Design & Development of a Cybernetic Rehabilitative Hand-Wrist Exoskeleton

Abstract:

Robotic devices are excellent candidates for delivering repetitive and intensive practice that can restore functional use of the upper limbs, even years after a stroke. Rehabilitation of the wrist and hand in particular are critical for recovery of function, since hands are the primary interface with the world. However, robotic devices that focus on hand rehabilitation are limited due to excessive cost, complexity, or limited functionality. A design and control strategy for such devices that bridges this gap is critical. The goals of the research effort are to analyze the properties and role of passive dynamics, defined by joint stiffness and damping, in the human hand and wrist during grasping and manipulation, and then mimic such properties in a wrist-hand exoskeleton for stroke rehabilitation. The project will culminate with device testing in collaboration with rehabilitation clinicians. A significant problem in robotic rehabilitation is how to provide assisted movement to the multiple degrees of freedom of the hand in order to restore motor coordination and function, with a system that is practical for deployment in a clinical environment. Armed with a clearer understanding of the mechanisms underlying passive dynamics and control of systems exhibiting such behavior, this project will inform the design of more effective wrist/hand rehabilitation devices that are feasible for clinical use. In addition, the proposed project will create a unique interdisciplinary environment enabling education, training, and co-advising of graduate students, undergraduate research, and significant and targeted outreach activities to underrepresented groups in science and engineering. In the second year of the project, the PIs have made significant progress towards the goal of an integrated wrist-hand exoskeleton for robot-assisted stroke rehabilitation. Specifically, the team has completed modeling and simulations of the kinematics and dynamics of an index-finger exoskeleton, and prototyping of the system. A virtual prototyping framework has been developed to facilitate exoskeleton design and controls. Additionally, a methodology for fast and robust estimation of finger pose using motion capture data has been established. For the wrist portion of the exoskeleton, the team has developed an assist-as-needed adaptive controller for effective human-robot interactions, a series elastic actuator for the RiceWrist, a force sensing grip for the RiceWrist, and completed system characterization and clinical trials with the RiceWrist-S rehabilitation robot in subjects with incomplete spinal cord injury. Several outreach activities have also been undertaken, including laboratory tours for K-12 groups of underrepresented students at both the University of Texas and Rice University and course development.