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Accuracy of Motion Plus data over time

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  • Accuracy of Motion Plus data over time

    I've only recently begun experimenting with using the Motion Plus data (mostly in Cyclic Mode).

    While the Roll data seems to maintain it's accuracy over time, and as the FAQ notes the Yaw data is inherently unreliable, I'm having issues with the Pitch data which are not seemingly explained.

    The Pitch data is accurate most of the time, but if I hold the Wiimote in an upright position (Pitch = 0.75), and quickly make a striking gesture with it, sometimes the Pitch moves in the wrong direction -- when returning the Wiimote to a horizontal position, the Pitch value rises to near 0.99 instead of returning to 0.5. Any suggestions?

    Thanks!
    Last edited by respect; 09-11-2011, 03:31 AM.

  • #2
    Furthermore, I'm experience one other oddity with the MotionPlus Pitch data -- occasionally, pretty drastic latency shows up -- around 0.5 seconds. I notice this when sending via OSC to Max/MSP, and the Quick Look seems to confirm this. It seems only to happen with the MotionPlus Pitch data (although I haven't tested all others thoroughly).

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    • #3
      Hey respect,

      Thanks for describing this problematic behavior.
      I will see what I can do to improve tracking, and come back to you soon.


      Cam

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      • #4
        Hi Respect,

        During my quick testing I have not been able to reproduce the problem you first described, but I know it can happen, I have users witnessing the same oddity. I am wondering now if there aren't different type of gyroscopic sensors and accelerometers that give different results. Of course, I have been only able to test with the Wiimotes and Motion Plus modules I have.

        About the latency you described:

        I believe this only happens when a strong gesture is applied to the device. The filter is confused and takes some time to recover. For 'softer' movements, the values should follow quite quickly and not suffer from such latency.

        If you need to perform analysis for strong gestures, I would suggest that you rather use the accelerometer data, and keep the MotionPlus data for positional info only. It's very hard to get best of both worlds especially with such an inexpensive device, and few knowledge about the true characteristics of the sensors.


        Best,
        Cam

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        • #5
          Hi Cam,

          Thanks for testing. I suppose there could be discrepancies between components. I've only tested with one Wiimote and MotionPlus.

          Yes, I believe the latency was induced by strong gestures. I'll do some more experimentation and let you know if I discover any patterns to the behavior or suitable work-arounds.

          Thanks,

          Red

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