Biomimetic Composite Tendon and Pneumatic Actuation for Soft Manipulator: Balancing High Load-Bearing Capacity, Repetitive Precision, and Active Softening Contact Safety

Abstract

Soft manipulator is a prominent research area in the field of soft robotics, but designing a soft manipulator capable of serving human life remains challenging, facing issues such as low motion robustness and poor accuracy. The trunk of an elephant, a unique biological tissue in nature, is characterized by its flexibility, strong load-bearing capacity, and dexterous yet soft tip, distinct from skeletal-dependent movements. Inspired by the thrust--deformation mechanism of the elephant trunk under multi-muscle action, this paper reports a novel composite tendon and pneumatic hybrid-driven tapered soft manipulator that mimics the multi-muscle action of the elephant trunk. In the design, a common Bowden tube is introduced as an artificial tendon to simulate the thrust of elephant trunk muscles. This paper first establishes an equivalent finite element model for Bowden tube tendons, along with an exploration of the impact of constraint ring distribution intervals on tendon buckling during thrust generation. This paper also establishes a finite element model for the entire experimental prototype, validating the effectiveness of Bowden tendon tension and thrust and demonstrating the large deformation curvature and flexible motion space of the soft manipulator. Finally, the paper experimentally tests the stability of repetitive motion, load-bearing capacity, and safety of active softening contact with humans of the soft manipulator, demonstrating that this biomimetic design exhibits not only flexibility and agility but also robustness in motion and precision in accuracy, closely resembling the capabilities of an elephant trunk, and holds promise as flexible supernumerary robotic limbs for mobile or humanoid robots.

Keywords: Biomimetic design, Artificial thrust tendon, Hybrid actuation, Soft manipulator, Finite element simulation, Load-bearing capacity, Active softening safety, Flexible supernumerary limb