Bill Machrone: Extreme Tech

After months of speculation and heavy press coverage, the mysterious Ginger (or "IT") made its debut on December 3, 2001, on national TV. The most anticipated invention of the past year, now known as the Segway, turned out to be an electric scooter. It thrilled some and disappointed others.

The underlying technology is breathtaking. You stand on a platform between two wheels, located at your sides instead of fore and aft. To control it, you grasp a T-shaped handlebar that comes up from the platform and just think about which way you want to go. The Segway turns the subtle pressure of your leaning one way or another into directional control. More amazing is that you can't tip it over. Internal gyros and torque inputs to the wheel motors keep it upright. The gyroscopic effect that keeps bikes and conventional scooters upright does not come into play here.

The Segway is just as stable at rest as it is at full tilt, and riders report no sign of twitchiness or unsureness in its balance. Yet the Segway is inherently unstable. Without constant input from its sensors and constant action by its gyros and motors, it would fall forward or backward with a thud.

Dynamic instability is a mind-boggling idea to anyone born before the microprocessor era. It began with modern fighter planes that would fall out of the sky were it not for continuous feedback from sensors and constant adjustment of control surfaces. To the pilot, the plane feels like a conventional aircraft that's designed to fly stably—straight and level, once it's trimmed. But in fact, the pilot's control inputs merely tell the plane's control circuitry to bias itself in the direction the pilot wants to go. The advantage is that a dynamically unstable aircraft can react far more quickly than a stable one, because it's not overcoming inherent stability other than inertia.

People are dynamically unstable, too. Nothing in our inherent design keeps us upright when we stand. Our senses, brains, and muscles work constantly to keep us from falling over.

Inventor Dean Kamen is best known for his inventions in the medical field, especially in the area of administering medicines and dialysis. He invented the first wearable infusion pump, a home dialysis machine, an arterial stent, and an astounding gyro-stabilized, microprocessor-controlled wheelchair called the iBOT. This latter device, currently under clinical trials, is a four-wheel-drive wheelchair that can traverse mud and sand, climb curbs and stairs, and actually rise up and maneuver on two wheels, balancing just as surely as we do on two legs.

The technological breakthroughs in the iBOT, along with patents filed by Kamen's company, DEKA Research and Development, first raised the speculation that the Ginger was a personal transportation device. A sketch on the first page of Kamen's patent application, "Personal Mobility Vehicles and Methods", shows a young woman riding a two-wheeled scooter with side-by-side wheels.

The potential for such a personal transportation device (PTD) is limited by our infrastructure. PTDs won't mix any more easily with cars and trucks than bicycles and scooters do today. Motorcycles also tend to be invisible to many drivers. The Segway clearly doesn't belong on automobile roadways.

A Segway is much better suited to the sidewalk. But it's hard to imagine significant numbers of them blending with pedestrian traffic. Despite its quicker-than-human reaction time and its ability to bring itself to a halt smoothly and quickly, collisions would be inevitable, through inattentive operators and the randomness of pedestrians.

So the ideal place for Segways would be in their own lane, like the bicycle lanes in many cities. In fact, a Segway would probably share bike lanes successfully, because the vehicle speeds and situational awareness of the operators are similar.

Another major factor is weather. Open vehicles, other than snowmobiles, are unpopular choices in cold or inclement weather. Golf cart communities are a potential market in the Southeast and Southwest, but Segways are unlikely to find much acceptance in snow country.

The Segway could, however, be used by foot-patrolling police, at industrial campuses, and in large warehouses and factories. I look forward to a significant technology trickle-down over the next few years.