A High-Strength, Highly-Flexible Robotic Strap for Harnessing, Lifting, and Transferring Humans

Safely harnessing and lifting humans for transfer is a challenging unsolved problem for current robots because of the high forces and gentle interaction necessary to do so. Straps, however, are highly beneficial for manually performing this task primarily because of their simultaneously high tensile strength and high compliant bending flexibility. We propose the Robotic Strap, a novel concept and design for a new type of manipulator that can passively harness and lift humans safely as straps can, as well as actively articulate itself around the human into the desired harnessing configurations. The passive structure is characterized by the high tensile strength and bending flexibility of straps. The design consists of a hyper-articulated backbone with rolling-contact joints fastened by dual-pulley cord mechanisms, and soft thin McKibben artificial muscles embedded along its length that collectively actuate the joints. We present the concept, framework, realization, and implementation of the Robotic Strap design, as well as model and experimentally validate the key characteristics. The prototype has a tensile load capacity of 1314.0 N, a maximum joint bending resistance of
$<\! 0.1$
Nm, and successfully demonstrated safe and effective harnessing and lifting of three human participants without any manual intervention.