Fuzzy control of four-point leveling system of isothermal forging hydraulic press

This paper studies the four-point leveling system of isothermal forging hydraulic presses. A multi-input and multi-output nonlinear model is established on the basis of analyzing its hydraulic structure and block kinematics. A cascade control structure is designed for the system. For the four corner cylinders, a fuzzy controller in the outer loop gives desired pressure for the inner loop according to the speed error and synchronization error; in the inner loop, the cylinder pressure is controlled using PD method. For the central cylinder, a PID controller in the outer loop gives desired pressure for the inner loop according to the average speed error; in the inner loop, the cylinder pressure is controlled using PD method. Simulation in Matlab shows that the designed control method has a good speed tracking and synchronization effect.