Two Degree of Freedom Automated Prosthetic Wrist

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WPI, MQP, Assistive, Technology, Resource, Center, ATRC, Joint, Prosthetic, Hand, Positioning


The goal of this MQP was to design and develop a prosthetic wrist with two degrees of freedom to enable the user of the prosthetic device to better position his arm for gripping, grasping, and turning items. Current powered prosthetic wrists have one degree of freedom, which allows the user to pronate and supinate the arm, or turn the palm outward and inward, respectively. Though these two motions allow individuals using the prosthetic wrist to turn doorknobs and dials, there are still several daily activities such as combing one’s hair and operating keys that require another degree of freedom. Therefore, a powered prosthetic wrist capable of not only pronation and supination, but also flexion and extension of the wrist with the ability to position the hand to grasp and grip objects could be beneficial to individuals using an artificial wrist. The design team determined that the prosthetic wrist should be compatible with pre-existing prosthetic hands, allow for a realistic range of motion, be constructed to have realistic dimensions, and contain a mechanism to allow the user to know the position of the wrist and return it to the neutral position. The design team considered various types of gears and linkage systems to determine which would best meet the design specifications and be most efficient. The gear allowing for the two axes of motion at the wrist was selected. The final design consisted of gears and rotation bearings within an outer tube. The prosthetic wrist was designed with the intention of being incorporated into an existing arm using screws and fasteners. Testing of the final design found that the wrist did incorporate two degrees of freedom to allow for gripping and grasping purposes and was able to generate appropriate torque outputs with a range of weights.

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