Abstract: A functional prosthesis socket should be safely wearable and be able to transfer force or movement between weight-bearing stump and prosthesis. This requires the man-machine interface in the socket to be both flexible and stiffer, which is apparently contradictory in its design. To solve this problem, a new design concept to apply the clamping pressure on stump only in needs is proposed, so the stump soft tissue can avoid longtime overload. To realize this concept, a pressure-adjustable chamber with negative stiffness is designed to form pressure units in sockets. The feasibility of the chamber in meeting the rapid switching the interface’s mechanical property from soft to hard is theoretically studied. Negative stiffness of these pressure units makes it easier to adjust the tightness of soft tissue compression, which means the driving force needed can be lower and the actuator can be smaller, and provides the socket with the property of overload protection. A physical model of prosthesis socket with four pressure-adjustable chambers is fabricated for the experimental confirmation of the conceptual design. Promising results are obtained both in its pressure-adjustability and response speed. The new design can help prosthesis socket gain high function transitivity and comfort.

Key words: Human-machine interface, Negative stiffness, Pressure-adjustability, Prosthesis socket