NRI-Small: A Novel Light-weight Cable-driven Active Leg Exoskeleton (C-ALEX) for Training of Human Gait

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Motorized exoskeletal orthoses are being actively researched today for gait training of stroke patients. These machines are typically designed to apply assistive/resistive forces on the impaired leg to help human subjects to improve walking, similar to what therapists do during training. While a number of such machines have been developed and used for gait training, these studies have only yielded "mixed" results in benefiting stroke patients clinically. The reasons for these disappointing results are the high inertia of the mechanisms, a mis-match in constraints between human and machine, and misalignment of the mechanism joints with the human joints. The proposed work investigates a novel and ground-breaking design of a cable driven exoskeleton to address these shortcomings. Based on extensive study of mechanisms and therapeutic control methods, cables will actuate the moving limbs and will also serve as structural members in tension. The design will consist of an inertial fixed cuff attached to the pelvis and three lightweight cuffs on the thigh, shank, and foot of each leg. This results in an order-of-magnitude reduction in the inertia of the links and eliminates rigid joints which, in turn, eliminates the mis-match and misalignment. Yet, the fact that cables can only pull and not push raises many scientific and design challenges that will be addressed theoretically and experimentally.Broader Impact: Each year, about 700,000 people in the U.S. have an incidence of a stroke and currently there are 4.5 million people in the U.S. living with the after-effects of stroke. This research can directly impact the quality of life of these individuals with potentially better rehabilitative equipment and better rehabilitative results for retraining of their gait. This project will broaden the application of cable-driven robots to the emerging field of "neuro-rehabilitation" and "functional learning." This project will also involve close co-operation with Professor Clement Gosselin's research group at Laval University, who along with the PI, is credited with fundamental developments to the field of "cable robots." The project will also encourage undergraduate involvement in research as well as provide training and examples for a high school teacher/student to incorporate into the local curriculum. The PI has active links with high schools through a college-wide NSF-funded RET program. Several high school teachers and students have worked in the PI's laboratory to identify technologies to improve quality of life of neural impaired subjects.