Control method for chuck device

A drive system for driving a chuck device including a piston displaceable in an axial direction under an effect of supply of fluid and a pair of fingers configured to be opened and closed according to the displacement of the piston, the drive system comprising:

• a controller;
• a detection sensor configured to detect an axial position of the piston;
• and
• a switching valve configured to switch a state of supply of the fluid to the chuck device,
• wherein the switching valve is a servo valve, of which degree of valve opening is controllable based on a control signal input from the controller, and an amount of displacement of the piston and an amount of opening and closing of the fingers are controlled by changing the degree of valve opening, and
• wherein:
• the switching valve includes a pair of 3-port servo valves;
• and
• one of the 3-port servo valves is connected to a first cylinder chamber of the chuck device, and another of the 3-port servo valves is connected to a second cylinder chamber of the chuck device.