University of Michigan engineers have developed an artificial foot that recycles energy otherwise wasted in between steps, which could make it easier for amputees to walk. A typical prosthesis doesn't reproduce the force a living ankle exerts to push off of the ground. As a result, test subjects spent 23 percent more energy walking with a conventional prosthetic foot, compared with walking naturally. To test how stepping with their device compared with normal walking, the engineers conducted their experiments with non-amputees wearing a rigid boot and prosthetic simulator.
In their energy-recycling foot, the engineers put the wasted walking energy to work enhancing the power of ankle push-off. The foot naturally captures the dissipated energy. A microcontroller tells the foot to return the energy to the system at precisely the right time. Based on metabolic rate measurements, the test subjects spent 14 percent more energy walking in energy-recycling artificial foot than they did walking naturally. Other devices that boost push-off power use motors and require large batteries. Because the energy-recycling foot takes advantage of power that would otherwise be lost, it uses less than 1 Watt of electricity through a small, portable battery.
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