Electromagnetic suspension system for prosthetic limbs that compensates for residual limb shrinkage

M.S. University of Hawaii at Manoa 2014.Includes bibliographical references.When an amputation of a lower limb occurs, forces due to walking are absorbed by the soft tissues of the residual limb. Due to the soft tissues of the limb no being accustomed to handling such high forces, one of the major issues that occurs is residual limb shrinkage. As the amount of pressure fluctuates, so does the balance between the fluids in the body. Shrinkage of the limb can lead to many issues such as damage to the limb and an uncomfortable socket fit. Currently, vacuum suspension is the leading method to compensate for limb volume changes. However, vacuum suspension has many flaws as well. There is a need for a new prosthetic suspension system with the capability to adjust and control the pressure at different points in the prosthetic. In this study, a new magnetic suspension system for lower limb prosthetics was designed and tested. This magnetic suspension system for lower-limb prosthetics uses electromagnets to control the amount of force exerted on the residual limb. When the electromagnets are turned on, they will attract the material on the liner, thus creating a secure attachment. The design incorporates an Arduino microprocessor and a motor driver to control the amount of negative pressure by the electromagnets. In this study, the physical model of the socket was prototyped and the strength of the electromagnetic suspension system was tested in an Instron testing machine. An amplified circuit was designed to control the electromagnetic attractive force based on the output of force sensors attached inside the socket. As the pressure decreased in the socket due to limb shrinkage, the electromagnets were programmed to inversely increase attractive force. The Arduino microprocessor and motor driver were used to adjust the power delivered to the electromagnets. This feedback loop was tested to ensure proper function. After reviewing all the results, it was found that an array of electromagnetics provided adequate force for attachment of the socket to the liner. The system was also capable of varying the attractive forces at different points based on the force sensor output. This research sets a completely new direction in the area of prosthetics, forever changing what we already know about prosthetics