Apparatus and method for automatically detecting and compensating for a backlash of a machine tool

1. A method of detecting a backlash which occurs by reversing a motor of a transfer system of a numerical control machine tool, the method comprising:

turning off a backlash acceleration function of the numerical control machine tool and setting a backlash correction amount parameter to be zero;

transferring a transfer table of the transfer system to a reference position;

reversing a servomotor;

measuring a torque variation of the servomotor of the transfer system;

recording the torque variation of the servomotor in a memory buffer;

detecting a torque peak in which an absolute value of torque is placed at a peak based on the recorded torque variation of the servomotor;

determining a backlash value by calculating a distance that an output shaft of the servomotor is transferred at the detected torque peak;

turning on the backlash acceleration function of the numerical control machine tool; and

recording the determined backlash value in the backlash correction amount parameter of the numerical control machine tool,

wherein the measuring and recording of the torque variation of the servomotor includes transferring an output shaft of the servomotor at a slower speed after reversing the motor than before reversing the motor, and measuring and recording torque of the servomotor at each position where the output shaft thereof is transferred, and the detecting of the torque peak in which the absolute value of the torque is placed at the peak by observing the torque variation of the servomotor includes detecting a peak by comparing an absolute value of torque at each position where the output shaft is transferred with an absolute value of torque at a previous position, and

wherein the determining a backlash value by calculating a distance that an output shaft of the servomotor is transferred at the detected torque peak includes determining a backlash value as the distance moved by the servomotor from a point where an inversion of the servomotor starts to a peak of the torque at which the absolute value of the torque of the servomotor is at a peak.

2. The method of claim 1 , further comprising:

detecting once more the backlash value in the opposite direction to a direction in which the backlash value is detected.

3. A numerical control apparatus having a backlash detection function configured to detect a backlash which occurs by reversing a motor of a transfer system of a numerical control machine tool, the apparatus comprising:

a memory buffer configured to record a torque variation of a servomotor, wherein the numerical control apparatus is programmed to detect a torque peak in which an absolute value of torque is placed at a peak by observing the torque variation recorded in the memory buffer, and programmed to determine a backlash value by calculating a distance that an output shaft of the servomotor is transferred at the torque peak,

wherein the numerical control apparatus is programmed to transfer the output shaft of the servomotor at a slower speed after reversing the motor than before reversing the motor, measure torque of the servomotor at each position where the output shaft thereof is transferred, and record the measured torque in the memory buffer, the memory buffer is configured to record an absolute value of torque of the servomotor at each position where the output shaft thereof is transferred, and the numerical control apparatus is programmed to detect the torque peak by comparing an absolute value of torque at each position where the output shaft thereof is transferred with an absolute value of torque at a previous position, and

wherein the numerical control apparatus is configured to determine a backlash value as the distance moved by the servomotor from a point where an inversion of the servomotor starts to a peak of the torque at which the absolute value of the torque of the servomotor is at a peak;

wherein the numerical control apparatus is further programmed to, before recording the torque variation of the servomotor:

turn off a backlash acceleration function of the numerical control machine tool;

set a backlash correction amount parameter to be zero;

transfer a transfer table of the transfer system to a reference position; and

reverse the servomotor; and

wherein the numerical control apparatus is further programmed to, after the determining of the backlash value:

turn on the backlash acceleration function of the numerical control machine tool; and

record the determined backlash value in the backlash correction amount parameter of the numerical control machine tool.

4. The numerical control apparatus of claim 3 , further comprising:

a correction parameter storage unit configured to store the backlash correction amount parameter, wherein the numerical control apparatus is programmed to record the determined backlash value in the correction parameter storage unit.

5. The numerical control apparatus of claim 3 , wherein the numerical control apparatus is programmed to detect once more the backlash value in the opposite direction to a direction in which the backlash value is detected.