Hydraulic system

A hydraulic system comprising:

• a cylinder that moves a moving object by extension and retraction of a rod and in which an interior of a tube is divided by a piston into a head-side chamber and a rod-side chamber;
• a first bidirectional pump connected to the head-side chamber by a first supply/discharge line, the first bidirectional pump being a variable displacement pump whose delivery capacity per rotation is freely variable;
• a second bidirectional pump connected to the rod-side chamber by a second supply/discharge line and coupled to the first bidirectional pump in a manner enabling torque to be transmitted between the first and second bidirectional pumps;
• a relay line connecting the first and second bidirectional pumps such that a hydraulic liquid is sequentially discharged from one of the first and second bidirectional pumps and introduced into the other of the first and second bidirectional pumps both when the hydraulic liquid is discharged from the first bidirectional pump and when the hydraulic liquid is discharged from the second bidirectional pump;
• a servomotor that drives the first or second bidirectional pump;
• a regulator that regulates a tilt angle of the first bidirectional pump in response to an electrical signal;
• a servo amplifier that controls a rotational speed of the servomotor;
• a controller that outputs a rotational speed command to the servo amplifier and outputs a tilt angle command to the regulator;
• and
• a head-side pressure sensor that detects a pressure in the head-side chamber or the first supply/discharge line, wherein
• when the moving object is moved to a predetermined position by extension of the rod, the controller outputs the rotational speed command to the servo amplifier such that the moving object is moved at a predetermined speed and outputs the tilt angle command to the regulator such that the pressure detected by the head-side pressure sensor is maintained within a predetermined range.