Implement state-feedback control on nonlinear aeroelastic model

[Alanpwu]

Hi,

I had modelled an aeroelastic wing and obtained the state-space(A,B,C,D) of the linearised system. Is it possible in SHARPy where i can obtain the states value (\eta \zeta) can calculate the control surface deflection all within the DynamicCoupled Solvers? I am doing this for gust load alleviation purposes.

Thank you!

[Norberto Goizueta (ngoiz)]

Hi,

I'm not sure if I exactly follow what you are trying to achieve. I assume that by value of the states you refer to a time domain simulation, if so, I would recommend you simulate the linear time domain system externally to SHARPy (i.e. using scipy.signal.dlsim() or Matlab). The typical output of a linear time domain simulation from these functions is the output y and also the states x of the system. In SHARPy, the DynamicCoupled solver is intended for nonlinear time-domain simulations.

Hope this helps

[Norberto Goizueta (ngoiz)]

I believe that is more for you to think about. Think of SHARPy as your real system where you are sensing the outputs/state via sensors. You may need to manipulate that information to feed it to your controller

[Norberto Goizueta (ngoiz)]

Hi, giving it another thought it would be very cumbersome to send the whole state via UDP. A colleague of mine was attempting this and it proved to be problematic. You may want to explore Kalman filters or some other estimation technique to recreate the state based on a few measurements that you can extract from the nonlinear time domain simulation in SHARPy. This may be of interest for that: https://doi.org/10.2514/6.2021-1392

[Alanpwu]

Thank you so much!

There is another issure. When i tried to output the tip node psi_dot(4,2,0) (4th element, 2nd node, 1st index), as i wrote position [4,2,0] or position[4,2] & index: 1. in the .yaml.

The result is always a [3x3x3] matrix. How can i configure the position or index so that SHARPy only output one value?

Thank you!

[Norberto Goizueta (ngoiz)]

You spotted a limitation of the system right there. Not sure how but we never used UDP to export the CRV. So, (without setting precedent, I had a spare minute :) ) I have quickly given it the functionality to export CRVs. Hopefully it will work. Please checkout the branch fix_udp_crv to use this.

So what you need to do is edit your yaml file for the CRV variables as follows:

- name: 'psi_dot'
  inout: 'out'
  position: 4
  index: [0, 2]
  var_type: 'elem'

where position refers to the element, and index is now a 2-list where the first index is the node index (0, 1 or 2) and then the second element is the vector component (again, 0, 1, 2).

Hopefully this works. Please let me know so we can roll it out to the release version.

[Alanpwu]

where i find the branch fix_udp_crv?

[Rafa Palacios (rafapalacios)]

https://github.com/ImperialCollegeLondon/sharpy/tree/fix_udp_crv