PURPOSE: To reduce a cost and to relieve a maintenance and inspection work by a method wherein a detecting signal passing first and second filters produces a feedback signal to first and second actuators.
CONSTITUTION: Displacement in a radial direction of a cutting tool 20 is detected by a displacement sensor 23, and detecting signals therefrom are inputted to an HPF 25 and an LPA 26. In the HPF 25, only the component of the operation frequency of a piezoelectric actuator 15, higher than a preset disconnection frequency fc, of operation frequencies of the detecting signal is caused to pass therethrough. In the LPF 26, the component of the operation frequency of a VCM 31, lower than the disconnection frequency fc, is caused to pass therethrough. The operation frequency component of each of detecting signals passing the HPF 25 and the LPF 26 produces a feedback signal for the piezoelectric actuator 15 and the VCM 31 and is inputted to a control system 41 of the piezoelectric actuator 15 and a control system 43 of the VCM 31, and a deviation with a command value is determined to perform feedback control.
HORI NOBUMITSU
YAMAKAWA YOICHI
TAKAHASHI TOSHIHIRO
