Trying to figure out the Segway...

[skimoose]

Originally Posted by KenWittlief

I think the feedback on the Segway is selectively loose - when you lean forward it compensates to keep you from falling over, but not completely, so the platform ends up moving forward - sorta like its perpetually falling

Good call, if I recall correctly from the book, that's how Dean got the project to finally work. He had fallen in the shower and the idea hit him of controlled falling.

Originally Posted by JBotAlan

I think it's a PID loop. As you lean, it adds the offset to a separate integral term that controls the speed. It seems simple, but for 5 grand, it seems that I'm missing something...or is it just overpriced?

JBot

It not just speed and direction, you're forgetting balance. You're not balancing the seg, it's balancing you.

You're also missing a lot of safety redundancy. There are (I think) eight gyros on board which are constantly polling and voting, similar to the way the systems work on the space shuttle where multiple redundant sensors provide data and then the results are voted on by the processors to weed out defective sensors or data.

And is it overpriced? I don't think so. If gas gets a little more expensive, say $4/gal., I'll be taking one to work, when I'm not mountain biking or roller-blading that is.

Just need one more mile of trail and I can commute about 75% of the way on the Quinnipiac River Linear Trail, and I saw the survey party out last week working on final designs!

[Capt.ArD]

actually, i saw a guy (some professor at a college) on the internet who explained how he built his own. it came out to $300 (i think). I'll try to find the link and post it in a bit.

these things don't really need 8 gyros, except for redundancy and safety.

edit: i'm not sure it's the same link, but here you go:http://www.tlb.org/scooter.html

[KenWittlief]

Originally Posted by Capt.ArD

these things don't really need 8 gyros, except for redundancy and safety.

I agree, if you are building your own to learn about solid state gyros and PID loops, a single point system is fine

if you do this, make sure you wear a helmet when you ride it, and skateboard gloves so your hands dont hit the pavement when you fall.

When you fall! Single point system => single point failures => total loss of functionality!

the segway is designed to be foolproof, so that even the leaders of great nations can ride them with ease

your SeGwAy-X can be a little more..... uhmmmm... interesting to ride, if you are not going to let your grandmother use it in the mall.

[Billfred]

Originally Posted by KenWittlief

When you fall! Single point system => single point failures => total loss of functionality!

Off-topic, but how would one go about utlizing multiple gyros in a system? The obvious solution to me would be to average out the values (or, given enough data, something like figure skating with the highest and lowest values thrown out, THEN average), but IANAEE.

[KenWittlief]

in redundant systems each gyro would be read and used as if it is the only gyro in the system. The signals from all gyros are compaired. If they dont agree, one of them is wrong

with a dual system you have no way of knowing which one is wrong, so you must shut the system down

with a triple or quad redundant system, the gyro that disagrees with the rest is flagged as defective, and taken off line. The system can keep functioning until you get down to two.

[JBotAlan]

OK, I get it. That doesn't keep me from trying it. I think I'm going to try it at a somewhat smaller scale. I will probably make a..box(?)...of some sort and play with that. I can probably get away with that. Just think if I used CIM motors on this thing and my code got away from me...rrrr..rrr..RRR..RRRRRRRRR BAM!

And the best part is it would probably keep going. BAM BAM AAAAHHH! BAM

Yeah, you get my drift...

I am going to try something like this, and if I succeed, it is probably going to show up at every regional I go to, so beware!

The patent on the real thing is really interesting...well, sorta:

http://patft.uspto.gov/netacgi/nph-P...&RS=PN/5971091

JBot