FWIW, we also have seen some inconsistencies with a few of our programs this season. I helped one of the kids cover part of the table with butcher paper and attach a sharpie to the robot. He then ran one of the troubled programs multiple times. It became clear after about 20 runs that the robot was failing in a consistent sort of way. Specifically, the robot started out following the same track. However, after the fourth move, which was a turn, the robot would take one of two different tracks. The difference in terms of number of trails was close to 50%. Half the time the robot would take the intended track, and half the time it would turn slightly too far. He measured it and estimated that the extra motor movement was about 14 degrees. He tried a number of strategies to fix this (changing the power level, for example) but to no avail. Eventually, he added motor resets after each of the move blocks and this seemed to work. There is still variances in the track, but it is much more consistent. My advice is try a few motor resets in your program. It seems like the rotation counter memory sometimes gets a little out of whack and the motor resets help to alleviate the compounding of errors. The second issue that he discovered by tracking the robot's trail on paper was that a two wheeled turn (for our robot using our motors (read as: your mileage may vary)) is not as consistent as a one-wheeled turn. Good luck! John -- John J. Barrett Industrial Medium Software, Inc. 1616 Anderson Road McLean, VA 22102 (c) 703-231-5094 (p) 703-286-0818 (f) 703-286-0888 http://www.industrialmedium.com On Oct 24, 2012, at 8:17 AM, Amy Sabarre wrote: > We are also having these issues with our robot. > > On Tue, Oct 23, 2012 at 7:16 PM, Bob and Ann Henshaw <[log in to unmask]> wrote: > I am a 5 year veteran home based coach with a 2nd year team of 10 year olds. We are working with a Mindstorms NXT system that we purchased new last year, with a fully recharged battery. We are experiencing several intermittent erratic behaviors (listed below) that is driving our team crazy. Please let us know if you have any debugging suggestions. > > > > Observed behaviors: > > > > 1. After completing a planned series of instructions, with the last instruction having 2 wheels turning equally (straight line), the robot suddenly makes an additional turn (one motor, rotating robot about 30 - 40degrees). This occurs even after deleting the program, recompiling and redownloading it, and even after adding an all motor stop block to the program. Our team is referring to this as a ghost and are convinced that the robot is now haunted, just to get us in the Halloween mood. > > 2. The robot, using a two wheeled turn (one motor going forward, one going backward) intermittently turns too far or too short. Programming is being done in rotations for both motors. Because both motors are running together, I canít tell if it is related to the problem above. This occurs about 1 in 5 runs. > > > > I do not think that this is a cable issue, as we are not seeing anything beyond the usual minor navigation errors due to lineup, wrinkles in the mat, etc. That leaves the motors and the NXT itself. Could this be a bad servo motor and if so, is there any way to test them? > > > > Appreciate your suggestions! > > Sincerely, > > Bob Henshaw > > To UNSUBSCRIBE or CHANGE your settings, please visit https://listserv.jmu.edu/archives/vadcfll-l.html and select "Join or leave the list". > VADCFLL administrative announcements are sent via VADCFLL-ANNOUNCEMENTS-L. Visit https://listserv.jmu.edu/archives/vadcfll-announcements-l.html to subscribe. > > > > -- > Amy Sabarre > PK-8 STEM Coordinator > PK-4 Science Coordinator > HCPS > One Court Square > Harrisonburg VA 22801 > > To UNSUBSCRIBE or CHANGE your settings, please visit https://listserv.jmu.edu/archives/vadcfll-l.html and select "Join or leave the list". > VADCFLL administrative announcements are sent via VADCFLL-ANNOUNCEMENTS-L. Visit https://listserv.jmu.edu/archives/vadcfll-announcements-l.html to subscribe. -- To UNSUBSCRIBE or CHANGE your settings, please visit https://listserv.jmu.edu/archives/vadcfll-l.html and select "Join or leave the list". -- VADCFLL administrative announcements are sent via VADCFLL-ANNOUNCEMENTS-L. Visit https://listserv.jmu.edu/archives/vadcfll-ANNOUNCEMENTS-l.html to subscribe.