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REV Hub IMU Accuracy Question

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  • REV Hub IMU Accuracy Question

    We have began planning where our team wants to put the hub on our robot and we also plan to use the IMU that comes with the hub. In order for an accurate reading to be aquired, does the IMU need to be dead center on our axis of rotation? If so, is there a way around it? Our team is utilizing a holonomic drive system so we spin on a dime, but we don't have any room on the center of our robot to mount the hub horizontally and it seems that teams are having trouble using the IMU in the vertical position and we'd like to avoid that if possible. Any help is appreciated.

    Thanks, Ben

  • #2
    If you are just using the Gyro, then the gyro doesn't need to be in the center of the robot. Rotation is rotation. So if you want to keep it flat, you can put it off to the side.

    However, if you are also trying to use the accelerometer for determining distance traveled, then having the imu off-center could cause inaccuracies, simply because the act of turning would introduce additional linear accelerations.

    Phil.

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    • #3
      Also, my experiment so far seems to indicate that the built-in IMU should be mounted horizontally. If mounted vertically, the readings are invalid especially the pitch axis. It seems, the sensor needs to be flat during the power up calibration.

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      • #4
        Awesome! I was hoping that it wouldn't effect it. Thanks for the help!

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        • #5
          Originally posted by Philbot View Post
          If you are just using the Gyro, then the gyro doesn't need to be in the center of the robot. Rotation is rotation. So if you want to keep it flat, you can put it off to the side.

          However, if you are also trying to use the accelerometer for determining distance traveled, then having the imu off-center could cause inaccuracies, simply because the act of turning would introduce additional linear accelerations.

          Phil.
          Phil, do you know where (exactly) the sensor is in the hub? It's big enough to have an effect if the sensor is near one of the outer edges.

          Technical Coach, Newton Busters FTC 10138, FLL 3077
          Chicago 'burbs, IL

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          • #6
            Originally posted by gof View Post
            Phil, do you know where (exactly) the sensor is in the hub? It's big enough to have an effect if the sensor is near one of the outer edges.
            From the Expansion Hub Guide, it appears the IMU is located at the word "PROUD" ...
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            This gallery has 1 photos.

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            • #7
              Originally posted by gof View Post
              Phil, do you know where (exactly) the sensor is in the hub? It's big enough to have an effect if the sensor is near one of the outer edges.
              So if I have the Hub about 3-6 inches from the center of my robot mounted horizontally, do you think that is far enough off that it could have an effect?

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