An actuating system includes a driving device fixed to a base part and operatively connected to a movable part. A sensor detects the rotational speed of the movable part at a reference measuring location, and a control system forms a differential of the rotational speed with respect to the time. The formed differential is compared in a comparison unit with a stored differential value which corresponds to a measuring point on a route of movement of the movable part. An obstacle is recognized when there is a difference above a threshold value between the formed differential and the associated stored value.