2012 Team Update 4

[wilhitern1]

Originally Posted by compwiztobe

But I think his point is that the robot is already flat on the bridge, the or only requiring one of them to make it legal. And of course what is "flat?"

I think you may be missing some of the physics. Your robot is not adhered to the bridge. Therefore you are lifting the weight off of one set of wheels and putting it all on the others. Yes, it changes the balance, but not necessarily enough to account for the distance raised. Think carefully...

[Paul Copioli]

If I have a 6 wheel drive robot and my CG is on one side or the other of the middle wheels, then I do not need the other set of wheels to remain flat on the bridge. If I stick something out between the wheels that are not needed (and hanging over the edge of the bridge) I will remain flat with respect to the bridge the entire time. Once balance, we retract. This update gives me the ammunition I need to fight for this mechanism.

What we really need is a clear and concise ruling on this bridge balancing device.

There is a reason many of us are asking the questions so specifically. The extra clarification in the latest update makes it clear to me that if my robot looks like it is not raising its bumper relative to the surface that it is on, then we are good.

The fact that so many of us are not in agreement means we may need further clarification.

[ebarker]

Originally Posted by Greg McKaskle

I'm also curious what you mean by FPGA overhead?

me too, inquiring minds want to know !

[cgmv123]

They should just put big sheets of lead all around the field to stop all the arena wireless signals.

[EricH]

Originally Posted by cgmv123

They should just put big sheets of lead all around the field to stop all the arena wireless signals.

Don't need lead. A Faraday cage ought to work just as well, and those aren't lead.

[pfreivald]

Originally Posted by Paul Copioli

The fact that so many of us are not in agreement means we may need further clarification.

Right-o. That's all I was saying; that this ruling isn't so much a ruling as an additional vaguery. I wouldn't count on the legality until something much more explicitly phrased comes along!

[cgmv123]

Originally Posted by EricH

Don't need lead. A Faraday cage ought to work just as well, and those aren't lead.

The point was that the lead would prevent everyone from seeing the field. Hence the

[mikegrundvig]

Hmm, I don't like the wireless bridge thing. To be blunt, I don't have a lot of faith in last minute swapping of parts by either officials or ourselves. Our team has had trouble with that in the past and it's been a real problem.

I think part of what it takes to do well in competitions like this is a matter of reducing risk and mitigating potential problems before they arise. For instance, last year the team counted on a potentiometer to determine position. They ended up destroying the pot (never heard how) and had to replace it. The new one wasn't of the same value and so they immediately burned up a motor by driving past the stop on the arm. The solution would have been some calibration system combined with limit switches. That would make it possible to swap parts and even if something went wrong and been working properly in minutes. We've learned this lesson so this year all parts with max/min extents have limit switches along with encoders and what not.

The problem is that something with configuration like the bridge isn't quite as amiable to swamping. A tiny setting off and nothing works and we are scrambling to track it down. We have the Axis camera, onboard computer, and cRIO all plugged into the bridge. There is a lot happening and it will have been extensively tested before the competition begins. Is there any way we could simply buy the newer bridge and use it in the competition so no swapping needed? The $100 cost isn't much compared to the piece of mind that having it already tested and working on the bot will bring.

-Mike

[RufflesRidge]

Originally Posted by mikegrundvig

Is there any way we could simply buy the newer bridge and use it in the competition so no swapping needed? The $100 cost isn't much compared to the piece of mind that having it already tested and working on the bot will bring.

-Mike

The update explicitly says this won't be allowed.

[apalrd]

I too am a skeptic on how the whole bridge swap will work.

-How will teams mount it in a few minutes? We usually velcro our radio to our robot, then zip tie around it so it has no way of falling off. We also zip tie all of the wires to the radio in such a way that they can't come out, and add duct tape to the wire connections since some of them are friction fit (which is really really bad, in our experience).

-The backup radio is significantly larger (~3" in one dimension) than the old one. I expect that it simply won't fit on some robots designed for the existing radio.

-Since the backup radio runs on 12v instead of 5v, they are giving us a 4.5' power cable to plug into our PD board? The update seems to indicate that the power cable goes with a bridge (and that each team will get a power cable in the queue line). I don't see how they expect teams to integrate it into their wire harness (zip tie it in) if the radio is decently far away from the PD board, in a few minutes. I don't see how they expect teams to assume reliable radio power (which is very critical) if they can't secure the wire from damage.

-All of this is done before every match (as many as 12 quals + up to 9 elim matches)?

[RufflesRidge]

Originally Posted by apalrd

I too am a skeptic on how the whole bridge swap will work.

I echo all of these concerns. Hopefully we'll never find out how it would work.

[mikegrundvig]

Rather than hope it never comes up, I think they should just let us use either if we are concerned about it. I know I'm going to have the team order one on Monday night just so we can make sure it will mount right in with our existing system. We were planning on tucking it in pretty tight and the larger one will simply not fit unless we do some work. The current plan was the mount everything low and tight to a removable base. We were even making custom cords to keep run lengths short and controlled between some of the components. This is the type of change that I foresee causing us lots of problems on competition day if we don't plan for it now.

-Mike

[pfreivald]

Having lived through FLR last year, I'll take any solution to the problem and be grateful for it.

[sanddrag]

Does anyone know how the replacement wireless radio will be furnished for mounting? I wish they would tell us it will have Velcro, and which side of Velcro it will have.