A position detecting and maintaining apparatus for use between a movable article and a movable base member. Track means are provided and extend parallel to the direction of movement of the movable article and guide means are provided for guiding the base member along the track means. A shaft is rotatably supported on the base member and has a lever fixed thereto and rotatable therewith and adapted to engage the article to effect a rotation of the shaft means upon a relative movement between the base member and the article. A spring is provided for urging the lever in a direction opposite to the direction of movement of the base member and the article. An electrical potentiometer is provided for converting the rotational movement of the shaft to an electrical output signal, which electrical output signal controls a servo-valve apparatus for maintaining a uniform relative spacing between the base member and the article.
