Vibration control of semi-active suspension with cam mechanism-based nonlinear stiffness structure

This paper proposes a novel semi-active suspension system with a cam mechanism-based nonlinear stiffness structure for vibration reduction. The cam mechanism has a specially designed curve on its contacting surface, which is designed and modeled using the virtual work principle and force-displacement simulation. The nonlinear stiffness structure mainly consists of a spring, a roller and a curved surface. Based on the surface contour design, the system shows variable stiffness characteristics and the required stiffness range can be obtained through the proper design of the curved surface. Then, the model parameters are analyzed, and the key structural parameters of the system are determined to achieve a high-static-low-dynamic stiffness. Additionally, a semi-active backstepping sliding mode controller is designed to enhance the vibration reduction capabilities. Finally, the vibration reduction performance of the passive systems with and without nonlinear stiffness and the semi-active system are compared. The results show both the nonlinear stiffness and the semi-active control are beneficial to reduce vibration. The RMS of acceleration of the nonlinear stiffness passive suspension and semi-active suspension in random excitation decreases 12.9% and 17.2%, respectively.