A robot including an end-effector and a robot arm having a proximal link, a distal link, and a joint assembly for controlling the relative position of the two links. The joint assembly includes an actuated linkage joint including a pair of stops and a passive linkage joint including a mechanical positioner for the end-effector located between the stops. The pair of stops are configured to constrain movement of the mechanical positioner to thereby constrain the ability of a user to manipulate the end-effector outside a predetermined range of motion and permit movement of the end-effector within the predetermined range of motion. The drive mechanism is configured to control a location of at least one stop of the pair of stops based on a position of a virtual object in a virtual space. The joint assembly is one of a prismatic joint assembly and a revolute joint assembly.
