dtgaebe
commented
1 year ago There is a paper currently under review that introduces the pto_impedance matrix from tutorial one. We will link the paper once it is published, but here is a quick rundown:
We use 2-port modelling techniques to combine the mechanical subsystems (drivetrain and gearbox) with the electrical subsystems (generator).
You can find a general introduction to flow and effort variables here: https://books.google.com/books?id=rSVHAAAAQBAJ&pg=PA17&source=gbs_toc_r&cad=3#v=onepage&q&f=false
The combined system dynamics are captured in the pto_impedance
The individual entries are obtained using open-circuit conditions (the Wikipedia page is actually not bad https://en.wikipedia.org/wiki/Impedance_parameters#Two-port_networks to read more)
To arrive at the individual values we modeled the drivetrain using newton's second law and assuming an ideal generator (simplified with a power invariant Park transformation --> back emf proportional to the generator rotational speed and the electromagnetic torque proportional to the load current, with the same factor $\sqrt{3/2}K_t$).
The signs are determined by the wecopttool convention $Zi {U} = F{e} + F{p}$.
Please note that the convention commonly used in control engineering would subtract the PTO force $F{p}$ and this would flip the signs of $Z{11} = Z{FU}$ and $Z{12} = Z{FI}$
smallduan
Hi
I am trying to understand tutorial 1, but PTO impedance is hard for me to understand because I don't know what is the formula involved in it. Can anyone please tell me what information I should look up to understand this section.
Best regards