Motion control apparatus for induction motor

Claim 1

A motion control apparatus for an induction motor comprising: means for generating first serial pulses having a period according to an instructed speed of said induction motor and for outputting commands resulting in a change of a rotation position of said induction motor; means for deriving the change in the rotation position of the induction motor and generating second serial pulse representing the change in the rotation position; droop counter means for accumulating sums of the first serial pulses and the second serial pulses to continuously obtain a difference between an actual position and a desired motor position; means for obtaining an actual speed of the induction motor based on an occurrence density of the second serial pulses; means responsive to the actual speed for reading out from a table an allowable slip speed |ω s '| predetermined in accordance with a characteristic of said induction motor; means for generating a torque instruction signal on the basis of a difference between an output of said droop counter means and the actual speed; means for continuously obtaining a slip speed |ω s | by using the torque instruction signal, the actual speed and constants based on an equivalent circuit of said induction motor; means for comparing the slip speed |ω s | and the allowable slip speed |ω s '| to control the generation of the first serial pulses such that when |ω s '|≧|ω s |, the first serial pulses are generated in accordance with an inclination of an acceleration/deceleration curve of the rotation selected in advance, and, when |ω s '|<|ω s |, the first serial pulses are generated so as to decrease the inclination of the acceleration/deceleration curve, thereby to control the motion including increment or decrement of the number of rotations of said induction motor with respect to an unit time interval.