Short Tutorial on Matlab Part 4 Simulink II

Description

Short Tutorial on Matlab(©2004 by Tomas Co)®Part 4. Subsystems in SimulinkSuppose we want to model the control of the temperature and flow rate as shown inFigure 1.TCHotColdFCFigure 1.where the temperature of the flow out is described by the following equation:dT/dt = [ F T + F T – (F + F )T ]/Vhot hot cold cold hot coldand we will control the flow F by manipulating F and control the temperaturecold by manipulating . (For our example, we will use V=0.5).T Fhot 1. Model the temperature mixing process.a) Load the blocks and change their names and parameters as given inTable 1.Remarks:i) To rename a block, double-click the name and then change the text.ii) To change the direction of the ports in Mult3 block, right click andthe select [ ]Format [Rotate block] twice.iii) To change the direction of the outport of block Sum1, right-click andselect [Format] [Rotate block] once.b) Next, layout the blocks and connect the blocks to match Figure 1.1Table 1.Simulink Blocks Name ParametersSublibraryIn1Sources F_hot Port number: 1In1Sources T_hot Port number: 2In1Sources T_cold Port number: 3In1Sources F_cold Port number: 4Out1Sinks T Port number: 1Out1Sinks F Port number: 2ProductMath Ops Mult 1Math Ops Mult 2ProductMath Ops Mult 3GainMath Ops 1/V Gain: 2SumMath Ops Sum List of signs: | + +SumMath Ops Sum1 List of signs: + + -IntegratorContinuous Integrator Initial Cond: 60Figure 1.2. Group the blocks into a subsystem.a) From the menu, ...

Informations

• Publié par: Nething
• Nombre de lectures: 126
• Langue: English

Extrait

1

Short Tutorial on Matlab

(©2004 by Tomas Co)

Part 4. Subsystems in Simulink

®

Suppose we want t

o

m

o

d

el the control of the temperature and flow rate as shown in

Figure 1.

TC

FC

Hot

Cold

Figure 1.

where the temperature of the flow ou

t

is described by the following equation:

d

T

/d

t

= [

F

hot

T

hot

+

F

cold

T

cold

– (

F

hot

+

F

cold

)T ]/V

and we will control the flow

F

by manipulating

F

cold

and control the temperature

T

by manipulating

F

hot

.

(For our example, we will use V=0.5).

1.

Model the temperature mixing process.

a)

Load the blocks and change their names and parameters as given in

Table 1.

Remarks:

i)

To rename a block, double-click the name and then change the text.

ii)

To change the direction of the ports in

Mult3

block, righ

t

click and

the selec

t

[

Format

]

[

Rotate block

] twice.

iii)

To change the direction of the outport of block

Sum1

, right-click and

selec

t

[

Format

]

[

Rotate block

] once.

b)

Next, layou

t

t

he blocks and connec

t

t

he blocks t

o

m

a

t

ch Figure 1.

2

Table 1.

Simulink

Sublibrary

Blocks

Name

Parameters

Sources

In1

F_hot

Por

t

n

u

m

b

e

r: 1

Sources

In1

T_hot

Por

t

n

u

m

b

e

r: 2

Sources

In1

T_cold

Por

t

n

u

m

b

e

r: 3

Sources

In1

F_cold

Por

t

n

u

m

b

e

r: 4

Sinks

Out1

T

Por

t

n

u

m

b

e

r: 1

Sinks

Out1

F

Por

t

n

u

m

b

e

r: 2

Math Ops

Product

Mul

t

1

Math Ops

Product

Mul

t

2

Math Ops

Product

Mul

t

3

Math Ops

Gain

1/V

Gain: 2

Math Ops

Sum

Sum

Lis

t

of signs: | + +

Math Ops

Sum

Sum1

Lis

t

of signs:

+ + -

Continuous

Integrator

Integrator

Initial Cond: 60

Figure 1.

2.

Group the blocks into a subsystem.

a)

From the menu, selec

t

[

Edit

]

[

Select All

].

b)

From the menu again, selec

t

[

Edit

]

[

Create Subsystem

].

c)

Rename the subsystem to be :

Temperature Mixing Subsystem.

3

d)

Resize the subsystem and move the inports and outports so they match

Figure 2.

Figure 2.

Note

: You can “open” the subsystem by double-clicking the subsystem block.

(you can continue to edi

t

t

he subsystem when the subsystem is opens as a

separate window).

3.

Create the PI controller subsystems.

a)

From the Simulink Library Browser, g

o

to the

Ports & Subsystems

subdirectory.

b)

Click-drag the

Atomic Subsystem

block into the Model window.

c)

Rename this block:

PI Temperature Controller

d)

Open the subsystem block (by double-clicking the subsystem block).

e)

Delete the line connecting

In1

block and

Out1

block.

f)

Rename

In1

as

error

, and

Out1

as

u

.

g)

Next, inser

t

b

l

o

c

ks into this subsystem window as prescribed in Table 2.

h)

Fix the block layou

t

a

nd connections between blocks to match Figure 3.

Table 2.

Simulink

Sublibrary

Blocks

Name

Parameters

Sources

Constant

Integral Time

Constan

t

v

a

l

u

e

:10

Sources

Constant

u_bias

Constan

t

v

a

l

u

e

:

0

.

5

Math Ops

Sum

Sum

Lis

t

of signs: | + +

Math Ops

Sum

Sum1

Lis

t

of signs: | + +

Math Ops

Product

Product

Math Ops

Gain

Kc

Gain: 0.05

Math Ops

Math Fcn

Reciprocal

Function: reciprocal

Continuous

Integrator

Integrator

Initial Cond: 0

4

"Go to

Parent"

button

Figure 3.

i)

Click on the "

Go to Parent

"-button.

This w

o

u

ld send you back to the

Model window.

j)

Right-click on "

PI Temperature Controller

" and selec

t

[

Copy

].

Right-click a

t

a differen

t

p

o

s

i

t

i

on in the Model window and select

[

Paste

].

Rename the new subsystem block as "

PI Flow

Controller

".

k)

G

o

back t

o

t

he Simulink Library Browser and add some more blocks into

the Model window as described in Table 3.

5

Table 3.

Simulink

Sublibrary

Blocks

Name

Parameters

Continuous

Transfer

Function

Valve 1

Numerator:[20]

Denominator:

[0.01, 0.14, 1]

Continuous

Transfer

Function

Valve 2

Numerator:[20]

Denominator:

[0.01, 0.14, 1]

Sources

Constant

T_set

Value: 65

Sources

Constant

F_set

Value: 20

Sources

Constant

T_hot

Value: 70

Sources

Constant

T_cold

Value: 50

Sinks

To

Workspace

T

Save Format:

Array

Sinks

To

Workspace

F

Save Format:

Array

Discontinuities

Saturation

Sat1

Upper Limit:

1

Lower Limit:

0

Discontinuities

Saturation

Sat2

Upper Limit:

1

Lower Limit:

0

Math Ops

Sum

Sum1

Lis

t

of Signs:

-+|

Math Ops

Sum

Sum2

Lis

t

of Signs:

|+-

Remark

: This means a valve transfer function which is slightly under-

damped.

l)

Next, delete all

inport

(1,2,3,4) and

outport

(1,2) blocks.

m)

Reposition and connec

t

t

he blocks t

o

m

a

t

ch the Model window shown in

Figure 4.

6

Figure 4.

n)

Run the simulation and plo

t

o

ut the response of T and F.

o)

Change the values for the PI ontrollers t

o

improve the response. One

possible se

t

of tuning variables are:

Temperature

Controller

Flow

Controller

Kc

0.1

0.1

Integral Time

2

5