3 Control systems - Laplace transform

66
©Dr inŜ. JANUSZ LICHOTA CONTROL SYSTEMS Laplace transform Transfer functions Block algebra Faculty of Mechanical and Power Engineering Wrocław 2007

Transcript of 3 Control systems - Laplace transform

Page 1: 3 Control systems - Laplace transform

©D

r in

Ŝ.

JA

NU

SZ L

ICH

OT

A

CO

NT

RO

L S

YST

EM

S

Lapla

ce t

ransf

orm

Tra

nsf

er

functi

ons

Blo

ck

alg

ebra

Fa

cu

lty o

f M

ech

an

ica

l a

nd

Po

we

r E

ng

ine

eri

ng

Wro

cła

w 2

007

Page 2: 3 Control systems - Laplace transform

CO

NT

EN

TS

•L

apla

ce tra

nsf

orm

def

initio

n

–Pro

per

ties

–Pro

ofs

–Exam

ple

s

•T

ransf

er funct

ions

–Exam

ple

s

•B

lock

alg

ebra

–Typic

al co

nnec

tions

–Puzz

les fo

r young a

nd o

ld

Page 3: 3 Control systems - Laplace transform

Lapla

ce t

ransf

orm

defi

nit

ion

[]

0

()

()

()

stL

ft

Fs

ft

edt

∞−

==∫

C –

com

ple

xnu

mb

ers

set,

s –

com

ple

xnum

ber

,

t –

tim

e.

Th

e L

apla

ce t

ran

sfo

rm e

xis

ts f

or

lin

ear

dif

fere

nti

al e

qu

atio

ns

for

wh

ich

the

tran

sfo

rmat

ion

in

tegra

l co

nv

erg

es.In

tegra

l is

conv

erg

ing

, w

hen

exis

tsfi

nit

ed

nu

mb

ers

K a

ndγ,

su

ch

, ,

Let

be

giv

en f

un

ctio

n, w

her

e f(

t)=

0 f

or

t <

0. T

hen

Lap

lace

tran

sfo

rmis

cal

led

,

:f

→�

s∈�

()

tf

tK

eγ≤

t∈�

Re(

)sσ

γ=

>

Page 4: 3 Control systems - Laplace transform

Inv

erse

Lap

lace

tran

sform

f(t)

(ti

me

fun

ctio

n)

is w

ritt

en a

s

1(

)(

)2

cj

st

cj

ft

Fs

ed

sj

π

+∞

−∞

=∫

j-im

agin

ary

num

ber

,

c-co

nst

ant

Lapla

ce t

ransf

orm

defi

nit

ion

Page 5: 3 Control systems - Laplace transform

Pie

rre-

Sim

on

mar

qu

isd

e L

apla

ce

23 I

II 1

749

–5 I

II 1

827

Port

rait

pai

nte

daf

ter

a tr

ansf

orm

.

Lapla

ce t

ransf

orm

defi

nit

ion

Page 6: 3 Control systems - Laplace transform

Pro

pert

ies

Lin

eari

ty

Sca

ling

Tim

esh

ifti

ng

Tt≥

0 (

righ

t)

Tt≤0

(le

ft)

Dam

pin

g

LA

ft

AL

ft

ii

n

ii

n

()

[(

)]=

=∑

=

11

[]

[]

[]

()

()

()

()

Lf

tf

tL

ft

Lf

βα

β+

=+

[]

[]

1(

)(

)L

fat

Lf

ta

=

[]

[]

()

()

tsT

tL

ft

Te

Lf

t−

−=

[]

0

()

()

()

t

t

T

sTs

tL

ft

Te

Fs

fe

ττ

−−

=−

[]

()

()

()

sL

ef

tL

fs

aF

sa

τ

=

−=

Page 7: 3 Control systems - Laplace transform

Dif

fere

nti

atio

n (

gen

eral

)

Inte

gra

tion

Co

nv

olu

tion

(Bo

rel

theo

rem

)

Fin

al v

alu

es

()

(0)

Lf

sFs

f•

=

12

1

12

()

(0)

(0)

...

(0)

()

nn

nn

n

nn

n

df

td

fd

fL

ss

fs

Fs

dt

dt

dt

−−

−−

=−

−−

−+

2

0(

)(0

)(

) tL

fs

Fs

sff

•••

=

=

−−

0

1(

)(

)

t

Lf

tdt

Fs

s

=

12

12

12

00

()*

()

()

()

()

()

tt

ft

ft

ft

fd

ff

td

ττ

ττ

ττ

=−

=−

∫∫

[]

12

12

()*

()

()

()

Lf

tf

tF

sF

s=

0li

m(

)li

m(

)t

sf

tsF

s→

+∞→

=0

lim

()

lim

()

ts

ft

sFs

→+

→∞

=

Pro

pert

ies

Page 8: 3 Control systems - Laplace transform

Theore

m’s

pro

of

Lin

eari

ty

Co

ncl

usi

on

fro

m l

inea

rity

isth

atL

apla

ce t

ran

sfo

rm c

an’t

be

use

d t

o d

escr

ibe

non-l

inea

r sy

stem

s()

12

0

12

00

12

()

()

()

()

()

()

st

stst

ft

ft

edt

ft

edt

ft

edt

Fs

Fs

αβ

αβ

αβ

∞−

∞∞

−−

+=

+=

+

∫ ∫∫

Page 9: 3 Control systems - Laplace transform

Theore

m’s

pro

of

Scaling

Sub

stit

uti

ngτ=

at w

e o

bta

in

Page 10: 3 Control systems - Laplace transform

Theore

m’s

pro

of

Tim

e s

hif

ting

=0

for

Tt>

0, bec

ause

f(t)

=0

fo

r t<

=0

Sub

stit

uti

ngτ=

t-T

tw

e ob

tain

Page 11: 3 Control systems - Laplace transform

Theore

m’s

pro

of

Dam

pin

g,

frequency s

hif

ting

Sub

stit

uti

ng

p=

s-a

we

obta

in

0

()

()

()

pt

ef

tdt

Fp

Fs

a

∞−

==

−∫

Page 12: 3 Control systems - Laplace transform

Theore

m’s

pro

of

Dif

fere

nti

ati

on

Inte

gra

tion

by p

arts

del

iver

s

12

1

12

()

(0)

(0)

...

(0)

()

nn

nn

n

nn

n

df

td

fd

fL

ss

fs

Fs

dt

dt

dt

−−

−−

=−

−−

−+

Co

nti

nu

ing

inte

gra

tio

ng

ener

alfo

rmu

lais

ob

tain

ed

Page 13: 3 Control systems - Laplace transform

Theore

m’s

pro

of

Inte

gra

tion

Tw

o c

onti

nuo

usl

y d

iffe

ren

tiab

le f

un

ctio

ns

can

be

inte

gra

te b

y p

arts

So

far

in

tegra

l ex

ists

Page 14: 3 Control systems - Laplace transform

Theore

m’s

pro

of

Convolu

tion

Sub

stit

uti

ngσ

=t-τ

we

ob

tain

Page 15: 3 Control systems - Laplace transform

Theore

m’s

pro

of

Init

ial valu

e t

heore

mIn

itia

l v

alu

eth

eore

m

IfF

(s)

= L

[f(t

)]an

dex

ists

lim

it

, th

en0

lim

()

(0)

tf

tf

→+

=+

Page 16: 3 Control systems - Laplace transform

Fin

alv

alu

eth

eore

m.

If F

(s)

= L

[f(t

)] a

nd

ex

ists

lim

it

Theore

m’s

pro

of

Fin

al valu

e

lim

()

()

tf

tf

→+∞

=+∞

Page 17: 3 Control systems - Laplace transform

La

pla

ce

est

au

ssi con

nu

pou

r sa

con

ce

ption

d'u

n d

ém

on

(ou

dém

on

de

Lap

lace

) cap

ab

le d

e c

onna

ître

, à

un

insta

nt don

, to

us le

s p

ara

tre

s d

e tou

tes le

s p

art

icu

les d

e l'u

niv

ers

. D

an

s c

ett

e p

ers

pe

ctive

, l'a

ute

ur

ad

op

te u

ne

po

sitio

n d

éte

rmin

iste

, so

it u

ne

positio

n p

hilo

soph

ique

et scie

ntifique

cap

ab

le d

'infé

rer

de

ce

qu

i e

st,

ce

qu

i do

it ê

tre

. C

e c

on

ce

pt de

dém

on

se

ra n

ota

mm

en

t re

mis

en

cau

se

pa

r le

prin

cip

e d

'ince

rtitude

d'H

eis

en

be

rg.

La

pla

ce

str

on

gly

belie

ved

in

cau

sa

l de

term

inis

m,

wh

ich

is e

xp

ressed

in

the

fo

llow

ing q

uo

te f

rom

th

e in

tro

du

ction

to

th

e

Essai:

"We

ma

y r

ega

rd the

pre

se

nt

sta

te o

f th

e u

niv

ers

e a

s t

he

eff

ect of

its p

ast and

the

ca

use

of

its f

utu

re.

An

in

telle

ct w

hic

h a

t

a c

ert

ain

mom

en

t w

ou

ld k

no

w a

ll fo

rce

s tha

t se

t na

ture

in

mo

tion

, a

nd

all

po

sitio

ns o

f a

ll item

s o

f w

hic

h n

atu

re is

co

mpo

sed

, if th

is in

telle

ct

we

re a

lso

va

st

en

ou

gh

to

su

bm

it th

ese

data

to

an

aly

sis

, it w

ou

ld e

mb

race

in

a s

ingle

fo

rmula

the

mo

ve

men

ts o

f th

e g

rea

test

bod

ies o

f th

e u

niv

ers

e a

nd

tho

se

of

the

tin

iest a

tom

; fo

r su

ch

an

in

telle

ct

no

thin

g w

ou

ld

be

un

ce

rta

in a

nd

the

futu

re ju

st

like

the

pa

st

wou

ld b

e p

resen

t befo

re its

eye

s."

Laplacescher Dämon

be

ze

ichne

t d

ie e

rkenntn

is-

und

wis

se

nschaft

sth

eo

retisch

e A

uff

assun

g,

de

rgem

äß

es m

öglic

h s

ei,

un

ter

de

r K

enn

tnis

säm

tlic

he

r N

atu

rge

se

tze

un

d a

ller

Initia

lbed

ingun

gen

jede

n v

erg

an

ge

nen

und

je

den

zu

künft

igen

Zu

sta

nd

zu

be

rechne

n. D

er

me

taph

ysis

che

Un

terb

au

die

se

r H

altun

g ist

de

r G

ese

tze

sde

term

inis

mu

s: fü

r Lap

lace

ist

die

Welt d

urc

h A

nfa

ngsbed

ingun

ge

n u

nd

Be

we

gun

gsge

se

tze

vo

llstä

nd

ig d

ete

rmin

iert

, so

da

ss d

ie A

ufg

abe

de

r

Na

turp

hilo

so

ph

ie, d

ie in

de

r H

imm

els

me

ch

an

ikih

r V

orb

ild b

esitzt,

aussch

ließ

lich

in

de

r In

tegra

tion

vo

n

Diffe

ren

tia

lgle

ich

un

gen b

este

ht.

Da

s w

äre

die

Aufg

abe

de

s D

äm

on

s,

de

n L

ap

lace

im

Vo

rwo

rt d

es Essai philosophique

sur les probabilités

vo

n 1

814

en

twirft

; e

r sp

rich

t do

rt jedo

ch

we

nig

er

eff

ekth

eis

che

nd

von

ein

er

Inte

lligen

z (

une

inte

llige

nce

).

Вф

ил

осо

фи

иЛ

апл

асб

ыл

пр

ивер

жен

цем

дет

ерм

ин

изм

а. О

нп

ост

ул

ир

овал

, ч

тоес

ли

бы

как

ое-

ни

буд

ьр

азум

но

есущ

еств

о

смо

гло

узн

ать

по

ло

жен

ия

иск

ор

ост

ивсе

хч

асти

цв

ми

ре

вн

еки

йм

ом

ент,

он

ом

огл

об

ыаб

сол

ютн

ото

чн

оп

ред

сказ

ать

эво

лю

ци

юВ

сел

енн

ой.

Так

ое

гип

оте

тич

еско

есу

щес

тво

вп

осл

едст

ви

ин

азван

од

емо

но

мЛ

апл

аса.

Mom

ent

of

rela

x.

Som

eth

ing

more

com

pre

hensi

ble

.

Page 18: 3 Control systems - Laplace transform

Tra

nsf

orm

table

Tra

nsfo

rmIn

vers

e

transfo

rm

Page 19: 3 Control systems - Laplace transform

Tra

nsf

orm

table

Page 20: 3 Control systems - Laplace transform

Lapla

ce, Louis

iana

Fro

m W

ikip

edia

, th

e fre

e e

ncyclo

pedia

Ju

mp

to

: na

vig

atio

n,

sea

rch

La Place

(som

etim

es s

pe

lled

LaPlace

or Laplace

) is

a c

en

su

s-d

esig

na

ted

pla

ce

loca

ted

in

St.

Joh

n the

Ba

ptist P

arish

,

Lo

uis

iana

, o

n the

Ea

st

Ban

k o

f th

e M

issis

sip

pi R

ive

r. A

s o

f th

e 2

000

cen

su

s,

the

CD

P h

ad

a t

ota

l po

pu

lation

of

27,6

84

.

It is t

he

sou

the

rn te

rmin

us o

f In

ters

tate

55

hig

hw

ay,

wh

ere

it

join

s w

ith

In

ters

tate

10

. La

Pla

ce

is lo

ca

ted

25

mile

s w

est

of

Ne

w O

rle

an

s.

Tra

nsf

orm

table

Page 21: 3 Control systems - Laplace transform

Fs

kedt

ke

s

k s

st

st

()=

=−

=−

∞−

+∞

∫ 00

Fin

dL

apla

ce t

ran

sfo

rm o

f H

eav

isid

e fu

nct

ion

f(t)

= k

dla

t>

0

So

luti

on

Tra

nsf

orm

table

Exam

ple

1

Page 22: 3 Control systems - Laplace transform

Dir

acim

pu

lse

δ δ

δ()

,

()

,

()

tt

tt

tdt

=≠

=∞

=

=

−∞

+∞ ∫

00 0

1

Lt

[(

)]δ

=1

Lap

lace

tran

sfo

rm o

f D

irac

im

pu

lse

tt

Geo

met

rica

l m

od

el

tria

ng

les

wit

hu

nit

y s

urf

ace

and t

op p

oin

t →

Of

cou

rse

11

ss

=S

ow

e h

ave

rela

tion

bet

wee

nH

eav

isid

efu

nct

ion

an

dD

irac

im

pu

lse

[]1

11

1()

1(

)d

tL

Ls

ts

dt

δ−

=

==

Tra

nsf

orm

table

Exam

ple

2

Page 23: 3 Control systems - Laplace transform

Pro

of

Tra

nsf

orm

table

Exam

ple

31

te

s

α

α±

→m

0

0

()

0

()

0

()

()

1

1

st

tst

st

st

Fs

ft

edt

ee

dt

edt e

s

s

α

α

α

α

α

∞−

∞−

∞−

∞−

=

= =

=−

=−

∫ ∫

Tra

nsf

orm

Page 24: 3 Control systems - Laplace transform

Fin

d t

ran

sfo

rm o

f an

equ

atio

n

()

()

yt

kut

=S

olu

tio

n

()

()

Ys

kUs

=

Lap

lace

tra

nsf

orm

conv

erts

tim

efu

nct

ion

f(t)

in

toco

mp

lex

fun

ctio

nF

(s),

th

eref

ore

Dynamic system

u(t)

y(t)

k -

coef

fici

ent

Tra

nsf

orm

table

Exam

ple

4

Page 25: 3 Control systems - Laplace transform

.

Ty

yku

+=

Tra

nsf

orm

of

dif

fere

nti

atio

n i

s

Fin

d t

ran

sfo

rm o

f an

dif

fere

nti

al e

qu

atio

n

So

luti

on

12

1

12

()

(0)

(0)

()

...

(0)

nn

nn

n

nn

n

df

td

fd

fL

sF

ss

sf

dt

dt

dt

−−

−−

=

−−

−−

Th

eref

ore

[]

()

(0)

()

()

TsY

sy

Ys

kUs

−+

=If

in

itia

l val

ue

isg

iven

y(0

) =

0, th

en

()

()

()

()

()

1(

)

TsY

sY

skU

s

Ys

Ts

kUs

+=

+=

Dynamic

system

u(t)

y(t)

Tra

nsf

orm

table

Exam

ple

5

Page 26: 3 Control systems - Laplace transform

Fin

d t

ran

sfo

rm o

f an

dif

fere

nti

al e

qu

atio

n

So

luti

on

...

12

Ty

Ty

yku

++

=

21

1

21

()

(0)

(0)

()

(0)

....

nn

nn

n

nn

n

df

td

fd

fL

sF

ss

fs

dt

dt

dt

−−

−−

=

−−

−−

Tra

nsf

orm

of

dif

fere

nti

atio

n i

s

[]

2

21

(0)

()

(0)

()

(0)

()

()

dy

Ts

Ys

syT

sYs

yY

skU

sd

t

−−

+−

+=

Th

eref

ore

Dynamic

system

u(t)

y(t)

In c

ase

of

init

ial

val

ues

eq

ual

zer

o 2

21

()

1(

)Y

sT

sT

skU

s

+

+=

Tra

nsf

orm

table

Exam

ple

6

Page 27: 3 Control systems - Laplace transform

..

Ty

yk

uu

+=

+

Fin

d t

ran

sfo

rm o

f an

lin

ear

dif

fere

nti

al e

qu

atio

n

So

luti

on

Dynamic

system

u(t)

y(t)

[]

[]

()

(0)

()

()

(0)

()

TsY

sy

Ys

ksU

su

Us

−+

=−

+

Inca

se o

f in

itia

l v

alu

es e

qu

alze

ro y

(0)=

0, u(0

)=0 w

e o

bta

in

()

()

()

()

TsY

sY

sks

Us

Us

+=

+

[]

[]

()

1(

)1

Ys

Ts

Us

ks+

=+

Tra

nsf

orm

table

Exam

ple

7

Page 28: 3 Control systems - Laplace transform

Fin

d i

nv

erse

tra

nsf

orm

of

()

()(

)F

ss

ss

()=

+−

++

1

1

20

13

22

3

()

()

()

()

()

()

Fs

s

A

s

B

s

C

s

D

s

E

s(

)=

+−

++

++

++

++

+

1

12

01

13

33

22

32

()

()

()

()

()

()

()

()

sF

ss

s

A

s

B

s

C

s

D

s

E

s+

=+

+−

++

++

++

++

+

11

1

120

11

33

3

22

22

32

() (

)(

)(

)(

)(

)(

)li

m(

)s

sF

sA

sB

sC

s

D

s

E

s→

−+

=−

++

++

++

++

+

1

22

32

11

20

11

33

3

()

()

()(

)(

)li

mli

ms

ss

ss

ss

A→

−→

−+

+−

++

=

−+

=

−1

2

22

31

31

1 1

20

13

120 3

120

12

0 81

20

−=

−A

AB

CD

E=

=−

==

=1 8

3 16

1 4

1 4

3 16

()

()

ft

te

tt

et

t(

).

..

.=

−−

++

−−

375

15

375

52

52

3

So

luti

on.

Ex

pan

din

g i

n a

par

tial

fra

ctio

n e

xp

ansi

on

Co

effi

cien

tA

(re

sid

ue)

is

eval

uat

ed

by m

ult

iply

ing

th

rou

gh

by t

he

den

om

inat

or

fact

or

of

equ

atio

n

corr

esp

on

din

g t

o A

an

d s

etti

ng

s

equ

al t

o t

he

roo

t

Fro

m t

ran

sform

tab

le w

e o

bta

in

Tra

nsf

orm

table

Exam

ple

8

Page 29: 3 Control systems - Laplace transform

Tra

nsi

ent

resp

onse

of

a fu

nct

ion

f(t)

Sch

eme

in S

imu

lin

k

Dif

fere

nti

atio

ns

giv

esu

s

imp

uls

ere

sponse

of

the

syst

em s

/s

= 1

We

use

step

inp

ut

1/s

, b

ecau

seof

lack

of

Dir

acim

pu

lse

inpro

gra

m

F(s)

u(t)=δ δδδ(t)

f(t)

()

()(

)F

ss

ss

()=

+−

++

1

1

20

13

22

3

()

()

ft

te

tt

et

t(

).

..

.=

−−

++

−−

375

15

375

52

52

3

Tra

nsf

orm

table

Exam

ple

8

Page 30: 3 Control systems - Laplace transform

Sy

stem

tra

nsf

er f

un

ctio

n

Page 31: 3 Control systems - Laplace transform

Syst

em

tra

nsf

er

functi

on

Ifw

e w

ill

futh

er t

ran

sform

e.g

. d

iffe

ren

tial

equ

atio

n(e

xam

ple

5)

.

Ty

yku

+=

()

()

1(

)Y

sT

skU

s+

=

we

wil

l fi

nd

inte

rest

ing

rela

tion

bet

wee

no

utp

ut

and

inpu

tsi

gn

al

()

()/

()

/1

Ys

Us

kT

s=

+

On

th

ele

ftsi

de

ther

ear

ed

ivid

edfu

nct

ion

s–

outp

ut

and

inpu

t, o

n t

he

righ

t si

de

ther

e is

rat

io o

f tw

o p

oly

no

mia

ls.

Page 32: 3 Control systems - Laplace transform

Syst

em

tra

nsf

er

functi

on

Def

initio

n.

Tra

nsf

er f

un

ctio

nG

(s)

isd

efin

ed a

s th

e ra

tio

of

a L

apla

ce

tran

sfo

rm o

f th

e ou

tpu

t v

aria

ble

to t

he

Lap

lace

tra

nsf

orm

of

the

inpu

t v

aria

ble

,

wit

h a

ll i

nit

ial

cond

itio

ns

assu

med

to b

e ze

ro.

()

()

()

Ys

Gs

Us

=Dynamic process

u(t)

y(t)

G(s)

u(t)

y(t)

Tra

nsf

er f

un

ctio

nca

nb

e use

dto

des

crib

eon

lyli

nea

r, s

tati

on

ary (

con

stan

t

par

amet

er)

syst

em.

A t

ran

sfer

fun

ctio

n i

s an

in

put-

outp

ut

des

crip

tio

n o

f th

e

beh

avio

ur

of

a sy

stem

.

Page 33: 3 Control systems - Laplace transform

Syst

em

tra

nsf

er

functi

on

()

()

()

Ys

Gs

Us

=

Iftr

ansf

er f

un

ctio

no

fa

syst

em i

s

and

inpu

tsi

gn

alis

U(s

), t

hen

outp

ut

sig

nal

can

be

det

erm

ined

()

()

()

Ys

Gs

Us

=

Uti

lizi

ng

Bore

l th

eore

m o

utp

ut

sig

nal

y(t

)in

tim

e-d

om

ain

can

be

com

pu

ted

()

()*

()

yt

gt

ut

=

Ano

ther

way

to g

ety(t

) is

to f

ind

inv

erse

Lap

lace

tra

nsf

om

atio

nfr

om

table

Page 34: 3 Control systems - Laplace transform

10

1(

)(

),m

ni

ii

ii

ii

Ts

Ys

ks

Us

nm

==

+=

∑ Ms

Ts

iii

im

()=

+

=∑ 1

1L

sk

s i

i

i

n

()=

=∑ 0

()

()

()

()

()

Ys

Ls

Gs

Us

Ms

==

Syst

em

tra

nsf

er

functi

on

Lap

lace

tran

sfo

rmof

lin

ear

dif

fere

nti

aleq

uat

ion

is

Rea

lsy

stem

sfu

lfil

lco

nd

itio

nn

<=

m.

Def

inin

gn

ewv

aria

ble

s

rati

o o

ftw

ora

tion

al p

oly

no

mia

ls i

so

bta

ined

Page 35: 3 Control systems - Laplace transform

Syst

em

tra

nsf

er

functi

on

Th

e d

eno

min

ato

r po

lyn

om

ial

M(s

), w

hen

set

equ

al t

o z

ero

, is

cal

led

th

e

char

acte

rist

ic e

qu

atio

n, b

ecau

se t

he

roo

ts o

f th

is e

qu

atio

n d

eter

min

e th

e ch

arac

ter

of

the

tim

e re

spon

se

()

()

()

()

()

Ys

Ls

Gs

Us

Ms

==

Th

e ro

ots

of

this

ch

arac

teri

stic

equ

atio

n a

re a

lso c

alle

d t

he

pole

s or

singu

lari

ties

of

the

syst

em.

Th

e ro

ots

of

the

nu

mer

ator

poly

no

mia

l L

(s)

are

call

ed z

eros

of

the

syst

em.

Page 36: 3 Control systems - Laplace transform

Syst

em

tra

nsf

er

functi

on

Exam

ple

1F

ind

tran

sien

tre

spo

nse

of

ano

utp

ut

sig

nal

y(t

), i

fsy

stem

tra

nsf

er

fun

ctio

nis

Gs

sT

s(

)(

)=

+

1

1

and i

npu

tsi

gn

al i

sli

nea

ru(t

)=t.

Ys

Gs

Us

sT

s(

)(

)(

)(

)=

=+

1

13

Ex

pan

din

gou

tput

in a

par

tial

fra

ctio

n d

eco

mp

osi

tion

Ys

sT

s

A s

B s

C s

D

sT

()

()

=+

=+

++

+

1

11

33

2(

)D

Cs

C TB

sB T

As

A T+

++

++

+−

=

32

10

Co

mp

arin

gco

effi

cien

tat

the

sam

e p

ow

eran

d s

etti

ng

th

em e

qu

al t

o z

ero

AB

TC

TD

T=

=−

==−

12

2

yt

tT

tT

Te

t T(

)=

−+

−−

1 2

22

2

Solu

tion

.

Fro

mtr

ansf

orm

tab

lew

e se

e, t

hat

U(s

)=1

/s2,

ther

efore

Th

eref

ore

outp

ut

sign

alin

tim

e-d

om

ain

is

Page 37: 3 Control systems - Laplace transform

Gs

sT

s(

)(

)=

+

1

1y

tt

Tt

TT

e

t T(

)=

−+

−−

1 22

22

Fun

ctio

n y

(t),

T=

1 s

econd

chan

ges

ver

sus

tim

e

21

()

12

ty

tt

te−

=−

+−

05

10

15

20

25

30

35

40

45

02

46

81

01

2czas t, sekundy

y(t)Syst

em

tra

nsf

er

functi

on

Exam

ple

1 –

tim

e r

esp

onse

Page 38: 3 Control systems - Laplace transform

[]

2()

(1)

()

()

()

()

Ys

sT

sU

s

Ts

Ys

sYs

Us

+=

+=

2

2()

()

()

()

dy

td

yt

Tu

tdt

dt

Ty

yu

t

+=

+=

&&&

Rev

erse

op

erat

ion

isposs

ible

too

. S

yst

em t

ran

sfer

fu

nct

ion

allo

ws

to o

bta

in d

iffe

ren

tial

equ

atio

n

Syst

em

tra

nsf

er

functi

on

Exam

ple

1 –

dif

fere

nti

al equati

on

Page 39: 3 Control systems - Laplace transform

Syst

em c

har

acte

rist

ic e

qu

atio

nis

(1)

0s

Ts+

=

Eq

uat

ion

has

two

po

les

0s=

1s

T=−

and

has

n’t

zero

s. I

fT

=1

sec

ond

, th

enpo

les

locu

sca

nb

e port

rayed

on

Gau

ss

pla

ne

jω=

j Im

(s)

-1/T

=R

e(s

)

s=σ

+ jω

Po

le l

oci

Syst

em

tra

nsf

er

functi

on

Exam

ple

1 -

pole

s

Page 40: 3 Control systems - Laplace transform

Syst

em

tra

nsf

er

functi

on

Exam

ple

2 –

tim

e s

olu

tion

Let

go

bac

kto

ex

amp

le5.

Th

isord

inar

ily

dif

fere

nti

aleq

uat

ion

is.

0y

ay

+=

Th

isis

ho

mo

gen

eou

s eq

ua

tion.

Ith

asso

luti

on

()

(0)

at

at

yt

Ce

ye

−−

==

y(0

) is

call

edin

itia

lva

lue.

,o

nho

mo

gen

eous

equ

atio

nis

.

Ty

ay

bu

+=

Ith

asti

me-

dom

ain

solu

tion

uti

lize

d b

y c

onv

olu

tion

()

0

()

()

t

at

at

yt

Ce

be

udt

ττ

−−

−=

+∫

Fir

stco

mp

on

ent

dep

end

s o

n i

nit

ial

con

dit

ion

s, s

eco

nd

on

co

ntr

ol

sig

nal

u(t

). I

fa>

0,

then

syst

em o

utp

ut

sig

nal

y(t

) is

hea

din

gto

war

din

fin

ity

. If

a<

0,

then

syst

emo

utp

ut

sign

alis

hea

din

gto

zer

o.

Page 41: 3 Control systems - Laplace transform

Syst

em

tra

nsf

er

functi

on

Desc

ripti

on o

f m

any s

yst

em

s at

the s

am

e t

ime

So

luti

on o

fone

tran

sfer

fun

ctio

nis

solu

tio

no

fin

fin

ity

nu

mb

ero

fsy

stem

s

des

cib

edb

y t

he

sam

e st

ruct

ure

of

dif

fere

nti

aleq

uat

ion

.

Even

those

we

don’t k

now

that th

ey e

xists

.

Page 42: 3 Control systems - Laplace transform

Blo

ck a

lgeb

ra

Page 43: 3 Control systems - Laplace transform

Blo

ck a

lgebra

Blo

ck d

iagra

m m

odels

U(s)

Y(s)

Th

e im

port

ance

of

the

cause

an

d e

ffec

t re

lati

on

ship

of

the

tran

sfer

fun

ctio

n i

s

evid

ence

db

y t

he

inte

rest

in

rep

rese

nti

ng t

he

rela

tion

ship

of

syst

em v

aria

ble

by

dia

gra

mm

atic

mea

ns.

Th

e b

lock

dia

gra

m r

epes

enta

tion i

s pre

val

ent

in c

on

trol

syst

em e

ng

inee

rin

g.

Blo

ck d

iag

ram

s co

nsi

sts

of

un

idir

ecti

onal

op

erat

ion

al b

lock

s.

Sin

gle

-in

pu

tsy

stem

is

show

n i

n f

igure

. 1

(1)

sT

s+

U(s)

Y(s)

()

Gs

More

gen

eral

ized

str

uct

ure

is

sho

wn

bel

ow

.

Page 44: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Blo

ck

model

Sin

gle

-in

pu

t, t

wo-o

utp

uts

syst

em

has

blo

ck d

iag

ram

11

22

()

()

()

()

()

()

Ys

Gs

Us

Ys

Gs

Us

= =

U(s)

Y1(s)

1(

)G

s

Y2(s)

2(

)G

s

Page 45: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Blo

ck

model

In o

rder

to

rep

rese

nt

a sy

stem

wit

h s

ever

al v

aria

ble

s und

er c

ontr

ol,

an

inte

rco

nn

ecte

dsy

stem

is

uti

lize

d.

Tra

nsf

er f

un

ctio

ns

G1

2, G

21

are

sho

win

gin

terc

onn

etio

nb

etw

een

inp

uts

and

outp

uts

111

112

2

22

11

22

2

()

()

()

()

()

()

()

()

()

()

Ys

Gs

Us

Gs

Us

Ys

Gs

Us

Gs

Us

=+

=+

U1(s)

Y1(s)

11(

)G

s

Y2(s)

22(

)G

sU2(s)

12(

)G

s

21(

)G

s

+

+++

Page 46: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Blo

ck

model U

1(s)

U2(s)

Y1(s)

Y2(s)

Y3(s)

Y4(s)

Page 47: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

MIM

O s

yst

em

1 2

()

()

()

...

()

p

Us

Us

Us

Us

=

Ys

Ys

Ys

Ys

q

()

()

()

... (

)

=

1 2

Gs

Gs

Gs

Gs

Gs

Gs

Gs

Gs

Gs

Gs

p p

qq

qp

()

()

().

..(

)

()

().

..(

)

...

()

().

..(

)

=

11

12

1

21

22

2

12

1

()

()

()

ss

s=

YG

X

In g

ener

al,

we

wri

te m

ult

i-in

pu

tan

d–

ou

tput

syst

em i

nm

atri

xfo

rm a

s

Or

short

ly

Page 48: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Exam

ple

–heat

exchanger

vzi,

Tzi

vp

i,T

pi

vzs

Tzs

vp

s

Tp

s

Gs

T T

T T

v T

v T

T v

T v

v v

v v

T T

T T

v T

v T

T v

T v

v v

v v

ps

pi

zi pi

ps

pi

zi pi

ps

pi

zi pi

ps

pi

zi pi

ps

zs

zi zs

ps

zs

zi zs

ps

zs

zi zs

ps

zs

zi zs

()=

Tp

i

vp

i

Tzs

vzs

Tp

s

vp

s

Tzi

vzi

T –

tem

per

atu

re,

v –

wat

er v

elo

city

Blo

ckd

iagra

m o

f

hea

t ex

chan

ger

Inle

t o

fw

ater

to b

e

hea

ted

Ou

tlet

of

hea

ted

wat

er

Inle

to

f a

war

m

wat

er

Ou

tlet

of

a

coole

d

wat

er

Hea

t ex

chan

ger

tra

nsf

er f

un

ctio

n

Page 49: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Exam

ple

–heat

exchanger

Hea

tex

chan

ger

of

typ

eJA

D

Pa

rall

elco

nn

ecti

on

bet

wee

n3

hea

tex

cha

ng

ers

Pa

rall

el c

on

nec

tio

n b

etw

een

2 h

eat

exch

an

ger

s

Page 50: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Blo

ck c

onnecti

ons

and r

educti

on

Th

e b

lock

dia

gra

m r

epre

senta

tion

of

a g

iven

syst

em m

ay o

ften

be

red

uce

d b

y

blo

ckd

iagra

m r

edu

ctio

n t

echn

iqu

esto

a s

imp

lifi

ed b

lock

dia

gra

m w

ith

few

er

blo

cks

then

th

e ori

gin

al d

iag

ram

.

Page 51: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Blo

ck c

onnecti

ons

1(

)G

s2(

)G

s(

)n

Gs

Ser

ies,

tw

o b

lock

are

con

nec

ted

in

cas

cade

1(

)G

s

2(

)G

s

Par

alle

l

Wit

h f

eed

bac

k 1(

)G

s

2(

)G

s

U(s

)Y

(s)

+ +

U(s

)Y

(s)

Y(s

)-

+U

(s)

1(

)G

s

2(

)G

s

Y(s

)

-

+U

(s)

Dis

turb

an

ce r

elate

d c

on

tro

l lo

op

Set

-po

int

rela

ted c

on

tro

l lo

op

Page 52: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Blo

ck

dia

gra

m t

ransf

orm

ati

on

Bas

ic r

ule

of

tran

sfo

rmat

ion

:

Ou

tpu

tsi

gnal

Y(s

) ca

n’t

chan

ge

afte

rm

ov

ing

a b

lock

india

gra

m

(inp

ut

sig

nal

, o

fco

urs

e, c

an’t

chan

ge

too

)

Page 53: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Blo

ck

dia

gra

mtr

ansf

orm

ati

on

1(

)G

s2(

)G

s(

)n

Gs

U(s

)Y

(s)

12

12

11

()

()

()

()

()

...

()

().

..(

)(

)(

)(

)(

)n

n

Ys

Ys

Ys

Ys

Gs

Gs

Gs

Gs

Us

Us

Ys

Ys

==

=

Eq

uiv

alen

ttr

ansf

er f

un

ctio

nin

seri

esco

nn

ecti

on

ism

ult

ipli

cati

on

of

giv

en

tran

sfer

fu

nct

ion

s

Y1(s

)Y

2(s

)Y

n-1

(s)

Page 54: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Blo

ck

dia

gra

mtr

ansf

orm

ati

on

1(

)G

s

2(

)G

s

U(s

)Y

(s)

+ +

Eq

uiv

alen

ttr

ansf

erfu

nct

ion i

n s

erie

s co

nn

ecti

on

is

sum

of

giv

en

tran

sfer

fun

ctio

ns

12

12

()

()

()

()

()

()

()

()

()

Ys

Ys

Ys

Gs

Gs

Gs

Us

Us

Us

==

+=

+

Y1(s

)

Y2(s

)

Page 55: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Blo

ck

dia

gra

mtr

ansf

orm

ati

on

1(

)G

s

2(

)G

s

Y(s

)+

+U

(s) Y

1(s

)

Tra

nsf

er f

un

ctio

n o

f po

siti

ve

feed

bac

k i

s

Y2(s

)

21

12 1

2

()

()

()

()

()

()

()

()

()

Ys

Us

Ys

Ys

Gs

Ys

Ys

Gs

Ys

=+

= =

Th

ere

are

rela

tio

ns

in c

on

nec

tio

n

Sub

stit

uti

ng

1-s

tan

d2-n

deq

uat

ion

to t

hir

d

11

2(

)(

)(

)(

)(

)(

)Y

sG

sU

sG

sG

sY

s=

+

1

12

()

()

()

1(

)(

)

Gs

Ys

Us

Gs

Gs

=−

,o

ise-

rela

ted c

on

tro

l sy

stem

Posi

tive

fee

db

ack

Act

ua

tin

g s

ign

al

Dis

turb

ace

sO

utp

ut

sig

na

l

Page 56: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Blo

ck

dia

gra

mtr

ansf

orm

ati

on

1(

)G

s

2(

)G

s

Y(s

)-

+U

(s)

More

imp

ort

ant

in p

ract

ice

is n

egat

ive

feed

bac

kco

ntr

ol

syst

em.

Eq

uiv

alen

t tr

ansf

er f

un

ctio

n i

s

1

12

()

()

()

1(

)(

)

Gs

Ys

Us

Gs

Gs

=+

Sig

nin

den

om

inat

or

isch

ang

ed.

,eg

ati

ve f

eed

back

con

tro

lsy

stem

Page 57: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Blo

ck

dia

gra

mtr

ansf

orm

ati

on

1(

)G

s

2(

)G

s

Y(s

)

-

+U

(s)

Y1(s

)Y

2(s

)

Eq

uiv

alen

ttr

ansf

erfu

nct

ion o

f n

egat

ive

feed

bac

k s

yst

em i

n s

et-p

oin

t

chan

nel

is

2 12

2

11

()

()

()

()

()

()

()

()

()

Ys

Us

Ys

Ys

Gs

Ys

Ys

Gs

Ys

=−

= =

In t

his

conn

ecti

on

th

ere

are

rela

tion

s

Sub

stit

uti

ng

1-s

ti

2-n

dto

th

ird

equ

atio

n w

e o

bta

in

()

12

12

12

()

()

()

()

()

()

()

()

()

()

()

Ys

Gs

Gs

Us

Ys

Gs

Gs

Us

Gs

Gs

Ys

=−

=−

12

12

()

()

()

()

1(

)(

)

Gs

Gs

Ys

Us

Gs

Gs

=+

Set

-po

int

cha

nge

Page 58: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Puzzle

1 f

or

young

and

old

Tra

nsf

orm

atio

n

Ori

gin

ald

iag

ram

Eq

uiv

alen

t d

iag

ram

Co

mb

inin

g b

lock

s in

cas

cad

e

Mo

vin

g a

su

mm

ing

po

int

beh

ind

a

sum

min

g p

oin

t

Mo

vin

g a

pic

koff

po

int

beh

ind

a

pic

ko

ffpo

int

Mo

vin

g a

su

mm

ing

po

int

ahea

da

blo

ck

Mo

vin

g a

su

mm

ing

po

int

ahea

da

blo

ck

Mo

vin

g a

pic

koff

po

int

ahea

da

blo

ck

Page 59: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Puzzle

1 f

or

young a

nd o

ldT

ran

sfo

rmat

ion

O

rigin

ald

iag

ram

Eq

uiv

alen

t d

iag

ram

Mo

vin

g a

pic

koff

po

int

beh

ind

a

blo

ck

Mo

vin

g a

pic

koff

po

int

ahea

d

sum

min

g p

oin

t

Mo

vin

g a

pic

koff

po

int

beh

ind

sum

min

g p

oin

t

Page 60: 3 Control systems - Laplace transform

Fin

dan

equ

ival

ent

tran

sfer

fun

ctio

nof

a sy

stem

G(s

) =

Y(s

)/U

(s)

Blo

ck

alg

ebra

Puzzle

2 f

or

young a

nd o

ld

So

luti

on

G2(s

)

G4(s

)

-

+

G24(s

)

224

24

()

()

1(

)(

)

Gs

Gs

Gs

Gs

=+

we

get

sing

le b

lock

Eli

min

atin

g

a fe

edb

ack l

oop

Uti

liza

tion

of

rule

wh

ich

eli

min

ates

feed

bac

k

giv

es n

ewb

lock

str

uct

ure

G1(s

)

G3(s

)

-

+G

24(s

)

Page 61: 3 Control systems - Laplace transform

G1(s

)

G3(s

)

-G

24(s

)

Blo

ck

alg

ebra

Puzzle

2 f

or

young a

nd o

ldT

hen

, el

imin

atin

g c

asca

de

conn

ecte

db

lock

s, w

e ob

tain

str

uct

ure

sho

wn

in

fig

.

G124(s

)

G3(s

)

- G124(s

)=G

1(s

) G

24(s

)

Fin

ally

, b

y r

edu

cin

gn

egat

ive

feed

bac

k l

oo

p, w

e ob

tain

124

12

34

124

3

()

()

1(

)(

)

Gs

Gs

Gs

Gs

=+

Th

e cl

ose

d-l

oop

syst

em t

ran

sfer

fu

nct

ion

21

24

1234

21

3

24

()

() 1

()

()

()

()

1(

)(

) 1(

)(

)

Gs

Gs

Gs

Gs

Gs

Gs

Gs

Gs

Gs

Gs

+=

++

Page 62: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Puzzle

2 f

or

young a

nd o

ld

12

123

4

24

12

3

()

()

()

1(

)(

)(

)(

)(

)

Gs

Gs

Gs

Gs

Gs

Gs

Gs

Gs

=+

+

24

12

31

()

()

()

()

()

0G

sG

sG

sG

sG

s+

+=

Sim

pli

fyin

g

Th

ed

eno

min

ato

r(c

har

acet

eric

tic

equ

atio

n)

is c

om

pri

sed

of

1 p

lus

the

sum

of

each

loo

ptr

ansf

er f

un

ctio

n

Page 63: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Puzzle

3 f

or

young a

nd o

ldF

ind

equ

ival

ent

tran

sfer

fun

ctio

ns

for

a sy

stem

sG

(s)

= Y

(s)/

U(s

)

sho

wn

in

fig

.

Page 64: 3 Control systems - Laplace transform

Blo

ck

alg

ebra

Hydra

ulic p

rocess

Mix

ing

of

two

flu

ids

wit

hdif

fere

nt

con

cen

trat

ion

s

C –

con

centr

atio

n,

m –

mas

s fl

ow

V –

volu

me

flo

w

t -

tim

e

So

luti

on f

or

a) c

on

cen

trat

ion

b

) m

ass

flow

s

Page 65: 3 Control systems - Laplace transform

Ca

Ca

we

1/(

Ts+

1)

V

1/m

Ca

-Vaw

y

Va

+V

aw

e1

/s

Th

eref

ore

equiv

alen

td

iag

ram

for

on

e pro

cess

is

For

two

iden

tica

lpro

cess

esco

nn

ecte

din

casc

ade

Ca

Caw

e1

/(T

s+

1)

Ca

Caw

e1

/(T

s+

1)

Blo

ck

alg

ebra

Hydra

ulic p

rocess

for

a) c

on

cen

trat

ion

b

) m

ass

flo

ws

Page 66: 3 Control systems - Laplace transform

Th

an

k y

ou

for

your

atten

tion