A controlled relative motion system comprising a base support, a manipulable support, and a plurality of hinged doubled pivoting links rotatably coupled to the base support and rotatably coupled to the manipulable support. A plurality of force imparting members has at least one coupled to one of the plurality of doubled pivoting links so as to be able to cause it to rotate. Also, at least one is coupled to the base support so as to be able to cause that base support to move toward or away.This joint can be used with a similar control joint, coupled thereto by coupling shafts held apart by a slidable separator, to form an extended length inserter for inserting an object positionable by the insertion joint in an obstructed location reached along a constricted passageway. These structures, positioned within a barrel, can rotate together but an activator slider, positioned at least partially about that barrel though not rotatable therewith, is coupled to the separator to cause sliding thereof.
