Robust Control of Active Suspensions Using Sliding Modes

In this study, a four degrees of freedom vehicle model is used in order to design and check the performance of sliding mode controlled active suspensions. Force actuators are mounted parallel to the suspensions and a non-chattering control is realized. Sliding mode control is preferred because of its robust character since any change in vehicle parameters should not affect the performance of the active suspensions. The aim is to improve ride comfort by decreasing the amplitudes of motions of the vehicle body. Body bounce and pitch motions of the vehicle are simulated both in the time domain, in the case of travelling over a single rectangular bump type road profile, and the frequency domain. Also the phase plane plots of them are checked. Simulation results are compared with the ones of the passive suspensions. The robust character of the controller has been demonstrated using different system parameters which it is possible to change depending on the conditions of the journey. At the end of the study, the performance of the controller and the improvement in the system performance have been discussed also by considering the ride comfort.