Re: What does a defense robot NEED?
 

I've really wanted to see a robot with a powerful fan or air cannon system, so they can just stand under the goals and blow air vertically, and the gust of air modifies the flight paths of the discs enough so that they hit the top of the goal, and fall to the ground. My team did some prototyping, and we had to eventually get a leaf blower to get the effect we needed, but we did notice differences with the smaller machines we used to blow air. The leaf blower just provided the needed scale of power. We looked at the rating on the motor of the leaf blower, and it would be very hard to recreate it with the motors we have provided, but then we did come up with the idea of an air cannon. We thought about having 2 aircannons fire one at a time, and it would be like an anti aircraft base style mechanism. My team ultimately chose to go with an disc shooting robot, and to some degree tabled the possibility of having fans on our robot, but I would really like to see another team test it further.

If I was the #1 seed, I would definantly pick a robot with a large fan as my #1 pick, because I want to have that advantage, and I really don't want to end up going against a robot that can do that!

Just my 2 cents, thoughts?

Re: What does a defense robot NEED?
 

Nearly any bot can play defense, although I don't recommend holomonic drive. Strong drive trains are always good but in this game I'd take speed over power. You need to be infront of them before you can worry about them pushing you away.

The most important thing for a defensive bot is good drivers. Make sure your drivers are practicing with a driving bot ASAP.

The second most important thing is a drive coach and drivers who know how to play offense. The best way to think about stopping an offender if from the perspective of an offender.

As far as specific features some sort of mechanical breaks could be very advantageous for a defensive bot whose drivers know how to use them.

Re: What does a defense robot NEED?
 

Why stand next to the goals, though? Since a disc flies in a nearly straight line, if you impact the disc's flight closer to the start of its flight, that impact grows as it flies along its path.

Assuming a disc is shot, on average, at the centre of the high goal, you need to change its height at the end of its path by 6" vertically. Let's also assume that the shooter is shooting from the auto line, 216" out from the alliance wall they are scoring on, and the disc leaves their shooter 50" above the floor. This means that the disc flies at about a 15.5 degree angle.

What we want to do is find the angle of the flight that will cause a disc to miss the goal for each position of the fan robot on the field. Just set up a couple right triangles to show this.

If you run your fan next to the shooter, your triangle has legs of 66" (the normal 60" of vertical travel plus another 6" to make it miss) and about 190" (about how far the fan might sit from the shooter), such that the tangent of theta (the angle required for the disc to miss) is 60/190. In this case, theta would be equal to about 19 degrees, 3.5 degrees more than the path the disc would take if not interfered with.

If you run your fan next to the wall, the disc begins at about 104" and is still traveling along its 15.5 degree path, so the triangle's legs are 26" (assuming you're as far from the wall as you were from the shooter earlier) and 12" (the 6" of normal vertical travel from 54" plus another 6" to make it miss), and the tangent of theta would be 12/26. That would make theta equal to about 24.8 degrees, about 9.3 degrees more than if you didn't interfere.

What this means is that if you interfere next to the wall, your fan needs to be able to change the path of a disc by nearly 10 degrees, while it only needs about 3.5 if you defend near the shooter.

Note that this doesn't take into account the fact that a disc doesn't fly in a perfect line, as well as the fact that some discs will be closer to the bottom of the goal than the centre, and will need more of an angle change (though this affects both positions equally). Also, it will be a great deal more difficult to keep yourself in position next to a shooter, since they will likely be moving and be near their pyramid when shooting, so you will want to avoid penalties.

Hope this makes sense!

Re: What does a defense robot NEED?
 

Someone did it for me, that explains a lot. Q&A

Re: What does a defense robot NEED?
 

I agree with the vast majority of replies: If you cannot score at all, you will not be a very valuable defensive bot. Even the best defensive bots in previous years often had the ability to score some quick auton or endgame points or to feed their alliance partners (A replica feeder slot on your robot that it could spit disks out of would be cool.....)

Secondly, you need to decide what type of defense that you want to play. If you want to play shot blocking defense, you need a tall bot that can block shots (possibly block the cross-field feeder station shot?).
You could also design a bot that would defend the game pieces themselves. Think Bomb Squad from einstein last year. How could the other alliance have won when they had NO balls to shoot? This would probably require a shorter (<30") robot that can zip around the field and spit the disks out to the other side for your alliance's use.

What you want to do is completely up to your team, but be warned you will need to score some points this year. It doesn't matter if it is in auto or endgame. But I believe that a defensive robot that cannot average 15-20 points by itself (between auto and climbing) will not be worth a pick at any strong regional.

Re: What does a defense robot NEED?
 

They definitely need to be tall this year so they can block any shots by the full court shooting robots, believe me there will be plenty of them this year.

Re: What does a defense robot NEED?
 

What does a defense robot NEED?

Use your vision tracking system to track the opponent's discs and then shoot them out of the air with your discs.

Bonus points if you can calculate their trajectories and only shoot down the ones that are going to score.

Double bonus if you can pick out the opponent's coloured discs, see if they are going to score in the 5 point goal, and then prioritize shooting them down.

Triple extra bonus if you can do it all in auto. Not because the code would be more difficult (it would be the same) but because you'd have to shoot them out of the sky from behind, rather than just get in their way.

Oh, sorry... I thought the question is what does a defense robot need to be more awesome than a good offensive robot!

Jason

Re: What does a defense robot NEED?
 

You'll call me crazy but make sure it has the ability to have something 84" tall on it. Just a sheet on two pieces of wood will do.

Teams are going for the sit-at-the-feeder station and score tons of points strategy. That feeder station happens to be on your side, and therefore you are able to play defense at 84" tall around it.

The opposing team is on your side, so they can only be 60" tall at a max. If you guys can just park infront of them (without getting too close!) they wont be able to make any shots. Period.

Retract your sheet down to 60" when they retreat to their side and follow them. Continue to be in their way at 60" tall. Most teams probably wont build a robot that tall because it isnt good for their climbing, so I feel a robot like this could actually be quite effective.

Im interested in everyone's thoughts on this. At first glance it seems overly simple but why wouldnt this work?