The Study Of Control For Semi-Active Suspension Systems With Input Constraints

With the development of economic and science,cars have become an important means of transport in people's lives.Suspension system as one of the important vehicle part,its performance will directly affect the vehicle's comfort and safety.In this paper,the control method of semi-active suspension system is studied.Based on the model of a quarter-vehicle semi-active suspension system,the controller is designed considering the parameter uncertainties and input amplitude constraints.Firstly,a controller design method based on sliding mode adaptive is proposed for vehicle semi-active suspension system containing parameter uncertainties and external interference problem.This method uses sliding mode control to reduce the influence of external disturbance and improves the chattering by using hyperbolic tangent function.At the same time,the adaptive backstepping method is used to track the uncertain parameters to improve system stability.Secondly,a nonlinear controller design method based on quarter-car model of semi-active suspension is proposed for input constraints problem.Taking the system nonlinear characteristics and input constraints into account sufficiently,an auxiliary system is introduced to combine backstepping method to cut down vibration of semi-active suspension.In the design process,we use a Nussbaum function to compensate for the nonlinear term arising from the input constraints.Due to the absence of any linearization method,the control input is limited to a certain range while maintaining the nonlinear characteristics of the system.Finally,a controller design method based on nonlinear adaptive backstepping is proposed for vehicle semi-active suspension system containing parameter uncertainties and input saturation problem.This method realizes the compensation of the control saturation by introducing an auxiliary system and design a new error variable,which solves the problem of amplitude constraint of the control input.Considering the parameter uncertainty of the suspension system,a control law is designed by using a projection adaptive algorithm to ensure the stability of the suspension system by constructing the appropriate Lyapunov function.