Robust Synchronization Control Of Dual Cylinder Hydraulic Drive Systems

With the urgent need for high-precision synchronous technology of hydraulic drive systems of the metal processing equipment, metallurgical machinery, engineering machinery and aerospace devices,it becomes increasingly important to investigate the synchronization control theory and method for the electro- hydraulic servo drive systems. To this end, the synchronous control problem is discussed in this paper for two kinds of engineering systems driven by the electro-hydraulic servo system.First, the dual-hydraulic drive lifting system is taken as the research object. According to the characteristic of nonlinearity, uncertainty and interference in the valve-controlled hydraulic cylinders and taking into account the existence of unavailable system state variables in practice, a reduced-order observer-based output feedback robust synchronous control scheme is presented. The synchroni- zation error as an additional state is incorporated into the system state variables to improve the synchronization performance. A reduced-order observer is constructed to estimate the velocity of pistons that are not easily directively measured. A reduced-order observer-based robust output feedback synchroni- zation controller is designed for the system with uncertainty and nonlinearity.Second, the thickness control system of cold rolling mills driven by two hydraulic cylinders is taken as the research object. Compared with the dual- hydraulic drive lifting system, difference lies in that system uncertainty and load disturbance have a distinct impact on the system performance due to the rolling force, the delayed strip thickness output measurement has an important effect in the control precision and the accuracy of synchronization control is higher for cold strip rolling mill. For this reason, in the light of the cold rolling mill thickness control system with delayed output measurement, two kinds of robust synchronization control schemes are proposed: one is a robust state feedback synchronization controller which is designed for the case with all measurable states, the other one is a robust output feedback synchronization controller based on reduced-order observer with delayed output measurement which is designed for the case with the unavailable velocity of the pistons.The integrated dynamics are modelled for these two kinds of engineering systems driven by electro-hydraulic servo systems. And the correctness and effectiveness of all the proposed robust synchronization controllers are demonstrated by both theoretical proof and simulation results.