> There are two, and only two, reasons for using feedback. The first is to reduce the effect of any unmeasured disturbances acting on the system. The second is to reduce the effect of any uncertainty about the system dynamics.
(Vinnicombe; *Uncertainty and Feedback: H-infinity loop shaping and the nu-gap metric*; Imperial College Press, 2001)
This is an excerpt from a book that I have for several years been struggling to comprehend. (The rest of the book, that is. This part I think I get.) This is meant to counteract the commonly held belief that the purpose of feedback is to modify the behavior of a system, e.g. to stabilize it. Vinnicombe's point, in essence, is that any such modification could be made in open loop for a dynamical system with no uncertainty and no disturbances. Indeed, control theorists and roboticists spend a lot of time in grad school working out precisely how to do this.
rosalyn
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2024-08-11 21:53:20 UTC
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