A Grasp Strategy with Flexible Contacting for Multi-fingered Hand Rehabilitation Exoskeleton

Abstract

To recovering the functions of hand after stroke, many hand exoskeletons and their control methods are developed. However, less research involves in the multi-fingered grasping. There are two primary problems: the fingers are correlative in the movement and the contacting part, the human finger, is flexible . This paper presents a method, which takes not only all the fingers but also their mechanical impedance into a dynamic system. The method is divided into three levels. First level, grasping planning, the desired interface force of each finger is derived by the geometric and external force information of object. Second level, multi-fingered coordinate force control, we see each finger’s impedance as a second-order subsystem to model an integrated coordinate dynamic system. Third level, single finger force control, execute the position and force command calculated in middle level by each finger, which has been presented in our early research. To verify the method, we set an experiment to grasp an apple assisted by a three fingers (thumb, index finger, and middle finger) exoskeleton. The results illustrate the effectiveness of the proposed method and also point out the direction for further research.