Ivan Masek
CEO
Novotechnik U.S.
Southborough, Mass.

The large-diameter tires with wider spacing better positions the x2 Personal Transporter for off-road work over its i2 sibling. Here the x2 is equipped with a golf-bag carrier for a day on the links. The balance sensor assembly (BSA) compensates the LeanSteer system for the slope of the ground.

The introduction of the Personal Transporter (PT) in 2001 by Segway Inc. created great excitement. It was the product that everyone wanted to try. The second-generation PT, unveiled last August, breaks new ground with the addition of LeanSteer technology.

Riders steered the first PT with a twist of the wrist. LeanSteer gives a more intuitive steering control that is almost instinctive.

Whether riding a bicycle, running, or walking, a person instinctively leans in the direction they want to go before actually moving in that direction. The PT now senses that lean and reacts by turning in the corresponding direction. It's as if the rider wears the PT rather than drives it. The reaction is almost like steering by mere thought.

The PT combines microprocessor controls, sensors, and feedback loops with wheels and motors in an operation described as "active mechanics in everyday use." Together the components form a tightly integrated system using Segway Smart Motion (SSM) and LeanSteer.

SSM dynamically stabilizes the PT so it self-balances even as the rider mounts or dismounts. It's this ability that distinguishes the Segway from other two-wheel transportation systems.

Each wheel motor connects to two motor drives and controllers for normal and backup operation. In case of a drive failure, the second drive takes over to bring the Segway PT to a safe stop. The balance sensor assembly mounts between the motor controllers near the centerline of the transporter.

Bicycles and traditional scooters typically need forward speed for balance. But the PT maintains its balance even when standing still. Segway's model for the PT's dynamic stabilization is the human body. Most people walk without conscious thought. They don't think, "left foot, right foot, left foot." Segway's goal was to make PT operation just as instinctive, for the best user interface is no user interface.

Chances are a person won't fall on their face when they stand up and lean forward because their brain knows they're out of balance. Fluid in their inner ear shifts, triggering a signal to put one leg forward for stability. If they keep leaning forward, their brain keeps placing one leg ahead of the other. They begin walking forward one step at a time.

The Segway PT works in a similar fashion, though it has wheels instead of legs, motors instead of muscles, and a collection of microprocessors instead of a brain. Sophisticated tilt and gyroscopic sensors monitor its balance just like the inner ear. As the rider leans forward, the PT starts rolling in that direction. When they lean back it slows down, stops, or even backs up.

As the PT approaches top speed, the handlebar pushes back against the driver. This gentle nudge forces the driver to straighten up and keeps the PT from going too fast.

LEAN TO STEER

The handlebar-control shaft connects to a dual potentiometric sensor that measures degrees of tilt in the shaft as riders lean into a turn.

Instead of twisting a control on the handlebar, LeanSteer adds the same lean-to-control idea to steering the Segway. Unlike a bicycle where the handlebar turns to go left or right, the Segway rider leans in the direction of desired travel. "Lean left to go left, lean right to go right," states Mike Gansler, Segway product development and systems engineer.

The secret is in the new control or handlebar shaft. As riders lean, they tilt the Segway handlebar and control shaft in the direction they're leaning. The PT responds to that input by turning in that direction. It has been likened to skiing without snow. It's the mechatronics in the PT that keeps the rider from falling.