METHOD OF CONTROLLING POSITION OF ORIGIN OF ROBOT ARM

PURPOSE: To prevent a runaway of an arm and damage and the like in a workpiece by automatically measuring a pulse number of a pulse generating means arranged in a motor from just after the actuation of an origin limit switch installed to the robot arm until just before generation of zero-pulse of a servomotor, comparing the pulse number with a set value, and returning the arm to the origin position. CONSTITUTION: In detection of an origin position of a robot arm 10 by means of an origin limit switch 14, a zero-pulse generating means and a continuous pulse generating means 30 are arranged in a servomotor 22 driving the robot arm. From just after the actuation of the origin limit switch 14 until an appearance of the next zero-pulse Po , a number of pulses obtained from the continuous pulse generating means 30 is counted. Then, the counted pulse number is compared with a reference pulse number showing that the robot arm is in the accurate origin position, so that it is determined whether the robot arm 10 is in the accurate origin position or not. If the robot arm 10 is not placed in the accurate origin position, the robot arm 10 is returned to the origin position, and a runaway of the robot arm 10 can be prevented.