30-01-2005 12:25

Max Lobovsky

Re: pic: Team 45 teaser

AHHH! No! That's my idea! Honestly.


What encoder are you using there?
Are you going to use three for truly absolute positioning, or just two and assume your robot won't slide sideways? (I assume your drivetrain is skidsteer of some sort)

30-01-2005 13:04

phrontist

Re: pic: Team 45 teaser

I can testify that Max has been talking about this for ages. At least a few months before build.

For those of you who are wondering what is going on, this is a navigation plan. Essentially by using encoders on omniwheels set aside for this purpose, you can get much more accurate navigation then counting the rotations of your drive wheels, because a lot of slippage will be eliminated. Theoretically.

30-01-2005 13:37

MattB703

Re: pic: Team 45 teaser

Max

I love your idea.

I've been dreaming about the same thing for years.

I think that with 4 identical motors this year, a flat playing floor, and with Dr. Joes pointer to the Dewalt trannies, this is going to be the year for a 4 omni-wheeled Kiwi-bot.

Matt B

30-01-2005 13:40

Max Lobovsky

Re: pic: Team 45 teaser

Those are exactly the points we were thinking of . Well at least some of us. Not everyone was convinced it would be a great idea.

I should have some very interesting pics by the end of next week. Our wheels in particular are interesting.

30-01-2005 13:48

Alex Cormier

Re: pic: Team 45 teaser

hey i saw some pics from your website on your idea and bot so far. I'd give ya a pointer that we are going with this year, why do you need 5/8" shaft when 1/2" shaft is enough? you will save weight for your arm and other features.

30-01-2005 13:51

Max Lobovsky

Re: pic: Team 45 teaser

That's just a prototype. The real thing is/will be a lot more efficient in a million ways.

Anyway, I didn't mean to hijack this thread, I just wanted to post a picture of my sensor wheels. I will have some nice pictures of the real thing shortly.

30-01-2005 14:57

Madison

Re: pic: Team 45 teaser

Team 488 has had "follow wheels" on its robot in the past and will again this season. They use those unpowered wheels, coupled with position encoders, to gain an accurate idea of how far the robot has traveled without being affected by wheel slip.

Who's to say that's what this teaser is, anyway?

30-01-2005 15:26

Max Lobovsky

Re: pic: Team 45 teaser

Very small omniwheels with some sort of sensor attached. Mounted on arm with single round attachment point that can clearly function as a suspension to keep it pressed on the ground. Doesn't seem to be any thing other than a "follow wheel". Do you have any pictures or drawings of the wheels your team used?

30-01-2005 22:31

Alan Anderson

Re: pic: Team 45 teaser

I don't recall the encoder part number or manufacturer. It's standard quadrature output, 64 counts per revolution, rated for several hundred RPM. I do know the one we're using is the less expensive version of its ball-bearing cousin.

We have three of them mounted on the robot, all in a straight line (figure how that works if you can). Slip in any direction is expected and accommodated. The software to deal with them is surprisingly simple (except for the extra hoops it takes to use the third hardware interrupt).

30-01-2005 22:36

Max Lobovsky

Re: pic: Team 45 teaser

If they are in a line but not oriented the same way, then I know how you are doing it. I realized that would be a better after that rendering was made months ago.

I assume there is going to be a torsion spring at the shaft (or a compression spring on the arm itself), or are you having gravity do the trick?

31-01-2005 12:30

Alan Anderson

Re: pic: Team 45 teaser

Gravity will probably be sufficient, but there's a small torsion spring just in case.