Designing shoulder prostheses with a small pneumatic actuator driven parallel mechanism for spatial accessibility in daily living use

In this study, several indexes for spatial accessibility were proposed for evaluating the shoulder prosthesis with a small pneumatic actuator driven parallel mechanism in daily living use. Using the spatial accessibility indexes and manipulability indexes, the configuration of the parallel mechanism was optimized. Especially, the effect of biasing spacer and trunk motions on spatial accessibility were taken into consideration. The results showed that biasing spacers could improve the spatial accessibility by moving the center of the working space of the shoulder prosthesis towards the center of two specified spatial regions, which correspond to the expected frequently accessed area and the reachable area for an individual user's upper limb in daily living. And trunk motions could enlarge the working space thus further improve the spatial accessibility.