Development of a compact wrist mechanism with high torque density

This paper proposes a new wrist mechanism for robot manipulation. To develop multi-dof wrist mechanisms that can emulate human wrists, compactness and high torque density are the major challenges. Traditional wrist mechanisms consist of series of rotary motors that require gearing to amplify the output torque. This often results in a bulky wrist mechanism. Instead, large linear force can be easily realized in a compact space by using lead screw motors. Inspired by the muscle-tendon actuation pattern, the proposed mechanism consists of two parallel placed linear motors. Their linear motions are transmitted to two perpendicular rotations through a spherical mechanism and two slider crank mechanisms. High torque density can be achieved. Static and dynamic models are developed to design the wrist mechanism. A wrist prototype and its position control experiments will be presented with results discussed. The novel mechanism is expected to serve as an alternative for robot manipulators in applications that require human-friendly interactions.