Cross-Coupled Pneumatic–Cable–Driven Soft Robotic Arm for Overhead Manipulation

Overhead-suspended robotic arms require both high payload capacity and agile motion, yet soft arms have difficulty achieving these capabilities simultaneously. Conventional approaches have relied either on using multiple anchored soft arms or reinforcing the structure, which inevitably increases stiffness and compromises compliance. We present a three-degree-offreedom pneumatic-cable-driven soft arm that achieves vertical lift with fast actuation, for both soft objects and high payloads while maintaining compliance for safe human interaction. Inspired by human lifting strategies, the arm performs a twophase motion: first forming a compliant S-shaped deformation in selectable vertical planes for under-grasping, and then axially straightening for efficient load transfer. Coordinated pressurization of three pneumatic muscles reproduces both concentric and eccentric contraction behaviors, enabling smooth transition from compliant grasping to stiff lifting. The arm’s trimmed helicoid architecture and cross-coupled cable routing allow each actuator to influence multiple joints and fingers, functioning analogously to multi-articular muscles. The lightweight 3Dprinted prototype was experimentally tested for lifting payloads of up to 10 kg and manipulating soft objects, demonstrating adaptable and robust overhead operation suitable for industrial, agricultural, and assistive applications.