Team Update #18

[MrForbes]

The spec is TRIGGERING the TOWER. The spec is not getting there first.

If 254's official towers use the design in the published field drawings, and the minibot does work on them, but not on the modified design tower switches, then I'd say we have a problem.

[Ether]

Originally Posted by squirrel

re: the force required to move the plate, vs. it's weight. If your minibot must lift the entire plate evenly, then it might take more than 4N to trigger the tower.

To lift the entire plate evenly it will take more than 4N.

If your robot contacts the plate on one side, then it only needs to lift that side of the plate. The plate should still rest on the two bolt heads on the other side of the pole. The force required to trigger the FMS should be significantly less than the full weight of the plate.

It's a simple second-class lever. I thought that was obvious so I didn't stated it explicitly. My bad.

[martin417]

Originally Posted by squirrel

The spec is TRIGGERING the TOWER. The spec is not getting there first.

If 254's official towers use the design in the published field drawings, and the minibot does work on them, but not on the modified design tower switches, then I'd say we have a problem.

G67> The RACE SCORE is assigned to each ALLIANCE based on the place of finish in the MINIBOT RACE (ties each receive the points for that place):
1st MINIBOT to TRIGGER the TARGET
30 points
2nd MINIBOT to TRIGGER the TARGET
20 points
3rd MINIBOT to TRIGGER the TARGET
15 points
4th MINIBOT to TRIGGER the TARGET
10 points

OK fine. Let's throw out the last paragraph of my post and concentrate on the rest. What is required to TRIGGER the TARGET? If I don't know the answer to that question, how do I design a minibot to reliably TRIGGER the TARGET? Does it take 4N of force? Does it take some force for a specified period of time? Do I need to hit the plate in a certain area? Do I need to tap out morse code on the plate when I get there? I don't care what the specs are, just let us know so we can design a device that meets those specs.

[Ether]

Where are these "published field drawings" I keep reading about?

2011 Game Field Elements_RevA.pdf mentioned in Team Update #18 does not contain any information about the sensor, or its location, or any details concerning how the signal is processed by the computer equipment to which it is attached.

[MrForbes]

The TARGET is described in the ARENA drawings. As far as I can tell, the only way to make sure your MINIBOT will TRIGGER it is to build it and try it--or do a detailed analysis of how the plate will behave when struck by your MINIBOT. The 2N to 4N thing in the ARENA description gives you an idea of what's required, but you still need to look at the design of the TARGET to be able to figure out exactly what's required.

As for the sensors...I guess we just have to guess at how it works, and make sure the plate will move a long ways when the MINIBOT hits it?

[Ether]

Originally Posted by colt527

As long as 1 of those contact points is hit for enough time for FMS to read the signal it will trigger.

There's the rub. How does FMS read the signal. What if FMS is busy doing something else when the switch is hit?

What are the wires from the switches attached to?

Are they generating an interrupt and being time-stamped? Is that happening locally and the information stored so that FMS can read it when it gets a chance?

The engineer in me wants to know.

[colt527]

I honestly don't think this is as big of a problem as it is being made out to be. So far as I could tell at Pittsburgh, the sensors were pretty darn reliable. The only times they did not trigger it seemed like 1 of these 3 were the causes:

1.) Hit the bolt
2.) Did not hit with enough force (like, creeped up really really slowly with the wheels slipping)
3.) Turned off / reversed immediately after hitting the bottom plate without pushing much at all

If your minibot avoids all those 3 things and are still getting false negatives during the practice day at Week 3's: talk to a FTA. They will help you work out whats going on. I think the practice day will be plenty of time to sort through those 3 issues and any others that come up. Like I posted before, the triggers are really simple, there are only a few possible causes for them not to go, so I really don't think it will be necessary to hit in an exact spot, other than not bolt, or with a super specific force or time (or tap out morse code )

Now, I must say that I am never crazy about automated scoring systems. I wouldn't have designed a minibot race at all because of how hard it is to score without some automation. However, this is the game thats been given to us and you can see my earlier posts about why I think that the automated scoring is necessary given this game. And only because I believe the automated scoring system is necessary am I advocating for teams to take whatever steps necessary to make sure they can trigger the setup.

But still, my gut instincts say that if those 3 little things are avoided, this whole thing will just not be an issue.

[Alan Anderson]

Originally Posted by s_forbes

Quick math suggests about 4-5 newtons of force just to cancel out weight of polycarb plate.

You don't have to lift the entire bottom plate. You just need to tip one side of it up in order for the switch to make contact. A naive analysis says it would take between 1/2 and 3/4 the weight of the plate to trip a switch, or -- hey, lookie here -- about 2-4 newtons.

[martin417]

Originally Posted by colt527

I honestly don't think this is as big of a problem as it is being made out to be. So far as I could tell at Pittsburgh, the sensors were pretty darn reliable. The only times they did not trigger it seemed like 1 of these 3 were the causes:

1.) Hit the bolt
2.) Did not hit with enough force (like, creeped up really really slowly with the wheels slipping)
3.) Turned off / reversed immediately after hitting the bottom plate without pushing much at all

I haven't witnessed it, but others have posted here that not all target triggers were reliable, ie: targets that should have triggered in week two didn't.

Originally Posted by colt527

Now, I must say that I am never crazy about automated scoring systems. I wouldn't have designed a minibot race at all because of how hard it is to score without some automation. However, this is the game thats been given to us and you can see my earlier posts about why I think that the automated scoring is necessary given this game. And only because I believe the automated scoring system is necessary am I advocating for teams to take whatever steps necessary to make sure they can trigger the setup.

I don't agree that reliable automated scoring is difficult. I was a Cub Scout leader several years ago, and our pack had a home-made Pinewood Derby track. The scoring was automated and home-made. A simple beam break trigger and a timer. It was 100% reliable (I never saw a failure to trigger in 4 years of races).

[Ether]

Originally Posted by Alan Anderson

You don't have to lift the entire bottom plate. You just need to tip one side of it up in order for the switch to make contact. A naive analysis says it would take between 1/2 and 3/4 the weight of the plate to trip a switch, or -- hey, lookie here -- about 2-4 newtons.

You're a little late to the party. That point has already been made.

[DonRotolo]

Originally Posted by A_Reed

to make sure your mini bot does not hit in the bolt pattern on the bottom of the plate.

Originally Posted by colt527

if those 3 little things are avoided, this whole thing will just not be an issue.

I dunno, having only been at a Week 1 regional I haven't witnessed towers triggering properly.

But clearly there are some pitfalls to be aware of, just make sure they are addressed. IF someone witnesses a reasonable hit not being recorded in Week 3, please post a video here. Then we can argue the point.

[MrForbes]

Assuming the problem has to do with the time it takes to TRIGGER the field system, not the force exerted, it seems that some means of controlling the deceleration at the time of impact with the TRIGGER plate, might help. Perhaps add a springy finger to the top of your MINIBOT?

[Ether]

Originally Posted by squirrel

Perhaps add a springy finger to the top of your MINIBOT?

Great idea. And simple to implement. Perhaps just a small loop of surgical tubing at the point of contact would do the trick.

[MrForbes]

I was thinking of a thin section of large diameter PVC pipe. We use a few of these on the bottom of our (heavy) MINIBOT to cushion the fall back to the BASE.

[Cory]

Originally Posted by squirrel

Assuming the problem has to do with the time it takes to TRIGGER the field system, not the force exerted, it seems that some means of controlling the deceleration at the time of impact with the TRIGGER plate, might help. Perhaps add a springy finger to the top of your MINIBOT?

Or FIRST should fix their system. Why should the customer fix a part that came to them out of spec? We are paying for something and if FIRST doesn't deliver the onus should be on them to fix the problem, not on us to work around their broken implementation.