Does H infinity control have to be limited to a simple 1Dof feedback architecture? | pressku.com

So I understand really H infinity power tin beryllium utilized to synthesize a controller that is successful nan modular error-feedback model shown here:

https://www.researchgate.net/figure/1-DOF-feedback-control-system_fig1_313128407

but I was wondering tin it beryllium utilized for different architectures for illustration a "2 dof" controller wherever nan reference and nan output are passed successful separately to nan controller:

https://www.researchgate.net/figure/General-2DOF-PID-controller-structure_fig3_327690406

or tin it beryllium utilized to creation a feedforward controller for illustration shown here:

https://apmonitor.com/pdc/index.php/Main/FeedforwardControl

As I understand it, nan only request for nan synthesis of an H infinity controller is that nan weighted strategy must beryllium representable by a linear fractional toggle shape pinch nan controller being connected to a generalized works for illustration so:

https://www.researchgate.net/figure/Closed-loop-system-TzwK-LF-T-P-K-formed-via-lower-linear-fractional-transformation_fig1_251939874

It seems for illustration for each of nan different controller frameworks we tin specify nan strategy arsenic this linear fractional transformation, truthful is it safe to presume that we tin use modular H infinity power synthesis to these different frameworks (like 2 dof aliases feedforward)? I thought it would beryllium but I cannot find immoderate examples doing this and I was wondering if location were facet to these systems that made nan synthesis infeasible. Sorry for nan links, I don't cognize really to straight nexus image diagrams, and thanks!