METHOD FOR DETECTING POSITIONAL DEVIATION FOR NUMERICALLY CONTROLLED STEP MOTOR

PURPOSE:To detect the positional deviation of a step motor by judging whether a returned position is an origin position or not each time when the step motor is returned to the origin position. CONSTITUTION:A disk 3 is fixed to the rotation shaft 2 of the step motor 1 and an origin hole 4 is formed in the vicinity of the periphery of the disk 3. The hole 4 is photoelectrically detected by an origin detector 5, an origin detection signal from the detector 5 is inputted to an NC device 8 and a programmable controller 9 and the whole system is controlled by the controller 9. Namely the controller 9 judges whether a light penetration signal is inputted from the detector 5 or not, and when the signal is inputted, stores the completion of origin determination. If the light penetration signal is not inputted, the system is stopped and the motor 1 is reversed only by the radius of the hole 4 to correct the origin.