Reflections on Robodox 599 LA 2011 Logomotion Regional

Wow… what a difference a few weeks makes.   The team performed very well in all aspects.  We picked up the Imagery Award and we were the number 1 ranked robot for most of the meet until a 330 strong alliance beat us and eventually we wound up as the 4th seed.   We teamed up with 207  Metalcrafters of Hawthorne and 973 Graybots of Atascadero for the elimination rounds and breezed into the semi finals where things got a little tougher.    We were beaten by the eventual champions 1197,968 and 3473.   This was a hard hitting match but we scored well and had the minibots done their job we could have advanced to the finals.

So…we live and die by the minibot deployment.  We lived early on and died when it counted.    The last match, 207 had its tower disabled due to a high minibot deployment violation and we had a no go deployment.  So zero points from the minibot race killed us.

Minibot Stuff

We diagnosed the missed deployments to a likely combination of several causes:

1) a weak spring tensioner on the end of the deployment beam.  This takes up the shock and is supposed to put pressure on the minibot wedge to keep it aligned.   But the spring had loosened up and wasn’t checked carefully enough by the kids to jump on it and get it fixed.  This was corrected prior to shipping the robot to St. Louis.

2) The deployment arm was drooping slightly because the slide rails were opening up slightly.  This was compensated for by tilting the arm up slightly.   A better fix might be to add a roller bearing that overlaps the support bracket and keeps the end of the arm from lifting off the slide when fully extended.

3)The minibot slide was missing two roller bearings on the very front of the slide.  This contributed to the droop mentioned in 2).

4) Hard collisions with other robots can jostle the minibot enough to cause the auto shutoff switch to activate from a strong hit on the cowling ceiling that protects the minibot.    I had cautioned the kids about this possibility but they were afraid to mess with the robot and felt that it probably wouldn’t happen.  But of course, I think it did and further analysis of match video might confirm this.   A partial fix was attempted prior to the final match, but this area needs a solid design fix since at Nationals, there will be a lot of hard hitting in an attempt to dislodge minibots from hostbots.   I will suggest that a latch be added that is released when the deployment is activated by pulling a pin out( like a dead man switch)

I did not catch the fact that the kids were not using the checklist that they used so well in San Diego.  I need a checklist for the checklist:) Proper use of a good check list certainly might have helped identify and correct the problem areas mentioned above.  Van gave them a good talking to.

Minibot 3.0:
Our minibot 2.0 and 2.1 run about 1.5 and 1.3 secs respectively.  This might be good enough to be competitive in St. Louis but we should continue to improve since other teams will.   At LA I spoke with several minibot mentors and we exchanged helpful tips.  The kids were mad at me for giving hints to a UCSB physics professor who used our scale and pole to tune up the 1717 minibot since they would probably be our opponents if we got to the finals:)    I learned from 207 that there is a silicon surgical tubing that is a little more sticky than the latex tubing.   We might give it a try along with reducing the normal force created by our magnet.   We should purchase another magnet that is more easily adjustable than the disc drive magnets we are using.   Team 330 had the fixed cantilever design which used polyurethane shrink tubing I think… but this really is not as good as latex in the friction dept.  but it does give them the ability to easily add layers of tubing to adjust the diameter of their roller to optimize the speed.
Our mini bot weighs about 2.5 lbs which is less than 1717s and other fast bots that I looked at so the main thing we can do is adjust the normal force and reduce friction and weight a little.   I am sure we can get to 1.2 sec climb time before St. Louis.    I believe our motors are slightly smoked and we are losing about 5 to 10% of power…but we may just live with this.
Autonomous:
This performed consistently during the meet.   It uses line tracking that is accurate but very lightly damped with large heading oscillations.   This may be cause by too high of speed on the motors or just due to the center of turn being too close to the location of the trackers.   Typically you want the trackers to be fwd of the center of turn.   The more forward , the better the damping.  When at the center of turn, the tracker is neutrally stable and will always oscillate.     I will suggest that we try a lower speed command….but if that doesn’t work we just live with what we have.

For sure, we should get the encoders working and have a backup heading hold with distance determined by encoders.   This is what the Beach Bots do and it works very well.   If a line sensor fails, we will be out of luck unless we are prepared.    A secoondary backup would involve just timed motor commands.
Strategy:
The main improvement would be in the area of defense.   Our team is offense oriented and this is ok…but I didn’t see the alliance partners playing tough defense against the opponent top scorers. When we went up against  the 330 alliance, their partners prevented us from deploying our minibot while both their minibots were allowed to score.    I think we need to show more leadership in getting our partners (who are less capable scorers ) to play better defense.

So we compete at the nationals in St. Louis on the last week of April and hopefully, these bugs will be fixed and improvements added.

Finally, my condolences to team 1366 and the young woman’s family re this accident.    It is a sobering incident and all teams should review how they watch out for the young team members that are on travel.

Logomotion blog links:

Reflections on Robodox 599 San Diego 2011 Logomotion Regional:

Note: Super minibot descent speed in brake mode

Note: Super minibot test run with PTC

Note: Minibot Normal force requirement

Note: Minibot current calculation vs battery voltage

Minibot Model


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