Now, robotic leg with a natural gait

Scientists are developing a new computer-controlled bionic leg that can help amputees walk more 'naturally'.
In cooperation with a Mayo Clinic scientist, researchers at Michigan Technological University are working on a microprocessor-controlled ankle-foot prosthesis that comes close to achieving the innate range of motion of an ankle.
These computerised artificial legs have pressure-sensitive sensors on the bottom of the foot that detect how the amputee is walking.
The sensors instantaneously send signals to a microprocessor, which in turn adjusts the prosthesis to make walking more natural.
The microprocessor-controlled prostheses on the market can move an artificial foot in only one direction, toe up and toe down, which is fine if you are marking time on a treadmill, said Mo Rastgaar, an assistant professor of mechanical engineering-engineering mechanics at MTU.

"But in reality, we never walk in a straight line for any length of time. When you walk and reach an obstacle, you have to turn, and there's always something in our way," he said.

So researchers designed an ankle-foot that can move on two axes, incorporating a side-to-side roll as well as raising the toe up and down.
And they moved the power and control mechanism up and away from the leg using a cable-driven mechanism. That lightens the prosthesis, making it much more comfortable and easy to use.
The cable that moves the prosthetic ankle-foot is similar to those used in bicycle brakes. It runs from the control box to the ankle mechanism and can turn the foot in almost any direction.

As part of their study, the team designed and built a large circular treadmill on which the robotic foot "walks" in circles. In tests, the prosthetic was able to copy the angles of a human ankle walking in a straight line and turning.
Kenton R Kaufman, director of the Biomechanics/Motion Analysis Laboratory at the Mayo Clinic in Rochester, is collaborating in the effort to refine the prosthesis and make it available to amputees, especially wounded warriors.
The researchers expect to begin refining their design at the Mayo Clinic in summer 2014.