Master–Slave Control for Active Suspension Systems With Hydraulic Actuator Dynamics

In order to solve the input nonlinearity of the hydraulic active suspension system, a master- slave control law is proposed through a nonlinear separation strategy. A Robust H
_∞
control is used as the master controller and an adaptive backstepping control scheme is designed as the slave controller. The robust H
_∞
master controller is studied to deal with the problems of input delay, parameter uncertainties, and multi-objective optimization in the linear system. A desired active control force is calculated by the master controller to guarantee the performances of the closed-loop system within allowable constraint ranges. The slave controller is applied to solve the problems of nonlinearity and the time constant uncertainty of the hydraulic actuator, an actual control law is obtained in this step. A quarter-car model with the hydraulic active suspension system is considered and the effectiveness of the proposed approach is illustrated by a realistic design example.