Testing of an Electronic Controlled Prosthetic System to Reduce Volume Limb Loss

Abstract

Residual limb shrinkage is a major concern for prosthetic users with below the knee amputations. The remaining limb will shrink as the fluid is squeezed out as an amputee walks and applies forces to the remaining limb throughout the day. This shrinkage can lead to a loss of orientation control, uncomfortable socket fit and possibly limb tissue damage. Vacuum control is the leading method for dealing with the limb shrinkage but lacks fine control. The system proposed uses electromagnets to add regional control while also being used to help with suspension of the limb. The rest of the system consists of pressure sensors, a microcontroller, and additional circuits to amplify the sensor outputs and control the amount of power to the magnets. The microcontroller reads the decreased pressure and sends additional power to the magnets of that region and vice versa. A prototype system had already been devised and initial tests were done on it. However the component used to drive the electromagnets was overly complex and limited in the number of magnets that it could drive. To replace this component a simple driving circuit was devised and as many as 12 of these circuits would be able to fit onto the prototyping breadboard. The controllers coding had also been started but it too was more complicated than it needed to be. The arduino control code was simplified and expanded to control 8 magnet/sensor pairs. To tests if our proposed system could work as a suspension system, we conducted two tests. The first was a tension test that would see if the magnets could suspend the weight of the limb and test the control system within the socket. The second was a pressure test to check the responses of the control system. Both test showed that the control system was working properly and that the magnets would be enough to act as a suspension system for the prosthetic limb. However, while building and testing the prototype it was concluded that while the control system and the electromagnets work as proposed, the electromagnets are large and cumbersome. Future work using the newer technology of electrostatic adhesion was proposed. It would use the same control idea of this system, to achieve a less bulky design.