Development of a sliding mode controller for semi-active vehicle suspensions

Sliding mode control of semi-active suspensions possesses excellent performance as well as high robustness. However, it is difficult to obtain sufficient data concerning the various states of the suspension. A model reference sliding mode controller that is easy to implement has been designed. The proposed controller needs only two acceleration sensors and eliminates the necessity of measuring road signals in real-time. The controller uses an approximate ideal skyhook system as a reference model, and the control law is determined so that an asymptotically stable sliding mode will occur in the error dynamics between the plant and the reference model states. The effectiveness of this controller has been verified via experimental studies. A real-time control system has been constructed with a virtual instrument system. Experimental rapid control prototyping for the proposed controller has been conducted on a quarter-car suspension system. The experimental results indicate that, compared with a practical skyhook controller and a passive suspension, the sliding mode controller can effectively improve ride comfort and safety performance. The designed controller should be directly transferable to commercial implementations of semi-active vehicle suspensions.