Toward Controllable Hydraulic Coupling of Joints in a Wearable Robot

• Published in: IEEE transactions on robotics Vol. 34; no. 3; pp. 748 - 763
• Main Authors: Treadway, Emma, Gan, Zhenyu, Remy, C. David, Gillespie, R. Brent
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.06.2018; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Cobots; Computational fluid dynamics; cooperative manipulators; Coupling; Cylinders; Exoskeletons; Fluid flow; Fluid power; haptics and haptic interfaces; Harvesting; Homology; Hydraulic transmissions; Hydraulics; Joining; Manifolds; Medical treatment; physical human-robot interaction; Rehabilitation; rehabilitation robotics; Rehabilitation robots; Robots; Stability; Task analysis; Valves; Wheels; Haptics and Haptic Interfaces; Physical Human-Robot Interaction; Cobots; Cooperative Manipulators; Rehabilitation Robotics
• ISSN: 1552-3098; 1941-0468
• DOI: 10.1109/TRO.2018.2799597

In this paper, we develop theoretical foundations for a new class of rehabilitation robot: body-powered devices that route power between a user's joints. By harvesting power from a healthy joint to assist an impaired joint, novel bimanual and self-assist therapies are enabled. This approach complements existing robotic therapies aimed at promoting recovery of motor function after neurological injury. We employ hydraulic transmissions for routing power, or equivalently for coupling the motions of a user's joints. Fluid power routed through flexible tubing imposes constraints within a limb or between homologous joints across the body. Variable transmissions allow constraints to be steered on the fly, and simple valve switching realizes free space and locked motion. We examine two methods for realizing variable hydraulic transmissions: using valves to switch among redundant cylinders (digital hydraulics) or using an intervening electromechanical link. For both methods, we present a rigorous mathematical framework for describing and controlling the resulting constraints. Theoretical developments are supported by experiments using a prototype fluid-power exoskeleton.