I just witnessed 2543 Titan bot, a wide front robot and a defensive robot for the winning alianace at the San Diego regional, pin the two top rated scorers 968 RAWC, and 1538 holy cows that were both skinny front robots. They were the reason this alliance one because they drew away the other scorers to help get them out of the struggle.
((TOM’S ADVCICE) long robots get pinned easily by wide robots due to the hitch differencial so pick well in the finals and if they get stuck their is almost no way to get out of the snag).
I was just wondering if anyone has any ideas or strategies to fight this innevitable struggle.
Stay off the walls/corners and learn how to drive when being hit from the side. Watch the driving at Kettering espeicially in the finals. There are some very good robots that are very good about not getting pinned. There are others that are very good at pinning.
The technique for not getting pinned in the when hit in the middle is a little counter-intuitive. The “initially logical” way will actually get you pushed straight to the side and then pinned against the wall. The other technique usually will help you get away as long as the other bot is not significantly faster.
I am going to leave this one a little open for others to contemplate. Feel free to post the solution if you figure it out. I want to diagram the physics of this technique as it is a really neat and “counter intuitive” thing.
Wouldn’t you just let go of the sticks? … and if that doesn’t work turn into them? (if you can get traction) That’s my first response to the situation…
I haven’t had the opportunity to be under heavy defense yet, so I’m not sure… Can’t wait for LA
When you say “middle” do you mean the geometric middle of the robot? If so doesn’t the answer to your question depend on the center of mass of your robot (among other things).
Assuming your center of mass is behind the center of your robot (as ours is) it seems like you would want to reverse the side away from the pinning robot adding to the rotational moment they are providing.
Brad, “turn into them” is a little vague. For our robot turning towards them by powering the far side forward will result in canceling the moment and us getting pinned. Reversing the far side will add to the moment and spin us around, likely letting us escape. Both of these maneuvers are trying to turn our bot towards the pinner, but only one will work.
Watching both Kettering and the SD webcasts, I can tell you that 2543 was a different breed than the defensive bots in Kettering. No offense to the defensive or offensive teams in Kettering, who both did outstanding jobs, but 2543 did it better.
They would hit 968 perfectly so that the contact could not be avoided or escaped from after initiated. They would often hit them in a wide-open section of field, no other bots or walls nearby. Then they would push them all the way into the wall (often halfway across the field) and hold them there.
Their pins on 1538 weren’t quite as pretty, but combined with the traffic generated by alliance partners and the corners, they made it almost impossible for 1538 to score.
http://img17.imageshack.us/img17/149/pinned.jpg
Heh, true. Well the pinning motion I believe is being described here, after watching san diego, is where a wide robot gets inbetween your trailer and the back of your robot. The initial reaction would be to try and “turn away” (to the right in the shown picture) or drive straight to get into it. But you would want to turn left, pushing your trailer into them, allowing you to eventually speed out of it. I also believe letting go of the sticks completely will help, because if your opponent ever stops accelerating you will be let free, and will have to accelerate at that point. Then again whoever is pushing you should never let go.
It seems to me that turning right into the pinning robot would be the thing to do to break the pin, especially if the pinning trailer is in your path to the right. If you turn to the left, you will be driving your trailer into them and they would push back on it and pull you back into the pin.
I meant getting hit in the middle of the regolith.
Bingo.
here is my take on it. For the record we have a crab drive and do a slightly different manuever, but essentially this works .
If you try to turn away from the attacking bot, the trailer wedges against theirs. At this point you trying to turn your bot (highest energy action), your trailer and their bot. Meanwhile your opponent is just trying to drive you sideways. The appearance on the field is a magic hit and then you get pushed across the field into a wall.
If you turn into their bot, your forces are opposing theirs which keeps you in place (center of regolith). It also causes your bot to rotate around theirs, and theirs to rotate about yours. As the speed of rotation increase, you will slip away (unless they are way faster), and your trailer will swing around the front of their bot and break loose.
Check out early 33 videos for what not to do, and then the last qualification match (towards the end) for a into the skid example.
Now the downside of this manuever is it exposes your trailer to the front (business end) of most robots. This will often result in a ball or two in your trailer, but that is better then the pinned and filled routine.
This principle also explains why it is so hard to turn off of the wall.
The key to avoiding defense is just that, avoiding it. Because of the low friction surface even impacts can throw you off a great deal, and pinning is deadly since you can’t count on a strong drive to break free. Also if you’re team is super high scoring, and the other alliance doesn’t also have a super high scoring bot I would suggest sending your own defensive bot to deal with the one playing on you.
Why not just drive backwards? The inertia of the defending bot will take it with you and turn it to its left, freeing you to do as you please.
Also this depends on your proximity to the wall. If the wall is directly to the left in this drawing, you’re in a bit of hurt.
we have found a trick that works for our robot, if you notice our robot has between 75% and 80% of its weight on the back two wheels, this essentially makes us a wide robot. (we are narrow) when we are hit the front of the robot pivots into the turn, which rotates the robot in a circle, pulling the trailer away from the pining robot. we can increase our turn by utilizing our turret. our robots turret is a large part of the robots weight, and by accelerating it we turn. (35lb turret with a 27.5" diameter provides a lot of rotational inertia) we designed our turret to act like a gyroscope.
After attending both the NJ and NYC regionals, and driving 25 matches between them, i found the best way to not get pinned is to drive backwards. Our robot was in the long configuration, and since the trailer is about the same width as our robot, i never had a problem getting out of getting pinned. Driving backwards lets you turn way easier, as the trailer helps spin you around. Another great way to not get pinned is to have a robot on your alliance pin the other alliances robots (thank you team 1796).
