precision of movement?

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barnabus
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precision of movement?

Postby barnabus » Fri Feb 15, 2013 12:24 pm

Hi guys,

I'm in the initial stages of completing my final year project for uni (comparison of pathfinding algorithms for optimal maze solving). I've got a few questions about the precision of the servo motors. I'm experimenting with the DifferentialPilot class and it's methods at the moment, trying to get my robot to move as accurately as possible. My question is could I ever get my robot to move precisely enough without the use of another sensor to complete a fairly complex 5 by 5 maze? I'm experimenting with the travel, rotation and acceleration speed to see if decreasing them will have a positive effect on precision, thoughts? Also does battery life affect precision? From my limited testing it seems to have an effect...

Thanks,

Barney

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gloomyandy
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Re: precision of movement?

Postby gloomyandy » Fri Feb 15, 2013 9:43 pm

To improve the accuracy use lower speeds and lower acceleration values, this will also mean that a low battery will have less of an impact.

Certainly errors will build up but you can calibrate a robot pretty well on a particular surface. You also need to pay attention to the actual robot construction, in particular take care if using a castor wheel and reversing as the castor can throw of the movement when you make a big change in direction. The following two videos may give you some insight into the sort of accuracy you can obtain and some possible techniques to help calibrate a robot:
http://www.youtube.com/watch?v=NJ_6Qm_B ... O3OHmYdYnw
http://www.youtube.com/watch?v=IMI63k5W ... O3OHmYdYnw

Andy

barnabus
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Re: precision of movement?

Postby barnabus » Sun Feb 17, 2013 12:13 pm

Cheers Andy! Lowering the travel, rotation and acceleration speed seems to have had a positive effect on precision

s.frings
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Re: precision of movement?

Postby s.frings » Tue Mar 26, 2013 2:58 pm

Anyway, the wheels always slip a little. I tried different robots (with and without Lego) and finally came to the conclusion that odometry sensors (as inside the Lego motors) are fine to control speed and straight/curve lines. But they do not work precise enough to track the position of the robot after several movements.

You need some fixed points thet the robot can use to sense its own position. E.g. markers on the floor that get detected when driving across them.


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