Www.tufts.edu ~Rwhite07 PRESENTATIONS REPORTS Simulink

8/12/2019 Www.tufts.edu ~Rwhite07 PRESENTATIONS REPORTS Simulink

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MATLAB SIMULINK - Simulation andModel Based Design

http://www.mathworks.com


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Simulink runs under Matlab. Firststart Matlab, then type simulink at

the Matlab prompt.


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The first window that

pops up is the Library

Browser.

This is a library ofblocks that are

available for putting

into the Simulink blockdiagram.


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Simulink Help

Select Simulink

Help from thehelp menu in thelibrary browser.

Here you canfind tutorials,demos,information onavailable blocks,and so on.


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A Simulink model is a block diagram. ClickFile|New|Model in the Library Browser. An empty

block diagram will pop up. You can drag blocks intothe diagram from the library.


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Sources: Produce Signals

Select sources from the library.

Drag any block you want to useinto the model.


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Sinks: Terminate Signals

Select sinks from the library.

Drag any block you want to useinto the model.


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Connecting Blocks

Drag a signal line from the output

of a block to the input of anotherblock.

Ctrl-Click will automaticallyconnect.


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Running the Simulation

Change parameters under

Simulation | Configuration

Parameters.


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Running the Simulation

Set start and

stop time for thesimulation here.

I often change

from variable-stepto fixed-step to get

a smoother-lookingsolution.

Note: numericalsolution usingode45!


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Viewing Results: Scope

Double click on the scope icon to

open up the viewer. You oftenhave to zoom out using thebinocular icon if the curve doesntfit in the default axes.

You can save data from the scope to

the workspace using the Parameters,Data History tab.


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Modifying Block Properties

Double click on any block tobring up a properties box.

Here are the sine waveproperties. If you dont knowwhat something is leave italone!!!


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Adding Comments

You can add text commentsanywhere in the block diagramby double clicking and typing insome text.

You can change the defaultcomments under the blocks bydouble clicking and editing thetext.

Do In-Class Problem #1. Should be 2:00 at the end of

the problem.


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Signal Routing

Under the signal routing library,the MUX block can be used tobundle a group of signalstogether into a single line.

The DEMUX block does thereverse.

This can be useful to:

1. Clear up clutter in acomplicated block diagram.

2. Send multiple signals to thesame scope; then bothsignals will be displayed on

the same plot.


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Transfer Functions

U(s) = 1/s

X(s)=1/(s(s+1))=1/s-1/(s+1)

So x(t)=1-exp(-t)

Do In-Class Problem #2. It should be 2:20 by the end of the problem.


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Closed Loop Control System:

Here is an example of a closed-loop system

with an on-off controller. Notice theoscillations in the response.


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Integrators and Derivatives

Integrators and derivatives are available in

the continuous library.


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Integrators

For integrators, you can set theinitial condition and limit theoutput to not be allowed to goabove or below some value onthe properties for that block.


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Setting Up Systems with Integrators

If you have a nonlinear equation system, you cant describe it with a transferfunction. One option is to put all of the operations in as individual blocks:

i(t)

J(t)=ki(t)-f()

where f(w) is coulomb and viscous friction.

Use integrators rather

than derivatives, andput in as many

integrators as there arestates. Thenbootstrap!

Do in-class problem #3. It should be 2:40 at the end of the problem.


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Subsystems

You can group a set of blocks together into a subsystem, by selecting them

and right clicking and saying Create Subsystem. They will all go under asingle block. If you double click the subsystem, you can see what is underthe mask.


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Running Simulink Models from M-files

[T,X,Y] = SIM('model',TIMESPAN,OPTIONS,UT)

Here is the heartof the m-file.

Constants in the

simulink modelcan be defined inthe workspace.


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Running Simulink Models from M-files

The input and output of

the simulink model aredefined in the block

diagram using input andoutput sources andsinks.


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Control and Estimation Tool

Set input and output

points by right clickingon a signal, and

selecting LinearizationPoints.


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Control and Estimation Tool SelectTools:Control

Design: LinearAnalysis fromthe simulinkmenu.

The control and

estimation toolwill pop up.Select the type ofplot you want to

generate, andclick linearizemodel. Thesystem will belinearized about

the operatingpoint (see Ogata3-10 andSimulink Help)


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Control and Estimation ToolThe selected type of

plot will pop up foryour linearizedsystem. If you wanta different type of

plot, look underEdit:PlotConfigurations.

To export thelinearized system tothe Workspace soyou can use it withother design tools inMatlab, select File:

Export.


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Communicating with the WorkspaceAny constant or variable defined

in the Matlab workspace isavailable in the block diagram.

The simin and simout blocksallow you to pass signals in fromthe workspace, and out to theworkspace. Change the saveformat to Array for easiest use

(double click on the ToWorkspace block for options).

The clock source allows you togenerate a time signal if youwant to send that back to theworkspace.


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Other Useful Blocks

Under Discontinuous youwill find coulomb friction,dead zone, saturation, andrelay.

Under Continuous thereis a delay block.

Under Simulink Extrasthere is a PID controller,transfer function with non-

zero initial conditions,some useful sinks (suchas power spectraldensity), and radians-to-

degrees and Fahrenheit-to-Celsius converters.

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