Toward controllable hydraulic coupling of joints in a wearable robot

Emma Treadway, Zhenyu Gan, C. David Remy, R. Brent Gillespie

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)748-763
Number of pages16
JournalIEEE Transactions on Robotics
Issue number3
StatePublished - Jun 2018
Externally publishedYes


  • Cobots
  • cooperative manipulators
  • haptics and haptic interfaces
  • physical human-robot interaction
  • rehabilitation robotics

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Computer Science Applications
  • Electrical and Electronic Engineering


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