Tracking a small robot

[ciVic]

Hi,

in my research lab we are working with the small humanoid robot Nao by Aldebaran Robotics [Aldebaran Robotics]. To investigate the executed motions we would like to use OptiTrack to track the real positions and orientations of the chest and the limbs of the robot. But we are not sure, if it is possible to track such small rigid bodies? The length of one body is ca. 10cm.

[DonBurroni]

yes i think it will work,

[NaturalPoint - Mike]

10cm? Shouldn't be a problem. What size volume do you want to use for motion analysis?

[ciVic]

It would be perfect to be able to track the robot on a field of 4x6 meters. But i think this would lower the resolution of the system too much, so in special setups we also could use a field of 1x1 or 1x0.5 meters. What would be the resolution of the tracked positions?

[NaturalPoint - Mike]

This depends entirely on the size of the markers, really.

If you are using V100R2 cameras and 5/8 markers, a 4x6m volume may be pushing it, but depending on your camera count and arrangement it may be obtainable to within sub-millimeter precision.

[ciVic]

So would it be better to use a larger number of V100R2 or a smaller number of S250e (beside its advantage of a higher frequency)?

[NaturalPoint - Mike]

We have been finding in testing that a smaller number of S250e cameras, when properly oriented, can outperform a higher number of V100R2 cameras due to the increase in framerate, and the higher resolution.

This would not work as well in high occlusion rate scenarios (2 actor motion capture, et. cetera). You would have to raise the number of S250e cameras closer to the number of V100R2 cameras to overcome that occlusion.

[ColinJones]

Hi - I've got a similar setup that I'm hoping someone can help me with.

I'm trying to track small car robots (10cm x 4cm) that move fairly quickly (max 3m/s) in a space about 6m x 4m. I'd like to have very small hemispherical markers on them (ideally 3-4mm), mostly for aesthetic reasons, but would also consider using active LEDs.

I was considering a set of 12 s250e cameras, but am having a lot of trouble figuring out what this setup is capable of in terms of resolution and whether it could actually handle this situation?

(In the future I'd like to have another set of small robots flying in this space, so ideally I'd like to track 4mm markers in 6m x 4m x 3m)

Thanks for any help!
Colin

[NaturalPoint - Mike]

12x S250e's would work well in this environment with active markers. A 4mm hemispherical marker such as our facial markers are only detectable by S250e cameras at approximately 12 feet. Beyond that, they appear as a single pixel or less, and precision is lost.