ABSTRACT
Control theory aims to develop methods for analysis and design of control systems. A simple control system consists of the controller and the plant. Electrical motors, machine tools, and airplanes are examples of plants. The controller obtains information about the plant by means of sensors. The information is processed, and a control signal
u
(
t
) is calculated, in order to influence the dynamic behavior of the plant. The goal of the control, despite disturbance
δ
(
t
) acting on the plant, is to keep the value of the controlled variable (the output variable)
y
(
t
) within tolerance of the value given by the reference variable (set-point)
r
(
t
). Figure 2.1 shows an elementary control system.
