FAST - pitch speed

Hello

  1. I like to import the pitch speed signal in source file UserSubs, routine PitchCntrl, by means of the AllOuts() routine. But the pitch speed signal is not available (it is at least not listed in the OutList file)?

  2. I would also like to add the pitch speed to the standard output of FAST. Can someone give a hint on how to accomplish that?

Thanks,
Gerrit.

Dear Gerrit,

By “pitch speed”, do you mean the blade-pitch rate?

FAST currently has no blade-pitch dynamics. That is, the blade-pitch angle command from the controller is simply used in FAST to orient the blade (instantaneously) with no dynamics. Certainly this misses some physics by decoupling the blade-pitch motions from the rest of the system equations of motion. For example, when the blade-pitch angles change because of commands from the pitch controller, because there is no blade-pitch degree of freedom (DOF), there are no associated pitch rates or accelerations computed by FAST and the inertia, Coriolis, and other potential loads from the pitch motion will not be included in the blade loads. The magnitude of these ignored terms will depend on how fast the blades pitch and on the degree to which the blades deflect.

Our to-do list includes introducing blade-pitch DOFs in FAST with all of the potentially important loads explicitly included, but it will be a while before this feature is available.

Until then, the blade-pitch rate is not an output of FAST.

If all you want to know is what the blade-pitch rate would be if the pitch dynamics where present, you could calculate the rate by numerical differentiation of the blade-pitch angle signal.

I hope that helps.

Best regards,