From the system of the Hydraulic Press, whether the feedback device is used, the system can be further divided into two categories: open-loop system and closed-loop system.

The open-loop system of a four-column hydraulic press is a system that does not use a feedback device, and its output specificity depends entirely on the individual components and the combination of components in the system. When the outside world is disturbed by the system, the output of the actuator generally deviates from the original set value and produces a certain error. Due to the poor anti-interference ability of the open-loop system, the quality of the control is greatly affected by the change of working conditions, so the accuracy of the system output is low, and the setting cannot meet the established target in severe cases.

The closed-loop system of the Hydraulic Tee Machine is a system using a feedback device that samples the state of the output, produces a feedback signal proportional to the output, and compares it to the input signal if there is a feedback signal between the input signal and the input signal The difference automatically corrects the output so that it matches the input requirements. Since the closed-loop system has strong anti-disturbance capability, the control quality is less affected by the change of working conditions, and the more accurate control system can be composed of general components, and the accuracy of the system output is high.