Feed system controlling method and apparatus for machine tool

A method for controlling a feed system of an NC machine tool, comprising the steps of:

• generating an operation command signal according to an NC program;
• generating a speed command signal by multiplying a deviation between the generated operation command signal and a current position signal fed back from the feed system by a positional loop gain;
• generating an electric-current command signal by multiplying a deviation between the generated speed command signal and a current speed signal fed back from the feed system by a speed loop gain;
• and
• controlling a drive motor for the feed system based on an electric-current command signal obtained by eliminating frequency components in a predetermined frequency band from the generated electric-current command signal, the method further comprising the steps of:
• detecting vibration level and vibrational frequency directly from the electric-current command signal obtained by eliminating frequency components in the predetermined band;
• and
• adjusting the band of frequency components to be eliminated from the electric-current command signal in response to the detected vibration level and vibrational frequency.

An apparatus for controlling a feed system of an NC machine tool, comprising:

• an operation command generating section for generating an operation command signal according to an NC program;
• a position controlling section for generating a speed command signal by multiplying a deviation between the operation command signal generated in the operation command generating section and a current position signal fed back from the feed system by a positional loop gain;
• a speed controlling section for generating an electric-current command signal by multiplying a deviation between the speed command signal generated in the position controlling section and a current speed signal fed back from the feed system by a speed loop gain;
• and
• adjustment means for detecting vibration level and vibrational frequency of directly from the electric-current command signal generated in the speed controlling section, and
• adjusting a value of the speed loop gain in response to the detected vibration level and vibrational frequency,
• wherein the control apparatus controls a drive motor for the feed system of the NC machine tool based on the electric-current command signal generated in the speed controlling section.

An apparatus for controlling a feed system of an NC machine tool, comprising:

• an operation command generating section for generating an operation command signal according to an NC program;
• a position controlling section for generating a speed command signal by multiplying a deviation between the operation command signal generated in the operation command generating section and a current position signal fed back from the feed system by a positional loop gain;
• a speed controlling section for generating an electric-current command signal by multiplying a deviation between the speed command signal generated in the position controlling section and a current speed signal fed back from the feed system by a speed loop gain;
• a filtering section for eliminating frequency components in a predetermined frequency band from the electric-current command signal generated in the speed controlling section;
• and
• adjustment means for detecting vibration level and vibrational frequency directly from the electric-current command signal processed by the filtering section, and adjusting a band of frequency components to be eliminated from the electric-current command signal by the filtering section in response to the detected vibration level and vibrational frequency,
• wherein the control apparatus controls a drive motor for the feed system of the NC machine tool based on the electric-current command signal processed by the filtering section.