Adaptive cross-coupled sliding mode control for synchronization of dual-cylinder electro-hydraulic servo systems

To improve the equality of continuous casting billet, synchronization control is investigated for continuous casting mold driven by dual-cylinder electro-hydraulic servo systems (EHSS) in this paper. A second-order super twisting sliding mode controller is developed for each cylinder EHSS, in which cross-coupled errors are employed to construct the sliding mode surfaces, which guarantee that trajectory tracking errors of each cylinder EHSS and the synchronization error can rapidly converge to zero in finite time even in presence of the parameter uncertainties and external disturbances. Furthermore, to reduce the chartering caused by the discontinuous control law of sliding mode control, adaptive gains are employed during the sliding mode controller design. Thus, an adaptive sliding surface cross-coupled synchronization controller is presented by employing Lyapunov stability theorems. Simulation results in a model obtained from a real continuous casting mold demonstrate the effectiveness of the method.