Giters

cybergalactic / MSS

The Marine Systems Simulator (MSS) is software that supplements the textbook "Handbook of Marine Craft Hydrodynamics and Motion Control," 2nd Edition, by T. I. Fossen, published in 2021 by John Wiley & Sons Ltd.

Home Page:https://mss.fossen.biz

Geek Repo:Geek Repo

Github PK Tool:Github PK Tool

Munk moments

joaobrittoneto opened this issue · comments

commented

Hi Prof. Fossen,

While having a look at Munk moments and it's destabilizing effect on simulation of UUVs, I came across this simplification for the Remus. I believe the term CA(5,4) was supposed to be CA(5,3), referring to term -X_udot * u_r in equation 6.54 (1st edition) or 6.60 (2nd).

For my case, I'll need to do a similar approach to compensate for the unmodeled nonlinear damping, and I was wondering if it could be generalized also for the roll part (i.e. CA(4,2) and CA(4,3)), zeroing the whole bottom left part of the CA matrix. Any though on that?

Best regards

commented
commented

You are right. It should be C(5,3) = 0. I will update the file on GitHub. Thanks!

Yes, you should also consider canceling the quadratic terms in the roll equation since they need to be balanced by nonlinear damping terms, which might be missing. You can see the effect by simulating with and without the problematic terms, and use this information to decide whether you should keep the terms or not.

commented

Thank you very much for your quick feedback.