Exoskeleton adds power to your step while reducing metabolic energy use
09 May 2014
A simple autonomous exoskeleton has been developed that both augments human walking and reduces the energy used when walking and carrying a load, according to research published in the open access Journal of NeuroEngineering and Rehabilitation. This could be of assistance to anyone carrying heavy loads over long distances and people who have difficulty walking without support.
Researchers from MIT Media Lab, led by Hugh Herr, designed a leg exoskeleton that consists of two fiberglass struts attached to a walking boot, a small motor attached to each strut, and a control and battery pack that is worn on the waist.
The exoskeleton was tested by seven male subjects walking on a treadmill at 90 meters per minute while wearing a 23 kg weighted vest. The subjects were tested on the treadmill without the exoskeleton to act as a control. The energy use - metabolic rate - was recorded by monitoring the amount of oxygen inhaled and carbon dioxide exhaled. A resting metabolic rate was established while the subjects stood still for five minutes while wearing the weighted vest and no exoskeleton.
The exoskeleton reduced the energy expenditure required to walk. The average energy used while walking with the weighted vest and no exoskeleton was 6.98 Watts/kg. Walking with the weighted suit and exoskeleton required 6.56 Watts/kg.
Hugh Herr says: “This is the first exoskeleton that actually augments human walking and significantly reduces metabolic cost. The metabolic reduction provided by the exoskeleton is equivalent to reducing the payload by approximately 7 kg or 30% of the original payload of 23 kg. Subjects noticed that their legs felt heavier and awkward when they took the exoskeleton off.”
This exoskeleton differs from previously developed models in that it operates untethered from a power supply and it reduces energy expenditure. This exoskeleton works by assisting in the push-off phase of walking with the motor adding muscle-like power to the step - reducing the amount of metabolic energy used by the biological muscles.
Further work needs to be done on increasing the versatility and controllability of the exoskeleton models. By reducing the protrusion of the fiberglass struts it may also be possible to provide a greater range of motion.
Hugh Herr says: “In future, this exoskeleton could reduce the metabolic burden of individuals expected to carry substantial loads. Instead of reducing the metabolic burden, the device may alternatively allow them to carry greater loads at their nominal metabolic cost.”
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Notes to editor:
Autonomous exoskeleton reduces metabolic cost of human walking during load carriage
Luke M Mooney, Elliott J Rouse and Hugh M Herr
Journal of NeuroEngineering and Rehabilitation
Article available at journal website here.
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