Position Tracking Control Law for an Electro-Hydraulic Servo System Based on Backstepping and Extended Differentiator

This paper investigates the problem of position tracking control for an electro-hydraulic servo system with parameter uncertainty. Superior to some existing results based on parameter estimation or fuzzy modeling, our proposed control scheme can guarantee the bounded tracking performance without parameter identification and model approximation. This is accomplished by using a novel differentiator-based backstepping control scheme, in which finite-time-convergent second-order differentiators are introduced to get the differential estimations of the system states. Then, the obtained differentials can be used to deal with the system uncertainties since such differentials contain the information relating to the system uncertainties. Moreover, in the backstepping control design procedure, the derivatives of the virtual control functions can also be approximated via the second-order differentiator, which can overcome the difficulty of calculating the derivatives of the virtual control functions. Finally, a design experiment is given to show the effectiveness of the proposed method.