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Introduction to Matlab and Simulink

Dr Martin Brown

E1k, Control Systems Centre

School of Electrical and Electronic Engineering

University of Manchester

Tel: 0161 306 4672

martin.brown@manchester.ac.uk

EEE Intranet

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Background and AimsMatlab and Simulink have become a defacto standard for system

modelling, simulation and controlIt is assumed that you know how to use these tools and develop

Matlab and Simulink programs on this MSc.

Over the next two weeks, we’re going to have a rapid introduction to Matlab and Simulink covering:

• Introduction to Matlab and help!• Matrix programming using Matlab• Structured programming using Matlab• System (and signal) simulation using Simulink• Modelling and control toolboxes in Matlab

Note that we’re not covering everything to do with Matlab and Simulink in these 4*2 hour lectures

Also, after every lecture block in this module, there is a 1 hour lab scheduled – programming is a practical activity

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ResourcesMathworks Information• Mathworks: http://www.mathworks.com• Mathworks Central: http://www.mathworks.com/matlabcentral • http://www.mathworks.com/applications/controldesign/• http://www.mathworks.com/academia/student_center/tutorials/launchpad.html Matlab Demonstrations• Matlab Overview: A demonstration of the Capabilities of Matlab

http://www.mathworks.com/cmspro/online/4843/req.html?13616• Numerical Computing with Matlab http://www.mathworks.com/cmspro/online/7589/req.html?

16880• Select Help-Demos in MatlabMatlab Help• Select “Help” in Matlab. Extensive help about Matlab, Simulink and toolboxes• Matlab Homework Helper http://www.mathworks.com/academia/student_center/homework/• Newsgroup: comp.soft-sys.matlabMatlab/Simulink student version (program and book ~£50)

http://www.mathworks.com/academia/student_centerOther Matlab and Simulink Books• Mastering Matlab 6, Hanselman & Littlefield, Prentice Hall• Mastering Simulink 4, Dabney & Harman, Prentice Hall• Matlab and Simulink Student Version Release 14• lots more on mathworks, amazon, …. It is important to have one reference book.

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Introduction to Matlab

Click on the Matlab icon/start menu initialises the Matlab environment:

The main window is the dynamic command interpreter which allows the user to issue Matlab commands

The variable browser shows which variables currently exist in the workspace

Variable browser

Commandwindow

Command history

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Matlab Programming EnvironmentMatlab (Matrix Laboratory) is a

dynamic, interpreted, environment for matrix/vector analysis

Variables are created at run-time, matrices are dynamically re-sized, …

User can build programs (in .m files or at command line) using a C/Java-like syntax

Ideal environment for model building, system identification and control (both discrete and continuous time

Wide variety of libraries (toolboxes) available

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Basic Matlab Operations

>> % This is a comment, it starts with a “%”

>> y = 5*3 + 2^2; % simple arithmetic

>> x = [1 2 4 5 6]; % create the vector “x”

>> x1 = x.^2; % square each element in x

>> E = sum(abs(x).^2); % Calculate signal energy

>> P = E/length(x); % Calculate av signal power

>> x2 = x(1:3); % Select first 3 elements in x

>> z = 1+i; % Create a complex number

>> a = real(z); % Pick off real part

>> b = imag(z); % Pick off imaginary part

>> plot(x); % Plot the vector as a signal

>> t = 0:0.1:100; % Generate sampled time

>> x3=exp(-t).*cos(t); % Generate a discrete signal

>> plot(t, x3, ‘x’); % Plot points

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Introduction to SimulinkSimulink is a graphical, “drag and drop” environment for building

simple and complex signal and system dynamic simulations.

It allows users to concentrate on the structure of the problem, rather than having to worry (too much) about a programming language.

The parameters of each signal and system block is configured by the user (right click on block)

Signals and systems are simulated over a particular time.

v s,

v c

t

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Starting and Running Simulink

Type the following at the Matlab command prompt

>> simulinkThe Simulink library should appear

Click File-New to create a new workspace, and drag and drop objects from the library onto the workspace.

Selecting Simulation-Start from the pull down menu will run the dynamic simulation. Click on the blocks to view the data or alter the run-time parameters

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Signals and Systems in Simulink

Two main sets of libraries for building simple simulations in Simulink:

• Signals: Sources and Sinks• Systems: Continuous and Discrete

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Basic Simulink Example

Copy “sine wave” source and “scope” sink onto a new Simulink work space and connect.

Set sine wave parameters modify to 2 rad/sec

Run the simulation:Simulation - Start

Open the scope and leave open while you change parameters (sin or simulation parameters) and re-run

Many other Simulink demos …