Repository navigation
Any plan for implementing disk margins? #726
Description
Activity
I wish I could do it, currently I am not familiar enough with the algorithm. FTTB, one can find an implementation here (in julia)
https://github.com/JuliaControl/RobustAndOptimalControl.jl/blob/master/src/diskmargin.jl
We do compute what this paper calls the S-based disk margin in
stability_margins; it's called "Stability margin" in our docs.Slycot already has a function to compute the transfer function matrix L-infinity norm (which is the H-infinity norm for stable systems), so the hard part to implement disk-margins is done.
Reacted by Ben GreinerSee also the published form of the disk margin paper, and Matlab's diskmargin command. One of the paper's authors, the late Andrew Packard, was an author of Matlab's Robust Control Toolbox.
The SISO disk margins are straightforward, and I've got prototype code to find the disk margin, and the associated destabilising complex perturbation and destabilising LTI system.
The MIMO version of disk margins needs structured singular values, or at least I'm pretty sure it does. SLICOT has AB13MD, which computes an upper bound on structure singular values, and if we want MIMO disk margins, I guess we'd start there. For now, one can get conservative upper bounds on (two of) these using
linfnormon the sensitivity and complementary sensitivity transfer functions.
This technique is much more robust than gain & phase margins.
https://arxiv.org/pdf/2003.04771.pdf
https://www.youtube.com/watch?v=XazdN6eZF80&list=PLn8PRpmsu08qFLMfgTEzR8DxOPE7fBiin&index=2&ab_channel=MATLAB