Difference between revisions 17750451 and 20025337 on enwiki

In [[control theory]], '''first-order control''' is when a desired result is attempted by adjusting a scalar (first order) control. Such mechanisms, where first order change successfully produces desired results, are called ''first order mechanisms''.  First-order control is contrasted to [[higher-order control]].

While many simple mechanisms are completely first order, most complex mechanisms are only first order within a range of operation.

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===Slack===

Closely related to "precision" and directly involved in most [[Negative feedback loop]]s is "slack" the difference in time or distance between the input to a system and the result of that input. Delay in time must be allowed for when adjusting the system: changes in the system in the future because of adjustments made in the past must be allowed for when making present adjustments. The simple solution o
tf this problem is to allow the system to "settle".  Examples of difference in distance generally come from [[Static friction]]: a control may be perfectly linear once static friction has been overcome, while being very non-linear from a standing start.  A common example is pushing a heavy crate across a not very slick floor: a great deal of force may be applied without moving the crate at all; a fraction more and it shoots across the floor: after that less force is needed to keep it moving.

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==References==

*<i>Change</i> [[Paul Watzlawick]] [find urls]
[[Category:Control theory]]