Swing Shift: A wobbly and robotic bridge benefited
Swing Shift: A wobbly and robotic bridge benefited
When London's Millennium Footbridge opened its doors 18 years ago, the 1,066-foot section swayed so much that it closed almost immediately.
Since then, engineers who study human locomotion have been confused by a dilemma: why did the pedestrians who tripped on the trembling bridge walk in a way that made the wobble worse?
The answer has helped researchers design robotic prostheses and portable exoskeletons to improve the mobility of victims of stroke, amputees and others.
"It's a road map," said Gregory Sawicki, a mechanical engineer at Georgia Tech who designs exoskeletons to support the weak ankles of the elderly. "We learn how humans do it first, and then we steal or improve the best ideas."
Go for a walk
The energy cost of walking increases when 400 pedestrians shake a bridge, compared to 80 that do not, but the cost decreases as pedestrians synchronize their steps with the swing of the bridge.
Metabolic cost of energy per unit distance.
About 80,000 people crossed the Millennium Bridge when it opened, with as many as 2,000 on it at a time. When it began to shake, pedestrians tended to widen their postures, walk in sync with each other and schedule their steps for the sway of the structure.
The bridge was expected to oscillate a bit, but it ended up changing in each direction up to 3 or 4 inches.
(The bridge was reopened in 2002 after the addition of shock absorbers).
"The classic strategy is to put your foot in approximately the direction you're falling," said Manoj Srinivasan, a mechanical engineer at Ohio State University who has studied how pedestrians responded to the bridge. "If you're falling sideways, put your foot to the side."
The uncomfortable walking of the pedestrians kept them erect. But why did they stay on it if it also amplified the movement of the bridge?
According to Dr. Srinivasan, humans deploy two strategies when they walk and run: they try to avoid falling and try to conserve energy.
Walking in synchrony With the oscillations of the lateral bridges, he said, the cost of energy decreases.
In other words, the synchronization of steps with the oscillating bridge may have increased its swing, but with enough people, it may also have helped them conserve energy.
"There is a lot of evidence that people prefer to walk in ways that minimize the amount of food needed to complete the task," said Max Donelan, professor of neuromechanics at Simon Fraser University in Vancouver.
In his latest study, published last week in the journal Biology Letters, Dr. Srinivasan and Varun Joshi, a researcher in his laboratory, drew on his earlier research by modeling how pedestrians adjusted their pace in response to environmental feedback.
"
We learn how humans do it first, and then we either steal or improve the best ideas.
'
"This happens all the time," said Dr. Donelan. "If you get to the fridge to pick up a jug of milk that someone has had a cup since you last drank it, it's lighter than you remember, you realize you threw it too hard. weight of the milk jug ".
Unraveling how people combine the desire for stability, the need to save energy and the feedback of the swing of a bridge or the weight of a milk carton helps engineers design better devices.
"If we thought that the goal was to be stable all the time, we could build devices that would compete against their real desire," said Dr. Donelan.
Interest in this area of research, which is relatively new, was stimulated in part by the military.
Shortly after the shocking London footbridge shook the confidence of its pedestrians, the United States Army, by chance, began to invest in exoskeletons to help soldiers carry their loads.
"That made the dial go up," said Dr. Sawicki.
Because the exoskeletons were cumbersome and used too much energy, the military lost interest, but the technology survived.
"That thing that cost the soldiers a lot of energy was reused to help people who can not walk in the first place," said Dr. Sawicki. "It was transformed into rehabilitation devices where the cost of energy is not the priority."
So far, the products are not widely used by the general public, but some companies are marketing the devices. Among them are
which one makes exoskeletons for the rehabilitation of injuries due to stroke and the spinal cord and for jobs involving heavy lifting and seismic, which integrates robotics in clothes designed to improve the resistance and stability of the user.
Eventually, engineers like Dr. Sawicki expect this type of technology to rival or even surpass human capabilities.
For now, that's a bridge too far.
"We are not close to what the human body can do," said Dr. Sawicki, "but we are getting closer."
Write to Jo Craven McGinty in Jo.McGinty@wsj.com
.
!function(f,b,e,v,n,t,s)
{if(f.fbq)return;n=f.fbq=function(){n.callMethod?
n.callMethod.apply(n,arguments):n.queue.push(arguments)};
if(!f._fbq)f._fbq=n;n.push=n;n.loaded=!0;n.version='2.0';
n.queue=[];t=b.createElement(e);t.async=!0;
t.src=v;s=b.getElementsByTagName(e)[0];
s.parentNode.insertBefore(t,s)}(window, document,'script',
'https://connect.facebook.net/en_US/fbevents.js');
fbq('init', '369524843414444');
fbq('track', 'PageView');
.
SOURCE LINK ERESVIRAL.COM https://www.beviral.online
Comentarios
Publicar un comentario