Zed X IMU odr issues

Hardware ZED X
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1

Hi,

I’ve been collecting some camera + IMU data on the Zed X and I noticed I am getting ~186Hz against the advertised 400Hz. I am using your APIs directly, no ROS. But, as the ROS2 implementation, I have two separate threads for getting camera images and sensors data. I tried on two different Zed X cameras and I get the same outcome. I’ve been using the Zed Box Orin mini NX 16gb.

I also get ~190Hz when dumping data with your Zed Sensor Viewer, although I am selecting 400Hz in the settings.

Lastly, the only setup where I can actually get ~400Hz is through Zed Explorer saving data into an .svo2

Moreover, I noticed that I am getting kind of two rate distributions in the data I collect. Here I am plotting the period between IMU samples. This is also visible in the data I collect using the Zed Explorer, or the sensor viewer. The only setup without this two distributions is using the Zed Explorer with 1080p 15Hz cameras.

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I would like to know why I am able to get the desired frequency through the explorer but not through other tools and through the APIs, and why the odr is so unstable with seemingly two distributions and with big spikes. Is there any fundamental difference in how the data is collected when using the different tools and APIs? Is the Zed Box Mini not keeping up with the data coming from the camera?

Thanks,

Marco

2

Hi @picci,

Welcome to the forums :waving_hand:

We’ve recently released the ZED SDK 5.2 and ZED X Driver 1.4, which come with improvements in IMU stability where the IMU rate spread improved from ~11 Hz (185–197 Hz) to < 1 Hz (199.5–200 Hz) and fixed data drop issues in complex setups involving 8+ IMUs.

You can find both releases and changelogs here:

However, in order to support multi-camera setups, we have reduced the rate from 400Hz to 200Hz on all cameras. As 400Hz IMU has an impact on the overall performance, we are investigating to add a mode when using a reduced number of cameras.

3

Hi @mattrouss ,

I updated to 5.2 and updated the drivers too, and I am getting weird results:

  • APIs are recording the IMU at ~125Hz regardless of the camera res
  • ZED Explorer records an .svo with IMU at ~90Hz
  • ZED Sensor Viewer recorded ~199Hz
4

Hi @picci,

Sorry for the late reply, we’re taking a look at this internally to reproduce