Dynamic feedback linearization for electrohydraulically actuated control systems

Using the dynamic inversion principal, a globally linearizing feedback control law is developed for an electrohydraulic servo system. The proposed control law is implemented on a rotational joint driven by a linear actuator. The results from experiments indicate that better uniformity of response is achieved across a wider range of operating conditions than would otherwise be possible. Improved symmetry is obtained for the extension and retraction phases of motion for an asymmetric actuator under various loading conditions and actuator positions. As a result of the improvements in linearity, significantly better performance is achieved when using linear controllers. To incorporate the effects of parametric uncertainties on the feedback linearization, a state space linear fractional representation of the parametrically uncertain linearized system is also developed. This uncertainty model is specifically suited for the design of robust control systems using the mu-synthesis and H-infinity based approach.