And yet, as the late great Jan Willems would remind us, a lot of control devices do not operate as feedback controllers. For example, heat sinks, pressure valves, shock absorbers are all controllers (they restrict the degrees of freedom of the system they are coupled with), but they are not feedback controllers.
Right, the important point here is that feedback is both powerful and dangerous. So perhaps the series title should be "with great power comes great responsibility."
This is a bit of a tangent, but in terms of heat sinks, pressure valves, and shock absorbers, these are just control devices for one small mechanical/electrical subsystem. You could argue that we cannot design any technological artifacts without feedback. If we zoom out and look at the bigger and more complex system that, say a pressure valve, is a part of, you must use feedback or else you're going to have a massive oil spill in the gulf.
Yes, any sufficiently complex control system will be hierarchical, involving nested feedback loops and such. But I don't think scale is determinative here. Plenty of large-scale systems get by without feedback (or, at the very least, combine open-loop and closed-loop controls in a nontrivial way). One can also turn things around a bit and say that there is no such thing as open-loop controls -- everything uses some sort of a sensor. There was a nice paper by Steve LaValle and Magnus Egerstedt, where they argued that open-loop controls should be properly interpreted as feedback controls that use clocks as their measurement devices. In that same paper they demonstrate what can go wrong if the clocks are inaccurate.
LOL. I like the way Astrom covers QFT in his survey "Horowitz design technique called quantitative feedback theory (QFT) is described in several books. It has been applied successfully to a wide range of problems."
This blog series should really just be
"feedback is all you need"
And yet, as the late great Jan Willems would remind us, a lot of control devices do not operate as feedback controllers. For example, heat sinks, pressure valves, shock absorbers are all controllers (they restrict the degrees of freedom of the system they are coupled with), but they are not feedback controllers.
Right, the important point here is that feedback is both powerful and dangerous. So perhaps the series title should be "with great power comes great responsibility."
This is a bit of a tangent, but in terms of heat sinks, pressure valves, and shock absorbers, these are just control devices for one small mechanical/electrical subsystem. You could argue that we cannot design any technological artifacts without feedback. If we zoom out and look at the bigger and more complex system that, say a pressure valve, is a part of, you must use feedback or else you're going to have a massive oil spill in the gulf.
Yes, any sufficiently complex control system will be hierarchical, involving nested feedback loops and such. But I don't think scale is determinative here. Plenty of large-scale systems get by without feedback (or, at the very least, combine open-loop and closed-loop controls in a nontrivial way). One can also turn things around a bit and say that there is no such thing as open-loop controls -- everything uses some sort of a sensor. There was a nice paper by Steve LaValle and Magnus Egerstedt, where they argued that open-loop controls should be properly interpreted as feedback controls that use clocks as their measurement devices. In that same paper they demonstrate what can go wrong if the clocks are inaccurate.
Also, I'm too much of an anarchist to take any "X is all you need" slogan seriously.
If you really want to lose 90% of your readership, blog about Quantitative Feedback Theory! https://link.springer.com/referenceworkentry/10.1007/978-1-4471-5102-9_238-1
LOL. I like the way Astrom covers QFT in his survey "Horowitz design technique called quantitative feedback theory (QFT) is described in several books. It has been applied successfully to a wide range of problems."
Indeed.