paul x wrote:
> acceleration, a is too small comaparing with gravity g. So, little
> tilte will
> become huge output of a. How can I canceal g from a, becomes critical!

Gravity IS accelleration from the device's point of view.  You can not
separate the two without some additional knowledge.

One useful fact about gravity is that it's constant.  This can let you do
calibration when you are known to not be moving, then subtract off gravity
as long as orientation remains known.  However, the latter is not easy, and
the error will increase over time.  You are unlikely to get acceptable
accuracy for more than a few seconds using MEMS accellerometers and gyros.


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