This paper investigates the tradeoffs between design variables important for the development of a mobility support soft exoskeleton for horizontal shoulder adduction. The soft exoskeleton utilizes discreet shape memory alloy (SMA) spring actuators to generate the required torque to move the arm segment, while preserving the qualities of a soft, wearable garment solution. A pilot benchtop test involving varying power input, actuator anchor position, actuator orientation, and added weight, was investigated to evaluate their effects against the degree of motion the soft exoskeleton allows. The results show that the power input, actuator anchor position, and simulated limb weight each affect the ultimate horizontal adduction angle the exoskeleton is able to induce. Further, the project highlights a crucial point in regard to the tradeoffs between functionality and wearability: when actuator orientation was investigated, we found a decrement in functionality (as measured by maximum achievable horizontal adduction angle) when the actuators were constrained close to the body. This shows that when aiming to improve the hypothetical system’s wearability/usability, the effective torque that can be generated is reduced. Together these findings demonstrate important design considerations while developing a wearable, soft exoskeleton system that is capable of effectively supporting movement of the body while more »
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- Proceedings of the 2019 Design of Medical Devices Conference
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- National Science Foundation
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Upper limb mobility impairments affect individuals at all life stages. Exoskeletons can assist in rehabilitation as well as performing Activities of Daily Living (ADL). Most commercial assistive devices still rely on rigid robotics with constrained biomechanical degrees of freedom that may even increase user exertion. Therefore, this paper discusses the iterative design and development of a novel hybrid pneumatic actuation and Shape Memory Alloy (SMA) based wearable soft exoskeleton to assist in shoulder abduction and horizontal flexion/extension movements, with integrated soft strain sensing to track shoulder joint motion. The garment development was done in two stages which involved creating (1) SMA actuators integrated with soft sensing, and (2) integrating pneumatic actuation. The final soft exoskeleton design was developed based on the insights gained from two prior prototypes in terms of wearability, usability, comfort, and functional specifications (i.e., placement and number) of the sensors and actuators. The final exoskeleton is a modular, multilayer garment which uses a hybrid and customizable actuation strategy (SMA and inflatable pneumatic bladder).
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