Manipulators: Claws vs rollers?

[Stephen of REX]

Who has experience using roller type tube manipulators? Like as opposed to a claw, which you have to carefully position to pick up a tube, a design with two rollers seems like it could pick up a tube faster. Thoughts?

[MrForbes]

Maybe make the claw wide, so you don't have to position it carefully?

http://www.youtube.com/watch?v=EqK_XTSoc1w

We have some experience with a narrow claw from 2007, it didn't work as well as we would have liked

[Jon Stratis]

Picking up tubes is all about positioning - So long as your mechanism can be positioned properly, and works quickly, you'll be fine. That can be done with both claws and rollers. Rollers work actively, and if left on automatically - you drive into a tube and the rollers have instant control of it. A claw, on the other hand, needs to be activated when you want to pick up the tube. This can be done by one of your drivers, or if your clever you might be able to come up with some sort of limit switch to automatically activate it. In the end, you can get a claw to close incredibly quickly, using either a motor or a pneumatic piston. Just think about the brakes on your bicycle... you don't need to squeeze them very far in order to get them to move in and grab the wheel.

[Stephen of REX]

Originally Posted by squirrel

We have some experience with a narrow claw from 2007, it didn't work as well as we would have liked

Same here, http://dulaneyrobotics.com/component...a/Atlanta3.jpg

We're brainstorming better ideas for tube manipulation right now.

[Domtech]

Suction cups on servos

[Chris is me]

Got some Vex? Try a roller claw out in that and play with the geometry. See if you can make it work. If you can, great! If you can't, new design.

The key to a good manipulator is not the kind of manipulator but how much prototyping you put into it.

[Brandon Holley]

Originally Posted by Chris is me

Got some Vex? Try a roller claw out in that and play with the geometry. See if you can make it work. If you can, great! If you can't, new design.

The key to a good manipulator is not the kind of manipulator but how much prototyping you put into it.

MAN, this looks familiar

-Brando

[Chris is me]

Originally Posted by Brandon Holley

MAN, this looks familiar

-Brando

And to give credit where credit is due and obvious - this is directly inspired by a 148 prototype from 2007.

That being said - it's a pretty good prototype! We've learned a lot about tube grip and tube rotation from this prototype, and we'll be able to determine whether or not our final claw needs to be spring loaded in the next few days.

[JesseK]

Got some Vex? Try a roller claw out in that and play with the geometry. See if you can make it work. If you can, great! If you can't, new design.

The key to a good manipulator is not the kind of manipulator but how much prototyping you put into it.

Well said, and I have a video to prove it (link below)!

The kids made 2 proof of concepts Saturday that were both pneumatically-actuated 'dumb' claws, in order to see the feasibilities of chute pickup vs floor pickup. One claw went through the center of the tubes with a 3-pronged approach, the other went for the outer edges of the tubes against 2 pieces of very smooth wooden slats (about 6"x6"). Both worked beautifully from the floor.

We're entertaining the idea of an inner-roller claw since in 2007 that one worked the absolute best* for us and was relatively simple. This year we'd have to modify it, and probably forego the ability to place one of the shapes (gasp!), however that's the tradeoff we'd let our alliances know about.

*look at 45 seconds into the video. We got the idea from Gael Force. In that same video, 340 uses a very simple pneumatic claw as well, adding more anecdotes to Chris's advice.

[BIGWILLI2081]

For a claw, you need a wrist or some other type of mechanism to adjust the position of the ring. With rollers, you can adjust your tube simply by spinning the rollers.

[Stephen of REX]

An idea I had for a manipulator, it would be sprung closed with surgical tubing and the wheels spun by banebots motors.

[Chris is me]

Originally Posted by BIGWILLI2081

For a claw, you need a wrist or some other type of mechanism to adjust the position of the ring. With rollers, you can adjust your tube simply by spinning the rollers.

That is, if you need to adjust the position of the ring.

[Brandon Holley]

Originally Posted by Chris is me

And to give credit where credit is due and obvious - this is directly inspired by a 148 prototype from 2007.

That being said - it's a pretty good prototype! We've learned a lot about tube grip and tube rotation from this prototype, and we'll be able to determine whether or not our final claw needs to be spring loaded in the next few days.

Just to be clear I wasn't trying to call you out for "stealing" a design or anything of the sort. I was just making a comment as to us having pretty much the same exact setup sitting in our lab too.

-Brando

[All Bones]

Has anyone thought about making a generic claw design but with extra space in the top part for a roller? That way you could pick up the tube as easily as with a claw and worry about manipulating it with the roller on your way towards the other side of the field

[IndySam]

Either one can be very effective but the most effective one is a manipulator on a robot that gives your drivers plenty of time to practice.

You can have the greatest picker-upper-thingy in the world but if you don't get practice with it the team with the uber-simple one that they have spent many hours driving will still kick your butt.