Power Walker

Nothing could match the Segway's initial hype, but how far has it come since?

The debut of the Segway Human Transporter in 2001 surely set the bar for anticipatory hype. Remember "Ginger"? Or was the code name "IT"? But sales of the "revolutionary," self-balancing two-wheeler never approached those of a truly paradigm-changing innovation, such as Apple's iPod. Even five years after the Segway's much ballyhooed introduction, fewer than 24,000 of them cruise the world's sidewalks, pathways, pedestrian malls, and (local laws permitting) bicycle lanes and streets. Still, engineer Dean Kamen's novel electric scooter has managed to attract a lively cult following.

Recently the Bedford, N.H., company rolled out its second-generation Segway Personal Transporter (PT), which comes in an urban/suburban model called the i2 and a beefier, wide-track cross-country version, the x2. The time seemed right to give this intriguing technology another look and perhaps to clarify its place in a wheeled-transportation spectrum dominated by cars, motorcycles, scooters, motorized carts and bicycles. I talked to Segway users, dealers and designers, then briefly drove the i2 and x2 myself.

"Just step up like it's a stepladder," Ed Tsang urges, having just finished sweeping a clear path among the windblown autumn leaves strewn across the parking lot of his Segway dealership in Basking Ridge, N.J. I am mounting what vaguely resembles a modernized version of an old push-type lawn mower, except with a low-slung footpad in place of the rotating scythe blades. Further inspection confirms that the PT is more slickly designed than the original model, but the layout looks similar. I grab the T-shaped handlebar, step onto the platform very gingerly (almost as if it could somehow cut my foot) and finally board the vehicle. As if from a distance, Tsang's well-worn teaching litany just manages to penetrate my consciousness: "Relax ... Don't look down; look forward ... Stand up straight with your knees bent ... Try not to rock back and forth ..."

You are sure to start your first Segway ride a bit jumpy and unsure, seemingly primed to tip over. But after shifting about a little, you realize that all you really need do is "trust the machine," as Tsang advises. Make that leap of faith, and the gyro-stabilized device's intuitive control system does the rest, allowing you to direct it nearly effortlessly. So I stand tall and lean my body forward, and the i2 powers ahead smoothly and silently at walking speed. No doubt about it, a few moments gliding about on the uncannily responsive Segway shows that it is great fun, confirming the dealer's comment that "the Segway always exceeds initial expectations."

The trick to the Segway's uniquely satisfying ride experience is its user interface, says Doug Field, the company's chief technology officer. As in the original version, the automated control's nearly instantaneous sensory feedback mechanism relies on two safety-redundant microprocessor-based controller boards, five micromachined gyros, and a pair of tilt-sensing accelerometers that check the two-wheeler's condition 100 times a second. Then it deftly maintains balance by directing the electric motors to rotate the wheels just enough to keep the machine directly below the user's center of gravity. When you pitch forward slightly, you upset the balance, and the Segway rolls ahead a tad to keep you from falling over. Angle back some, and the machine compensates at once. Soon, standing in place is no chore at all. Tilting back a bit (even by extending your rear end a little) while traveling forward immediately brings the device to a smooth stop via a regenerative braking system that stores wheel-rotation energy in the battery.

To develop the machine's distinctive operation, Field says, Segway designers drew lessons from the familiar act of walking. Human environments are built around the assumption that people are standing and walking, he explains, adding that "walking is actually a form of controlled falling." During each step, your brain senses you are out of balance, because fluid in your inner ear shifts, so it triggers you to put your leg forward and stop the fall. Engineers conceived the Segway "as a way to graft wheels, motors and batteries onto a person so as to amplify walking in a way that mirrors walking, which is suited to our environment."

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