Quote:
Originally Posted by Michael Hill
This blows my mind. With code available online that does the work for you, how do teams let this happen to them?
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Having done mecanum and octocanum successfully (or not) for about 4 seasons with 3309. I had to debug a lot of other teams's mecanum drives. The number one reason I saw was not implementing a gyro. With inadequate practice, drivers just revert tank. Some just avoid strafing, others just use the tank code instead. I think most teams I met did not know the gyro was important, the remainder could not get their gyro to work. I speculate the later was due to a lack of time for the programmers to work on their robot.
the second issue I have seen is that teams over tighten the Andy-Mark mecanums, locking the rollers preventing the strafe. this issue can very from all the rollers to just one. Even with one roller jammed, strafing is awful with every rotation of the wheel.
I had lot of fun with mecanum, its a cool off season project but I am having 3309 go back to tank. To explain I will steer this conversation back to the t-bone topic. There are defensive analogues for mecanum. 3309 and 3476 have practiced a fair bit together. 3309 ran a octocanum this year. 3476 had a west coast tank that were slightly faster than 3309.
Two moves that tanks can do against mecanum are:
1. Plowing: Essentially a T-Bone but you carry through with your hit. this was common tactic in the wedge robot era. 3476 would ram the side of 3309. 3309 would attempt to roll dodge. then its a battle of skill , 3309 would try to roll off and continue but if 3476 turns with 3309, 3476 would keep pushing or rather chasing 3309. So its essentially looks like a high speed t-bone. If 3309 stops moving, 3476 will push them or if 3476 lets off, 3309 would escape. If 3309 can't escape, eventually the robot will wither run out of room to roll dodge and get pinned into a wall (with pining rules being applied) or attempt to straighten out to shoot where the pushing force 3476 will start shoving 3309 off course. typically, 3309 would roll to the goal and thus 3476 would shove 3309 into the wall forcing 3309 to low goal score.
2. Wall defense (I know this as crossing the T): i think this is the best against mecanum. 3476 would drive back a forth perpendicular to 3309. We tried having 3309 strafing to get around but the drive was not quick enough. Mecanum could not push through, so 3309 dropping to tank mode to push 3476, it would work but wasted a lot of time. So it forced 3309 to adopt V turns and fake outs to get around. This was when 3309 decided to not do mecanum again because the bulk of the moves that would work were tank drive moves that 3476 uses. We just started running out of uses for the strafe.
I think these are the terms that are colloquial to FRC. It would be interesting if anyone know the history of these driving techniques and how they evolved over time. Personally I feel mecanum is safe from the 20 second long t-bone but they are not immune to defense. More importantly, mecanum can't excecute a t-bone without being a octocanum. finally with ballistic nylon and sail cloth bumper material options, any team can build a very t-bone resistant tank drive.