Sliding mode control of double-wishbone active suspension systems based on equivalent 2-degree-of-freedom model

As a critical component of transportation vehicles, active suspension systems (ASSs) have widely attracted attention for their outstanding capability of improving the riding comfort and the maneuverability. However, due to the effects of the suspension kinematic structure and the rubber elements containing bushings and top mount, the practical double-wishbone ASS cannot achieve the desired performance resulting from the control design based on a simple 2-degree-of-freedom (DOF) model. In this paper, a sliding mode control (SMC) based on an equivalent 2-DOF model is proposed to suppress the sprung mass vibration of a double-wishbone ASS, which is to improve the riding comfort of vehicle. The SMC for a double-wishbone ASS is designed in four steps. First, an equivalent 2-DOF model of a double-wishbone ASS, which considers suspension kinematic structure and rubber properties, is established. The parameter values of an equivalent 2-DOF model are identified by using least square method. Second, an SMC is designed for an equivalent 2-DOF model, and the effect of the parameter value of the 2-DOF model on the riding comfort is investigated by experimental results. Third, a control compensator for a double-wishbone ASS is developed by considering the suspension kinematic structure. Four, the control for double-wishbone ASS is obtained by integrating the compensator into the SMC based on the equivalent 2-DOF model. The numerical simulation results show that the control can effectively suppress the sprung mass vibration of the double-wishbone ASS when the SMC design is based on an equivalent 2-DOF model.