LPS configuration

All discussions related to the Loco Positioning system
arnaud
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Re: LPS configuration

Post by arnaud » Thu Apr 12, 2018 8:48 am

Is your system in TDoA mode (only 3 LED flashing on the deck) and all Crazyflie running the same latest firmware?
Are the deck LED blinking once at startup? If so, it is a firmware problem, if not there is something wrong with the deck connection to the Crazyflie.

mn14jg
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Re: LPS configuration

Post by mn14jg » Thu Apr 12, 2018 3:12 pm

Yes that is correct, LED's flash at start-up and disconnect after 10/15 seconds until just one Crazyflie LPS deck remains flashing. All CF's are using the latest firmware (I re-updated them prior to the latest test to check). I do not believe it is a connection problem as the deck that remains flashing is on a different CF with each test.

arnaud
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Re: LPS configuration

Post by arnaud » Mon Apr 16, 2018 7:31 am

You did not answer the most important, I need to know how your system is setup:
1. In what mode are you running, TDoA or TWR?
2. What is the LED blinking pattern, is there 3 or 4 LEDs blinking on the deck (ie. is TX blinking)?

mn14jg
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Re: LPS configuration

Post by mn14jg » Tue Apr 17, 2018 7:04 am

Hi Arnaud,

I'm running swarmSequence.py so that should be TDoA unless I've misunderstood something.
I have very limited access to the lab now (my project is almost completed) so I will have to check the LEDs but my videos albeit low resolution suggest that the TX LED is flashing on the deck that is alight - as I said before however only one of the four decks have any LEDs flashing at any one time.

arnaud
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Re: LPS configuration

Post by arnaud » Tue Apr 17, 2018 7:48 am

Hi,
TDoA/TWR are the positioning mode used by the Crazyflie, it is something you need to setup as part of the system setup and it has nothing to do with how the crazyflie is controlled: swarmSequence sends position setpoint to multiple Crazyflies independent of the way the crazyflies gets their position information.

TWR does not work with multiple tags because in TWR mode the Crazyflies sends packets all the time which affects each-other ranging. I have seen in some occasion that when two TWR are switched ON at the same time they can lock each-others. I though I fixed this bug but its behavior looks exactly what you are observing.

mn14jg
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Re: LPS configuration

Post by mn14jg » Wed Apr 18, 2018 8:09 am

Ah. I misunderstood how the positioning system works, my understanding was that the LPS sends a position setpoint to the Crazyflie and then the Crazyflie uses TWR/TDoA to position itself to the setpoint, hence why I observed a difference in the flashing LEDs.

This explains a lot, my system seemed to be working fine until I reset the LPS due to inconsistency (and hence I assume it reset to TWR). After I reset the LPS, flying with two Crazyflies using swarmSequence.py produced good, consistent results - showing that TWR can work with two CF's which I think was mentioned at one point on a forum or setup page? The problems started when I introduced four CF's. I misinterpreted your post on 5th March but reading back now makes perfect sense. I don't have time to change the LPS to TDoA but at least I have a good explanation for the odd results.

Thanks for all your help!

arnaud
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Re: LPS configuration

Post by arnaud » Wed Apr 18, 2018 9:09 am

You might have gotten lucky because normal TWR (without TDMA) should not work for more than one. For 4, TDoA would be indeed much better.

Glad I could help :).

willv
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Re: LPS configuration

Post by willv » Fri Jul 13, 2018 5:28 pm

To run the Crazyflie with LPS and a flow deck would I need a special attachment? or would the flow deck just go on the bottom and the LPS deck on top?

arnaud
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Re: LPS configuration

Post by arnaud » Tue Oct 09, 2018 5:27 am

You can attach the flow on the bottom and the Loco deck on the top. Hardware and driver-wise it will work fine, though there might still be some bug in the way the Kalman filter handles simultaneous information from the LPS and the loco deck.

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