Improved Tracking Control of Hydraulic Systems

Abstract

Tracking control for hydraulic systems is a key system requirement, as these devices must often follow prescribed motions. Tracking control of hydraulic systems has been approached using both linear and nonlinear control laws. The latter provides improved performance, but at the expense of additional sensors. Further, the control laws often employ hydraulic fluid bulk modulus—a difficult-to-characterize quantity—as a parameter. To overcome these difficulties, we have developed a control design procedure that requires no additional sensors and is robust to variations in the bulk modulus. A dual approach of singular perturbation theory and Lyapunov techniques form the basis for the procedure. For the cases of a small-amplitude sinusoidal input and large-amplitude polynomial input, a candidate system achieved good tracking performance and exhibited outstanding robustness. The ability to accomplish good tracking in a robust manner with no additional sensors provides advantages over other nonlinear tracking algorithms.