Continuing from above
The yellow line for the nonlinear model. The blue line for the linear model.
The Tower fore-aft VS Simulation time ( m VS seconds)
If I calculated the azimuth of the linear model by continuous integration of generator speed divided by gear ratio
It gives me a continuous ramp which makes all the results not logical. So, I always use the azimuth of the non-linear model in the transformation matrices between the rotating and non-rotating frame. The comparison between the linear and the nonlinear model in azimuth angle is shown below
The azimuth VS Simulation time ( deg VS seconds)
I hope everything becomes clear.
Regards
M.Fekry