Machine tool control device having function of diagnosing malfunction in sensor for detecting one-rotation signal

A machine tool control device for driving a feed axis or a main axis by a motor, comprising:

• a feedback counter for obtaining A-phase and B-phase signals of rectangular waves or sine waves and a one-rotation signal generated whenever the motor or the main axis rotates one turn, the A-phase and B-phase signals and the one-rotation signal being outputted from a sensor for detecting the position or speed of the driven axis or the motor, to calculate a feedback count value that is a count value of the number of feedback pulses generated from the A-phase and B-phase signals;
• a feedback count value storage unit for storing an inter-one-rotation-signal feedback count value that is the feedback count value counted between the two sequential one-rotation signals;
• a reference value storage unit for storing an anomaly determination reference value for determining the presence or absence of an anomaly in accordance with the inter-one-rotation-signal feedback count value;
• and
• an anomaly cause determination unit for determining the cause of the anomaly by comparison between the inter-one-rotation-signal feedback count value and the anomaly determination reference value, wherein
• when the inter-one-rotation-signal feedback count value is higher than the anomaly determination reference value, and when a first error corresponds to an integer multiple of a second error, the anomaly cause determination unit determines that noise disturbs the A-phase and B-phase signals, and
• when the inter-one-rotation-signal feedback count value is higher than the anomaly determination reference value, and the first error does not correspond to an integer multiple of the second error, the anomaly cause determination unit determines that there is an anomaly in the one-rotation signal,
• wherein the first error is an error between the inter-one-rotation-signal feedback count value and a standard count value which is an inter-one-rotation-signal feedback count value when the sensor operates normally, and
• wherein the second error is an error that is calculated from the number of pulses or waves of the A-phase and B-phase signals per rotation as an error being likely to occur whenever noise disturbs the A-phase and B-phase signals.