pic: Toltechs drive-train teaser

[Rick TYler]

Originally Posted by Andrew Blair

This is actually the same exact idea that I had towards the beginning of the season. We are not using it either though...

Sorry for making humorous jokes and not being clear. This is how we will be lifting balls from the floor. The biggest advantage is that it only takes up 10 inches of length on the robot, leaving the rest of the real estate for the hopper/loader/shooter mechanism.

[Andrew Schuetze]

As promised, mentor D. Sean Kelly did a quick edit and uploaded a .wmv to our site, you can view the first cut of our robot driving in the shop. Not seen in this video is the code addition which allows us to complete zero degree spins in C.W. or C.C.W. via a second controller.

http://www.toltechs.com/Rocket/Uploa..._Holonomic.wmv

[Andrew Schuetze]

Originally Posted by greencactus3

very nice. once you get it driving, tell us if 8inches of clearance is always good enough .i was wondering if bouncing balls will bounce off the frame that is "too low" like 8in maybe? or if they just get dragged under..

With all the excitement, we didn't test it with poof's on the floor much less bouncing around. Maybe Wednesday before it is driving again as the electronics board is being finished. The demo plywood board with the quickclamps is not the final version I'll post another update when we test the drive with poofs.

[Kris Verdeyen]

Love the video - that base looks slick. Do you have closed-loop speed control over the wheels? It looks like the lines it's moving in are way too straight to be from open loop motor commands. Of course, I've never built a base like that, so what do I know.

[Andrew Schuetze]

Originally Posted by Kris Verdeyen

Love the video - that base looks slick. Do you have closed-loop speed control over the wheels? It looks like the lines it's moving in are way too straight to be from open loop motor commands. Of course, I've never built a base like that, so what do I know.

Quite the exacting eye you have. Yes there was an immediate concern about that very issue. The video edit cuts outs the shots of a slight drift in one direction. It is more pronounced in one direction more so than any other so the one motor/transmission that is making all the noise in the video was completely rebuilt after the test.

Now how best to get closed-loop feed back from such a drive. Encoders on the wheels may be one way to ensure that all the wheels are spinning at the desired rates but with the large amount of scrub in such a system we are not certian that solves the problem. What does provide true feed back would be one of the electronic chips. Gyro / 2D accelerometer We are getting those items wired and the programmers will work with those a bit while they also work on the camera system being the feedback system for shooting solutions.

Lots of work to do in just two weeks.

[Andrew Rudolph]

Looks like you guys are wel on your way to having a drivable holonomic system. Good luck with that!

Just a question, have you guys tried doubling up the omniwheels with an offset so that theres always a roller in contact with the ground?

We found it to work better with 2 offset wheels, basically the problem without the offset is that without it, the wheel isnt really round, so it bounces and doesnt slide quite as well.

Good luck to you guys and i hope to see you in houston!

[Andrew Schuetze]

Originally Posted by Andrew Rudolph

Looks like you guys are wel on your way to having a drivable holonomic system. Good luck with that!

Just a question, have you guys tried doubling up the omniwheels with an offset so that theres always a roller in contact with the ground?

We found it to work better with 2 offset wheels, basically the problem without the offset is that without it, the wheel isnt really round, so it bounces and doesnt slide quite as well.

Good luck to you guys and i hope to see you in houston!

Have you tried the new plastic omni-wheels from AM? They've made the rollers wider and with a lower profile so you don't see much bounce with these. I've got another set on order in case we need them or as replacements.

work now is focused on autonomous modes and getting the mechanics of the ball harvesting complete and shooting


Thanks,


APS