Patent ID: 8531149
Filing Date: 2013-09-10
Classification: G05B

Abstract:
1. A control device which, in a machine tool which controls a servo motor that drives a workpiece or a tool according to an instruction from a numerical control device, controls the servo motor in the event of power failure, the control device comprising: a servo motor amplifier, which drives the servo motor; a power failure detecting unit, which monitors an input power supply, and, in turn, when power failure is detected, instructs the servo motor amplifier to decelerate and stop the servo motor while maintaining a controlled state; an alarm threshold changing unit, which, in response to a power failure detection signal from the power failure detecting unit, changes an alarm threshold value for direct current voltage reduction abnormality of the servo motor amplifier from a value for a normal operation to a lower value for power failure, wherein application of electricity to the servo motor is suspended when direct current voltage becomes lower than the alarm threshold value; and a retraction operation instructing unit, which, in response to the power failure detection signal from the power failure detecting unit, instructs the servo motor amplifier to perform a retraction operation of a small distance which is defined in advance.