Geometric design of eight-bar wearable devices based on limb physiological contact task

• We formulated a methodology for eight-bar wearable devices design based on limb contact task.
• Two RR links are added to a parallel 3R chain with one 3R based on human limb dimensions.
• Limb contact task of the fingertips are specified as first and second order motion.
• The approach is applied to design a passively actuated index finger wearable device.

This paper describes a geometric design method for the motion generation of mechanical wearable devices based on desired limb physiological contact task, parametrized by first and second order motion specifications. Specifically, our approach combines the higher order motion task specifications with anthropometric back-bone chain to synthesize planar eight-bar linkages that achieve the desired motion task. The method is demonstrated by an example that offers a novel alternative approach for wearable devices design: a comprehensive systematic process to create devices, based on a backbone chain that is sized according to the physical dimensions of the human limb. Once it is ensured that the backbone chain motion is close to the physiological one, the rest of the multi-loop wearable device is designed. In the end of the process the wearable device is attached, so that the backbone chain parallels the human's limb itself to provide the skeletal structure for the limb yet passively follow its motion. This results in mechanical devices with compact size, minimal actuation and better wearability.