Robust sliding mode control of a full vehicle without suspension gap loss

A seven-degrees-of-freedom full vehicle model is used to design a robust controller and to investigate the performance of active suspensions without losing the suspension working space. Zero reference for vehicle body displacement finishes suspension working distance. Thus, a new approach is suggested in this paper. Force actuators are placed parallel to the suspensions and non-chattering sliding mode control is applied. Since any change in vehicle parameters because of different load or road conditions adversely affects the performance of the ordinary control methods, a robust control method is preferred. To obtain the desired improvement in ride comfort, we aim to decrease the magnitudes of the body vibrations and their accelerations. We present body bounce, pitch and roll motions of the vehicle with the conventional approach and the proposed approach without suspension gap loss, both in the time domain in the case of traveling over a step road profile and in the frequency domain. The results of both approaches are compared. The solution to the suspension gap loss problem has also been presented on periodic road surfaces. At the end of the paper, we discuss the improvement in the performance of the new controller with its robust behavior and the advantage of the new approach