Re: Tipping opponents robots
 

I mean no rudeness, just to give warning. I'd expect to get tipped at least twice during the qualifications with this mindset. I'm not a driver, coach, or even participating in this years game other then reading on CD and watching online so I am no threat to tip anyone over. However, anyone out there is. Back in 2006 our robot tipped at the end of 75% of our matches because we couldn't make it up the ramp but continued to try. Our robot received no damage because it was built properly. Also, in 2007 our robot got tipped from a foot of the ground multiple times because we weren't seated on the lift properly. It happens. Accept it, expect it and build your robot robust. Otherwise you will regret it.

Re: Tipping opponents robots
 

Here's the link to that Q&A response:

http://forums.usfirst.org/showthread.php?t=14598

The important part of the response is:

This is pretty much normal for FRC. I always tell people, "It's a non-contact sport... like Basketball." :) Bring on the bumps!

Jason

Re: Tipping opponents robots
 

How is this being enforced in practice?

We have a robust robot chassis with very grippy tires. Given our design and seeing 3 competitions live, I believe that our robot has a low enough CG together with enough traction, power and torque (and I use those terms advisedly) to basically tip over 80-90% of the robots in any given competition by just driving into them (the grippier their tires, the easier the task).

Forgetting for the moment about whether or not my braggadocious claim above is true, suppose it is true for some team out there. GP and <G36> tell me that going around tipping robots is not a FIRST Appropriate Strategy (FAS), but where do you draw the line? When can the driver of that mythical robot put the pedal to the metal and when should she back off?

Can she push a robot up and over a bump? How about under the tunnel? Into the goal? What if it is a straight up pushing match in the middle of the field -- if the other robot starts to go over, does she have a moral obligation to back off to prevent a tip? Morals aside, what are the ref's going to call?

I am looking for advice on a real dilemma not a theoretical possibility. In this case, where do you draw the line between FAS and non-FAS?

Your thoughts are welcome, no more than that, sought out and celebrated.

Joe J.

Re: Tipping opponents robots
 

Joe,
The refs are well versed in this and have a good handle on how the match is progressing by watching the robots up close and the faces of the drivers. This game is a little more difficult than most since many robots tip when coming over the bump. However, it is not as hard to tell that an opposition robot is in a position to help the fall or get out of the way. For instance, a robot that is already on two wheels and gets pushed over by another robot is not the same as the same robot backing off so there is no contact. A repeated hit on a robot that is already on the bump and terribly off balance is obviously an attempt to tip the robot. Pushing and shoving is expected, repeated charging from across the field is overly aggressive behavior.

Re: Tipping opponents robots
 

Joe,

We found that the grippier your wheels are the more chance that you will be tipped. We believe the reason for this is that the bumpers are 10" off the ground this year, giving a larger lever arm to rotate the robot in the 'roll' direction. Wheels that slip more tend to help a robot not go over while wheels with higher CoF 'dig in'.

Just an observance ;)

Re: Tipping opponents robots
 

I think you're describing 2 different situations here, tipping versus being tipped.

When tipping (intentional or not), you're either head to head, or you're pushing on the side of their robot. In both of those situations, higher CoF -> Greater force vector -> Better "tipper". I think this is the situation Dr. Joe was describing.

When being tipped, you're often being pushed from the side. Maybe in this case lower CoF makes it more difficult for you to be tipped over. I think this is the situation you're describing.

Re: Tipping opponents robots
 

Certainly one way to ensure that you are hard to tip in the middle of the field is to have slippery wheels. Having grippy wheels also make you more vulnerable to tipping from the side.

We can debate the physics of this years bumper etc, but I remain firm in my thought that there are robots out there (my team's robot one of them, in my opinion) that could be quite effective at tipping other robots if they wanted to be.

So... ...what are the ethics and rules regarding this behavior?

That is what I would like to discuss.

Joe J.

Re: Tipping opponents robots
 

We also have a robot whose CoG seems to be lower than 75%+ of those who we have faced. In head-to-head pushing matches (and even moreso in head-to-side cases), the other robot usually starts to tip. We didn't really try to use this to our advantage (especially after the story below), but some teams clearly did in the playoffs at NYC when facing some high-CoG bots - their first action in teleop was to ram their opponent and force them to flip. I believe that there were penalties for this, but no red cards.

At NYC, we did receive a red card for "aggressive robot behavior". We were pushing the bot that was playing defense on us, and they flipped over. Had we pulled back a split second earlier, they probably would have landed on their wheels (but it was impossible to see this at the time - the action was right in front of our player station and the collision was blocked by the body of the robot that was tipping).

Although the referee did not clarify the reason for the red card short of "aggressive robot behavior", I think that we probably would have been alright had we not then made repeated contact (though not explicitly intentional or damaging) with the flipped bot while we were scoring - the bot flipped right in front of our left goal, and the right goal had one of our teammates lodged in it, so we tried our best to squeak by the opponent and score. So my takeaway was that head-to-head pushing matches are fair game, but once somebody has been flipped you must take extreme care not to contact them - at least that's how things were called at NYC.

Re: Tipping opponents robots
 

Joe -

To me, it's the difference between the old 5-yard and 15-yard facemask penalities. It's really a judgement call on the refs part, and I would have a student talk to your head-ref to see how they're going to call it.

If you tip somebody because you're both driving and it happens quickly, probably not a penalty/yellow/red card. To me, this is an FAS.

If you tip them because they're already off-balance and it looks intentional, that's probably a penalty and a non-FAS.

Re: Tipping opponents robots
 

Refs can tell a lot about intentions after seeing teams play for 3 days. If you're driving aggressively (and most people are) but back off before tipping people most of the time, they're more likely to assume it was an accident the one time you do tip someone. On the other hand, if they see you tipping people match after match, they're going to start acting on it to make you stop. Likewise, if a match is close and tipping an opponent is likely enough to change the results, they're going to look closely at that.

As with most FIRST games, hard impacts and pushing people around is expected. The refs will do their best to determine intentional and accidental occurrences, but we can all help them out by remembering gracious professionalism, and acting in a way that leaves no doubt as to your intentions.

Re: Tipping opponents robots
 

I have been watching quite a few matches and the referees seem to be pretty consistent on the tipping calls. There is a difference between tipping from incidental contact and intentional tipping. The ones I have seen called were incidents in which two robots are pushing head to head and one gains the advantage when the other one begins to tip. At this point, if the "grounded" robot continues to push their advantage by driving through and flipping the other robot, then a yellow card is almost always called for "causing intentional robot damage". However, if a flip is imminent and the "winner" stops or backs off, then no call is made. I have not seen any calls where flips resulting from contact with the humps are coincidental with robot contact...as long as there is no obvious aggressive move to take advantage of a precarious position.

Re: Tipping opponents robots
 

I have reffed 3 competitions this year and can offer my opinion. Be clear that this is a head ref call at each competition so my opinion is only that unless I have on the yellow shirt. That said, from my experience and what I read, we are pretty consistent.

The penalities I and others have called have been mostly described in this thread. When you lift a bot up and it appears to be tipping, your behavior at that point determines the penalty. If you clearly keep pushing it over or hit it again (in the ref's opinion, not yours) we have to decide intentional tipping. It's not a clear cut thing and subject to the viewer. Your driver may be pulling back on the joysticks before the other bot tips but maybe your wheels spin or there is a lag. We see one thing while you are trying and seeing another.

We also must decide if the tipped bot had a chance not to tip. Say 2 bots rear up (horse lingo) on each other in the middle of the floor. If one tips but could have backed away instead of fighting the rearing war then the call is questionable.

Clearly the GDC says this is a contact sport but the spirit of the game is not to turn the other alliance on their backs so your bots can win. Play hard, play clean, and if you get penalized when you think you shouldn't and you can't remember a single time that you didn't get penalized when you should have then you need to think harder! :yikes:

Re: Tipping opponents robots
 

Joe,
I don't think the culture has ever changed for this. Tipping on purpose is bad, and won't get you picked in the finals. Tipping on accident and feeling bad about it, is what is expected using GP as a guide. It will happen in the contact type of game we have. Avoiding it will demonstrate GP. Trying like mad to help keep an opponent from tipping while in contact with you in my opinion is also a good thing. I know many drivers that come in contact with a robot that is driving hard will just stop moving and let the other robot decide the next course of action. If they continue and tip, that was their decision. If you meet at the top of the bump and the opposing robot continues to try and drive over you ( while you hold your ground), they will suffer when they fall off and turn turtle.

Re: Tipping opponents robots
 

I hope refs are also looking for robots that are "tippy" and yet still choose to get into pushing matches with machines that have a low CG.

Just as it behooves teams to not intentionally tip a robot, teams who have tippy robots should also bear the responsibility to avoid situations where they might be tipped.

It might not be gracious to intentionally tip and opponent, but it sure isn't professional to make your robot try and do something it wasn't designed to do. Teams with tip-resistant (or self-righting) good pushers sacrificed something during build to gain those characteristics and should be able to use them in competition.

Jason

Re: Tipping opponents robots
 

Seems to me that tipping is a very rare occurrence during qualifications, most teams are live and let live. The only time that heavy defense is played during qualifications is when two highly ranked teams, near the end of qualifications are looking to gain a few ranks on one another.

Other than that, it would seem that everything is much more competitive in the finals and its no holds barred. Tipping seems a much more common occurrence when a robot is going to score by pushing balls in... the ramp leading up to the goal seems to cause more problems for teams than the bump. This is probably because the teams, rules, and refs don't seem to see it as a problem area until its too late.

I hope to never hear an alliance say "You need to disable this robot through any means necessary." I'd much rather hear "Play heavy defense," or "Don't let them score." The intent behind the actions will determine how the team responds to averse situations.