A linear model of quarter car active suspension system using composite nonlinear feedback control

The composite nonlinear feedback (CNF) control technique is successfully applied to design the controller based on control law for an active suspension system. The CNF control law is composed of a linear control law and a nonlinear feedback part. The main idea of CNF is to design the linear control law with a low damping-ratio to achieve fast rising time and to design the nonlinear feedback part to result in a high damping-ratio to remove the overshoot caused by the linear control law when the system controlled output approached the reference. Such the CNF control laws can improve the tracking and regulating performances of the resulting closed-loop systems. The active suspension system is hierarchically divided into two subsystems with the system transformation based on the system structural properties at first and then the CNF control laws are designed for the two subsystems each One of the CNF control laws is designed for tracking control and the other is designed against the mismatching disturbance. The complete control law is made by combining the two CNF control laws and the system transformation. The simulation results show that CNF controller is better than LQR controller and passive model. The computer simulation is done to prove the CNF control performance.