×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

#### Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

# Control design for finite element model

## Control design for finite element model

(OP)

I am coding up a non-linear dynamic simulation of some wind turbine blade test equipment. The blade is cantilevered from a mounting structure and fatigue tested by reciprocating a large mass that is mounted to the blade at the resonant frequency of the system. The blade and its mounting structure can be simplified to the system inside the red box in the picture.

In the finite element model, the displacements are solved for based on externally applied forces. I therefore need to calculate what force needs to be applied in order to get the displacement d(t) to follow a prescribed sinusoidal path given by d(t)=A*sin(2*pi*f*t) where A is the amplitude, f is the resonant frequency of the system and t is time. I intend to model the hydraulic actuator as a beam element with length l and a very low axial stiffness, and apply a force F(t) to the mass and the structure so that l follows the equation above.

My question is: given all of the above information, how do I calculate what force to apply at the next time step, given the desired length at the new time step (d(t)), the length at the previous time step (l) and the equivalent model of the blade given by K, C and M?

Any help will be much appreciated!

#### Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

#### Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Close Box

# Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!