Manipulators: Claws vs rollers?

[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.

[s_forbes]

Originally Posted by 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.

This needs to be reiterated. Get those prototypes done fast, get your robot built quickly, and drive it around for a few days before you ship it! Too many teams look as though they're driving their robot for the first time on Thursday morning at competition.

The same concept applies to all the other parts of your robot, too. "Testing" is indeed part of the design process.

[pfreivald]

We are prototyping several different tube manipulators, including a simple claw and a 'roller claw'...

We are also making our robot modular, so that whatever ends up working best in practice is what ends up on the field!

[IndySam]

Originally Posted by pfreivald

We are also making our robot modular, so that whatever ends up working best in practice is what ends up on the field!

That's is a great way to go. In fact I seriously doubt we even ship our robot with a picker-up-thingy.

[pfreivald]

It's a lesson I learned in real-life engineering that I forgot at first in FIRST, and then remembered, and now am getting more and more insistent upon...

[jblay]

Ive found that in essentially every game but 05 rollers are best for picking up an object. With rollers you can have a very active control on the object and pick up the object wthout stopping.

[Rob Colatutto]

My personal experience with my teams roller gripper from 2007 was this, too much weight. Its very important to keep the weight down on these, its quite easy to get carried away. One other challenge was to design a gripper structure that was light enough to meet our weight goals and work with our wrist actuator design, but at the same time being strong enough to withstand taking a beating on the field and still grab the tubes correctly. We had a match or two where a robot hit us head on with the gripper out, and then it required some 'tweaking' to get the opening size correct. We also prototyped a few different wheel configurations, and tried many different wheel materials, this was very, very useful.

[Ian Curtis]

A claw doesn't need to require precise positioning. You can make it wider so the driver only needs to drive into the game piece, and the game piece settles into a position where you can pick it up. (granted, this will probably be much harder this year than it was in 2007)

Whatever you do, make it idiot-proof. Not because your drivers are idiots, but because the fewer precision maneuvers they have to do, the more awesome driving (and scoring!) they have time to do.