Fiber Reinforced Elastomeric Enclosures (FREEs) are soft pneumatic actuators that deform in a predetermined fashion upon inflation. They are constructed using a hollow elastomeric cylinder reinforced by two families of helical fibers. This thesis analyzes the deformation behavior of FREEs by formulating a simple calculus of variations problem that involves constrained maximization of the enclosed volume. The model accurately captures the deformed shape (kinematics) for FREEs with any general fiber angle orientation, and its relation with actuation pressure, material properties and applied load (kinetostatics). The accuracy of the model is verified by benchmarking with existing models for a popular McKibben Pneumatic Artificial muscle (PAM) actuator with two helically wrapped families of fibers having equal and opposite orientations. For FREEs with any general fiber orientations and other novel designs with no prior literature, the model is validated experimentally. This model is deemed to be useful in the design synthesis of fiber reinforced elastomeric actuators for any desired motion and force requirement. FREEs are soft, compliant, and have a high power to weight ratio, which makes them suitable for orthotic devices for upper extremities. The second part of the thesis considers the design and fabrication of a soft pneumatic sleeve for arm orthosis that uses a contracting FREE is shown. The sleeve is designed to reduce wrist loads in patients that use crutches for ambulation, thereby reducing the risk of joint injury. It forms an alternate load path between the crutch and the forearm, circumventing the wrist. The constricting force generated by the sleeve on the arm is analyzed by a string model and validated with experiments.
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Design and analysis of fiber reinforced elastomeric enclosures with application in upper arm orthosis
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