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November 2013


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Bob and Ann Henshaw <[log in to unmask]>
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Bob and Ann Henshaw <[log in to unmask]>
Sat, 30 Nov 2013 23:42:34 -0500
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Dear FLL community:


We are looking for advice regarding an unexpected programming problem with
our robot. Sorry for the long explanation, but I wanted to clearly state
what we are observing.


We are trying to combine 4 separate missions into a single mission with 4
sections triggered by a touch sensor. To do this, each separate mission has
been saved as a myblock (eg MB1, MB2, MB3, MB4), which run in sequence
between wait loops triggered by the touch sensor (eg. MB1, wait, MB2, wait,
MB3, wait, MB4). 


The first problem we encountered was that the A motor (which controls our
attachments) was locked and not moveable as we tried to exchanged our
attachments and reset the position of the motor between segments. We
addressed this by using a motor stop at the end of each myblock to unlock
the A motor. (eg. MB1, stop, wait, MB2, stop, wait, etc). This allowed the
motor to be freely moveable and allowed us to reposition each attachment at
the right angle. 


However, when running this program, we found that the A motor, starting in
our second segment (MB2), moves much further than programmed. For instance,
the A motor would move over 200 degrees instead of 120 degrees, causing the
robot to get stuck. 


Our initial thought was that we were running afoul of the rotation sensor of
the A motor as we manually moved the motor with each exchange of
attachments. To address this, we attempted to reset the rotation sensor
using the rotation sensor block, with the A motor checked, Action set to
Reset, and the compare degrees set to 0. We tried placing this reset block
both before and after our wait loops, with no change in the observed
behavior. (eg. MB1, stop, reset, wait, MB2 etc   no different than MB1,
stop, wait, reset, MB2, stop, wait etc). 


We also tried unplugging the A motor between missions, trying to see if this
would manually reset the A motor, without any change in this behavior.


Our 4 missions continue to work well as individual programs and we will
likely continue to operate with 4 separate programs. However, we have spent
a fair amount of time as a team trying to determine why the robot is
exhibiting this behavior. 


Thanks for any and all suggestions.



Bob Henshaw




Ann and Bob Henshaw

3808 Fort Worth Ave

Alexandria, VA 22304


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