A Wearable Force-Sensitive and Body-Aware Exoprosthesis for a Transhumeral Prosthesis Socket

Upper limb prostheses are commonly mounted to the human residual limb by a passive socket. By this design, the sensitive residual limb is exposed to high reaction wrenches, which can be a source of medical complications. In this article, we introduce an active force-sensitive robotic socket, which carries the prosthesis, offloads the residual limb, and allows guidance via small interaction forces at the same time. We investigate the feasibility of this concept by a force-sensitive and wearable shoulder exoskeleton, called exoprosthesis when being combined with a prosthesis. We provide a first mechatronics prototype, two floating base controllers, and an analysis of the loads acting on the user body. Simulations and experiments confirm the concept and reveal that the wrench at residual limb can be fully compensated for the static case and by $\approx \text{50}\%$ for the investigated motions. Human-in-the-loop tests are successfully performed by three able-bodied users showing the later real-world use case in a complex grasping situation. Overall, we believe that a force-sensitive robotic socket has the potential to advance prosthetics to a new level as it provides an intuitive and seamless user control interface.