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Thread: uNav INS

  1. #676
    Junior Member
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    Feb 2018
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    16
    I have the same problem

  2. #677
    Junior Member
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    Feb 2018
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    what about GPS/INS now?

  3. #678
    Junior Member
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    Feb 2018
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    why not update ?

  4. #679
    Senior Member brtaylor's Avatar
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    Mar 2016
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    I'm too busy with client projects at the moment.

  5. #680
    Junior Member
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    Feb 2019
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    11
    Hi All,

    I have some questions! I've been using the Kalman filter as described within this post. However, I'm really struggling with it.

    Did anyone post a stable version that works?

    I'm wondering if I'm updating it frequently enough? I'm using a Teensy 3.2 that's doing other things at the same time but I'm managing to run the filter at approx 40-50Hz. Is that fast enough?

    With the device sitting flat on my desk I'm getting wildly drifting pitch/roll/yaw and the values I'm getting from the filter don't make sense.

    Like:
    pitch: 3 to -30 degrees
    roll: 2 to -115 degrees
    yaw: 25 to -164 degrees

    I've definitely calibrated the MPU9250 correctly - getting reasonable results from it. The values from it are pretty stable, so I don't understand how the filter can vary so wildly. The GPS inputs to the filter are relatively (but not totally) stable - within the normal variations. If GPS is lost, the filter goes waaay off really quickly, suggesting huge speeds and the like.

    Any help would be greatly appreciated as this is the final stage of a major project!

    Thanks,

    Andrew

  6. #681
    I tried but was never able to get the uNav-INS to work, even when injecting static GPS values into the filter. Have you tried the uNav Attitude and Heading Reference System (AHRS)? That uses the MPU9250 but not the GPS. I was able to get that to work, and was relatively stable as long as I didn't leave it running without moving the MEMs chip once in a while.

  7. #682
    Senior Member+ mjs513's Avatar
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    Jul 2014
    Location
    New York
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    4,112
    Finally catching up here.

    Same comment as @willie.from.texas. Tried several variations of the Kalman filter with the MPU-9250 with no luck - a lot of yaw drifting even though pitch and roll may be fairly stable. Had better luck with the various AHRS filters.

    Somewhere in this thread is a Sketch that actually contains about 4 of the different filters you can use. I will see if I can find it and repost it. Funny thing is that I had more luck with the Kalman filter implemented for the prop shield with the prop shield.

  8. #683
    Senior Member brtaylor's Avatar
    Join Date
    Mar 2016
    Location
    Portland, OR
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    537
    Quote Originally Posted by r5gordini View Post
    Hi All,

    I have some questions! I've been using the Kalman filter as described within this post. However, I'm really struggling with it.

    Did anyone post a stable version that works?

    I'm wondering if I'm updating it frequently enough? I'm using a Teensy 3.2 that's doing other things at the same time but I'm managing to run the filter at approx 40-50Hz. Is that fast enough?

    With the device sitting flat on my desk I'm getting wildly drifting pitch/roll/yaw and the values I'm getting from the filter don't make sense.

    Like:
    pitch: 3 to -30 degrees
    roll: 2 to -115 degrees
    yaw: 25 to -164 degrees

    I've definitely calibrated the MPU9250 correctly - getting reasonable results from it. The values from it are pretty stable, so I don't understand how the filter can vary so wildly. The GPS inputs to the filter are relatively (but not totally) stable - within the normal variations. If GPS is lost, the filter goes waaay off really quickly, suggesting huge speeds and the like.

    Any help would be greatly appreciated as this is the final stage of a major project!

    Thanks,

    Andrew
    Hi Andrew,

    We flight test often with the version of the EKF implemented in our flight software without issues on both fixed wing and multi-rotor vehicles (https://github.com/bolderflight/RAPT...on/uNavINS.cpp). This version does not use the magnetometers and I'm sure the EKF gains are different (they're based on flight test data using a post-processed camera based system as a true reference for attitude). One piece of advice, the filters will not perform well when they are static. They require motion to warm up the filter and keep the filter operating well (without motion, the filter lacks the dynamic information needed and is dominated by GNSS noise).

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