Monolithic TPU flexure joints for confined-space tendon-driven robotic arms

Abstract

Traditional rigid robotic manipulators operate precisely and reliably in structured environments; however, they are constrained by limited degrees of freedom and structural rigidity when deployed in complex and restricted spaces. Inspired by biological models such as octopus arms and elephant trunks, soft robotic arms offer a viable alternative; however, they often suffer from compromised flexibility due to conventional joint mechanisms, including inflatable chambers and ball joints. This paper introduces a novel approach to enhancing the manoeuvrability and safety of flexible soft robotic arms by integrating a 3Dprinted flexure joint designed using thermoplastic polyurethane (TPU) filament and fabricated via Fused Deposition Modelling (FDM). The flexure joint serves as a connector between flexible segments, providing a reliable, low-friction connection that enhances adaptability and dexterity while addressing the limitations of traditional rigid joints in confined spaces. Experiments demonstrate a maximum bending angle of 29.2° under a force of 15.5 N, with a linear force-displacement relationship that ensures predictable performance. Additionally, a kinematic model is developed to describe the motion dynamics. The results validate the joint’s applicability in tendon-driven flexible robotic systems, improving their operational capabilities in confined spaces and advancing the field of soft robotics.