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CHAPTER 3 3 3
Control Systems
3.1 INTRODUCTION
In this chapter, we present a brief introduction and overview of control systems. Some of the terms commonly
used to describe the operation, analysis and design of control systems are presented.
3.2 CONTROL SYSTEMS
Control systems in an interdisciplinary field covering many areas of engineering and sciences. Control
systems exist in many systems of engineering, sciences and in human body. Control means to regulate,
direct, command or govern. A system is a collection, set, or arrangement of elements (subsystems). A control
system is an interconnection of components forming a system configuration that will provide a desired
system response. Hence, a control system is an arrangement of physical components connected or related
in such a manner as to command, regulate, direct or govern itself or another system.
In order to identify, delineate or define a control system, we introduce two terms: input and output here.
The input is the stimulus, excitation or command applied to a control system, and the output is the actual
response resulting from a control system. The output may or may not be equal to the specified response
implied by the input. Inputs could be physical variables or abstract ones such as reference, set point or
desired values for the output of the control system. Control systems can have more than one input or
output. The input and the output represent the desired response and the actual response respectively. A
control system provides an output or response for a given input or stimulus, as shown in Fig. 3.1.
Input: stimulus Output: response
Control system
Desired response Actual response
Fig. 3.1 Description of a control system
The output may not be equal to the specified response implied by the input. If the output and input are
given, it is possible to identify or define the nature of the system’s components. Broadly speaking, there
are three basic types of control systems:
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