More than 2 Lighthouse Base Stations?

Discussions related to positioning systems where the position is calculated outside the Crazyflie and sent to the device using radio, including MoCap systems
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NicksonYap
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Joined: Mon May 07, 2018 5:04 pm

More than 2 Lighthouse Base Stations?

Post by NicksonYap » Fri May 10, 2019 7:08 am

Hi Bitcraze team,

I have a HTC Vive with 2 light house base stations (v1)
Don't mind purchasing v2 if it helps

I'm planning to have lighthouse deck replace our LPS deck, on 50 or even hundreds of Crazyflies.

However, I'm concerned that in dense situations the line of sight will easilt be obstructed.

For that I'm considereding to place more lighthouse base stations, directly on top, and at more angles

I'm also considering to use both lighthouse deck and LPS at the same time

Will these these methods work to improve the reliability of lighthouse deck?

Or else, what other methods would you suggest?

Regards Nickson



arnaud
Bitcraze
Posts: 2043
Joined: Tue Feb 06, 2007 12:36 pm

Re: More than 2 Lighthouse Base Stations?

Post by arnaud » Mon May 13, 2019 1:29 pm

Hi Nickson,

Unfortunately there is no easy way to setup more than 2 Lighthouse V1 base stations, for that you would need base station V2 and the support for it is not yet finalized (I have been working on it on my spare time but the hope is that V2 support is going to become a main focus in a couple of weeks). The main issue is that Lighthouse V1 broadcasts synchronization signals as omnidirectional IR pulse, and there is no space in the protocol to add more than 2 base stations.

The kalman filter in the Crazyflie will take care of temporary loss of sight, depending of how agressive/tight your swarm is it might just work as it is. One of the current limitation is that the Crazyflie currently needs line of sight with both lighthouse in order to position itself, we are working at making it possible to use only one base station for positioning which will make the system much more resilient.

I am not sure if combining LPS and lighthouse will help at all while lightouse is in sight: combining both would be very interesting to be able to cover the space outside the lighthouse coverage, but while you have contact (even intermittent) with the base stations, lighthouse would likely be very good still. This needs to be tested of course, the most we have flown in a lighthouse system so far is 6 Crazyflies at the same time without problems.

One note about using LPS and lighthouse: the two decks are not compatible out of the box, the LPS deck needs to be patched to use alternate pins for reset and chip select and the Crazyflie firmware needs to be compiled with a special flag to enable the alternate pins: https://github.com/bitcraze/crazyflie-f ... xample#L54

For now I would suggest placing the base station in a way that minimize obstruction by the other Crazyflies (for example directly overhead might work) and testing to see if obstruction is really an issue. If it is, lighthouse V2 is most likely a better solution than the hybrid system but I do not know when it is going to be ready.

/Arnaud

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