Can we get by with only 3 or 4 anchors?

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ricardo.halfeld
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Joined: Tue May 22, 2018 1:40 pm

Can we get by with only 3 or 4 anchors?

Post by ricardo.halfeld » Tue May 22, 2018 1:55 pm

Hello!

My lab is assessing a small investment in programmable quadcopters. Our lead project in this area is related to landing, so we are looking into the flow deck to accomplish the sensory tasks. It would, however be interesting to have LPS capability.

The Loco Positioning System seems like a great choice, but this is still a shy investment for now. Could we use only 3 or 4 anchors to get the job done?

One thing to keep in mind is that we'd probably be ok with a 30-ish cm accuracy in this case. If the system works (without modifications) with less than 6 anchors, do you have any performance data in such conditions?

I appreciate your input and hope to hear from you soon!

Best regards,
Ricardo.
Last edited by ricardo.halfeld on Mon Jun 11, 2018 10:42 pm, edited 1 time in total.

arnaud
Bitcraze
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Joined: Tue Feb 06, 2007 12:36 pm

Re: Can we get by with only 3 or 4 anchors?

Post by arnaud » Mon Jun 11, 2018 6:47 am

LPS has two modes, TDoA and TWR, you can see the difference there: https://www.bitcraze.io/loco-pos-system ... ning-modes

In TWR, 4 anchors would definitely be OK, 3 might work, mostly when you are also getting info from at least the Z-ranger from the flow deck (the flow deck contains a Z ranging chip).

In TDoA with 3 anchors I would expect only 2D position to be OK, 3D is possible when using the Z-ranger. With 4 in theory you will get 3D but I would expect it to be quite inaccurate in at least one direction.

All this can be helped with the flow, at least in theory: working with fewer anchors in TDoA will lead to much more noise, the flow should be able to give the extra info to get stable flight. The flow is currently pushed in the Kalman filter together with LPS, but it is still no very stable so running TDoA with few anchor and the flow might require some more work.

ricardo.halfeld
Beginner
Posts: 4
Joined: Tue May 22, 2018 1:40 pm

Re: Can we get by with only 3 or 4 anchors?

Post by ricardo.halfeld » Mon Jun 11, 2018 10:41 pm

Thank you for your thorough answer, Arnaud!

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