Method for determining the rotational position of the drive shaft of a direct current motor

摘要

A method for determining the position of an element driven along a travel segment by a shaft of a motor includes counting current ripples detected in an armature current signal of the motor as the motor shaft rotates to drive the element. A first time interval between when the motor is turned on with power being supplied to the motor and when the first current ripple is detected is determined. A second time interval between when the last current ripple is detected after the motor has been turned off with the power supplied to the motor being interrupted and when the motor shaft stops rotating is determined. First and second current ripple components corresponding to the first and time intervals, respectively, are estimated. The position of the element along the travel segment is determined based on the counted current ripples and the estimated first and second current ripple components.