Unpowered Heavy Tool Support Exoskeleton

This Unpowered Exoskeleton is capable of lifting 20 lbs, without any springs or force mechanisms placed within the arm structure.

The device weighs a little over 13 lbs, with most of that weight being in the steel arm. Reducing the material used in the two back pieces and adjusting the cross section of the arm for a larger moment of inertia could reduce the weight even further.

WearRAcon 2021 Innovation Challenge Finalist

Within the construction and manufacturing industry, repeated stress injuries are far too common. Devices which reduce the stress incurred while lifting and using a heavy tool job could improve people's quality of life.

Our previous paper involved a quickly built hybrid active / passive exoskeleton. The fully passive device is largely an iteration on the hybrid's design concept, with the intent of demonstrating the feasibility and benefits of an unpowered pantograph exoskeleton.

Design

‍

‍

Several different methods of transferring gas spring force to webbing were considered. Ultimately, we chose a design that would provide decent force outputs while easily sitting within a two-plate structure. The pantograph arm architecture was the same as used for the first paper I co-authored.

‍

‍

Several different methods of transferring gas spring force to webbing were considered. Ultimately, we chose a design that would provide decent force outputs while easily sitting within a two-plate structure. The pantograph arm architecture was the same as used for the first paper I co-authored.

Fabrication

Fabrication was suprisingly quick. Due to Covid and part delays, Josh and I were unable to meet in the lab for almost a year. We actually met up & completed the entire fabrication in under two days. Because Everything fit nicely between the two plates, most of the time spent was in cutting the arm bars and trouble-shooting a plastic piece that slightly overlapped a bolt-hole.

About 6 months later, Dr. Alan Asbeck was able to replace the gas spring of the device and put it back together within 3 hours.

Review of the Device

The device behaved incredibly well, despite the limitations of our pull point location. Due to gas spring hysteresis and friction/damping inherent to the arm, there were more stable heights than anticipated! Because the pull direction of the webbing wasn't completely vertical, you can see in the video that the tool-head of the arm would weakly drift towards what we call the "neutral plane" which is angled 7 degrees forward from a plane parallel with the device plates.
‍

Future devices, using better arm materials, and cross sections could increase the ratio of arm-bar length to panto-bar length, which would mean less link travel behind the back, more vertical webbing pull, and subsequently, even less drift. The ratio could also be increased with a lighter end-weight. The device is already very good, and it is very close to being competitive with commercial products.

Acknowledgements

The unpowered exoskeleton and the associated paper would never have been finished without the efforts of the co-authors Joshua Hull and Dr. Alan Asbeck. Additionally, Dr. Authulya Simon and Evan Claessen provided amazing assistance towards the fabrication and testing of the device.

More Projects

Motorized Heavy Tool Support Exoskeleton

Unpowered Heavy Tool Support Exoskeleton

Lightweight, Passive Arm Support Exoskeleton

Leg Pad Design for Material Lifting Exoskeletons

Blender Doodles

Op Amp Circuit Custom PCB

Super Smash Bros. Melee Texture Modding