Controller

A controller, for force-controlling a drive source of a controlled object, having a position control circuit inside a force control circuit in order to define a relative position of the controlled object to a workpiece, and a contact force occurred between the workpiece and the controlled object, the controller comprising:

• a first data acquiring portion for acquiring a time constant of the position control circuit based on a position command value to the drive source and an actual position value, during operations of the controlled object;
• a second data acquiring portion for acquiring a rigidity value for the controlled object and the workpiece based on a force data obtained when the controlled object is brought into contact with the workpiece;
• and
• an automatic gain calculating portion for calculating a force control gain of the force control circuit from the time constant of the position control circuit acquired by the first data acquiring portion and the rigidity value acquired by the second data acquiring portion, under conditions where a time constant of the force control circuit is larger than the time constant of the position control circuit.