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9DoF Razor as 3D position tracker

Posted by Hari on July 23, 2010 at 8:02am

I feel this topic is not exactly related to UAV's. But i am seriously working on ...

I am working on 3D position tracking in space.At first, i got my hands at 9DoF IMU from sparkfun as you all know well about this.
Many people tried making a tilt mouse using 3-Axis accelerometer by experiencing "linear motion" is difficult to get from accelerometer in 3D space ( since we can't move our hands in space exactly linear in x,y,z directions).
As you all know, the accelerometer gives acceleration = Gravity(causes tilt)+ Linear acceleration.
I want to remove the Gravity to get the Linear acceleration from the acceleration data.
And then i can use kalman filter to get the position from linear acceleration. 

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                                     IMU writing instrument.pdf

 

The PDF file just gives brief idea how to get linear accelerations in 2D. 

Is it possible to remove the gravity by sensing the tilt from accelerometer. 

I appreciate equations are steps involved to do this.

Thanks

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Replies

  • Developer
    Doug Weibel July 24, 2010 at 12:23pm
    Harinath - I am afraid that this board will be completely worthless for the task you propose unless you only want a position estimate for a short time with poor accuracy. The accelerometers on this board are not high quality. The double integration will magnify all the error and your position estimate will diverge very quickly. I would expect a position estimate for any kind of a moving vehicle with modest vibration and vehicle dynamics to depart by meters (or more) in a matter of minutes.
  • Tom Yochum July 23, 2010 at 9:50am
    You would need to use the gyros to sense the angular velocity. At that point you have built an inertial navigation system (INS).
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