Re: Tote Grapping Strategy
 

Speaking from experience I think that if you could pull it off, you'd better to do it really well. Because if you do go this route and your only okay at picking them up, then you have spent much time and effort into developing a mechanism that may or may not win you any awards or alliance selections. I personally don't think that the suction cups would be able to handle the weight of very many totes, or get simply bumped around enough while driving, to maintain suction. Just like in a car with a GPS system, if you hit a hard bump or swerve out of the way, or maybe even turn to sharply, you will lose the suction and then all your totes fall. But if you could do it well it would be impressive and memorable.

Re: Tote Grapping Strategy
 

This year more than most, every robot on an alliance must contribute to the scoring in some way in every match or will be written off come alliance selection time. Mercilessly test your prototype as soon as you can since you will not have the luxury of drawing on the experience of other teams. After you are done trying to make it fail in every way possible, have someone else try to make it fail. If it still is reliable, you have a great way to pick up the totes. If not, you hopefully have enough time to implement a different way to pick up totes.

Please note that I do hope that you succeed in this since it would be really cool to see an alternative way of playing the game.

Re: Tote Grapping Strategy
 

Easy and cheap to prototype.
http://www.harborfreight.com/4-1-2-h...cup-40993.html

Re: Tote Grapping Strategy
 

We did a curved rectangle suction test using thundercord as the seal, a pneumatic tube hard mount as the port to draw air out, and a pneumatic cylinder as the vacuum generator. It worked really well with human hands. It lifted that RC up quite nicely, even when the vacuum was placed at the very bottom of the RC and rotated up from a laying down position.

We then started to work on what it would take to get a good seal around a recycle bin every time with a robot. It is these auxiliary components which start to make everything complicated, since the two basic requirements of the overall mechanism aren't met without some serious extra 'stuff'. All told, it would take 8 buttons just to drive this mechanism, and it isn't even the primary mechanism (ironically that one only takes 2 buttons...).

We haven't written the concept off yet, but we did do a pros & cons list. Most of the cons are about complexity in one dimension or another, which tells me the design is very likely to be unreliable if we try it. We have some other designs which use some features that are similar to the auxiliary components of the suction design, so we're moving forward with detailing the little things out first.

If you do decide to go in the suction device direction, keep in mind the simple movements of the robot, and the workload you'll put on your driver.

The only advice I'll give outside of that is to not use suction for totes unless you have great drivers or a great alignment/counter force mechanism.

Re: Tote Grapping Strategy
 

Personally, I would be worried about two things with this design:

1) Having a piston moving up and down on the robot using a chain. Is it possible? Yes. Would it be very difficult to get to work, especially for a relatively new team? Definitely.

2) Using suction cups. The design could work, but the totes would have to be in exactly the right place to be grabbed (not near handles or bends in the plastic), which is not going to happen often in real life.

None of the designs that our team suggested required anything more complicated than a two-motor setup, and yet we found seven different ways to get a four-to-six-tote stack, with three of them able to grab a recycle bin as well. This design would be kind of overly complicated, considering the fact that it could really only grab and carry a single tote at a time.

That being said, this is a clever idea. Best of luck on whatever design you end up choosing.

Re: Tote Grapping Strategy
 

We used an old suction device at the end of a small shopvac and found that it can form a nice seal on the flat portions of the totes on either short end (where the FIRST logo it). You would still have to find a way to raise the totes and control for rotation of the tote as you raise them (similar to how many hook designs have to control for rotation), but it's potentially do-able. We will not be pursuing this design further, though. We liked our other prototypes more, for numerous reasons.

Re: Tote Grapping Strategy
 

This thread might fit better in a more robot-focused board rather than one devoted to game-play strategy, but that's just me ::rtm::