Time delay creates a better feedback system??

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Leon
Leon 2014-1-3
评论： Azzi Abdelmalek 2014-1-3
Hey all,
I'm not sure if this is the right place to ask a question like this, but I'm studying control engineering and ran into a weird phenomenon while working with Simulink. If I enter a unit delay block in my feedback loop (controller is an observer) just before this enters my system/plant, performance improves (a lot less overshoot but some more oscillations).
Now my question is: Am I doing something wrong in Simulink or is it possible that entering a time delay can actually improve performance? It seems rather counterintuitive. The system that needs to be control is pretty unstable (1/(s^4+s^3+s^2) in CT).
Does anyone know if this is possible?
Thanks in advance!
Leon

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回答（1 个）

Azzi Abdelmalek
Azzi Abdelmalek 2014-1-3
This is not true. Adding an element hazardously can be beneficial or harmful. Adding a unit delay without any reason is not logical, but if your feedback is already bad, adding another error to your system, sometimes can be beneficial.
  2 个评论
Leon
Leon 2014-1-3
The thing is that I'm working on an exercise in which I need to evaluate several different possible controllers and now add a time delay to each of them. But could it be the case that, because my observer does not know the initial conditions of the system, inserting a time delay causes the "searching" of the observer state to be somewhat more balanced? Sorry if I'm not making too much sense, I'm still rather new to this field..
Azzi Abdelmalek
Azzi Abdelmalek 2014-1-3
Your system is at the limit of instability (one unstable pole =0). Just make your controller, a PID for example, and try to find the appropriate parameters. If you a control system toobox, you can use a tunable PID controller

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