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  • Marking starting positions in base

    Hi-- first year coach, first year team, very much a newbie.

    Team had a question today that I couldn't answer, nor could I find it online. Hoping someone can answer:

    Can they use small piece of black electrical tape to mark their starting positions on the mat in base?

    Thank you!

  • #2
    No. You can only use LEGO parts. Some teams build an alignment jig out of LEGO. I think this is a horrible idea, but it is really popular. I have to judge at a tournament on Saturday and I don't plan to get there by carefully aiming my car while it is still in my driveway.

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    • #3
      Thanks, Dean. Helpful. But curious, if an alignment jig is a bad idea, what are better ways to mark starting positions? Team is very young, and very green. Using dead reckoning but learned how to keep the robot straight using gyro sensor. Their robot relies on starting from the same spot.

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      • #4
        OP - we use jigs and gyro extensive (and frankly, we have always scored very highly). We a jig to allow our robot to back up in base in the event of a rear attachment, to get us a bit closer to where we are going, and to position the robot a fixed distance from the wall (which, with good gyro programming, has been very effective for us). I totally agree that using a jig as a dead-reckoning aiming guide is bad, but also, if dead reckoning is what a team is currently capable of, might as well aim it more consistently.

        A better way that positioning perfectly in base is to just deal with however you're positioned. For instance, if you're going to drive to core sample, you can start in base facing east (anywhere in a general vicinity in base). Now back west into the wall, and proceed a certain distance east. Once you're there (maybe odometry, maybe light sensors), turn north-ish, and back up into the wall to square up and face north for real. Now, you've got a pretty good idea of where you are. Drive north, turn left, and maybe use some mechanical squaring to center yourself on the core sample model. No jig needed, and it'll tolerate starting in a variety of spots.

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        • #5
          Originally posted by Dean Hystad View Post
          No. You can only use LEGO parts. Some teams build an alignment jig out of LEGO. I think this is a horrible idea, but it is really popular. I have to judge at a tournament on Saturday and I don't plan to get there by carefully aiming my car while it is still in my driveway.
          That is most excellent.
          FIRST LEGO League Mentor and Referee/Head Referee since 2011.

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          • #6
            Originally posted by bc91404 View Post
            Thanks, Dean. Helpful. But curious, if an alignment jig is a bad idea, what are better ways to mark starting positions? Team is very young, and very green. Using dead reckoning but learned how to keep the robot straight using gyro sensor. Their robot relies on starting from the same spot.
            Marking the starting positions is not allowed, nor practical. Many other teams are going to use the same field at your tournament - none of them can mark up the Base area, nor bring a paper overlay, etc.

            The robot ideally is designed so it doesn't matter where it starts.
            Last edited by Tom Mosher; 11-17-2018, 02:32 AM.
            FIRST LEGO League Mentor and Referee/Head Referee since 2011.

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            • #7
              The problem with repeatable starting positions, straight driving and accurate turns is that your missions are MORE likely to fail than if the robot jerks slightly at the start of moves, turns are always a bit off, and your team forgets how they are supposed to set up the robot before each outing. This sounds counter-intuitive, but it is true.

              When you count on accurate turns and straight driving you have very little margin for error. If the kids are excited and this messes up their aiming your odometry mission is doomed. If the mat isn't aligned properly in the table your mission is doomed. If the robot gets a little loosey goosey and you get more drag on the left wheel the mission is doomed, If the mat is a little dirty or a little worn or there is a tiny bump under the mat or the table isn't flat your mission is doomed. Teams that solve missions by controlling exactly what the robot does are doomed because there are more variables than you can possibly hope to control, and your tournament will bring a host of new variables that you've never tried to control.

              On the other hand. teams that have a sloppy robot design solutions that are robust. Their robot isn't predictable, so they design solutions that are tolerant of variation. If a turn is critical they square against a wall or register against a model. Their attachments often have self-aligning features so the robot can miss the model by an inch and the mission still works. Come tournament day the teams with messy robots are the teams that don't bother to sign up for the practice table. The new variables introduced by different tables and mats and lights and excitement are comfortably handled by the same tools that let their sloppy robot reliably complete missions at home.

              A sloppy robot is a happy robot. Embrace the slop, don't try to control it.
              Last edited by Dean Hystad; 11-23-2018, 04:06 PM.

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