Roll and pitch estimation corrected for coriolis forces
(10% to 25% improved roll and pitch estimates)
"
According to
http://en.wikipedia.org/wiki/Coriolis_effect
|omega_earth|=2*PI/day=2*3.14/(24*60*60)=7.27e-5[rad/s]
assume aircraft diving at 20m/s in earth reference frame
|ac|=2*7.27e-5*20=0.003[m/s^2]=3e-4[G]
assume we have 16bit ADC which covers 100% range of the useful voltage (overly optimistic),
and the accelerometer is quite sensitive with 6G full span (+/-3G) (overly optimistic, procerus claims +/-10G).
Therefore 6G is divided into 65536 counts.
3e-4G equals then to around 3 ADC counts which is below noise level of most
accelerometers which would be around 2^4, by eye.
Therefore coriolis acceleration is barely detectable (you can attach a plane to the rails, push it down, and the only deviating force will be at most those poor 2-4 counts on extremely sensitive ADC, overswamped by natural sensor noise).
How did they come to 10%/25%?
Where is an arorr in my calculation?
Comments
but qw-rv numerator in the first line... not sure.
-Beall
;)
Tom
I am rarely thinking in non-inertial reference frames unless it's as big as earth, therefore I have attached Coriolis to a very large scale (coriolis is a clever name to imaginary force when you want to those simple Newton laws work when you are in rotating reference frame).
My guess is that they are including something in the algorithm to compensate for an IMU not being placed at the center of rotation of the aircraft.