What is for "Avoidance / Collision prevention error"

  • Hi guys,

    I'm on testing Collision prevention as like below link


    Also, I already verified VIO data and position mode but, as you can see below picture, I got a message Avoidance / collision prevention error.

    because of this error, I cannot arm my flight in pre-check.

    Could you please let me know why collision prevention error is occured in pre-check and how to revolve it?


    Screenshot from 2021-04-02 23-56-36.png

  • Dev Team

    Hi @shlee853 ,

    Can you check your settings compared to these?


    Please advise if they are the same and you're having issues.


  • @modaltb yes I already set this parameter as you show me.

    If stereo vision camera has problem or uncalibrated, is it possible to make this error?

  • Dev Team

    We calibrate the stereo sensors before shipping on the Flight Decks and m500s. Not sure if you have that or the VOXL + image sensors.

    Without stereo calibration, yes there's likely to be issues.

    How about trying this and seeing how things look?

  • @modaltb I calibrated stereo camera and tracking camera. and I found calibrated file here

    yocto:/# ls /home/root/.ros/camera_info/
    left.yaml right.yaml tracking.yaml

    I also verified depth information using stereo camera and tracking information using tracking camera.

    But, I'm not resolve Avoidance/Collision prevention Error so far.

    Also, I cannot perform object avoidance function.

    Could you please let me know some advice? why Avoidance/collision prevention error message appeared on QGC?


    my flight s/w version is like this.

    yocto:~# voxl-version

    system-image: ModalAI 3.2.0 BUILDER: ekatzfey BUILD_TIME: 2021-02-05_19:54
    kernel: #1 SMP PREEMPT Fri Feb 5 20:03:22 UTC 2021 3.18.71-perf
    factory-bundle: 1.0.1 (Yocto installation)

    architecture: aarch64
    processor: apq8096
    os: GNU/Linux

    Package: voxl-suite
    Version: 0.2.0
    Depends: docker, imu_app (= 0.0.6), libvoxl_io (= 0.5.2), voxl-cam-manager (= 0.2.2), voxl-docker-support (= 1.1.1), voxl-hal3-tof-cam-ros (= 0.0.2), voxl-modem (= 0.10.0), voxl-nodes (= 0.0.8), voxl-rtsp (= 1.0.2), voxl-utils (= 0.5.2), voxl-vision-px4 (= 0.6.8), voxl_imu (= 0.0.4), voxl-time-sync (= 0.0.1), voxl-vpn (= 0.0.2), librc_math (= 1.1.2), libmodal_pipe (= 1.2.2), modalai-vl (= 0.1.3)
    Status: install user installed
    Section: base
    Architecture: armv7a
    Maintainer: james@modalai.com
    MD5Sum: af706cd3c1ea59f274f2ed9b93141f1d
    Size: 870
    Filename: voxl-suite_0.2.0.ipk
    Description: meta-package to install all of the voxl-suite
    Installed-Time: 245

  • Dev Team

    This thread is related to this

  • I ran into the same issue where QGC displays:
    Avoidance/collision prevention Error

    I think i know what is causing this issue in case there isnt any resolution yet.

    It seems that QGC is interpreting what is sent from the AP the onboard_control_sensors_health bitfield in the MAV_SYS_STATUS_SENSOR message. And the bit responsible for this is MAV_SYS_STATUS_OBSTACLE_AVOIDANCE.

    Looking at the PX4's Commander module, it also seems that the MAV_SYS_STATUS_OBSTACLE_AVOIDANCE bit is used for both obstacle avoidance AND collision prevention. While the VOXL-CAM is communicating with the AP for Collision Prevention, this health bit will always be false because the Avoidance system is not setup.

    But i have yet to confirm if in spite of this, the Collision Prevention function still works. FYI i have a brand new Seeker which i have not tested in flight yet. Will anyone be able to advise before i go for my first flight?

  • Dev Team


    Yes, PX4's obstacle avoidance and Collision Prevention are separate features. We only support the Collision Prevention functionality which is governed by the PX4 CP_DIST and similar parameters. Make sure the COM_OBS_AVOID parameter is OFF (0) in PX4


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