# Control Systems/Adaptive Control

## Adaptive Controllers

What we\'ve been studying up till this point are fixed systems, that is
systems that do not change over time. However, real-world applications
and experience tells us that the environment can change over time: New
noise can be added to a signal, the signal quality can be degraded, or
the specifications of the signals can be changed at the source.

There is a distinct need then for controllers which can modify
themselves to produce the same output regardless of changes to the
input. Herein lies the problem of **adaptive control**. We will
introduce some of the concepts in this chapter, and discuss them in
greater detail in future chapters.

