[patrick5415]

I did my PhD in controls too, and I’d pretty much agree with all of that. There is a ton of really heavy math flying around with little to show for it. If your system is anything beyond weakly nonlinear, you are basically screwd. The best and effectively only tool we have otherwise was invented over a 100 years ago by lyapunov. And using it requires, I’m not joking, nearly divine inspiration.

[sunstone]

Magnetic bearings for example, are an entertaining system to control.

[miketery]

Can you expand on what this tool is?

[creatornator]

Lyapunov functions indicate Lyapunov stability. A system that is Lyapunov Stable will settle into a global minimum state and stay there stably indefinitely. Kind of like a ball in a bowl, where all gradients point in to the middle. Non linear systems can "refuse to settle". I may be misremembering something from my controls courses

[dreamcompiler]

https://en.m.wikipedia.org/wiki/Lyapunov_function