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082-Engineering-Mathematics-Anthony-Croft-Robert-Davison-Martin-Hargreaves-James-Flint-Edisi-5-2017

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22 Differenceequations

andtheztransform

Contents 22.1 Introduction 681

22.2 Basicdefinitions 682

22.3 Rewritingdifferenceequations 686

22.4 Blockdiagramrepresentationofdifferenceequations 688

22.5 Designofadiscrete-timecontroller 693

22.6 Numericalsolutionofdifferenceequations 695

22.7 Definitionoftheztransform 698

22.8 Samplingacontinuoussignal 702

22.9 TherelationshipbetweentheztransformandtheLaplacetransform 704

22.10 Propertiesoftheztransform 709

22.11 Inversionofztransforms 715

22.12 Theztransformanddifferenceequations 718

Reviewexercises22 720

22.1 INTRODUCTION

Difference equations are the discrete equivalent of differential equations. The terminology

is similar and the methods of solution have much in common with each other.

Differenceequationsarisewheneveranindependentvariablecanhaveonlydiscretevalues.

They are of growing importance in engineering in view of their association with

discrete-timesystems based on the microprocessor.

InChapter21theLaplacetransformwasshowntobeausefultoolforthesolutionof

ordinary differential equations, and for the construction of transfer functions in circuit

analysis,controltheory,etc.Generally,Laplacetransformmethodsapplywhenthevariables

being measured are continuous. Theztransform plays a similar role for discrete

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