Gravity Balancing Flexure Springs for an Assistive Elbow Orthosis

Gravity Balancing Flexure Springs for an Assistive Elbow Orthosis

Tschiersky, Martin (University of Twente)
Hekman, Edsko E.G. (University of Twente)
Brouwer, Dannis M. (University of Twente)
Herder, J.L. (TU Delft Precision and Microsystems Engineering; TU Delft Mechatronic Systems Design)

Precision and Microsystems Engineering

2019

In this paper, we propose a flexure spring based gravity compensation device which provides assistance to lift the forearm. Three different spring designs are obtained and evaluated. The synthesis method to obtain these is explained in detail and an experimental evaluation validates the desired gravity balancing properties. It is found that in comparison to a flexure spring with constant thickness, a variable thickness distribution along the spring leads to a drastic reduction of its width, which amounts to 81 % in the presented case, and offers an energy to weight ratio that is 94 % higher. Employing a nested spring design further increases the storable elastic energy of the variable thickness design by 145 % through utilization of the otherwise unused space within the original spring envelope. A proof-of-concept prototype is built to illustrate a practical implementation. The presented synthesis method provides a tool to obtain gravity balancing flexure springs that offer a promising solution for the design of assistive devices which aim to be both wearable and inconspicuous.

Gravity balancing
wearable device
assistive orthosis
arm support
flexure spring

http://resolver.tudelft.nl/uuid:6fcdaf3c-0517-4575-822a-bbb23bf20549

https://doi.org/10.1109/TMRB.2019.2930341

2576-3202

IEEE Transactions on Medical Robotics and Bionics, 1 (3), 177-188

Institutional Repository

journal article

© 2019 Martin Tschiersky, Edsko E.G. Hekman, Dannis M. Brouwer, J.L. Herder