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

A method for determining the position of a movable element driven along a travel segment by a shaft of a motor, the method comprising:

• counting current ripples detected in an armature current signal of the motor as the motor shaft rotates to drive the movable element along the travel segment;
• determining 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;
• determining 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;
• estimating a first current ripple component corresponding to the first time interval;
• estimating a second current ripple component corresponding to the second time interval;
• and
• determining the position of the movable element along the travel segment based on the counted current ripples and the estimated first and second current ripple components.