How bionic limbs work

There are not so many subjects that can be called real biomechanical hybrids on the earth so far, so a meeting with farmer David will come as a surprise to anyone. A redhead, full of health and unquenchable fun, a big man meets us on a gravelled driveway leading to his workshop. The 30-year-old mechanic without hesitation jumps off his huge tractor, makes his way among all-terrain vehicles and tractor spare parts scattered everywhere. He grasps at one thing or another thing, without even thinking that to some extent he is no longer a man, but a car.

Lost leg David Johnson is an engineer at Ossur. He is testing the Power Knee prosthesis and he has all the possibilities for self-tuning the prosthetic electronics and for testing its algorithms in real conditions.

Break it - don't be shy

David wears a cunning left leg prosthesis that he lost in a car accident. Today, the prosthesis should be replaced. That is why engineers from Essur came to the farm where David Ingwason lives and works. The headquarters of this major prosthesis manufacturer is located in Reykjavik (Iceland), an hour's drive from David's farm. An ordinary Icelandic peasant, he was in a select circle of disabled people, who were provided with a prosthesis of the brand Symbionic Leg. This is an integral bionic design including artificial knee, ankle and foot.

Ingvason regularly breaks his artificial leg, hosting on a farm, driving around the surrounding wastelands covered with tall grass, climbing volcanic plateaus covered with moss. The drives are clogged with clay, the mechanics groan under continuous loads, until a technical masterpiece worth more than another sedan turns into a dead piece of metal full of electronics. As Magnus Oddson, who is responsible for the development of new technology at Essur, explains, for any complications, Ingvason just needs to call and the company’s employees will immediately bring him a new leg, and for free. Indeed, for the company, all the damages that the tester causes to the prosthesis as a result of extremely careless handling are a source of very valuable information.

Today we are on the verge of realizing long-standing fantasies about a “mechanical strength”, that is, about real bionic amplifiers of human muscles. It’s enough to add to the technologies of “smart prostheses” and exoskeletons a suitable neuro-machine interface that will not be associated with an invasion of the brain.

When the foot doesn't need a brain

Last fall, Essur launched the Symbionic, the world's first electronically controlled artificial foot, refined to mass production. This is an outstanding milestone in the history of prosthesis development. Ingvason’s leg acts, in fact, in the role of an independent robot, stuffed with sensors that examine the environment and guess the intentions of the owner. Special processors calculate what angle the artificial leg should extend at a step. The same ideology is laid down in the design of artificial hands, when sophisticated algorithms help determine with what force you need to grab a plastic bottle of water or how to spring it, resting on the floor when it falls. Dentures, whose action is based on independent vision and hearing, completely dispense with damaged sensory organs. All these bionic systems are able to actively adapt to the nature of their owners. Serving the human body, they restore its functions.

Modular Prosthetic Limb looks just like a good bionic prosthesis. In fact, this is a whole swarm of autonomous robots. Each removable segment with its own electric drive also contains its own processor, which harmonizes its work with the rest of the elements.

Let us take one of the characteristic cases when a prosthesis of a traditional design can fail a person. Typically, a mechanical knee is locked tight when the heel touches the ground. Thus, the prosthesis supports the weight of the human body. When the weight goes to the toe, the knee unlocks. But if the sock touches the ground too early, the artificial leg can spontaneously fold under the weight of the owner. A prosthesis like Symbionic Leg is not easy to fool. Force sensors and accelerometers constantly monitor the position of the leg in relation to its owner and to surrounding objects. Built-in processors analyze all input data with a frequency of 1000 measurements per second and promptly make optimal decisions - when to make an effort and when to take it off. In order to fix or release the knee joint, there is more to it than just a sensitive touch of the ground with the toe of the foot.

But, let's say, a smart prosthesis somehow makes a mistake when calculating the situation - then the very first impulse, indicating that its owner is ready to fall, starts the program to restore balance. The drives will immediately slow down in half, and the magnetic fluid filling the knee will become more viscous, increasing resistance. According to Ingvason, the whole system works so that it almost never crashes - at least less often than it did when he walked on his feet.


How does a prosthetic robot work?

The use of prostheses entails, as a rule, new health problems. Purely mechanical prostheses use a complex system of levers and latches. It is she who allows people with disabilities to walk, but this gait will never be free, since the owner of the prosthesis is forced to pull his hip up at every step so as not to cling to the road with his toe of the prosthesis. Electric prosthetic hand prostheses must be fixed somehow when walking, and this ballast disrupts posture and balance when walking. About 70% of people with prostheses have complications in the spine and joints.

Experts believe that such side effects lead to the fact that obese or suffering from chronic pain patients become even less mobile, which undermines their health and shortens life. The solution to this problem was found in special algorithms. When using Ossur's Symbionic Leg prosthesis, the patient no longer has to support his hip. All the necessary movements are performed by a robotic prosthesis. At each step, the sock rises up, performing a movement, which is commonly called “back flexion”.

Other algorithms turn out to be more complicated - with their help the robot analyzes the flow of data coming from outside, and they constantly change depending on the nature of the terrain on which you have to step. If the leg rests against a raised surface when moving down, when the knee is still not fully bent, the robot concludes that there is a staircase in front of it and adjusts its movements accordingly. If upon contact with the ground the toe lifts up and the heel falls somewhat, artificial intelligence concludes that there is a slope underfoot and it changes angles and efforts so as to best overcome this obstacle.

Ingvason’s new prosthesis is the next Symbionic Leg model charged with upgraded software. With their help, the knee and ankle can intelligently interact with each other. In the coming years, Essur is going to create a kind of “network intelligence”. But the new prosthesis is already on the leg. At first, Ingwason waddled rather awkwardly through his dirty yard, littered with rusty remains of tractors and cars. But after only a few minutes, the robot adjusted to its owner.

In order to recreate a human organ, for example, a bladder, the Wake Forest Institute of Regenerative Medicine is populating a blank of biodegradable material with cells taken from a patient. This lab is run by Anthony Atala, a 2006 Breakthrough Award winner from 2006. Now they are busy growing more complex organs - such as the liver and heart.

First build, then grow

How does essur see the future? “It would be nice, ” says Oddson, “to collect all the knowledge that has been accumulated in Essur and to develop something that generally ignores the human nervous system. It will not be an exoskeleton. It would be more correct to call such a concept “Smart pants”. At first, it can be of help to the paralyzed. Such a device would stimulate the muscles, generating those commands that are no longer able to give out the brain or damaged nerves. It would be possible to use existing drives, that is, human muscles, but add a new central controller to them. ”

At Essur, an engineer diagnoses the Rheo Knee motorized joint. This element is part of the Symbionic Leg prosthesis and contains angle and force sensors. From them, the data goes to the on-board computer.

And in the long-term perspective, Oddson believes, prosthetics as a separate branch of science and technology should disappear altogether, giving way to future technologies for restoring lost organs. By 2050, he predicts, limbs can be created from scratch. Who knows whether they will be grown or built on the basis of printing technology? All the intimate biomechanical secrets revealed by companies such as, for example, Essur, will be put together into a single team to restore human flesh using new technologies.

It is amusing to listen to such optimistic forecasts in which the specialist predicts that his industry will leave the stage due to its own effective development and will give way to other areas of knowledge. True, all the elaborated sophisticated technology will not be wasted - it will be implemented in new devices that will change the lives of millions of people, both sick and quite healthy.

The article “Man and smart parts” was published in the journal Popular Mechanics (No. 7, July 2012).

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