Kinematic Design of a Three Degree of Freedom Parallel Hand Controller Mechanism

This paper presents the kinematic design of a 10 link “inparallel” mechanism for use in a three degree of freedom forcereflecting haptic interface. The mechanism linkage couples three coplanar rotary electric motor shafts to the endpoint grasped by the human operator. The linkage permits all motor housings to be supported on a common base, thereby reducing the inertia and weight that the interface actuators and human operator must support and move. Furthermore, because only rigid links and rotary ball bearings are used, the linkage avoids the compliance, friction, and/or backlash associated with other types of transmission elements. The linkage workspace is bounded by the singular sphere of maximum reach and separated into two hemispheres by singularities in the plane of the motor shafts.