Reduced-order Observer-based Dynamic Output Feedback Control For Electro-hydraulic Servo Position System

As the actuator of high-precision position control,electro-hydraulic servo position system has been the research focus in the field of control, since it contains strong nonlinearity, uncertainty and unmeasurable system states. Thus, the reaseach on reduced-order observer-based dynamic output feedback control is meaningful in practice and theory. The reduced-order observer-based dynamic output feedback control strategy is investigated for both the electro-hydraulic servo position system and the gauge control system of rolling mills driven by electro-hydraulic servo system.Nonlinear mathematical model is first established for the electro-hydraulic servo position system by analyzing its dynamic mechanism and considering the nonlinear characteristics of each component. And then a mathematical model oriented controller design is derived by some reasonable simplification for the gauge control system in rolling mills driven by electro-hydraulic servo system.A nonlinear reduced-order observer-based output feedback controller is proposed for the electro-hydraulic servo position system. First, a nonlinear reduced-order observer with undetermined variable function is constructed by employing the nonlinear state feedback transformation and the design idea of Luenberger-type observer. And then, the undetermined variable function of the reduced-order observer and an output feedback controller are obtained in the proceeding recursive design on the basis of backstepping technique for the augmented system. Meanwhile, the simulation results are given to illustrate the effectiveness of the proposed control strategy.In view of the case that time-delay arises in the output measurements, a reduced-order observer-based robust controller is proposed for the gauge control system in rolling mills driven by electro-hydraulic servo system. Based on Lyapunov-Krasovskii functional stability theory, a sufficient condition is first given under which there exists an asymptotically stable reduced-order observer and a robust stabilizing controller for a class of the uncertain nonlinear system with output delay. And then, with the help of this result, a robust output feedback stabilizing controller is designed for the gauge control system in rolling mills driven by electro-hydraulic servo system. And simulation is researched on a certain rolling mill gauge control system with practical physical parameters. The effectiveness of the proposed controller is illustrated by the simulation results.