Development of a Spherical 2-DOF Wrist Employing Spatial Parallelogram Structure

A spherical two-degree-of- freedom wrist adapting the structure of the spatial parallelogram is proposed. A U type extended link out of three UU type limbs of the spatial parallelogram is selected as an output link. As a result, the wrist can be interpreted as being formed by combination of a U type limb and a (2-UU)+U type hybrid limb. Screw theory is employed to analyze its first-order kinematic model. Then a compact wrist prototype suitable for wrist module supporting the robot hand is designed and implemented. Finally, experiments with the prototype confirm that the wrist has a very high potential application for wrist modules in terms of dexterity and maximum load handling capacity.