 
Summary: ME 413 Systems Dynamics & Control Chapter 9: Frequency Domain Analyis of Dynamic Systems Systems
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Chapter 9Chapter 9Chapter 9Chapter 9
FrequencyFrequencyFrequencyFrequencyDomain Analysis ofDomain Analysis ofDomain Analysis ofDomain Analysis of
Dynamic SystemsDynamic SystemsDynamic SystemsDynamic Systems
A. Bazoune
9.1 INTRODUCTION
The term Frequency Response refers to the steady state response of a system to a sinusoidal
input.
An input ( )f t is periodic with a period if ( ) ( )f t f t+ = for all values of time t ,
where is a constant called the period. Periodic inputs are commonly found in many
applications. The most common perhaps is ac voltage, which is sinusoidal. For the common
ac frequency of 60 Hz, the period is
1
60
s = . Rotating unbalanced machinery produces
periodic forces on the supporting structures, internal combustion engines produce a periodic
torque, and reciprocating pumps produce hydraulic and pneumatic pressures that are
periodic.
Frequency response analysis focuses on sinusoidal inputs. A sine function has the
