Design of a Knee Exoskeleton actuated with Artificial Muscles of SMA

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This project presents the preliminary design of a powered exoskeleton for the knee joint, build upon the structural framework of DonJoy’s X-Act Rom Lite - Knee Brace. The device allows exclusively one degree of freedom, intended for the flexion and extension of the lower limb. The actuation mechanism is based on artificial muscles of Nitinol fibers, which are a type of Shape Memory Alloys (SMA). These wires contract 4% of its original length as the temperature rises due to the Joule Effect, when connected to a power supply. Thanks to this phenomenon, the proposed robotic orthosis presents portability, lightness and noiseless performance, in comparison to similar products. The main role of these instruments is to conduct medical rehabilitation therapy for those patients who have suffered from neurological diseases, musculoskeletal lesions or spinal cord injuries. Consequently, the wearer might recover -partially or fully- the movement on the joint. The results from several trials were obtained after mimicking real rehabilitation positions -like sitting, standing or lying down- and are analyzed thoroughly in this thesis. All in all, this prototype proves how the SMA actuators are a viable alternative to create lower extremity robotic devices for rehabilitation.
Knee, Lower limb, Shape Memory Alloys (SMA), Rehabilitation exoskeleton, Powered orthosis
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