DifferentialPilot with caterpillar tracks

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DifferentialPilot with caterpillar tracks

Postby jt18 » Thu Mar 08, 2012 12:05 am

I've created a simple robot working on caterpillar tracks. (NXT 2.0). I was wondering if it was possible to use the DifferentialPilot with these. They have two motors contained at the front of the robot which rotate the tracks.

I don't have to official measurements (if someone has the track measurements that would be excellent). However I measured the tracks with a ruler to get an estimate and used trial and error to fine tune the value. Now the travel function works perfectly (to the mm-ish). However if I call the rotate function despite measuring the trackWidth with a ruler the rotation is very inaccurate. 360degrees will be significantly shorter.

I know this post is kind of vague, I was more wondering if anyone has any experience with this class and if it suitable for a vehicle using tracks? If i change it to tyres and only control two wheels will this work?

Cheers!
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Re: DifferentialPilot with caterpillar tracks

Postby gloomyandy » Thu Mar 08, 2012 12:20 am

Tracks work fine with the differential pilot. See this video which used a pilot as the basic control mechanism...
http://www.youtube.com/watch?v=IMI63k5W ... ature=plcp

I assume you have fine tuned the wheel diameter values to get travel function to work accurately. You basically tune the trackWidth parameter (note that trackWidth for a conventional wheeled robot is the distance between the wheels), to get turns to work. I seem to remember that a good starting point for a tracked vehicle is the diagonal distance of the two tracks, but I may be wrong on that. Try it and see, then try reducing and increasing the value to see how it impacts the turn. It should not take long to get things working reasonably well. One thing you may find is that the surface that the robot is on has a big impact on how the robot turns.
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Re: DifferentialPilot with caterpillar tracks

Postby KnowledgeLover » Mon Apr 23, 2012 9:16 pm

gloomyandy wrote:Tracks work fine with the differential pilot. See this video which used a pilot as the basic control mechanism...
http://www.youtube.com/watch?v=IMI63k5W ... ature=plcp

I assume you have fine tuned the wheel diameter values to get travel function to work accurately. You basically tune the trackWidth parameter (note that trackWidth for a conventional wheeled robot is the distance between the wheels), to get turns to work. I seem to remember that a good starting point for a tracked vehicle is the diagonal distance of the two tracks, but I may be wrong on that. Try it and see, then try reducing and increasing the value to see how it impacts the turn. It should not take long to get things working reasonably well. One thing you may find is that the surface that the robot is on has a big impact on how the robot turns.

Thank you very much, this was very useful :)
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