How to see variations of blade pitch through graphic file?

Hi,
I ran the FAST for OC3-Hywind.The wind data was extracted from TurbSim for 18m/s mean wind speed.Simulation was done well.
The related adm and acf file was created as well, because of ADAMSPrep=3.
Then run created adm and acf through Adams/solver.
The outputs of ADams and FAST have good compatibility with each other.
There also created a numeric *.plt and a graphic file *.gra in Adams output.
By checking plt file for blade pitch angle, i see that the blade pitch angle is varying versus time due to used control strategy. But by checking graphic file through Adams/Postprocessor or Adams/View i can’t see blade pitch variations with time at all. I mean by zooming on blades during the simulation in Adams/View, the blade pitch do not change and is fix at the all the time of the simulation. Whereas I expected changes in blade pitches during simulation.
For example my initial blade pitch angle is zero, whereas the graphic file dont show that. It shows greater than zero(e.g 15Degree).
Actually i amazed why the graphic file doesn’t show the blade pitch variation whereas the plt file shows.

Did i do something wrong that i encountered with these problem? If so how to fix?
Is there any way to fix this problem to see the variations of blade pitch within graphic?

Any help will be appreciable.

Best Regards,
Mehdi,

Dear Mehdi,

I have viewed many animations (.gra) of ADAMS simulations run from FAST-generated ADAMS models (.adm / .acf) and the animations always match the numerical results given in the output (.plt) file. I’m not sure what could cause these results to be different.

Are you sure the blade-pitch angle movements are not visible? Sometimes small variations in blade-pitch angle are difficult to see. Could the approximately 15-deg angle you are reporting be the inboard blade aerodynamic twist instead of the blade-pitch angle? I suggest you run a simulation with a rapid pitch-angle ramp–say from 0 to 90 degrees to verify that the animation is not correct (you could set this up through the “overide pitch maneuver” feature of FAST).

Best regards,

Dear Jason,

Thanks for your reply.
According to created plt file, the fluctuations of blade pitch angle is sufficient to see that in graphic file. And as i said the initial blade pitch is zero but in graphic file it is nonzero at all the time of the simulation.
Now i set the blade pitch angles to 90 degree(pi/2=1.5708) and generator torque to 1kN.m within adm file to see what happened.
Here are my changed adm statements:
!---------------------------------- Generator ----------------------------------
! adams_view_name=‘Generator_SF’
SFORCE/3150
, ROTATION
, I = 3150
, J = 2050
, FUNCTION = 1
!------------------------------------- Hub -------------------------------------
!------------------------------------ Blade 1 ----------------------------------
! adams_view_name=‘Pitch1Demand_V’
VARIABLE/10000
, FUNCTION = 1.5708
! adams_view_name=‘Pitch1Error_V’
VARIABLE/10001
, FUNCTION = VARVAL(10000) - AZ(4011,10000)
! adams_view_name=‘Pitch1Actuator_SF’
SFORCE/10000
, ROTATION
, I = 10000
, J = 4011
, FUNCTION = -9.71350E+05VARVAL(10001) - 206WZ(10000,4011,4011)
!------------------------------------ Blade 2 ----------------------------------
! adams_view_name=‘Pitch2Demand_V’
VARIABLE/20000
, FUNCTION = 1.5708
! adams_view_name=‘Pitch2Error_V’
VARIABLE/20001
, FUNCTION = VARVAL(20000) - AZ(4012,20000)
! adams_view_name=‘Pitch2Actuator_SF’
SFORCE/20000
, ROTATION
, I = 20000
, J = 4012
, FUNCTION = -9.71350E+05VARVAL(20001) - 206WZ(20000,4012,4012)
!------------------------------------ Blade 3 ----------------------------------
! adams_view_name=‘Pitch3Demand_V’
VARIABLE/30000
, FUNCTION = 1.5708
! adams_view_name=‘Pitch3Error_V’
VARIABLE/30001
, FUNCTION = VARVAL(30000) - AZ(4013,30000)
! adams_view_name=‘Pitch3Actuator_SF’
SFORCE/30000
, ROTATION
, I = 30000
, J = 4013
, FUNCTION = -9.71350E+05VARVAL(30001) - 206WZ(30000,4013,4013)

But by running simulation I encountered with following error and simulation stops:
a large platform displacement,…
It seems that setting FUNCTION = 1.5708 do not change the blade pitch angle to 90degree and so wind thrust exceeding the platform motion and simulation stops.
Is there anybody knows why setting FUNCTION = 1.5708 do not change the blade pitch angle to 90degree in the simulation?

Note that setting the blade pitch angles to 90 degree(pi/2=1.5708) and generator torque to 1kN.m with FAST-Simulink interface i receive lowest platform pitching motions.

Regards

Dear Mehdi,

You didn’t indicate if the *.plt file shows that the blade-pitch angle is 90 degrees before the simulation stops. Does it? If not, have you removed the MOTION/10000 statement from the *.adm file or included a DEACTIVATE/MOTION, ID = 10000 command in the *.acf file (likewise for ID = 20000 and ID = 30000)? (The blade-pitch angle won’t change if the pitch motion is fixed.)

Your statements for a 90-degree blade-pitch command look correct. However, if the *.adm file was created by FAST with an initial blade-pitch angle of 0 degrees, a 90-degree command will generate a major impulse to the model, which itself may lead to a simulation failure. It would be better to regenerate the ADAMS model by FAST with an initial blade-pitch angle of 90 degrees.

Your statement for a 1-kN generator torque looks correct, except that the sign is such that it will motor the rotor. (Opposite to FAST’s GenTq output sign convention, a positive value of SFORCE/3150 indicates motoring and a negative value of SFORCE/315 indicates generating power.)

I hope that helps.

Best regards,

Dear Jason,

Thanks again,
About generator torque sign, you mean to control the generator torque by using various control strategies, I must exert torque with negative sign in below statement instead of positive sign.
!---------------------------------- Generator ----------------------------------
! adams_view_name=‘Generator_SF’
SFORCE/3150
, ROTATION
, I = 3150
, J = 2050
, FUNCTION = -1

Please confirm my understanding if it is true. Or no guide to fix it.

Regards,

Dear Mehdi,

Correct. Opposite to FAST’s GenTq output sign convention, a positive value of SFORCE/3150 indicates motoring and a negative value of SFORCE/315 indicates generating power. This is due to the orientation of MARKERs in the SFORCE.

Best regards,