Patent ID: 6657407
Filing Date: 2003-12-02
Classification: G05B,H02H,H02P,Y02P

Abstract:
A method for determining the position of a movable element driven along a travel segment by a shaft of a motor, the method comprising:using a counter to count current ripples contained in an armature current signal of the motor as the motor shaft rotates to drive the movable element along the travel segment; determining the position of the movable element along the travel segment 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, estimating an amount of current ripples expected to be contained in the armature current signal of the motor during the slowdown of the motor shaft; and determining the position of the movable element along the travel segment during the slowdown of drive shaft of the motor based on the estimated amount of current ripples.