Design of Virtual Reference Feedforward Controller for an Active Suspension System

This paper presents a method to design a virtual reference feedforward controller (VRFC) for an active suspension system. Generally, it is not easy to apply a feedforward control to an active suspension system because a reference or disturbance is difficult to measure or estimate. Instead of measuring references or disturbances, a virtual reference on heave motion of a sprung mass representing a bump is defined and used for feedforward control in this paper. Feedforward controller with the virtual reference is combined with feedback controllers such as linear quadratic regulator (LQR) and linear quadratic (LQ) static output feedback (SOF) controller. To fully take advantages of the virtual reference for an active suspension system, it is necessary to find optimal parameters of the virtual reference which maximizes control performance. For the purpose, a simulation-based optimization is formulated and solved by a heuristic optimization method. A simulation with a simulation package shows that the proposed VRFC is quite effective in improving the ride comfort with an active suspension system.