Australian researchers have developed a simple, lightweight (3 kg) fully-passive exoskeleton. This system uses Bowden cables to attached to a rigid backpack frame. The cables run down the back and legs to the base of the boot and transfer approximately two thirds of the backpack load to the ground
. This load force bypasses the user’s body, reducing compression forces from the backpack load through the torso and legs.
The benefits of such a system compared to a powered exoskeleton include: simplicity, no requirements for heavy batteries; low cost; easier to integrate with the user and equipment and redundancy when no longer required – remove and add to pack.
The development is at a proof-of-concept stage with early testing showing encouraging results. However, the biomechanics of the system require extensive refinement to ensure it is integrated optimally with the soldier and truly fit for purpose.
While the technology is being developed around use in the military it might be applicable to many civilian scenarios such as firefighting, trekking and personal load carriage roles that require assistive technology.
The US unpowered ankle exoskeleton that reduces the metabolic cost of walking by approximately 7 percent. The results are roughly the equivalent of taking off a 10-pound backpack, and are equivalent to savings from exoskeletons that use electrically-powered devices.
Walking with a passive-elastic ankle exoskeleton. An unpowered clutch engages a spring in parallel with the Achilles tendon when the foot is on the ground, offloading the calf muscles and making walking easier. Credit: Stephen Thrift, North Carolina State University