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Friday, February 08, 2008 Knee PowerContinued from page 1 By Stephen Ornes
If Donelan's approach to energy harvesting sounds familiar, it's because he uses the same strategy employed by hybrid automobiles. When a driver applies the brakes of a hybrid, the electric motor begins to act as a generator. The generator slows down the car and at the same time converts kinetic energy into electricity, which is then used to recharge the battery. Conventional braking systems rely on friction to slow down, and the car's kinetic energy is dissipated as heat. "Walking is like stop-and-go driving," Donelan says. "Within every stride, the muscles are accelerating and then decelerating the body. Hybrid cars take energy and give it to the battery." Donelan's prototype weighs in at just over three pounds, and he is currently developing a lightweight model that could be used by prosthetics manufacturers and the military. Demand for human-energy harvesters like Donelan's knee brace and Rome's backpack is increasing, thanks in part to the proliferation of small electronics like cell phones and handheld GPS units, especially in the military. "A soldier with a 24-hour mission [might have to] carry nearly 30 pounds of batteries with him," Donelan says. "They have to power everything from GPS to communications to night vision." In addition, Donelan says that his knee brace has potential in medical markets: it could augment a paralyzed limb or power a prosthetic. "You could take a healthy limb and use it to power the injured limb," he says. |
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From the Labs: Information Technology
04/22/2008
Comments
nekote on 02/08/2008 at 12:35 AM
109
Normal muscle "braking" use every other stride?
Every 1 of 100 strides?
Alternate active knee every hour, day or week?
How perceptible / noticeable is it?
How quickly do people adapt to the unit being turned on?
Turned off?
A stride or two?
A minute or two?
Any risk of stumbling during such transitions?
SVE on 02/08/2008 at 7:16 AM
41
What about how to precisely align generator pivot axis with knee pivot axis? Otherwise the pressure plate rubs up & down shin with each stride.
Is is easy to run with? Soldiers sometimes have to do that.
Crank radios may require effort, but at least when you're done, you put it away and are back to being a normal person.
Looks geeky. But so do Segways. Anyone look at propeller beanie hats in windy cities? Must be some energy possibilities there.
You could also use a piezo shoelace to tie the two shoes together. It would generate juice at the end of the strides, too (but you might sometimes trip).
hachi on 02/09/2008 at 5:37 AM
16
I'd love to see a lightweight version (say around 300 grams) that you could attach to a laptop or mp3 player, though I could only imagine transferring the power through wire, which could be a bit of a hassle for the user.