Wrote up a wind estimator today. It is based off of a simple model which requires very little inputs from sensors.
psi - true heading (not course over ground)
theta - pitch
GPS lat and long
It is a simple model. The wind model has no dynamics which helps simplify the solution. This asusmption is mostly true beings the wind direction and velocity doesn't change all that much for a given flight. The filter starts off by assuming the soltion is a zero wind scenario and then moves towards reality. It takes about 2-3 seconds to converge.
The non-linear state update equations are as follows:
Pn_dot = Vair*cos(psi)*cos(theta) - Wn
Pe_dot = Vair*sin(psi)*cos(theta) - We
Wn_dot = 0
We_dot = 0
Notice the filter resolves on a wind velocity of 15 ft/s and 090 deg heading.
Pretty slick how quickly it finds a solution.
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To get your turning right in one flight do you control the gains via telemetry uplink ?
Or do you mean that your first guess on gains and downloaded into the firmware is usually correct by the second flight ?
We could then identify the airplane linearized aerodynamic coefficients CL,CD,... CnB,Cla,... by recording the reaction of the airplane to some normalized maneuvers (pitch then roll then yaw), and compute the gains.
But this is a lot of work and given the modelization errors I'm not sure this is worth the pain.
It seemed to me that the ailerons, elevator and rudder could still have high speed oscillations (even though the commanded roll, pitch and yaw was very good). Did you see that as an issue ? It was a major project. Exactly what I needed to see.
Ryan, Thank you very much for posting that.