measuring states in real system

In eq 2.8 of Alan D.Wright’s report, page 24, Which states (x1,x2,x3,x4,x5,x6,x7,x8,x9) are measurable in real system?
I mean do we have tools to measure those noisy states in real world?
If there are such tools, is it economical or feasible to use it in real system?
Any other infos about measuring states will be appreciable.

Could you post the title of the report? I can have a look,


Modern Control Design for
Flexible Wind Turbines


I don’t believe these states would be practical to measure. Instead, the report discusses the design of observers to estimate these states given more practical measurements such as generator speed, and nacelle acceleration. See for example appendix C-1.5 or section 4.2 for some examples.

Hope this helps!


According to second part of that equation(y=Cx) we have four states in output(x1,x3,x7,x8). It means that we must measure those 4 states.
Is it possible to measure those 4 states? Specially x1 and x3 and x8?

Which equation number are you referencing? Y is your measurement variable, depending on your C matrix you may have x terms which are themselves directly measured, but if your output equation is a linear combination of states you will need an observer.

this eq says that the system have 3 outpust(y1=0.5x1+0.5x3, y2=x7, y3=x8).
In another word if x1=x3, the output is directly equal to states x1,x7 and x8 . As we know the outputs must be measurable, My question is how we measure these outputs (y1,y2,y3) in real system? How we measure blade-1&2 perturbed flap tip displacements,perturbed generator rotational speed and perturbed tower-top first fore-aft mode deflection in real system?

Hi, in looking at page A-11, I see that the author writes:

Here we assume that we measure perturbed generator speed (x7), tower-top fore-aft deflection, and the rotor first
asymmetric mode deflection(x1-x2)/2

Generator speed is almost always measured, you can use either feedback from the power electronics or an optical encoder on the generator shaft.

Tower fore-aft deflection I would say is never measured, but fore-aft acceleration is sometimes measured, which is a more practical control signal, you could use an IMU or an accelerameter.

Rotor first asymmetric mode deflection would also be tricky to measure, much more typical would be to use the blade root flap loads measured by a strain gauge as a stand in.

Hope this helps!


is there any report about Modern Control Design for Flexible Floating Wind Turbines?

There are publications on control design for floating wind turbines, but don’t believe a report with this name exists. Have you looked at:

[1] J. M. Jonkman, “Influence of Control on the Pitch Damping of a Floating Wind Turbine,” in ASME Wind Energy Symposium, 2008?

It’s on the publications site,


Dear Paul,
Yes i have read Jason’s paper.
I was meant that the report about modern control of floating wind turbine like Alan D.Wright’s report’s for land based ones.

Any way thank you.

Best Regards,