Characterization of pneumatic muscle actuators and their implementation on an elbow exoskeleton with a novel hinge design

•Development of a pneumatic muscle for an elbow exoskeleton application.•Muscles with lower tensile modulus bladders demonstrated a higher contraction and force characteristics.•Stiffer bladders had lower hysteresis, good load handling capability, but had lower contraction and force characteristics.•The 12 mm styrene-based muscle with larger braided sleeve was the best fit for the elbow exoskeleton application.•The novel hinge provided real-time angular feedback and compensated for the antagonistic nature of the muscle actuator. 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 [Display omitted]