Use motion capture with crazyflie-lib-python

[cc299792458]

Hi, Bitcraze!

I'm sorry to bother you but I have some problems when I use motion caputure(VICON) with crazyflie-lib-python. I'm also confused if this is available.
I think the main step is sending the data gets from mocap to crazyflie. So I've just tried a sample demo but it doesn't work.
The demo is:
(1)I use crazyflie.extpose.send_pose() to send the data(which I set x=0, y=0, z=0, qx=0, qy=0, qz=0, qw=1, just used to test) to my crazyflie.
(2)I use Logger(implied by LogConfig) to check the position and rotation of it.
I think if position and rotation are: x=0, y=0, z=0, roll=0, pitch=0, yaw=0, that means I successed.
But I can't see the change after I do so. Data print in step(2) has no difference between when I check it without step (1).

Meanwhile, I also encounter a strange thing that when I do step(2) both with and without step(1), the x value and y value equals to 0 all the time, even if I change the position of crazyflie in the real world manually.

So my question is:

1. If I can use motion capture with crazyflie-lib-python in this way?
2. Is there any mistake in my demo?
3. I wonder what's the reason of the "strange thing", is that normal or not?

Thanks in advance!

[krichardsson]

It sounds like you are on the right track

I don't think crazyflie.extpose.send_pose() exists but you probably mean cf.extpos.send_extpose() :-)

crazyflie.extpose.send_extpose() pushes your data to the kalman estimator, pretty much like any other sensor data and if you do it repeatedly it should work as you expect.

If I can use motion capture with crazyflie-lib-python in this way?

Yes. We don't have a Vicon example, but we have one for Qualisys. Lines 228-245 is where the pose data is sent to the Crazyflie. Also note that you can use cf.extpos.send_extpos() if you only want to send position data and not full pose.

Is there any mistake in my demo?

The two things I can think about is that you perhaps did not activate the kalman estimator, or that you do not call send_extpose() repeatedly?

I wonder what's the reason of the "strange thing", is that normal or not?

If you only log (not pushing anything to send_extpose()) I would expect x, y and z to change. You can use the client to set up logging of the variables to see what happens when you move around, just to rule out programming errors in your code.

[cc299792458]

Thank you very much!
As you mentioned, I think probably I forgot to activate the kalman estimator and used the default one(complementary filters).
I will try it later and also use the client to check variables, Thank you for your suggestions!
By the way, you also suggest that I can use cf.extpos.send_extpos() if I only want to send position data. I remember someone said they got into trouble(crazyflie became crazy, etc) when they used cf.extpos.extpose() (but maybe happened a long time ago). May I ask, if I use cf.extpos.send_extpose() correctly, I can send the full pose to crazyflie, right?

[krichardsson]

send_extpose() should work fine, but if I remember correctly it is a bit sensitive to noise (mainly for orientation) when the yaw is close to +-90 degrees. When the data is too noisy it has a tendency of "going bananas" (diverging).

[cc299792458]

Get, thanks!

[krichardsson]

I just wanted to add that I recently found a bug in the qualisys_hl_commander.py that has been fixed now. I also added functionality to tune down the sensitivity of the orientation information that is pushed to the estimator.

[mbaytas]

We recently published the open source Qualisys Drone SDK for controlling the Crazyflie (and soon, hopefully, the Robomaster TT) with Qualisys motion capture systems: https://github.com/qualisys/qualisys_drone_sdk

The SDK is not designed to be universal, it is specific to Qualisys systems. However, you might find inspiration in our code, and adapt it to your own application @cc299792458.

[cc299792458]

How nice of you to remind! I will check it, thank you!