Driver Talking about Playing Bridge Defense

Hi everyone, I am the team captain and the driver from team 1683 TechnoTitans, we just competed in the Peachtree regional in the past weekend. Despite our cold start (ranked 42nd after first 2 matches), we managed to win everything else and ranked 10th after all the seeding matches. We are the best bridge robot from Peachtree Regional (scoring sheet http://www2.usfirst.org/2012comp/events/GA/rankings.html ). This was partly due to the fact that we did not get our autoaiming and autoshooting back until elimination matches. I have read a lot of discussion on ChiefDelphi about playing defense this year, and this time, I want to talk about defense from a driver’s perspective, to give some insight to other drivers in the following regionals.

First of all, let me give a bit information about our robot this year, so it is easier for me to talk about playing defense. We have 4 CIM motors plugged into 2 two-speed gearboxes from Andymark, and we are using 6 pneumatic wheels. We are using 2 RS775 with Cimulator gearboxes to drive the shooter, which can shoot close to 27 feet, but usually we shoot from the key. With autoshooting, we can achieve 90% accuracy (sadly this did not happen at Peachtree Regional till Elimination due to cRIO overload, but we figured out the problem).

Here is the video of the match i am about to talk about, it starts at 48:48.

http://www.ustream.tv/recorded/21166431

The match I want to show you guys was our last seeding match. We had 1311 on our side, which was 1st seeding, and 1771 as an opponent who was 2nd seeding. Before the match, our alliance decided that my team should play defense, and go to the other side to stop 1771 from balancing on the bridge at any cost, and 590 and 1311 would attempt a double balance on our alliance’s bridge.

I was really nervous before the match because it was my first time playing defense. Although I knew that our robot would be good at it, our strategy never asked me to try playing defense since it was only the seeding matches.
In the video, at around more than one minute, my coach told me to cross the bump and start playing defense. Without hesitation, I crossed the bump and parked right in front of the blue alliance bridge. One problem that occurred was that I ran over a ball during this process, and my initial position was pretty bad. I think one of the most important defensive strategies of defending the bridge is to park facing out, not facing in. This way it gives you more room and easier control. From the video, you can see me quickly correcting my position and ready to play defense.

And here 1771 comes; one strategy that many teams will try against bridge defense is causing the defender a foul. This was the only time throughout the whole event where I gave my robot full throttle. I know that behind me is the bridge and if I touch it, it’d be a foul. But be aware of your opponent, they might suddenly back off and retreat to the key area, and causing you a foul in another way. In the video, you can see that 1771 tried that a couple of times. Concentration is the key of successfully playing bridge defense without causing a foul.

With time expiring, our alliance’s robots successfully double balanced, and another robot came to help 1771 to get me away so they can attempt bridge balancing. When there are two robots around the bridge, things get tricky. As a driver, you should quickly identify what they are trying to do, which robot is trying to balance. If both robots have the capability of balancing, you cannot just play defense against one and leave the spot. One common mistake a driver makes in this situation is leaving too much of a gap between the defending robot and the bridge so that another robot might slip past the defense.

Last important point of playing bridge defense was not to give up till the last second. A good bridge balancing robot only needs about 10 seconds to balance, maybe even less. (in one of the matches I played, I only used 7 or 8 seconds for a single balancing, including bringing the bridge down). Keep playing defense till the last second, like what I did in the video, because they can still cause you a foul at the end if you let your joystick loose.

This is written for drivers who want to try playing defense during their matches, and also a real example for the discussions that are happening on ChiefDelphi about how to play defense in this game. Using this strategy, preventing a triple balance is not going to be that hard.

Someone did that to us at Chesapeake, but they left too soon. I’m not sure why they left and didn’t stop us from getting the double, but they did a very good job up until then. We had success going next to the bridge, and then trying to wedge ourselves between the bot and the bridge, either scaring them off from causing a foul, or actually just getting on the bridge.

My question for you is what are you going to do about robots that just use their alley to get to the bridge? We were unlucky enough to have that blocked by our own tipped alliance member, but that’s not a regular situation.

[G25]
Robots may not contact or otherwise interfere with the opposing Alliance Bridge.

[G44]
Generally, a rule violation by an Alliance that was directly caused by actions of the opposing Alliance will not be penalized. Rule [G28] is an exception to this rule.

If they push you into the bridge you are covered by G44

But, if they get in contact with the bridge while touching you, it’s under [G28], and you will get the foul.

[G28]
Robots may not touch an opponent Robot in contact with its Key, Alley, or Bridge.
Violation: Foul; Technical-Foul for purposeful, consequential contact.

This rule applied at all times, no matter who initiates the contact, see [G44].

True but that’s not what they were facing.

Also one is a technical and the other isn’t

Another successful defensive strategy that I have seen is by taking a long based robot and parking it parallel to the fender, essentially eliminating the fender scorer’s ability to shoot. It also puts you in a perfect position to push any stray robots into your loading alley. From here, you are also a stone’s throw away from being able to play bridge defense.

This was attempted on us several times, and it would have worked, but we have two speed transmissions :smiley:

True, but watch finals match 3 at NYC for an example of bridge defense gone horribly wrong. 333 tries to stop the three robots from getting onto the bridge by blocking their approach, but somehow ends up under the bridge and spontaneously fails, and can’t pull out. The refs didn’t give them a red card only because it would add insult to injury and not change the game, but under a strict interpretation of the rules, they would have been carded.

Lesson: Stay between the bridge and robots trying to get on it, and if you’re playing defense, don’t spontaneously fail.

Is there a video of said match somewhere? I can’t seem to find one. A link would be greatly appreciated :smiley:

There is indeed.

Impressive job. Fending off two bots at once is never easy. As our driver said above, we had to deal with a bot that parked itself in front of the bridge, but I hadn’t really considered a mobile defense. Pushing the other robots away is a pretty good way to avoid penalties. Your shifting gearbox must have really helped in that regard.

I’m not really sure what happened with 333, as they actually helped the opposite team balance…