally, the performances of the controller are validated under the following two typical road profiles: the random road and half-sine speed bump road. The simulation results show that the proposed control algorithm can offer a good coordination between ride comfort and handling stability of a vehicle.