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Control System Design - Index | Book Contents |
Chapter 1
| Section 1.5
1. The Excitement of Control Engineering
1.5.9 Disturbances and Uncertainty
One of the things that makes control science interesting is that
all real-life systems are acted on by noise and external
disturbances. These factors can have a significant impact on the
performance of the system. As a simple example, aircraft are
subject to disturbances in the form of wind gusts, and cruise
controllers in cars have to cope with different road gradients and
different car loadings. However, we will find that, by appropriate
design of the control system, quite remarkable insensitivity to
external disturbances can be achieved.
Another related issue is that of model uncertainty. All real-world
systems have very complex models, but an important property of
feedback control is that one can often achieve the desired level
of performance by using relatively simple models. Of course, it is
incumbent on designers to appreciate the effect of model
uncertainty on control performance and to decide whether attention
to better modeling would enable better performance to be achieved.
Both of the issues raised above are addressed, in part, by the
remarkable properties of feedback. This concept will underpin much
of our development in the book.
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