Team Update #18

[Tristan Lall]

Originally Posted by Chris Hibner

Can't the silly force triggers be replaced with light sensors or proximity switches?

That's exactly what I was thinking, but unfortunately it's too late now. Teams have already designed minibots with the pressure plate as a constraint, and played that way for two weeks.

If I'd designed the thing, I probably would have used a series of three or more sensors at the desired level, and used some logic to have them "vote". When a majority say you've reached a discrete position, you'd score. (And it would fail gracefully if it didn't work: a human could still judge the position visually, rather than have to estimate whether a switch was or was not tripped.)

Originally Posted by Chris Hibner

Here's my issue: if they only specify a minimum, then how to you guarantee you trigger the sensor?

According to the logic embodied in the rules, you can't.

[Al Skierkiewicz]

Guys,
Lets not get crazy. The towers work. There is no complicated issues here. If your minibot can climb the pipe in under five seconds it will trigger the top. If it struggles to get up, then the plate may be able to push back with enough force to stop the minibot and not trigger. I saw more than one minibot over the weekend climb the tower with the drive wheels spinning faster than the climb rate. If the minibot made it to the top, only one was not able to trigger the tower in ten seconds. That one was spinning the tire on the pipe at the top. It was simply a matter of equalized forces. The plate did not move.

[pfreivald]

Good call on the math, Ether.

A lesson I seem to have to re-learn every single season is that every measurement FIRST gives is nominal, whether it's said to be nominal or not.

[Brandon Holley]

Originally Posted by Al Skierkiewicz

Guys,
Lets not get crazy. The towers work. There is no complicated issues here. If your minibot can climb the pipe in under five seconds it will trigger the top.

Al-
What your describing is in complete contradiction with some other long time FIRST vets. I've taken both yours and their advice many times, so I'm at a sort of impasse. We haven't competed yet (this week at Bayou we will) but I'm moderately concerned our minibot may not trigger the tower every single time based on its similarity to minibots these other veterans have. While I don't doubt that most minibots will trigger the tower, how can we make sure the towers are triggered EVERY time?

-Brando

[Al Skierkiewicz]

Brandon,
Have faith. Participants, FTAs and Refs are not going to allow teams to miss out should there be field issues. If there is reasonable doubt, I am sure the staff will take action and/or resort to manual scoring. There are contingency plans. We know how hard you work to get to the point of competition.

[Brandon Holley]

Originally Posted by Al Skierkiewicz

Brandon,
Have faith. Participants, FTAs and Refs are not going to allow teams to miss out should there be field issues. If there is reasonable doubt, I am sure the staff will take action and/or resort to manual scoring. There are contingency plans. We know how hard you work to get to the point of competition.

Thanks Al.

-Brando

[Tetraman]

Originally Posted by Al Skierkiewicz

Brandon,
Have faith. Participants, FTAs and Refs are not going to allow teams to miss out should there be field issues. If there is reasonable doubt, I am sure the staff will take action and/or resort to manual scoring. There are contingency plans. We know how hard you work to get to the point of competition.

Yes.

If an issue ends up complicating a regional, the head ref and FTA has the right to make the call and go to scoring the races manually. In fact, I'm sure many head refs will ask for the refereeing volunteers to take mental notes as to the finishes, so if a problem arises mid-match, that match's scores will still end up counting.

[MrForbes]

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. 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.

So Ether's math seems correct, but his lack of a free body diagram might lead one to an erroneous conclusion.

Interesting how so many people get upset about a game challenge that is not quite what they anticipated.

[colt527]

I guess a description of the new tower triggering mechanism would be useful for some here who did not get to see it at a week 2 regional. There are NO force sensors up there. There are simply 3 metal contact points that act as simple switches (note, this is as of week 2. week 1 had 3 limit switches). As long as 1 of those contact points is hit for enough time for FMS to read the signal it will trigger. The setup itself is dead simple.

One problem is that any changes made to the tower need to be so cheap, simple, and easy to assemble that FIRST can ship it to all the regionals and they can put put together by the field staff there. I think FIRST did a reasonable job with those constraints in mind. I would love for the bolts to not be there at all because I still think thats the cause of most robots that reach the top and don't trigger. Maybe the bolts could be reversed so that they are anchored to the bottom plate? (this would increase the effective mass of the bottom plate, so more force would be required to push it up)

Regardless, these are the current constraints of the system and I think with a few small mini bot modifications you will be able to trigger that setup every time. And if it still doesn't, then you have a better case for there being a major flaw in the triggering mechanism.

I believe that FIRST and the teams need to work on getting the automated triggering to work with very very high reliability. I believe the reason for that becomes clear if you examine the following case. For this case, lets make 2 assumptions. First, that teams and FIRST do not continue to refine the triggering. Second, that we allow the refs to manually override the triggering results.

With those assumptions, lets say we are in the final match of Archimedes deciding who will go to Einstein. All 4 minibots go up and all hit the trigger with imperceptible differences in arrival time. However, 1 minibot does not trigger. Now what do you do? A precedent was set in previous matches that the refs can make a judgement call based on what it looked like. Even if in that case the minibot was not as close of a call, but you know that will not stop the team from flooding the field with shaky video footage and their first hand accounts to try and show when it hit. I think these 2 assumptions lead to a messy future.

Now, if teams and FIRST work to refine the automated triggering mechanism then we will probably never even have this problem to deal with. And even if there are a very very small number of cases where it seems like it should have legitimately triggered but did not, then at least there is a consistent precedent of not counting it unless the robot triggers the sensors and the playing field will still remain even for all teams.

[MrForbes]

Originally Posted by colt527

And even if there are a very very small number of cases where it seems like it should have legitimately triggered but did not, then at least there is a consistent precedent of not counting it unless the robot triggers the sensors and the playing field will still remain even for all teams.

Yes...playing by the rules that have been there since the beginning.

[Tom Bottiglieri]

Originally Posted by squirrel

Yes...playing by the rules that have been there since the beginning.

Yeah, we get it.. That's the rule. I don't think anyone is arguing that you need to trip the sensor. The issue at hand is that there is some obfuscation in the method of doing so. Sure, there is plate you need to lift, and it takes some amount of force. But we as teams have no way to actually test what we believe will trip the sensor short of going to the regional and trying it. Sure we can guess all we want at what will and will not trigger the sensor, but in the end it turns out the process for tuning these things is not as black and white as you would hope for. Sure, things don't work perfectly, that's engineering. But there might be a more deterministic way to see who won the race. Beam breakers? We dump way too much time and money into these regionals for "just trust us" to cut it. Real time scoring has never been very reliable, we all know that. It's not an issue if there is an accurate backup. While I'm certain (now more than before with Al's post) that this issue can be resolved at the regional level, the wording of the update was a bit disconcerting. I also look forward Einstein Finals Match 2-2 when everyone's minibot is more or less the same speed.

TL;DR: We all just got told "you're holding it wrong".

[MrForbes]

Do you know if any teams built a TARGET using the field drawings, designed a minibot to make it work every time, and it's not working on the actual field?

If so, then I'd say we have a problem. If not, some teams just didn't do their homework.

[Tom Bottiglieri]

Originally Posted by squirrel

Do you know if any teams built a TARGET using the field drawings, designed a minibot to make it work every time, and it's not working on the actual field?
.

You can build poles until the cows come home. It's the triggering settings that are the issue.

[Vikesrock]

Originally Posted by squirrel

Do you know if any teams built a TARGET using the field drawings, designed a minibot to make it work every time, and it's not working on the actual field?

If so, then I'd say we have a problem. If not, some teams didn't do their homework.

Cory of 254 said exactly that in post 15 in this thread.

[martin417]

Originally Posted by squirrel

Yes...playing by the rules that have been there since the beginning.

As an engineer, I work to engineering specs. If I meet those specs, I expect to be paid. You can imagine that I might be a wee bit upset if I were to design a product that meets the customer's specs, deliver that product, and be told "I'm not paying you because the product didn't do what I expected it to do". If your specs are not written clearly enough, that is your fault, not mine.

In FIRST, the manuals and rules are the specs. Your argument that the 4N force was not in the rules is not valid. The peg heights are not in the rules either. The entirety of the game documentation is the specification document to which all teams work. Our minibot cannot hit the bolt heads, and I can guarantee that it imparts far more than 4N of force. Therefore, by any definition, it meets the specs. If we get to competition this weekend, and our minibot doesn't trigger the tower, am I supposed to just accept that and go on? Is that proffessional? In the real world, it would not be tolerated.

More importantly, this is supposed to be a race. The tower trigger is just a means of scoring that race. Imagine an Olympic sprinter that happens to be too short to reach the tape. If he crosses the finish line first, but runs under the tape, does that mean he didn't win the race? I think this whole argument is silly. The first minibot to reach the top should be declared the winner. All this argument about how to decide that winner is a side note. FIRST should come up with a foolproof method of determining the winer.