Design and Modeling of a Cable-Driven System for Delivering Balance Perturbations
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This thesis explores the design and modeling of a cable-driven system able to provide balance perturbations for rehabilitation purposes. These balance perturbations can be used for both rehabilitation and prevention of falls. Many current rehabilitation strategies focus on exoskeletal designs with rigid links. These systems are costly, can inhibit subjects' movements, and can induce subjects to make less effort by not challenging balance enough in an effective way. Cable-driven rehabilitation is an alternative solution that can be more cost-effective as well as addressing some of the issues inherent in previous systems.The cable-driven system developed in this thesis provides balance perturbations with a stepping force in one direction via a DC motor that is connected through a cable and a load cell to a harness worn by the subject. Before testing on human subjects, the motor was tested by attaching the system to a heavy object to measure the force of the stall torque during various duty cycles. Through this testing, the motor was found to provide perturbations of up to a maximum of approximately 100 N within 130 milliseconds. Once the force of the stall torque was determined, the system was tested on eight healthy adults with the harness secured to the participants waist and the cable pulling for 0.5 seconds in the posterior direction parallel to the floor. When tested on human subjects, the average measured force was up to approximately 17% lower than the desired force, but the control panel can be recalibrated according to the force measured for improved accuracy in the future. Overall, the system was shown to be a successful method for providing waist-pull force perturbations to human subjects.