Dmg Mori Seiki Co., Ltd.

The University of Tokyo

Teruaki Ishibashi

Hiroshi Fujimoto

Koji Yamamoto

Shinji Ishii

Yuki Terada

A controller has a varying speed signal generation unit generating a varying speed command signal varying at predetermined amplitude and period, a current control unit generating a current command signal based on the varying speed command signal, a feedback control unit generating a correction signal based on a deviation between the varying speed command signal and a present rotational speed of the spindle motor and adding the correction signal to the current command signal, and a learning control unit calculating a disturbance component caused by cutting resistance based on the deviation every predetermined rotation angle of the spindle motor and, in synchronism with a rotation angle of the spindle motor corresponding to the varying speed command signal input into the current control unit, generating a compensation signal based on the disturbance component corresponding to the rotation angle and adding the compensation signal to the varying speed command signal.

Controller for spindle motor

Using a machine tool, a workpiece is machined while periodically varying the rotational speed of a spindle thereof. Correlation data on correlation between a speed variation rate RVA of the spindle rotational speed, a speed variation period ratio RVF thereof, and vibration of a tool when machining the workpiece while periodically varying the spindle rotational speed is previously obtained. Based on the correlation data, the speed variation rate RVA and the speed variation period ratio RVF are set so that the vibration of the tool and machining accuracy are within their respective allowable ranges, and based on the set speed variation rate RVA and speed variation period ratio RVF, a variation amplitude and a variation period of the spindle rotational speed are determined. The spindle is rotated at the rotational speed varying at the determined amplitude and period with respect to a target rotational speed, thereby machining the workpiece.

Growing community of inventors

Tokyo, Japan

Teruaki Ishibashi