Faculty Publications
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Item Design and characterization of a pneumatic muscle actuator with novel end-fittings for medical assistive applications(Elsevier B.V., 2021) do Rosario Carvalho, A.D.; Karanth P, N.; Desai, V.Pneumatic muscle actuators (PMA) are a class of soft actuators known for their high power to weight ratio and inherent compliance. The pneumatic muscle's inherent properties make them very favorable for assistive applications (e.g., medical exoskeletons). This study presents a novel end-fitting design that makes the developed pneumatic muscle actuator lightweight, cost-effective, and modular, thus simplifying the process of assembly and maintenance. The pneumatic muscle actuator assembled using the novel end fittings achieves a shorter overall length without compromising its contraction. The pneumatic muscle actuator has been assembled using a commercial bladder and a braided sleeve alongside a pair of 3D printed novel end-fittings. The paper also details the developed actuator's characterization for force and deflection parameters at various operating pressures. A total of four muscle actuators of varying diameters with constant actuation length (100 mm) were developed and tested to showcase the effect of size on the muscle actuator's behavior. The study presented here also involved comparing three mathematical models developed for pneumatic muscles in order to find a model which closely resembles the developed muscle actuator. Finally, the developed pneumatic muscle actuator's behavior is compared with a commercially available muscle to determine the efficacy of the developed muscle's design. The tests showed that the muscle using a bladder of smaller volume but higher tensile modulus had a higher accuracy and stable performance. As the muscle is intended for medical applications, it was also put through an endurance test with realistic loading and pressure conditions, which revealed very promising results. © 2021 Elsevier B.V.Item Characterization of pneumatic muscle actuators and their implementation on an elbow exoskeleton with a novel hinge design(Elsevier B.V., 2022) do Rosario Carvalho, A.D.D.R.; Karanth P, N.; Desai, V.The exoskeleton plays an essential role in the field of physical rehabilitation. Several actuators are used for the exoskeleton application, but the pneumatic muscle actuator has proved to be the best due to its high power to weight ratio, compliance, and safe operation. The objective of this paper involves the fabrication and experimental characterization of a pneumatic muscle actuator to actuate an exoskeleton for the elbow joint. This paper presents the development and testing of twelve pneumatic muscles of varying materials and sizes, to find the best combination to suit the intended application. The characterization process involved several tests, which related force, deflection, and pressure at various loading conditions. A modular test rig was developed to conduct all the tests with minor adjustments to the test setup. The study also involved designing and developing an elbow exoskeleton to test the pneumatic muscle in the real-world scenario. The exoskeleton is designed with a novel hinge to compensate for the antagonistic nature of the pneumatic muscle actuator. The tests showed the muscles with higher tensile modules bladders having a lower hysteresis and better load handling capability, but these suffered from lower contraction and force characteristics. The styrene-based muscle with a 12mm bladder (S12LB) showed the best force and deflection characteristics at various pressures and loading conditions. The styrene bladder has a modulus closer to the skeletal muscle, therefore demonstrating higher compliance and making it a preferred choice for the exoskeleton application © 2022