A Discrete-Time Sliding Mode Control Method for Multi-Cylinder Hydraulic Press

In this paper, a discrete-time sliding mode control method for multi-cylinder hydraulic presses is proposed, which can be applied exactly for computer real-time discrete control in practical engineering. Proposed method bases on discretetime multi-cylinder hydraulic press model and adopts the design method of the distributed controller. First, the expected virtual force is designed according to the overall output demand, and the discrete-time sliding mode controller is designed to obtain the virtual force. Then the virtual force is separated by control allocation method to obtain the desired output force of each cylinder, finally, the second discrete-time sliding mode controller is designed to control the actual output force of each cylinder. The simulation results show that the proposed method has a good effect on output and leveling control of multi-cylinder hydraulic press and solves its problems of non-linear control and redundancy in discrete-time model.