LPS and z-ranger

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Unibasudent
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Joined: Wed Sep 05, 2018 2:06 pm

LPS and z-ranger

Post by Unibasudent » Wed Sep 05, 2018 2:21 pm

Hi crazyflie team, i'm working on a research project utilizing the Crazyflie 2.0 quadcopter, z-ranger, and Loco Positioning System (8 Nodes). I've been trying to obtain accurate position readings utilizing a Python script similar to the one called "AutonomousSequence". Is there a way to use the z-ranger only to calculate the z cordinate and x,y with the lps?

Sometimes, I believe when the sensors (LPS and z-ranger have too far results on z), the crazyflie goes crazy and can no longer maintain the hover position or the assigned trajectory.

Thanks in advance.

arnaud
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Re: LPS and z-ranger

Post by arnaud » Mon Sep 10, 2018 9:20 am

The current implementation of the kalman filter is supposed to use the z-ranger reading when the Crazyflie is close to the floor and gradually start using more LPS when the altitude grows. So there should be a good match between the z-ranger measured height and the LPS height at this transition, the transition is arround 1m if I remember well (we are going to update the zranger deck with a new ST sensor that works to much higher distance, at least 2m).

Where are you seeing the instability, is it closer to the ground or around 1m altitude?

Unibasudent
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Joined: Wed Sep 05, 2018 2:06 pm

Re: LPS and z-ranger

Post by Unibasudent » Fri Sep 14, 2018 9:06 am

Hi Arnaud and thank you for your reply.

As you mentioned, there are problems when the crazyflie reaches the height of around 1 m. I found this: (ESTIMATOR=kalman
CFLAGS += -DUPDATE_KALMAN_WITH_RANGING -DKALMAN_DECOUPLE_XY) on the wiki, should i recompile the firmware or it's already scripted in there?

Thanks.

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