Electronic Design

What's All This Ginger Stuff, Anyhow?

Most of you have seen the big splash about the "Segway," previously known as "Ginger," previously known as "It." It's a high-tech motorized scooter with two wheels that are—no kidding—side by side. Obviously, Ginger is a great technical accomplishment. Read the write-up of it in Time magazine (Dec. 10, 2001, p. 77), which was quite good, or see www.segway.com, especially the FAQs. Amazing. No argument. (I don't know if this is done with or without Fuzzy Logic. The FL guys all say that nonlinear problems like this one are best done with FL. Either way is okay with me.)

Let's say its unit price drops rapidly from $8k to $3k to $2k. There's just one problem for Dean Kamen and his investors: no matter how many patents they have, or how well they're written, it will be too easy for competitors to do "work-arounds."

Kamen's ingenuity solves the problem of how to balance and drive a Ginger where the wheels are side by side, using two motors, five processors, a few gyros, and many fancy electronic things. (Wonderful!)

But I have seen motor-driven scooters that had zero microprocessors. (That's about twice as many microprocessors as in my car, a very strong 1970 VW Beetle.) Mr. Kamen solved a problem that hardly anybody asked to be solved.

Yes, his compact design is small—smaller than most scooters. But any engineer knows how to make a motor-powered scooter fold up to an even smaller size than Ginger. It will be great if Mr. Kamen leads us all to consider compact, efficient transportation. Some may be electric powered. Some may be gasoline powered and have more speed and more range than electric Ginger.

But here's the key point. A conventional scooter layout will always be much cheaper, easy to drive, and safe. Who knows what kind of accident the Ginger will get into, from which it won't be able to figure a way out?

Conventional motorized scooters, whether gas or electric, are going to get a lot of attention. Their drawbacks are finite and have been well understood for over 50 years. The key is that such a scooter will always cost a small fraction of what Ginger costs—maybe 1/3 or 1/4. So while a rich yuppie might scoot down to get his mail with a Ginger, a guy on an ordinary motorized scooter can pass him. The Ginger, while cute and compact, still weighs 80 lbs. You can't very well carry it up your stairs, unless you're a real tough guy.*

So, there's another small fraction: the weight of an ordinary motorized scooter versus Ginger's weight. Existing motorized scooters are under 25 lbs—much less than 1/2 of Ginger—not to mention, close to $600. When you fold it up, it's smaller too. Is gasoline too messy? Use a little bottle of propane.

What a heck of a way for these brilliant guys to waste $100 million dollars—to develop such a cute, but disadvantageous, machine. It's not imperfect, nor necessarily flawed, just not nearly as good as a much-lighter, simpler, cheaper conventional machine.

Then I spotted a serious technical problem. As the makers say, you make Ginger stop "just by thinking that you want to stop," sort of by intending to lean back. Still, while its normal braking rate may be very adequate, there's a problem: When you need to slow down hard, or stop fast, I don't think that you can make Ginger stop soon, or quickly. The reaction time is going to be lousy.

If you're rolling along at 12 mph (maximum rated speed) and want to slow down fast, the motor must speed up and push the wheels ahead of the center of gravity (CG) of the rider. Then it can start decelerating. Well, I think that's a lousy way to respond to the needs for slowing down. Even with lousy brakes, a conventional scooter can surely stop quicker, without that delay. That's scary. This seems to be a serious flaw. Tell me I'm wrong.

Similarly, if you're going along at 12 mph and come to a downgrade, the Ginger will have to speed up and get its wheels ahead of the CG, just to maintain a constant speed, not to mention any ability to slow down.

How does an ice skater stop? He leans back and gets his feet in front of him, then turns his skates sideways and decelerates vigorously as the skate blades dig in, while still leaning back. At the last second, he stands up straight. A Ginger won't get its wheels "sideways" to stop, but it will have to lean back considerably if it wants to slow down at a decent rate. If it doesn't lean back to a scary-looking degree, it won't have good braking capability.

Any conventional scooter can stop faster. As I noted previously, that sounds scary. I'll believe Ginger when I see her. Maybe. Can Ginger tell the difference between going down a hill at constant speed, and decelerating on a level area? Oh, sure, but that doesn't make the problem easy!

All for now. / Comments invited!

RAP / Robert A. Pease / Engineer
[email protected]—or:

Mail Stop D2597A
National Semiconductor
P.O. Box 58090
Santa Clara, CA 95052-8090

*P.S. One guy said he wanted some brackets to hook his Ginger onto his car, and some connectors to recharge its batteries. These connectors would be called—Ginger Snaps. /rap

TAGS: Components
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