Saturated PD-SMC method for suspension systems by exploiting beneficial nonlinearities for improved vibration reduction and energy-saving performance

Abstract

In this paper, through purposely employing beneficial nonlinear stiffness and damping with a constructed bioinspired reference model, a novel saturated PD with sliding mode control method (referred to as saturated PD-SMC method), is designed for active suspension systems under saturated control input constraints. The designed control method has several distinct benefits, including the simple structure of PD control method, strong robustness of SMC method with respect to model uncertainties and external disturbances, without requirements of exact system parameters associated with traditional SMC method, as well as taking input constraints into consideration. In the designed control method, the PD part is employed to stabilize the controlled active suspension system, the SMC part is applied to provide strong robustness, and the saturation functions are introduced to prevent the violation of control input constraints. The corresponding stability analysis is provided by Lyapunov techniques. Several experimental results show that, the proposed control method dramatically improves transient performance in comparison with some existing methods, including significantly decreasing control energy by 30% for sinusoidal road profile, and decreasing control energy up to 66% for random road profile, which achieve a satisfactory trade-off between costs and results for suspension system control. As far as we know, it is the first time to combine PD control, SMC method, and saturation structures together, to achieve obvious performance improvements for suspension systems, and simultaneously, complete stability analysis is given.