An apparatus for adjustably positioning an object of interest is described, and which includes a wave propagator and a wave detector which are both mounted in spaced relation to an object of interest, and which allows determination of a distance between the wave propagator and wave detector and the object of interest during operation; an adjustment device mounted in force transmitting relation relative to the object of interest an which imparts force to the object of interest to maintain the object of interest along a predetermined course of travel, and a controller coupled in controlling relation relative to the wave propagator and the adjustment device, and in signal receiving relation relative to the wave detector.