I also wonder too- we all know the robots are often not 100%
consistent- but the children do have a chance to show their
programming- and "programming" will show during the robot design
judging.....I have told my team that cause they did some very nice
programming- battery power equally makes things erratic. Laura
On Nov 4, 2010, at 3:29 PM, Mandy Wilson wrote:
> Turns out that our problem was a faulty motor on the left side which
> caused the merry go round effect when it turned right. My son, who
> is homeschooled, read all of the emails and helpful suggestions that
> came in and ran upstairs to test. Sure enough when the right turn
> was changed to a left, the program worked perfectly. (It didn’t
> occur to me that was the only right turn the team had done in the
> last few days). When he replaced the motor the right turn in that
> program worked perfectly. Always nice to have a motor burn out 2
> days before the competition! Now apparently many things are just
> slightly off as this motor is a little different than the last and
> my son is not pleased that he and his friends now have to redo
> almost everything! Maybe this is why people drop out of events? No
> the team is not dropping out, but it will be nice if they can get
> back to where they were. Thanks to everyone who helped. I don’t
> know what this team would have done without all your help as today
> the merry go round effect was occurring 50% of the time. I’m sure
> the motor would have been completely dead in 2 days.
>
> Mandy
>
> From: First Lego League in Virginia and DC [mailto:[log in to unmask]
> ] On Behalf Of Eric Palmer
> Sent: Thursday, November 04, 2010 1:43 PM
> To: [log in to unmask]
> Subject: Re: [VADCFLL-L] NXT merry go round effect
>
> My team this year had a robot with a particular mission and
> attachment set that had a "veer left bias" They changed the whole
> robot to our backup and it "veered very slightly right" on further
> inspection the first robot has an axle going through a beam that has
> been damaged so there was more friction on the left side.
>
> For the right bias they moved a counter weight to the left and the
> robot goes straight most of the time. But even with that it varies,
> sometimes badly.
>
> We are using disposable batteries this year and they monitor voltage
> closely. The front missions they use fully or nearly fully changed
> batteries and the last mission they use batteries whose top voltage
> has been lowered.
>
> They use a slight moist cloth to wipe the dust off the table before
> practice and we occasionally wipe the dust off the wheels and let
> the tires dry. They store the robot upside down so the wheels don't
> get flat spots.
>
> The team pays attention to many more factors for repeatability as
> well.
>
> But that said we still have problems with erratic behavior. Turing
> for example seems to work best (for repeatability) one wheel at a
> time. That slows down the missions but makes the missions more
> repeatable.
>
> All learning opportunities.
>
> Eric
>
> On Thu, Nov 4, 2010 at 1:24 PM, Nagesh Chintada <[log in to unmask]
> > wrote:
> This is hard to figure out without seeing it, but couple of
> questions come to mind:
> 1. Has your team tried to reduce the power, to say, 50 or below?
> 2. How is the robot balance and center of gravity? For example, does
> it happen if the attachments are removed?
> 3. I noticed that sometimes loose wheels can cause strangest
> behaviors in movement, so not a bad idea to check if the any part of
> the attachments/ frame and wheels are not loose.
>
> Just a comment: The great fun of FLL is ruined especially to rookie
> teams because of all the variability in the NXT Robots. These are no
> doubt complex products, and it is not easy to get consistent
> behavior. It requires some experience and lots of practice. This is
> not my first year, but I am still learning.
>
> I wish Lego or FLL would make it easier for all the teams - and
> improve the fun factor - by providing some basic information/
> instructions/ best practices to reduce variability as part of the
> NXT kit or FLL kit. Just a thought. I'd like to see more teams
> having more fun than struggle so much.
>
> Nagesh
>
>
>
> On Thu, Nov 4, 2010 at 10:15 AM, Mandy Wilson <[log in to unmask]>
> wrote:
> This turn does not involve sensors. It’s just a plain point turn.
>
> From: First Lego League in Virginia and DC [mailto:[log in to unmask]
> ] On Behalf Of Eric Palmer
> Sent: Thursday, November 04, 2010 10:09 AM
> To: [log in to unmask]
> Subject: Re: [VADCFLL-L] NXT merry go round effect
>
> I wish I knew what causes this. We see it occasionally. Something
> lose wires. Sometimes changes in battery levels. Do check to make
> sure that if you are using sensors that they are working reliably.
>
>
> On Thu, Nov 4, 2010 at 10:06 AM, Mandy Wilson <[log in to unmask]>
> wrote:
>
>
> Our team has a part of its program where the robot is supposed to
> turn some nominal amount (around 30 degrees) and for some reason
> every 5th run or so, it spins about 120 degrees. They have put a
> reset motor block, a break block and even a 1 sec wait block in
> front of the errant turn in order to stop the issue, but nothing
> they have done works. They’ve even tried deleting the block and
> putting another one in. They thought it was the gearing on the
> wheels coming loose which also causes it to act up, but on the 6-9th
> run it works fine and then at run 10 it does it again. Well not
> quite that predictable, but you get my point. Has anyone else had
> this problem and is there a way to fix it, or should the team just
> be resigned to blow a round at the tournament? Thanks for all the
> help – this is our first year!
>
> Mandy
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>
> --
> Nagesh Chintada
> Phone: 703-829-0284
>
>
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