Different Pitch rate in and outside FAST SFunction in Simulink

Dear Dr. Jonkman,

I meet some problem when I’m trying to modling a modified pitch control loop in Simulink.
In my pitch control loop, the pitch rate been limited between -8deg/s to +8deg/s, however the output signal show very large fluctuation and the pitch rate in output signal is largly over my limitation. (you can find the time series of pitch angle & pitch rate in attachment.)

May I know why my opration signal been changed in FAST, is there a mechanism in the FAST to modify the received control signals?

Thanks

Best Regards,
SONG

Dear Yunpeng,

Similar questions have been asked and answered before, e.g.:
http://forums.nrel.gov/t/pitch-control-error/1319/17
http://forums.nrel.gov/t/pitch-and-torque-spikes-on-variations/1762/2
http://forums.nrel.gov/t/s-function-input-output-signal-mismatch/1502/2
http://forums.nrel.gov/t/start-up-of-nrel-5mw/2277/3

Best regards,

Thank for your kind reply. These topics realy helped me a lot.

Best regards,
SONG