BladedDLL Yaw Control problem

I’m developing a wtg control as DISCON.dll coded in C++. I’m implementing step by step pitch, torque and yaw controls. I’m OK with pitch and torque, but the FAST model seems not to respond to Yaw motion: I made it as simple as request costant yaw rate so I would expect a linear rotation of the nacelle (to do so I write arraySwap[47] = 0.0174 that should be approx 1deg/s, note that 48th parameter in the array has index 47 in C++ due to the 0 based indexing ). Instead nothing happen. Is this a bug or I’m missing something? Are there other parameters I have to set in order to perform a yaw manouver?


Dear Ste,

I’m not aware of any issue with the yaw control. Have you set YCMode = 1 and TYCOn = 0.0 in FAST’s primary input file to enable user-defined yaw control?

Best regards,

Dear Jason,
I set YCMode=1 and TYCOn=0 … I did some tests and here follows the most significant finding: with all DOF = FALSE yet I can move the Yaw (note that I implemented a sine YawRateDemand)
wind is 0m/s from 0deg, rotational speed 5m/s but could be 0 too

from the .fsm

and obtained yaw motion even if #DOF=0

is this normal behavior?


Dear Ste,

Yes, the behavior is normal. Disabling a DOF in a FAST simply means that the equation of motion for that DOF is not formulated, resulting in no acceleration of that DOF. For example, you can still have generator/rotor rotation in FAST when the GenDOF is disabled. For nacelle yaw, the yaw controller’s effect on the FAST model depends on whether or not the yaw DOF is enabled as follows:

YawDOF = False: If the yaw DOF is disabled, then the commanded yaw angle and rate will be the actual yaw angle and yaw rate used internally by FAST (in general, you should ensure these are correlated). In this case, FAST will not compute the correlated yaw acceleration, but assume that it is zero.

YawDOF = True: If the yaw DOF is enabled, then the commanded yaw angle and rate, YawPosCom and YawRateCom, become the neutral yaw angle, YawNeut, and neutral yaw rate, YawRateNeut, in FAST’s built-in second-order actuator model defined by inputs YawSpr and YawDamp.

See the “Nacelle Yaw Control” section of the FAST User’s Guide, especially Figure 24, for more information.

Best regards,