Comments on: HOWTO Calibrate a differential robot: UMBMark Explained

By: Miguel

Miguel — Sun, 08 Jun 2014 17:51:11 +0000

I see. There are times when the program goes nuts and I really need to kill it. I will add this into the installing leJOS tutorial.

By: Miguel

Miguel — Sun, 08 Jun 2014 17:50:11 +0000

Just copy it where you placed the other file.
About the program try downloading it again, I fixed an issue with acceleration that could result in a problem like the one you are talking about.

By: gloomyandy

gloomyandy — Sat, 07 Jun 2014 22:28:57 +0000

Hi,
in reply to your comment…
“This class is a helper class to finish the program when you press the back button… I was quite surprised leJOS didn’t that by default.”

leJOS does do this by default, but the keys you need are Enter+down (using just escape would mean this key is not usable by user programs) this key combination will kill your running program. But it is always better to exit your program in a clean way, stopping motors and freeing resources. Only you know the best way to do this.

Andy

By: What does happen when you run a Robot with different size wheels? ← LEGO Reviews & Videos

Sat, 07 Jun 2014 11:48:10 +0000

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By: What does happen when you run a Robot with different size wheels? ← LEGO Reviews & Videos

Sat, 07 Jun 2014 11:48:10 +0000

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By: Michael

Michael — Fri, 06 Jun 2014 13:43:50 +0000

How do I make this class part of Eclipse and/or part of my program?

The previous program was the “Draw a square: using motors in lejos EV3″. I was just happy the program ran. I have not had a lot of time this week to play. Hopefully I will have some time this weekend or next week.

Thank you for all your help.

By: Miguel

Miguel — Fri, 06 Jun 2014 10:27:06 +0000

My fault.
You can download the TerminateRobot class from above or this link ( http://thetechnicgear.com/resources/TerminateRobot.java )

This class is a helper class to finish the program when you press the back button… I was quite surprised leJOS didn’t that by default.

Which one is the previous program?

By: Michael

Michael — Fri, 06 Jun 2014 03:45:06 +0000

I entered, copy and paste, after initial setup of a new program and a new class. I get this error message:
Multiple markers at this line
– TerminateRobot cannot be resolved to a type
– TerminateRobot cannot be resolved to a type
On this line:
TerminateRobot terminate = new TerminateRobot(brick);

What am I doing wrong?

Also, I did manage to get the previous program to work but the robot turns in a complete circle before moving forward again.

By: Miguel

Miguel — Tue, 03 Jun 2014 06:58:18 +0000

I did the test removing the strange result ( that I am sure it is an error measuring ) and it didn’t get much better. Definitively I want to try this afternoon fixing the acceleration issue Andy told me about and replacing the caster wheel for the metallic ball… I want a zero mean error :D

By: Aswin

Aswin — Mon, 02 Jun 2014 21:38:38 +0000

Hi,
Nice article.
You could try using the median instead of the mean in the UMBmark method. The advantage of median is that it is not influenced by a single odd result in your test data. It might give better results.

By: Miguel

Miguel — Sun, 01 Jun 2014 21:53:48 +0000

Oh, now I see what you mean with the acceleration. I will fix and reupload the code tomorrow. I will give a try with the metallic ball… I hope it doesn’t scratch the marble or i am a dead man :D

By: gloomyandy

gloomyandy — Sun, 01 Jun 2014 21:20:28 +0000

Hi,
as I mentioned before. If you change the wheel diameter, which means you need to change the motor speed, then you must also change the acceleration used. If you don’t then during the acceleration phase both motors will be the same speed (instead of one being slightly slower than the other), and the slower motor will stop accelerating before the faster one. Also remember that to get good movement (and no wheel slip), you may want to use a relatively slow acceleration and not just keep the default value. Remember that a very small error as the robot starts to move is magnified by a linear movement.

Oh and also remember that the initial alignment of the robot is very critical. You may want to use some sort of jig for this to help with the setup. In particular if you use a caster take great care over the initial alignment as it can easily throw things off. The ball baring based caster from the edu kit is much better for this!

Andy

By: Paul R

Paul R — Sun, 01 Jun 2014 21:16:37 +0000

Miguel, this is awesome – thanks for sharing at this level of detail!