Toward Controllable Hydraulic Coupling of Joints in a Wearable Robot

Abstract

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.

Vector Field Control Methods for Discretely Variable Passive Robotic Devices

“…In a digital hydraulic cobot [14], a set of cylinders with face areas collected into a diagonal matrix A are connected to N joints. The nature of the connection and the moment arms between the cylinders and the joints q are encoded in the Jacobian matrix J 1 (q).…”

“…A discretely variable passive robotic device has the ability to physically constrain motion in certain directions determined by the settings of the device's transmission(s), selecting transmission ratios from among a finite available set. We have previously proposed digital hydraulic transmissions [14] as a method for realizing discretely variable passive robotic devices. Digital hydraulic devices use hydrostatic transmissions in which multiple cylinders span each joint.…”

Upper limb rehabilitation using robotic exoskeleton systems: a systematic review

“…Some of these selected studies focused on exoskeleton assisted therapy versus conventional therapy method [8,22,50,51,57,[71][72][73]. Another studies looked at the effects of the individual robotic device on upper limb rehabilitation following stroke [35,43,46,48,49,58,60,62,63]. Two studies compared the bilateral training method with unilateral training using exoskeleton device [54,55].…”

“…The robotic systems used for upper limb rehabilitation can be studied based on their mechanical structure, control system, and clinical applications. The mechanical configuration [8,[19][20][21][22][23][24][25][26][27]and control systems [28][29][30][31][32][33][34][35][36] have been reviewed previously. A detailed insight on various end effector based system and their application in stroke rehabilitation have also been carried out [37].…”

Influence of bimanual exercise on muscle activation in post-stroke patients

“…Current bimanual therapy relies heavily on specific training devices [20,21]. These devices are based on passive mechanics, in which the system is driven by forces generated by the patient [22][23][24] or by active robotics [25,26] to provide symmetric repetitive motion patterns for arm movement. These devices are, however, unsuitable for investigating the biological mechanisms underlying bimanual motion training because they can only provide simple bimanual motions [27].…”