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Tuning ArduIMU

Posted by Daniel Wee on April 13, 2010 at 12:38pm
In my latest flight test with the ArduIMU, I found that I probably need to tune it a bit. First of all, the data:-

http://vimeo.com/10887900

My preliminary observations are that the output converges onto the accelerometer settings too quickly. This in-spite of the 1G vector magnitude guard in the code.

Can someone explain to me the relationship between the Ki and Kp to the tuning. I have some idea of what they do but am not sure how they interact with each other.

Thanks,
Daniel Wee

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Replies

  • Loris April 15, 2010 at 9:44am
    I made some experiments last week. This graph shows the sum of 16 gyro samples

    gyros.jpg




    As you can see there is a lot of noise. If you right shift it 4 times, you remove a lot of noise but you keep the ADC resolution of 10bits. (so around 1°/s).

    On the yaw there is no correction and after a flight of 10 min, it was drifting at a speed of 1°/s.
    I also tried to put a motor close to the IMU to generate noise and in static conditions the yaw drift is very important

    euler_4_shift_rampe_moteur.jpg

    (X unit is 100ms so the total experiment length is 100s)

    With a Kalman filter (of DCM which is use in ArduIMU) of course you can made it but if you don't rely on acceleros for 10s I am not sure you will manage to have a correct angle estimation.

    Loris
  • Developer
    Doug Weibel April 13, 2010 at 9:00pm
    Ki and Kp are integral and proportional gains for the drift correction PID controller. Increasing Kp will cause a faster response, but if too high will produce oscillation. Ki will tend to reduce steady state error, but again too much will cause oscillation
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