Removing gravity effect from accelerometer readings

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I am developing an application, in which i have used Accelerometer for sensing linear accelerations but after some time i get to know that Accelerometer does not show linear accelerations(also have gravity effect on it).

So for removing gravity i have tried some method and reach at conclusion that i must have to design a filter.

And for designing filter i have tried the following code

public void onSensorChanged(SensorEvent event)
 {
      // alpha is calculated as t / (t + dT)
      // with t, the low-pass filter's time-constant
      // and dT, the event delivery rate

      final float alpha = 0.8;

      gravity[0] = alpha * gravity[0] + (1 - alpha) * event.values[0];
      gravity[1] = alpha * gravity[1] + (1 - alpha) * event.values[1];
      gravity[2] = alpha * gravity[2] + (1 - alpha) * event.values[2];

      linear_acceleration[0] = event.values[0] - gravity[0];
      linear_acceleration[1] = event.values[1] - gravity[1];
      linear_acceleration[2] = event.values[2] - gravity[2];
 }

which is taken from Android Developers.

Now i have some problem in code shown above-

1. What are alpha, t and dt ?


2. How to get the value of t and dt and how to calculate them?


3. Also let me know that the code i am using for getting linear accelerations will work or not?

asked 15 secs ago

Suraj

6