
2
Linear systems
2.1 Introduction
The dynamics of biological systems are generally highly nonlinear — what
then is the justification for using linear contro l system analysis techniques
to study such systems? The answer to this question will be familiar to any
engineering undergraduate, since it is a fact that while almost all real-world
control systems display nonlinear dynamics to some extent, the vast majority
of the methods used in their design and analysis a re based on linear systems
theory, from the flight control system on the Airbus A380 to the controller for
the servomotor which a c cesses the hard disk on your computer. Essentially,
we have