METHOD FOR DETERMINING THE ROTATIONAL POSITION OF THE DRIVE SHAFT OF A DIRECT CURRENT MOTOR

摘要

A method for determining the position of a movable element driven by a motor shaft includes using a counter to count current ripples contained in an armature current signal of the motor as the motor shaft rotates to drive the element. The position of the element is determined based on the counted current ripples. Upon power to the motor being interrupted such that the motor shaft slows down during the power interruption and upon the counter being prevented from counting the current ripples contained in the armature current signal of the motor during the slowdown of the motor shaft, an amount of current ripples expected to be contained in the armature current signal of the motor during the slowdown of the motor shaft is estimated. The position of the element during the slowdown of the motor shaft is determined based on the estimated amount of current ripples.