Patent ID: 8072173

Claim:
A servo motor monitoring apparatus equipped in a servo motor control apparatus which controls a servo motor based on a present position detected by a position detecting member attached to the servo motor, the servo motor monitoring apparatus comprising: a magnetic pole position calculating member to extract a magnetic pole position signal of the servo motor from a motor drive line connected to the servo motor; a present position signal inputting member to receive an input of a present position signal of the present position from the position detecting member attached to the servo motor; and a monitoring member to monitor an operation of the servo motor based on two types of signals of which are the magnetic pole position signal and the present position signal of the servo motor, to compare the operation monitored based on the magnetic pole position signal with the operation monitored based on the present position signal, and to output a stop instruction signal for cutting off a power supply to the servo motor when detecting disagreement on the operation of the servo motor.