A Wearable Joint Sensing Device Based on the Inverted Slider Crank

Abstract

The used of conductive fabric (CF) strain sensor to measure joint motion, has recently received many interest in a variety of applications such as robotics, rehabilitation, personal wellness, sports and entertainment. However, one key limitation of existing design is that anthropometric information is required to related the joint parameters to the fabric strain readings, which make the resulting device user specific. This paper proposed an alternative design to overcome the existing limitation based on an inverted slider crank topology. To design the inverted slider crank linkage, we model the human joint as a revolute backbone chain and constraint it with an RPR chain, under specific sensor working range. To study the feasibility of our approach as a joint sensing device, we synthesis and analyze the resulting linkage to achieve specific flexion-extension range of motion (ROM) measurement as required by the wrist, ankle, elbow, and knee joint. Our results show that the proposed sensor topology can effectively measure each joint ROM.