Pneumatic Positive-Pressure Soft Actuator: Design, Fabrication, and Integration into a Novel Robotic Arm

Abstract

This thesis presents the design, fabrication, and experimental validation of a positive-pressure origami-inspired soft pneumatic actuator (PP-OSPA) and its integration into a 4-degrees-of-freedom PP OSPA driven robotic arm (PRA). A novel self-tightening endcap and modular external ribs were introduced to enable safe operation at positive pressure while simplifying assembly. The fabrication process was streamlined using a redesigned mold, better controlled heating, and a rotating heat-treatment phase to improve safety and reduce fabrication difficulty. Four actuator lengths were built and characterized. Measured stroke percentages decreased as actuator length increased. Blocked-force testing up to 400 kPa yielded maximum forces of 642–702 N and peak force-to-weight ratios up to 270.4, surpassing prior OSPA baselines. A durability test of two 8-unit actuators cycled a 25.3 kg load for 19,000 ten-second cycles with negligible degradation until an external-rib fracture caused leakage, identifying the rib as the life-limiting element under these conditions. A PRA was designed, manufactured and tested to demonstrate the practicality of the PP-OSPAs. Structural plates and key components were sized by FEA, and hand calculations. Using topology optimization, nine parts were weight-reduced with an average mass reduction of 26.3%. Assembled arm tests with a 5.8 kg payload showed that all four joints produced end-effector linear accelerations exceeding the acceleration target. The results also identified significant torque losses due to friction. Collectively, the PP-OSPA design, its streamlined manufacturing, and its validation in a robotic arm, demonstrate a viable path to safe, lightweight, and high-force soft actuation for collaborative manipulation, while clarifying design trade-offs and directions for future research.