Patent ID: 8310185

Claim:
A method for determining an actuating quantity of a mechanically commutated DC motor in an actuating device for a motor vehicle, wherein the DC motor has, as a result of mechanical or electromechanical modification, a standard ripple pattern that includes at least one index ripple in each motor cycle or motor half cycle that is distinguished with respect to an amplitude, a duration, and/or a position in time, the method comprising: measuring the motor current and the motor voltage during an operation of the DC motor; calculating a back electromotive force from the measured motor current and the measured motor voltage via a motor model; extracting an AC component corresponding to the current ripples from the back electromotive force; detecting the current ripples from the AC component; identifying the index ripple in at least one motor cycle or motor half cycle; counting all of the identified current ripples as a measure of the actuating quantity or a change therein; and correcting the count result when the index ripple is not counted at the expected position.