PURPOSE: To make precision and speediness compatible by passing a force- detectedvalue through a low-pass filter, converting a position-detected value into a force, passing it through a high-pass filter, and feeding the sum of the both back.

CONSTITUTION: The low-pass filter 12 removes a high frequency component from the force signal detected by a force detector 4. Thee signal passed through the low-pass filter 12 is, therefore, a signal which is deficient as to the high frequency component. A position-force converter 13, on the other hand, converts the position detected value P from an angle detector 2 into a force signal according to the Hooke's law. The converted force signal is passed through the high- pass filter 14 and becomes a signal corresponding to the deficiency. This signal is added by an adder 16 to the signal passed through the low-pass filter 12 to become a signal which covers nearly the entire range and the signal is fed back to a force compensator 9. The high frequency component is, therefore, compensated and the speedy responsibleness is secured. Further, since a force detection noise is removed by the low-pass filter 12, high-precision force control can be performed.