High Performance Pressure Control for the Hydraulic Press Based on the Soft Relief Fuzzy PID Controller

A soft relief controller is proposed to solve the pressure overshoot problem of the hydraulic press. Whose basic idea is to make the proportional relief valve open in advance to limit the pressure rise rate to reduce the pressure overshoot. What’s more, the fuzzy PID controller is introduced to improve the control performance. Based on the mechanism modeling method, the complete mathematical model of the hydraulic press is established to conduct the simulation research. The correctness of the mathematical model is proved through experiments. Simulation and experiment results demonstrate that the soft relief fuzzy PID controller which combines the soft relief controller and the fuzzy PID controller can guarantee the hydraulic press has no overshoot during the pressure building-up process. Furthermore, a high steady precision is achieved and the adjust time can meet the demands of most hydraulic presses.