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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: EEE Intranet EE-M110 EFIS, W
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Background and Aims Matlab and Simulink have become a defacto standard for system modelling, simulation and control It 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 EE-M110 EFIS, W
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Resources Mathworks Information Mathworks: http://www.mathworks.com
Mathworks Central: Matlab Demonstrations Matlab Overview: A demonstration of the Capabilities of Matlab Numerical Computing with Matlab Select Help-Demos in Matlab Matlab Help Select “Help” in Matlab. Extensive help about Matlab, Simulink and toolboxes Matlab Homework Helper Newsgroup: comp.soft-sys.matlab Matlab/Simulink student version (program and book ~£50) Other 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. EE-M110 EFIS, W
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Introduction to Matlab
Command window Variable browser 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 Command history EE-M110 EFIS, W
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Matlab Programming Environment
Matlab (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 EE-M110 EFIS, W
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Basic Matlab Operations
>> % This is a comment, it starts with a “%” >> y = 5*3 + 2^2; % simple arithmetic >> x = [ ]; % 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 EE-M110 EFIS, W
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Introduction to Simulink
Simulink 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. vs, vc t EE-M110 EFIS, W
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Starting and Running Simulink
Type the following at the Matlab command prompt >> simulink The 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 EE-M110 EFIS, W
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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 EE-M110 EFIS, W
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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 … EE-M110 EFIS, W
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Day 1: Matrix Programming in Matlab
Full notes/syntax will be recorded in the diary Setting directory and diary Simple maths Matlab workspace, and help Variables, comments, complex numbers and functions Matlab desktop and management Script m-files Arrays Creating and assigning arrays, standard arrays Array indexing and orientation Array operators Array manipulation Array sorting, sub-array searching and manipulation functions Array size and memory utilization Control structures for and while loops if else and switch decisions EE-M110 EFIS, W
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Day 2: Structured Matlab Programming
Full notes/syntax will be recorded in the diary Functions Input and output arguments File structure, search path Exception handling Debugging and profiling Strings Dynamic function and expression evaluation Cell arrays Data structures Data plotting (2D/3D), figures GUIDE Simulink REMINDER Path, diary Help Scripts variable scope Basic matrix commands and operations NEW Functions Names, filenames, running and path Input and output arguments (names, variable number, nargin/nargout) Look at existing (Matlab) functions Debugging and profiling Strings eval and feval Cell arrays 2D string arrays Difference with normal arrays 1D/2D/ … Data structures Fieldnames Dynamic creation of fields exist, isfield 2D plot command Plot Figure saving and export Figure editing 3D plot command meshgrid Mesh GUIDE Create a simple data plotting application EE-M110 EFIS, W
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Day 1: Laboratory Remember
Change directory to your local filespace so that your work is saved Turn on the diary on to save the commands and results from the lab session to a file for future reference Questions Use the help and lookfor commands and look at the normal Matlab help section in the pull down menu (F1). How does the sin() function work? Evaluate expressions such as 7*8/9, 8^2, 6+5-3 Using the in-built Matlab functions, evaluate sin(0), sin(pi/2), abs(-3) Using the editor, write a Matlab script to solve the quadratic equation 2x2 -10x + 12 = 0 Evaluate, using a for loop, the first twenty numbers of the Fibonacci series xn = xn-1 + xn-2, x0 = 1, x1 = 1 Create the two vectors [1 2 3], [4 5 6] and calculate their inner product Create the 3*3 matrix A = [1 2 3; 4 5 6; 7 8 9] and the column vector b = [1 2 3], and multiply the two together A*b. Solve the equation A*x = b, where A and b are given in (6) Modify (8), so that you neglect the 3rd row & column of information. … EE-M110 EFIS, W
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Day 2: Laboratory Write a function that returns the two roots of a quadratic equation, given the three arguments a, b and c. Test the function from the command line Write a function that returns the mean and standard deviation of a vector of numbers (input vector). While Matlab supplies the mean() and std() functions, try just using the sum() and length() functions. Write a function that reverses the order of letters in a string, and returns the new string. Use the eval() Matlab function to evaluate strings such as: exp1 = ‘5*6 + 7’; Note this, and feval(), is very useful for dynamic programming Use a cell array to store a list of expressions, stored as strings. Then use eval() and a for loop to iterate over the expressions and evaluate them. Create two simple data structures to modify your solution to (1). Use one data structure to pack the parameters of the quadratic equation into a single variable, and use another to return the roots inside a single data structure Create the vector 0:pi/20:2*pi and use it to sample the sin() function. Plot the results and edit the figure window to put labels on the figure. Save the figure (.fig) and export a .jpg file. Use the meshgrid() function to sample a 2 dimensional input space between 0 and 2p, then use the data to sample the function sin(x1)*cos(x2). Plot the results using the mesh() function. Create a GUI that prompts the user for a number and then displays double that number next to the entered value. Start Simulink and using a sin() source and a scope sink, view the signal over 10 seconds. Change the frequency of the sin() source and again compare the results. Next change the simulation length. Build the first order system H(s) = 1/(1+3s) in the model and pass a sin() signal through the system. Make sure you run the simulation for a long enough time for the transients to die down and the system to settle. Replace the first order system in (6) with the second order system, what is the difference when the system settles down H(s) = 1/(1+2s+s^2). EE-M110 EFIS, W
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