Wearable Sensors in Prosthetic Socket

Abstract: There is a great interest among researchers and clinicians to monitor pressure distributions within prosthetic sockets. Such an application may allow the assessment of the user's comfort and identify problematic areas inside the socket. The sensor that is used within such an application is the Force Sensitive Resistor (FSR). In our research, two types of those FSR's; QTSS (Quantum Technology Supersensor) prototype and Interlink FSR, were tested under different static and cyclic loading conditions to compare sensor properties namely hysteresis, drift and repeatability. The sensors were placed on two types of surfaces; silicone shore 20 A and plexiglass, in order to study the effect of hardness on the performance of the sensors. QTSS performs its worst with 109.5 percent static drift under silicone surface with 185 kPa. Its performance significantly improves under a higher load for plexiglass, with 5.4 percent drift at 348 kPa. Interlink, on the other hand, performs relatively well in both cases, with a highest recorded percentage static drift of 3.2 percent with a silicone surface and a pressure of 185 kPa. Moreover, it was shown that not allowing the sensor to rest between load application had a positive effect on the QTSS, as it recorded a drift of 3.1 percent on plexiglass at a pressure of 348 kPa. QTSS recorded worse performance for hysteresis as well as repeatability than the Interlink FSR. Finally, a sensor matrix was fabricated with the QTSS in order to create a pressure-sensing map that was placed underneath the shoes as one participant walked. The results looked promising as clear identification of at least 3 phases within the gait cycle. It needs to be stated that the QTSS sensor used for this project is an early prototype and many modifications have been made to this sensor since the start of this thesis. Therefore, new study should be performed on this sensor before drawing any firm conclusions on its performance.