ACTUATOR, ACTUATOR CONTROL METHOD AND PROGRAM
The difference between the target position and the current position of a piston is obtained. Further obtained are the pressure from proportional control proportional to said difference, the variable offset pressure based on the value obtained by differentiating the difference, and the constant base offset pressure. The pressure in the chamber which is on the driving side in the cylinder is set to the sum of the pressure from the proportional control and the offset pressure, which is calculated by subtracting (adding) the variable offset pressure from the base offset pressure. The pressure in the chamber on the resistance side is set to the offset pressure obtained by adding (subtracting) the variable offset pressure from the base offset pressure.