A stepper motor driving a driven member is calibrated by periodically driving the member from its current operational position to an end stop of the driven member's total travel range; however, the driven member approaches the end stop in a series of ever-shorter travel segments. The first travel segment is less than 1/3 the total travel range to compensate for a possible sudden speed reversal, which can be accidentally triggered by the driven member reaching and bouncing off the end stop. Limiting the commanded first travel segment to less than 1/3 the total travel range prevents the driven member from reaching an opposite travel limit should the driven member suddenly reverse direction at three times the normal forward speed, wherein such triple speed is characteristic of reverse-speed situations.