OX is a passive (unpowered) exoskeleton system that uses a semi-flexible cable system to transfer a controlled proportion of the weight of a heavy backpack off the wearer’s skeletal system. Initially developed by Defence Science and Technology Group (DST), the system was intended for use by Australian soldiers to ease the burden of excessive and frequent load carriage. Cobalt was selected as part of a competitive tender to take DST’s exoskeleton concept to the next level of design development.
DST’s Project Lead Tom Chapman had developed OX to early (TR3 level) prototypes. These successfully transferred loads, even during bent leg positions. His work had enough merit to justify external development by Cobalt to further validate the concept and take it to a far more advanced level (TR5+ level).
In contrast to powered exoskeletons, OX is lightweight, low cost, adjustable and easily put on and removed. However, without the addition of a separate power source, use of the system would come at some metabolic cost to the user. The design challenge was to develop a system that maximised the benefit of load carriage reduction whilst minimising this metabolic cost to the user.
Through a two-year, multi-phase development project, Cobalt designed, engineered, tested and optimised the exoskeleton, culminating in TRL5 level working prototypes ready for extended testing by a variety of military personnel replicating expected operational demands.
Through optimised design, the exoskeleton was capable of load transfer of up to 60% for a maximum payload of 35kg.
The total weight of the system is only 5.2kg.
The system was designed to be adjustable to suit a range of users. Dynamic load transfer adjustability was incorporated to the system to maximise effectiveness and allow user customisation.
The exoskeleton was designed to minimise the restriction of the user’s mobility, providing significant improvement to overall metabolic efficiency (compared to original DST design concept).
The construction is robust and strong, well suited to survive harsh environments that it could be exposed to in the field.
The Team We believe good design happens by expert people working as a team.
Kynan Taylor Project Leader
I can’t speak highly enough of the ‘above and beyond’ attitude of the Cobalt team as they shared the passion of this ‘crazy’ concept with me. Shared passion is not something tangible you can write in a contract, but it’s something that I witnessed in abundance with the team at Cobalt.
Tom Chapman Defence Science and Technology Group OX Project Lead
Rethinking the Future
To date, exoskeleton development for military applications has been primarily focused on powered and motorised systems. These mechanically complex devices effectively turn wearers into hybridised robots. So far, this approach has been favoured by big defence industry players and has resulted in heavy, complex, and expensive devices that need to be tailored for each wearer. The impracticalities of batteries and regular recharging within tactical operations also pose fundamental safety and redundancy limitations to these systems.
DST’s concept, developed by Tom Chapman – or OX as it is known – takes a completely different, almost acoustic approach. The human gait has evolved to be a very efficient process, and any disruption to this results in a steep rise in metabolic cost. OX aims to offset loads from the user, without providing any additional energy input, therefore requiring the wearer to support and actuate the system. The challenge with this approach is to balance the metabolic cost of this against the ‘benefit’ of reduced loads and impacts on the wearer’s musculoskeletal system.
Early stages of our development were focused on understanding the behaviours of the system and how each had to integrate with the human form and external inputs. We started this mathematically, then practically through engineering design, simulation, and prototyping. Several demonstration prototypes were constructed and tested in-house to verify ideas, performance, and usability. This culminated in laboratory trials conducted in collaboration with Victoria University at their world-class sports science facility.
The second phase of the project focused on the design’s optimisation. Data generated from the first phase lab test highlighted areas for further focus including improved user fit and adjustability, enhanced bracing of the cables to the user and overall weight minimisation. The final design included a number of key improvements including the use of advanced materials such as carbon fibre composites, miniaturised mechanisms and refined sub-system integration.
Our on-time and on-budget deliverables were handed over in May 2018; three TRL5 level working prototypes able to be tested by a variety of military personnel replicating operational demands. Currently the subject of university and defence force testing, the prototypes and project are being considered for further commercialisation by DST.