Study of a Hybrid Actuated Exoskeleton for Upper Limb Rehabilitation

In this paper, an upper arm rehabilitation exoskeleton is studied. An appropriate solution is sought for the exoskeleton design and actuation that provides transparency and natural safety as well as sufficient force and performance. To achieve this, a hybrid actuation with back-drivable electric and pneumatic drives is studied. A hybrid actuation controller is introduced, in which pneumatic drive takes care of the initial force response, and the electric drive complements the pneumatic drive. In the paper, the feasibility of the basic therapy modes "patient in charge" and "robot in charge" is simulated. An approach for dynamic estimation of elastic propulsion in the second joint through imposed motions is used. The influences of the inertial, frictional, gravitational, and elastic forces that resulted from the hand and the exoskeleton impedance are reported. The pneumatic drive's influence as an elastic balance of the gravitational forces is considered. Finally, a conclusion and discussion are added.