Nonlinear indirect adaptive control of a quarter car active suspension

In this paper, an indirect adaptive controller is applied to the vehicle active suspension with a hydraulic actuator. The inner loop controller, which is a nonlinear adaptive controller, is designed to control the force generated by the nonlinear hydraulic actuator. The spool valve dynamics of the hydraulic actuator is reduced using a singular perturbation technique. The parameter estimation error used in an indirect adaptation is decreased asymptotically. The absolute velocity of a sprung mass is damped down by its negatively proportional term (sky-hook damper) adopted as an outer loop controller