Force range extension and high force accuracy with pinching support device by presenting haptic sense based on fingertip sensitivity

This paper introduces a mechanical structure of a pinching force support device in order to extend force range and to improve force accuracy based on fingertip sensitivity when the device augments human's pinching force more than twice his/her maximal pinching force. High force accuracy is an important factor to grasp an object stably and not to damage the grasping object. In the previous research, our exoskeleton achieved high pinching force accuracy at the same level of human ability and extended range of the human pinching force to about twice by 46% reduction of affecting force to the finger part from the exoskeleton. However, 46% load reduction of the exoskeleton is not enough to exert more than twice human pinching force which is required by some workers because a user's sensitivity to recognize change of the force is getting worse by fingertip deformation. For extension of the pinching force range maintaining high force accuracy, the characteristics of fingertip sensitivity is considered so that the wearer could estimate the support force precisely. Then we developed a new exoskeleton which reduces affecting force to 67%. Through experiments, our exoskeleton can augment a user's force by about triple, maintaining its force accuracy at the same level of human ability.