Chapter 4 Dynamic Systems: Higher Order Processes

65
Chapter 4 Dynamic Chapter 4 Dynamic Systems: Systems: Higher Order Processes Higher Order Processes Prof. Shi-Shang Jang National Tsing-Hua University Chemical Engineering Dept. Hsin Chu, Taiwan May, 2013

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Chapter 4 Dynamic Systems: Higher Order Processes. Prof. Shi-Shang Jang National Tsing-Hua University Chemical Engineering Dept. Hsin Chu, Taiwan May, 2013. 4-1 Non-interactive Systems – Thermal Tanks. 4-1 Non-interactive Systems –Thermal Tanks – Cont. 4-1 Non-interactive Systems. - PowerPoint PPT Presentation

Transcript of Chapter 4 Dynamic Systems: Higher Order Processes

Page 1: Chapter 4 Dynamic Systems:  Higher Order Processes

Chapter 4 Dynamic Chapter 4 Dynamic Systems: Systems: Higher Order Higher Order ProcessesProcesses

Prof. Shi-Shang JangNational Tsing-Hua UniversityChemical Engineering Dept.

Hsin Chu, TaiwanMay, 2013

Page 2: Chapter 4 Dynamic Systems:  Higher Order Processes

4-1 Non-interactive Systems – 4-1 Non-interactive Systems – Thermal TanksThermal Tanks

21 2 1

21 2 1

42 3 4 2

1

Let ;

2

A A

p v

A p A p v

A p B p A B p v

Tank

duf h t f h t V

dth C T u C T

dTf C T t f C T t V C

dtTank

dTf C T t f C T t f f C T t V C

dt

Page 3: Chapter 4 Dynamic Systems:  Higher Order Processes

4-1 Non-interactive Systems –4-1 Non-interactive Systems –Thermal Tanks – Cont.Thermal Tanks – Cont.

1 22 1

1 2 1

2 44 2 3

2 4 1 2 2 3

1

1

2

1

v

A p

A p B pv

A B p A B p A B p

Tank

V C dt t

f C dt

s s s

Tank

f C f CV C dt t

f f C dt f f C f f C

s s K s K s

Page 4: Chapter 4 Dynamic Systems:  Higher Order Processes

4-1 Non-interactive Systems4-1 Non-interactive Systems

1 1 11 1 1 1 1

1

2 2 22 2 1 2 2 1 2 1 2

2

;2

;2

i o i o

dh dH kA A f k h f F aH F a

dt dt h

dh dH kA A f k h F bH aH bH b

dt dt h

To Workspace

simout

Subtract 2Subtract 1

Subtract

Scope

MathFunction 1

sqrt

Math

Function

sqrt

Integrator 1

1s

Integrator

1s

Gain 3

1.5

Gain 2

0.1

Gain 1

0.1

Gain

1.5

Constant 1

1

Constant

4.5

Page 5: Chapter 4 Dynamic Systems:  Higher Order Processes

4-1 Non-interactive Systems4-1 Non-interactive Systems

1 1 11 1 1 1 1 1 1

2 2 21 2 2 2 1 2 2 2 2 1

1

1

i oi o i o

F FA dH dHH K F F H s H s K F F

a dt a dtA dH dHa

H H K H H s H s K H sb dt b dt

Page 6: Chapter 4 Dynamic Systems:  Higher Order Processes

Transfer Fcn 1

26 .667 s+1

1

Transfer Fcn

26 .667 s+1

2.667

SubtractScope

Constant 2

4

Constant 1

0

Constant

1

Add

NumericalNumerical ExampleExample

21 2 1 2

3 3

3 3

1 21/ 21/ 2

1

1

1

2

11 2

10 ; 4

4 / min; 1 / min

4 1 / min / min1.5

41.5

0.3752 22

12.667

1

1026.667 min

0.375

i o

A A m h h m

f m f m

m mk k

mmk

a bh

Kab

Ka

A

a

Page 7: Chapter 4 Dynamic Systems:  Higher Order Processes

4-1 Non-interactive Systems4-1 Non-interactive Systems

1112 2

2

1

122

s

K

s

K

ss

K

sm

sy p

1 21 2

1 2

1 22 2

; ;2

;1 1

1222

ss

K

sm

sy p

An over-damped second order system has two negative real poles. Therefore, 2s2+2s+1=(1s+1)(2s+1); hence

such that

12

2

sK

= 11

1

sK

Page 8: Chapter 4 Dynamic Systems:  Higher Order Processes

4-2 Interactive Systems – 4-2 Interactive Systems – Thermal Tanks with RecycleThermal Tanks with Recycle

Page 9: Chapter 4 Dynamic Systems:  Higher Order Processes

4-2 Interactive Systems – Thermal 4-2 Interactive Systems – Thermal Tanks with Recycle- Cont.Tanks with Recycle- Cont.

21 4 2 1

1 22 1 4

1 2 1 1 2 4

42 3 4 2

2 44 2

Tank 1

1

Tank 2

A p R p A R p v

v A R

A R p A R A R

C p B p C B p v

C p Bv

C B p C B p

dTf C T t f C T t f f C T t V C

dtV C d f f

t t tf f C dt f f f f

s s K s K s

dTf C T t f C T t f f C T t V C

dtf C fV C d

tf f C dt f f C

3

2 4 3 2 4 31

p

C B p

Ct

f f C

s s K s K s

Page 10: Chapter 4 Dynamic Systems:  Higher Order Processes

4-2 Interactive Systems – 4-2 Interactive Systems – Thermal Tanks with Recycle- Thermal Tanks with Recycle- Cont.Cont.

Page 11: Chapter 4 Dynamic Systems:  Higher Order Processes

0 1 2 3 4 5 6 7 8 9 100

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

2-5 Step Response of Second-Order 2-5 Step Response of Second-Order Processes – Over-damped processProcesses – Over-damped process

1112 21

22

ss

K

ss

K

sm

sy pp

m(s)=A/s

12 /2

/1

21

ttpp ee

AKAKty

Inflection point

=3

=2

=11

3s+1

Transfer Fcn1

1

s+1

Transfer Fcn

simout

To Workspace

Scope

1

Constant

Page 12: Chapter 4 Dynamic Systems:  Higher Order Processes

4-2 Interactive Systems4-2 Interactive Systems

1 1 11 1 0 1 1 2 0 1 2

1 2

2 22 2 1 1 2 2 2 1 2 2 1 2

2

2

;2

;

; ;2

i i

dh dH kA A f f k h h F F aH aH a

dt dt h h

dh dHA A k h h k h aH aH eH fH gH

dt dtk

e f a g a eh

f1

Cross-sectional=A2

h2V2

f2

h1V1

fi

Cross-sectional=A1

fo

Page 13: Chapter 4 Dynamic Systems:  Higher Order Processes

4-2 Interactive Systems4-2 Interactive Systems

01 1 11 2 1 1 0 1 2

1 1 1 0 2

2 2 21 2 2 2 1 2 2 2 2 1

1

1

ii

i

F FA dH dHaH H K F F H H

a dt a a dts H s K F F H s

A dH dHfH H K H H s H s K H s

g dt g dt

H1(s)

H2(s)+

+

1

1

1 s

H2(s)

111

1/

2

212

2

21

221

sK

sK

KKK

F0(s)

Fi(s)+

-

F0(s)

Fi(s) +

-

11

1

sK

12

2

sK

Page 14: Chapter 4 Dynamic Systems:  Higher Order Processes

Numerical ExampleNumerical Example

21 2 1 2

3 3

3 3

1 21/ 21/ 2

1

1 2

2

2

1

2

11

22

10 ; 8 ; 4

4 / min; 1 / min

4 1 / min / min1.5

8 41.5

0.3752 22

0.3752

0.75

12.667

0.5

1026.667 min

0.37510

13.333min0.75

i o

A A m h m h m

f m f m

m mk k

mmk

ah h

ke

h

g a e

Kaf

Kg

A

aA

g

180711s

667.2

15.01

333.13667.265.01

333.13667.265.01/5.0667.2

111

1/

)(

2

2

2

212

2

21

2212

s

sssK

sK

KKK

sF

sH

i

Page 15: Chapter 4 Dynamic Systems:  Higher Order Processes

4-1 Second Order Systems4-1 Second Order Systems

2 1

pKY s

X s as bs

A second order system is of the following form:

2 2 2 1

pKY s

X s s s

Another form:

Kp is called process gain, is called time constant, is calleddamping factor. The roots of the denominator are the poles of the system.

Page 16: Chapter 4 Dynamic Systems:  Higher Order Processes

4-1 Second-Order Processes - 4-1 Second-Order Processes - ContinuedContinued

Definition 4-1: A second order process is called over-damped, if >1; is called under-damped if <1; is called critical damped if =1.

Property 4-1: Consider the roots of denominator, in case of over-damped system, the poles of the system are all negative real numbers.

Property 4-2: The poles of a under-damped system are complex with negative real numbers.

Property 4-3: The pole of a critical damped system is a repeated negative real number.

Page 17: Chapter 4 Dynamic Systems:  Higher Order Processes

State Space ApproachState Space Approach

112

1

21

22221

11211

2

1

21

22221

11211

2

1

KKNNNN

KNKNN

K

K

NNNNN

N

N

N

MBXA

M

M

M

bbb

bbb

bbb

X

X

X

aaa

aaa

aaa

X

X

X

dt

dX

Consider the following linear system with N differential equationsK inputs and P sensors

where X is termed the state vector and M is the input vector. The followingobservation equation is available:

112

1

21

22221

11211

2

1

21

22221

11211

2

1

KKPNNP

KPKPP

K

K

NPNPP

N

N

P

MDXC

M

M

M

ddd

ddd

ddd

X

X

X

ccc

ccc

ccc

Y

Y

Y

Y

Page 18: Chapter 4 Dynamic Systems:  Higher Order Processes

State Space Approach _ State Space Approach _ Cont.Cont.

Assume that it is desirable to realize the input/output transfer functionsand neglecting the state variables.

sMsG

sMDBAsIC

sDMsBMAsICsY

sBMAsIsX

sBMsXAsI

sBMsAXssX

KP

1

1

1

Page 19: Chapter 4 Dynamic Systems:  Higher Order Processes

State Space Approach _ State Space Approach _ ExampleExampleInteracting TanksInteracting Tanks

)(0

1.0

075.00375.0

0375.00375.0

)(

)(

)(0

1.0

)(

)(

075.00375.0

0375.00375.0

)(0

1.0

)(

)(

075.00375.0

0375.00375.0

)(

)(

10

01

)(0

1.0

)(

)(

075.00375.0

0375.00375.0

)(

)(

0

1.0

075.00375.0

0375.00375.0

75.0375.010

375.0375.010

1

2

1

2

1

2

1

2

1

2

1

2

1

2

1

2

1

212

211

sFs

s

sH

sH

sFsH

sH

s

s

sFsH

sH

sH

sHs

sFsH

sH

sH

sHs

FH

H

H

H

dt

d

HHdt

dH

FHHdt

dH

i

i

Page 20: Chapter 4 Dynamic Systems:  Higher Order Processes

State Space Approach _ State Space Approach _ ExampleExampleInteracting Tanks – Cont.Interacting Tanks – Cont.

1s08711s

2.66667)(

0375.0075.00375.0

00375.0

)(0

0375.0075.00375.0

00375.00375.0075.00375.0

075.01.0

10

)(0)(

10

)()()()(

)(

375.075.00375.0

0375.00375.0075.00375.0

075.01.0

)(0

1.0

0375.0075.00375.0

0375.0

375.0075.00375.0

0375.00375.075.00375.0

0375.0

0375.075.00375.0

075.0

)(

)(

22

2

2

2

1

2

2

2

22

22

2

1

sFss

sF

ss

ss

s

sFsH

sH

sDMsCXsHsY

sF

ss

ss

s

sF

ss

s

ss

ssss

s

sH

sH

Page 21: Chapter 4 Dynamic Systems:  Higher Order Processes

State Space to Transfer State Space to Transfer Function-MATLABFunction-MATLAB>> A=[-0.0375 0.0375;0.0375 -0.075]

A =

-0.0375 0.0375

0.0375 -0.0750

>> B=[1;0];C=[0 1];D=0;

>> [num,den]=ss2tf(A,B,C,D,1)

num =

0 -0.0000 0.0375

den =

1.0000 0.1125 0.0014

>> ss=den(3)

ss =

0.0014

>> num=num/ss

num =

0 -0.0000 26.6667

>> den=den/ss

den =

711.1111 80.0000 1.0000

>> tf(num,den)

Transfer function:

-9.869e-015 s + 26.67

---------------------

711.1 s^2 + 80 s + 1

Page 22: Chapter 4 Dynamic Systems:  Higher Order Processes

Rise time

A

B

C

time

Resp

ons

e

2-5 Step Response of Second-2-5 Step Response of Second-Order Processes – Under-damped Order Processes – Under-damped processprocess

1222

sss

AKsy p

/1sin1

2/

2te

AKAKty tp

p

21/ eA

B1. Overshoot=

21/2eB

C 2. Decay Ratio=

3. Rise time=tr=2

1

2

1tan

1

4. Period of oscillation=T=21

2

5. Frequency of oscillation (Natural Frequency)=1/T

Settling time

T

Page 23: Chapter 4 Dynamic Systems:  Higher Order Processes

Example: Temperature Example: Temperature Regulated ReactorRegulated Reactor

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000100

100.5

101

101.5

102

102.5

103

time(seconds)

tem

pera

ture

(C)

t=3060st=1000sFeed flow rate0.4→0.5kg/sat t=0.

1. What is process gain?2. What is transfer func?3. What is rise time?

Page 24: Chapter 4 Dynamic Systems:  Higher Order Processes

Textbook Reading Assignment Textbook Reading Assignment and Homeworkand Homework

Chapter 2, p41-49Homework p58, 2-9, 2-15, 2-16Due June 8th

Page 25: Chapter 4 Dynamic Systems:  Higher Order Processes

Non-isothermal CSTRNon-isothermal CSTR

Page 26: Chapter 4 Dynamic Systems:  Higher Order Processes

Non-isothermal CSTR- Non-isothermal CSTR- Cont.Cont.

20

M.B. for component A

where

E.B. for the tank

E.B. for the cooling jacket

AAi A A

ERT

A A

p i p A c v

cc c pc ci c c pc c c c c cv

dcf t c t f t c t Vr t V

dt

r t k e c

dTf t C T t f t C T t Vr t H UA T t T t V C

dt

dTf t C T t f t C T t UA T t T t V C

dt

Page 27: Chapter 4 Dynamic Systems:  Higher Order Processes

Non-isothermal CSTR- Non-isothermal CSTR- Cont.Cont.

;56.1

);/(1;36);/(75

/000,12);/(88.0;/55

)/(987.1;/27820

min)/(1033.8;26.13

3

22

3

380

3

ftV

FlbBtuCpcftAFfthBtuU

lbmoleBtuHFlbBtuCpftlb

FlbmoleBtuRlbmoleBtuE

lbmoleftkftV

c

r

Process Information

Steady State Values

min/8771.0;540

9.678;/2068.0

min/3364.1;7.602

635;/5975.0

3

3

3

3

ftfRT

RTftlbmolec

ftfRT

RTftlbmolec

cci

A

c

iAi

Page 28: Chapter 4 Dynamic Systems:  Higher Order Processes

Non-isothermal CSTR- Cont.Non-isothermal CSTR- Cont.Cooling flow rate Cooling flow rate 0.87710.87710.80.8

62.4*1

thou*cp2

62.4*1

thou*cp1

55*0.88

thou*cp

55*0.88

thou*cp

8.33e8

k0

0.8

fc(t)

1.3364

f(t)

12000

dH

0.5975

cAi(t)1s

cA(0.2068)

13.26

V1

13.26

V

75/60*36

UA

635

Ti(t)

1s

Temp (678.9)

540

Tci

1s

Tc(602.7)

Subtract

Scope2

Scope1

Scope

1.987

R

Product5

Product4

Product3

Product2

Product1

Product

eu

MathFunction

[jacket_energy_in]

Goto9

[heat_transfer_out]

Goto8

[reaction_rate]

Goto7

[Tc]

Goto6

[energy_out]

Goto5

[energy_in]

Goto4

[Temp]

Goto3

[mass_out]

Goto2

[jacket_energy_out]

Goto10

[cA]

Goto1

[mass_in]

Goto

[reaction_rate]

From9

[mass_out]

From8

[mass_in]

From7

[Tc]

From6

[Temp]

From5

[cA]

From4

[cA]

From3

[Temp]

From2

[heat_transfer_out]

From17

[jacket_energy_out]

From16

[jacket_energy_in]

From15

[Tc]

From14

[heat_transfer_out]

From13

[reaction_rate]

From12

[energy_out]

From11

[energy_in]

From10

[Temp]

From1

[cA]

From

-27820

EDivide1

Divide

Add2

Add1

Add

1/13.26

1/V

1/(1.56*55*1)

1/(Vc*thouc*Cv)1

1/(13.26*55*0.88)

1/(V*thou*Cv)

Energy Balance of the Reactor

Material Balance of the Reactor

Energy Balance of the Jacket

Inlet and Outlet Energy and Material fluxes of the Reactor

Inlet and Outlet Energy fluxes of the Jacket

Rate Constant Heat Exchange between Jacket and Reactor

Page 29: Chapter 4 Dynamic Systems:  Higher Order Processes

Transfer Functions Derived Transfer Functions Derived by Linearizationby Linearization

DUCX

F

F

CC

y

BUAX

F

F

C

b

b

bbC

aa

aaa

aaC

dt

d

dt

dX

Fbaa

Ff

g

T

g

T

gfTTg

dt

d

dt

dT

bFbaaCa

T

gF

f

g

T

g

T

gC

c

gTfTTcg

dt

d

dt

dT

FbCbaCa

Cc

gF

f

g

T

gC

c

gcfTcg

dt

dC

dt

dc

c

i

Ai

c

A

c

i

Ai

c

A

c

A

cc

cc

cc

cccc

icA

ii

cc

AA

icA

AiA

AiAi

AA

AiAAA

0000010

0

0

000

b0

0

0

0

,,

,,,

,,

34

2322

1211

3332

232221

1211

343332

3333

2322232221

22222,2

12111211

1111,1

Page 30: Chapter 4 Dynamic Systems:  Higher Order Processes

Linearization of the Reactor ExampleLinearization of the Reactor Example

Page 31: Chapter 4 Dynamic Systems:  Higher Order Processes

48.026.13/2068.01033.826.1323364.1/2 9.678987.127820

80

1

1

111

eVceVkf

c

g

x

ga A

TRE

A

It can be shown as generated as above:

Transfer Functions Derived by Linearization – Cont.Transfer Functions Derived by Linearization – Cont.

[num, den]=ss2tf(A,B,C,D,4)num = 0 1.33226762955019e-015 -2.81748023 -1.356898478768den = 1 1.3804 0.3849816 0.038454805392

>> ss=den(4)>> den=den/ssden = 26.0045523519419 35.8966840666205 10.0112741717343 1>> num=num/ssnum = 0 3.46450233194353e-014 -73.2673121415962 -35.2855375273927

Page 32: Chapter 4 Dynamic Systems:  Higher Order Processes

SIMULINK of Linear System - SIMULINK of Linear System - CSTRCSTR

Transfer Fcn

2.07s+1

26 .27s +36 .31s +10 .14s+13 2

To Workspace

simout

ScopeGain

-35 .77

Constant 1

678 .9

Constant

-0.0771

Add

Page 33: Chapter 4 Dynamic Systems:  Higher Order Processes

Non-isothermal CSTR- Cont.Non-isothermal CSTR- Cont.Cooling flow rate Cooling flow rate 0.87710.87710.80.8

0 5 10 15 20 25 30 35 40 45 50678.5

679

679.5

680

680.5

681

681.5

682

Time (min)

Tank

temperature

Page 34: Chapter 4 Dynamic Systems:  Higher Order Processes

Non-isothermal Non-isothermal CSTR- Cont.CSTR- Cont.Linearized Model Linearized Model (page 127)(page 127)

3 2

35.77 2.07 1

26.27 36.31 10.14 1c

s s

F s s s s

0 5 10 15 20 25 30 35 40 45 50678.5

679

679.5

680

680.5

681

681.5

682

Time(min)

Tan

kTem

pera

ture

Page 35: Chapter 4 Dynamic Systems:  Higher Order Processes

The problem of The problem of nonlinearitynonlinearity

Page 36: Chapter 4 Dynamic Systems:  Higher Order Processes

4-3 Step Response of the 4-3 Step Response of the High Order SystemHigh Order System

1 1 1

s s

a b

Ke Keor

s s s

systemsorder high theseeapproximat to

model timedead plusorder first

following theimplement wecases,many In

/1

1

1

( ) 1itnn

in

ii j

jj i

eY t K

1

( )

( ) 1n

ii

Y s K

X s s

X(s)=A/s

n=2

n=3

n=5

n=10

time

Response

s

Page 37: Chapter 4 Dynamic Systems:  Higher Order Processes

4-3 Step Response of the High Order 4-3 Step Response of the High Order System- ContinuedSystem- Continued

11.41

1 3.2

5

s

e

s

s

Method of Reaction Curve:

time

Respons

e

inflection point

Page 38: Chapter 4 Dynamic Systems:  Higher Order Processes

4-3 Step Response of the High 4-3 Step Response of the High Order System- ContinuedOrder System- Continued

time

Response

s

Real

Approximate

Page 39: Chapter 4 Dynamic Systems:  Higher Order Processes

4-3 Response of Higher-4-3 Response of Higher-Order Systems – Cont.Order Systems – Cont.

1

2

1

1 2 1 3 1

0.5 1

1 2 1 3 1

Y s

X s s s s

Y s s

X s s s s

Page 40: Chapter 4 Dynamic Systems:  Higher Order Processes

4-4 Other Types of Process 4-4 Other Types of Process ResponseResponse

( )op o p

i o

df tf t K m t

dtdh t

f t f t Adt

Integrating Processes: Level Process

Page 41: Chapter 4 Dynamic Systems:  Higher Order Processes

4-4 Other Types of Process 4-4 Other Types of Process ResponseResponse

1

1

1

1

i o

po

p

pi

p

H s F s F sAsK

F s M ss

KH s F s M s

As As s

Page 42: Chapter 4 Dynamic Systems:  Higher Order Processes

4-4 Other Types of Process 4-4 Other Types of Process ResponseResponse

Page 43: Chapter 4 Dynamic Systems:  Higher Order Processes

4-4 Other Types of Process 4-4 Other Types of Process ResponseResponse The most general transfer function is as

the following:

p1, p2,…,pn are called the poles of the system, z1, z2,…,zm are the zeros of the system, Kp is the gain.

Note that nm is necessary, or the system is not physically realizable.

n

mp

nn

n

mm

mm

pspsps

zszszsK

asasas

bsbsbsb

sm

sy

21

21

011

1

011

1

Page 44: Chapter 4 Dynamic Systems:  Higher Order Processes

4-4 Poles and Zeros - Example4-4 Poles and Zeros - Example

2

2

243

12

1

222

21

1,

/1

0

1

121

jss

s

s

ssss

KsG

Imaginary part

Real

part

2

21

2

21

1

1

2

1

0

0

Left Half PlaneLHP Right Half Plane

RHP

Page 45: Chapter 4 Dynamic Systems:  Higher Order Processes

4-4 Poles and Zeros - 4-4 Poles and Zeros - ExampleExample

time

Respons

e

Page 46: Chapter 4 Dynamic Systems:  Higher Order Processes

4-4 Location of the Poles and Stability in a Complex Plane

Re

Im

Purdy oscillatory

Purdy oscillatory

Fast Decay Slow Decay

Exponential Decay

Exponential Decay with oscillation

Slow growth

Fast Exponential growth

Exponential growthwith oscillation

Stable (LHP) Unstable (RHP)

Page 47: Chapter 4 Dynamic Systems:  Higher Order Processes

4-4 The Stability of the 4-4 The Stability of the linear systemlinear system

)(lim tyt

Definition 4-2: A system is called stable for the initial point if given any initial point y0, such that ∣y0∣≦ε, there exists a upper bound , such that:

Definition 4-3: A system is called asymptotic stable if given any initial point y0, then

0)(lim

tyt

Page 48: Chapter 4 Dynamic Systems:  Higher Order Processes

4-4 The Stability of the 4-4 The Stability of the linear systemlinear systemDefinition 4-4: A system is called input

output stable if the input is bound, then the output is bounded. (Bounded Input Bounded Output, BIBO)

Property 4-4: A linear system is asymptotic stable and BIBO if and only if all its poles have negative real parts.

Page 49: Chapter 4 Dynamic Systems:  Higher Order Processes

4-4 Stability - Example4-4 Stability - Example

time

Resp

ons

e

G4

G2 G3G1

13011015

1)(

)(

)(1

sss

sGsm

sy

105.011.01

1

)(

)(2

sss

sGsm

sy

1

1)(

)(

)(233

sss

sGsm

sy

113

1

)(

)(24

ssssG

sm

sy

m(s)=1

Page 50: Chapter 4 Dynamic Systems:  Higher Order Processes

Open Loop Unstable Open Loop Unstable Process- Process- Chemical Reactor (text page Chemical Reactor (text page 139)139)

0

M.B. for component A

where

E.B. for the tank

AAi A A

ERT

A A

p i p A c v

dcf t c t f t c t Vr t V

dt

r t k e c

dTf t C T t f t C T t Vr t H UA T t T t V C

dt

Page 51: Chapter 4 Dynamic Systems:  Higher Order Processes

Open Loop Unstable Open Loop Unstable Process- Process- Chemical ReactorChemical Reactor

3

2 3

3

2 3

At 566

9.79 1;

9.75 1 6.6 1

9.75 1 6.6 1

At 620

7.47 1;

11.3 1 11.47 1

11.3 1 11.47 1

i

A

i

i

A

i

T R

s K s

s s s

C s K K

s s s

T R

s K s

s s s

C s K K

s s s

Page 52: Chapter 4 Dynamic Systems:  Higher Order Processes

HomeworkHomeworkText p1484-4, 4-5, 4-7, 4-8, 4-10, 4-11,4-12Due April

Page 53: Chapter 4 Dynamic Systems:  Higher Order Processes

Supplemental Material Supplemental Material

Development of Empirical Development of Empirical Models from Models from Process DataProcess Data

Page 54: Chapter 4 Dynamic Systems:  Higher Order Processes

S-1 IntroductionS-1 IntroductionAn empirical model is a model that

is developed from experience and their parameters are found based on experimental tests.

The most frequent implemented empirical models are first order, second order and/or with time delays.

The input changes is basically a step or an impulse.

Page 55: Chapter 4 Dynamic Systems:  Higher Order Processes

S-2 First Order without Time S-2 First Order without Time Delay Systems Using Step InputDelay Systems Using Step Input

/1)(

1)(

)(

1)(

)(

teKAty

ss

KAsy

s

Asm

s

K

sm

sy

Consider a first order system with a output signal y(t) and input signal m(t), then:

Page 56: Chapter 4 Dynamic Systems:  Higher Order Processes

First Order with Time Delay First Order with Time Delay Systems Using Step InputSystems Using Step Input

/1)(

1)(

)(

1)(

)(

t

s

s

eKAty

ss

KAesy

s

Asm

s

Ke

sm

sy

Consider a first order system with a output signal y(t) and input signal m(t), then:

Page 57: Chapter 4 Dynamic Systems:  Higher Order Processes

Example: A Typical Example: A Typical ExperimentExperiment

Time (second)

Y(temperature,oC,70-100oC)

Y(temperature,mA,4-20mA) Y (temperature, %) ln(1-Y)

0 70 4 0. 0

1 71.74 4.928 0.058 -0.0598

2 76.51 7.472 0.217 -0.2446

3 80.8 9.76 0.360 -0.4463

4 84.64 11.808 0.488 -0.6694

5 88 13.6 0.600 -0.9163

6 90.76 15.072 0.692 -1.1777

7 93.16 16.352 0.772 -1.4784

8 94.99 17.328 0.833 -1.7898

9 96.64 18.208 0.888 -2.1893

10 97.75 18.8 0.925 -2.5903

Page 58: Chapter 4 Dynamic Systems:  Higher Order Processes

Graphical Fitting MethodsGraphical Fitting MethodsFit 1: Method of 63.2% ResponseFit 2: Method of initial slopeFit 3: Method of Log plot

Page 59: Chapter 4 Dynamic Systems:  Higher Order Processes

Example: An Experiment Example: An Experiment PlotPlot

Fit 1Fit 2

15.51)(1

s

sG

18.6

5.0

2

s

esG

s

Page 60: Chapter 4 Dynamic Systems:  Higher Order Processes

Method of log plotMethod of log plot

intercept;1

)(ln

)(1

)1()(

/)(

/)(

slope

t

y

tyy

eKA

ty

eKAty

t

t

Consider a First-Order Plus Dead Time Model

Page 61: Chapter 4 Dynamic Systems:  Higher Order Processes

Method of log plot - ContinuedMethod of log plot - Continued

13.443)(

5969.1443.3*463/0

443.3290.0/1

1.5969

s

esG

tau

s

Fit 3

Page 62: Chapter 4 Dynamic Systems:  Higher Order Processes

Method of log plot - ContinuedMethod of log plot - Continued

0 1 2 3 4 5 6 7 8 9 100

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Fit 3

real

Fit 2Fit 1

Page 63: Chapter 4 Dynamic Systems:  Higher Order Processes

S-3 Over-damped Second Order S-3 Over-damped Second Order Systems Using Step InputSystems Using Step Input

tteKA

eeKAty

eeKAty

s

Asm

ss

Ke

ss

KesG

sm

sy

t

tt

tt

ss

2

2

2/

21

/2

/1

21

/2

/1

2221

1sinh

1

1cosh1

1)(

0 If

1)(

)(

1211)(

)(

)(

21

21

Page 64: Chapter 4 Dynamic Systems:  Higher Order Processes

Smith’s Method for Second Smith’s Method for Second Order SystemsOrder SystemsStep 1: Get time delay by observing the response curve.Step 2: Find time t20 such thaty/y=0.2, find t60 such thaty/y=0.6Step 3: Get t20/t60, then and From the right figure.

Page 65: Chapter 4 Dynamic Systems:  Higher Order Processes

ExampleExample

104.532.4

1)(

2

sssG

t20=1.9

t60=5

t20/t60=0.38From the figuret60/=2.4 =5/2.4=2.1=1.22=4.32, 2 =5.04

0 1 2 3 4 5 6 7 8 9 100

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1