Patent ID: 7230401

Claim:
An apparatus for controlling an electric motor provided to drive a movable object such that a detected actual amount of motion of a movable portion of said electric motor or said movable object coincides with a target amount of motion, comprising: a pulse generator operable to periodically generate signal pulses such that each of the signal pulses is generated each time said movable portion of said electric motor or said movable object is driven by a predetermined amount; an edge counter operable to count the number of at least one of a rising edge and a falling edge of said signal pulses generated by said pulse generator, a control-condition changing device including (a) a target-motion-amount setter operable to set said target amount of motion of said movable portion or said movable object, (b) a resolution selector operable to select one of different manners of counting said signal pulses by said edge counter, for thereby selecting a degree of a resolution of detection of said actual amount of motion, depending upon said target amount of motion set by said target-motion-amount setter, and (c) a target-count calculator operable to calculate a target number of the edges of said signal pulses which corresponds to said target amount set by said target-motion-amount setter, on the basis of said degree of the resolution of detection selected by said resolution selector, and a feedback motor controller comparing the number of the edges of said signal pulses counted by said edge counter with said target number of the edges calculated by said target-count calculator, and performing a feedback control of said electric motor for coincidence of said number of the edges of said signal pulses counted by said edge counter with said target number.