Published October 11, 2013
| Road & Track
Those of you who follow tech news may have already seen the groundbreaking mind-controlled bionic leg. It took $8M to develop, and will soon be helping amputee soldiers return to civilian life. A cool story, sure, but it could get a whole lot better: Buried within the new leg’s technology might be the answer for millions of enthusiasts deprived of the driving experience.
It all starts with two lower branches of the sciatic nerve that control movement for the outer part of the leg, the calf, and the foot. After leg amputations, these nerves usually wind up as dead ends, but a recent surgical technique keeps the branches firing by rerouting them into the thigh and hamstring. To compliment the surgery, Dr. Levi Hargrove, director of the Neural Engineering for Prosthetics and Orthotics Laboratory at the Rehabilitation Institute of Chicago, developed a new neuroprosthetic—a bionic leg that joins with the rewired nerve ends. It reads their signals to the missing limb, and then uses software to interpret these impulses into commands for movement in a bionic knee and ankle. It’s an insanely complex piece of kit, packed with loads of mechanical sensors, gyroscopes, and accelerometers; enough to make an iPhone 5 look like your grandfather’s woodworking tools. The first person to receive one of these seemingly miraculous new neuroprosthetics is a 32-year-old motorcyclist who lost his right leg in a crash. You can see that prosthetic in action in the video below.
Dr. Hargrove says that, as of now, he can’t recommend using this bionic leg to drive or ride a motorcycle—which is disappointing, until he explains that the new prosthetic’s innovative interface could offer a more ambitious, permanent, and fascinating solution for amputee drivers.
“It is not necessary that the leg itself move to push on the pedal,” he says. “Muscle signals from the leg could be integrated into the car’s computer system, which would bypass the leg altogether. Long-term, the technology in this device could potentially be used to eliminate the hand controls on automobiles.”
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It could work like this: A car’s ECU is equipped with the same interface as the mind-controlled bionic leg, allowing the redirected nerve sensors to link up with throttle-position and braking systems instead of an artificial limb. Amputees could then “ghost drive” through canyon twisties and rural two-lanes, all controlling the pedals via muscle memory—think The Six Million Dollar Man with Bluetooth connectivity.
And this sort of system could mean big things in motorsports, too. Racers with conventional prosthetics usually employ a "straight-leg" technique—since the ankle doesn’t rotate, they adjust to feel brake pressure or tip-in higher up in the leg, where the prosthetic is attached.
Nobody is more versed in this than former Ganassi Racing star Alex Zanardi.
Maybe you were lucky enough to be watching live when he executed the gutsiest overtake of the post-Senna era:“The Pass” at Laguna Seca in ’96. Or perhaps you were witness to the horrific wreck that took both of his legs and ended his open-wheel racing career in 2001.
Five years later, he tested a BMW Sauber C24B modified with hand controls, yet Zanardi found that steering through corners with his right hand impeded his use of the car’s left-hand throttle controls.
Though he made a miraculous comeback and eventually raced in the WTCC, Zanardi sees the limitations of artificial legs as a major obstacle.
“I have had experiences with some of these types of electronic legs,” he explains. “In terms of motorsports, there are issues of charging and durability and moisture.”
“The weight of a race car is very powerful, especially on the brakes. The deceleration can be over 2G, maybe even at the 3G mark. Getting into the brake pedal, what you really need is accuracy for moving the weight.”
He thinks there's still work to be done exploring existing prosthesis, particularly ones that utilize gas-tuned valving. Some even incorporate magnetorheological dampers, the same wizardry responsible for MagnaRide active suspension in theCamaro ZL1 and Corvette.
“I’m amazed nobody has done more studies with that. You wouldn’t need so many complicated pieces. These legs are simple and act like a shock absorber, with a piston and fluid. It can be fine-tuned for each driver and car and course, which are all very different.”
When it comes to racing, though, Zanardi believes that mindset – not technology – is the issue.
“It used to be that I would do laps in the car, then come back to find something slightly different. Maybe the steering wheel was moved slightly left or right, and it would upset me because it wasn’t perfect. Now, I put things like that behind me after the first turn. It doesn’t matter. Racing is about being flexible in the mind. When you’re not able-bodied, you must be even more flexible – you must adapt even more. No magical technology is going to come along and fix that.”
Zanardi makes a good point, but a car running something like Hargrove’s bionic-leg interface could be the answer to some of these problems, and the next advancement is already in the works. While amputees can’t “feel” ankle resistance through artificial limbs, the mind-controlled prosthetic can measure how hard the leg is trying to push. Engineers may be able to relay this information to the user through what’s known as sensory substitution.
“For example, a sensor placed beneath the thigh could vibrate more or less intensely depending on how hard the ankle is pushing [in a car], so the user has feedback regarding how hard they are pushing the pedal,” says Dr. Hargrove.
Hargrove and his team at the Rehabilitation Institute of Chicago are working on a less expensive bionic leg prototype, and they’re hoping to see it in widespread use within three to five years. Of course, the leg’s software would need to operate flawlessly to be safe, but given that the interface already operates with over 98% accuracy, it isn’t far-fetched to think it could be perfect in the near future. Might some clever automaker or aftermarket operation swoop in and begin mating a car with nerve-sensory software in the meantime? We certainly hope so.