Cross-wire assist suit concept, for mobile and lightweight multiple degree of freedom hip assistance.

In this paper, we present our cross-wire assist concept, for assisting a single joint in multiple degrees of freedom. It is comprised of four motor driven Bowden cable actuators (wires) per assisted joint, with the wires crossed over each other at the front and rear. Simulation results show that selectively actuating a subset of these wires allows torque to be generated in 6 directions, with the torque magnitude dependent on joint angle. We have built a fully wearable prototype of our assistance device for both hip joints, with 8 high-speed and independently controllable actuators each providing force up to 100 N. The prototype has a total mass of 9.3 kg, and is shown in motion capture testing to generate movement in 6 directions around the users joint, including internal and external rotation. Mobile, multi-degree of freedom assistance cross-wire system will enable assistive devices to better match human movement, allowing support and rehabilitation in tasks beyond straight line walking.

Power-efficient low-temperature woven coiled fibre actuator for wearable applications.

A fibre actuator that generates a large strain with high specific power represents a promising strategy to develop novel wearable devices and robotics. We propose a new coiled-fibre actuator based on highly drawn, hard linear low-density polyethylene (LLDPE) fibres. Driven by resistance heating, the actuator can be operated at temperatures as low as 60 °C and uses only 20% of the power consumed by previously coiled fibre actuators when generating 20 MPa of stress at 10% strain. In this temperature range, 1600 W kg-1 of specific work (8 times that of a skeletal muscle) at 69 MPa of tensile stress (230 times that of a skeletal muscle) with a work efficiency of 2% is achieved. The actuator generates strain as high as 23% at 90 °C. Given the low driving temperature, the actuator can be combined with common fabrics or stretchable conductive elastomers without thermal degradation, allowing for easy use in wearable systems. Nanostructural analysis implies that the lamellar crystals in drawn LLDPE fibres are weakly bridged with each other, which allows for easy deformation into compact helical shapes via twisting and the generation of large strain with high work efficiency.