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At 08:58 AM 4/20/02, you wrote:my
i have designed and built a yaw stabilisation system for an airplane for
it.project at uni. i used a pid controller to achieve this. i am writing my
report for it but i cannot define a pid controller. how would i define
value,it reads in a signal then what?
PID means Proportional, Integral, Derivative.
A controller which compares a desired output with the present output
and makes corrections based on a function of the error term itself, andits
integral and 'rate of change' forms, is a classical way to design acontroller
which can be set up to deal with a variety of different environments whichby
have a strong effect on the usable bandwidth of the loop.
Unfortunately, the appropriate settings for each of these three terms is
no means intuitively obvious, so that controllers of this kind tend towork
sub optimally.state,
As a thumb-nail description, one could say a PID controller generates a
correcting drive mostly responsive to the size of the [proportional]
difference between a desired output setting, and a present output.
Particularly for small and slow changing departures from the desired
this error is also accumulated over time to add in an increasingrules
(integral) correction.
At the other end of the control bandwidth - a fast changing error,
which otherwise might well lead to an overswinging output, is
opposed by a [differential] signal proportional to the rate of change
of the error, and set up to oppose the correction, which CAN have
this happy result: a recovery from an upset or
transient change in minimal time with minimal overshoot.
It is found that using a 'fuzzy logic' approach, which develops control
from considering common sense statements of measurable controlcontrol
objectives and the spans of output levels in which they should apply
and weighting them together by straight-forward centroid of area of
objectives often leads to superior performance in practice, where
tuning for concrete results allows much more intuitive modifications.
Brian Whatcott
Altus OK Eureka!