Elements of MATLAB and Simulink - Lecture 1 - Percro

COURSE OVERVIEW

Applications• Where we can find MATLAB and Simulink?• Which are success stories of MATLAB and Simulink?NASA X-43ADoheny EyeNissanPERCRO VRPERCRO BEDLR Robotics

History and Versions• History (see this)– Born as script system in 70s for accessing the originalFORTRAN LINPACK and EISPACK libraries by Cleve Moler– Company founded in 1984 after contact with Stanford engineer– Simulink introduced 1990– Using LAPACK since 2000• MATLAB Versioning– Year based, Two per year– This course uses R2008a

Alternatives• GNU Octave http://www.gnu.org/software/octave/– Script Language compatible with MATLAB– Active Development– Large number of modules• SciLab http://www.scilab.org/– Open Source developed by Digiteo (French research park)– Simulink equivalent: Scicos– Google Summer of Code Mentor http://code.google.com/soc/

MATLAB StructureMATLAB GUISimulink GUIJavaToolboxesBlocksetsM EngineSimulinkLAPACKMuPADFFTW…

MATLAB in Simulink PipelinePreSimulinkPostData andModelpreparationEmbeddedMATLABsubsetData AnalysisVisualization

MATLAB Interface• MATLAB was and essentially is still a shell• Workspace is the set of variables• Basic commands:– help– doc– clear/clearvars/clear all– !cmd– editWorkspace– cdCurrent DirShellHistory

Matrix• Matrices are the fundamental type of data in MATLAB– Dense or Sparse– Different element types (usually double)• Which is the meaning of Matrix Data?– Linear Algebra Matrix– Mapping– Image– Representation of Graphs• Operators: + * / ^• Transposition: „• Element operators: .* .+• Most of the functions accept matrices and vectors– Operations on matrices are by columnsSee also Matrix Cookbook http://matrixcookbook.com/> Entering and Manipulating Matrix - lesson1_ex1

Programming MATLAB• M-file language– Dynamically Typed– Scripted language• Syntax:– no {} as in C– more similar to Pascal style– if .. else .. elseif … end– for .. end– while .. end– boolean operators: && ||– bit operators: & |

Loop vs Indexed Operations• When programming in MATLAB prefer indexed operations respectloop operations• Exploit: find, sum, min• Exploit Vectorized logic• Example Vector Normalization:– vMag = sqrt(sum(v.ˆ2));– v = v./vMag(ones(1,size(v,1)),:);See Writing fast MATLAB Code

Types• Matrix (with type double,int,int8 …)• Strings– Matrix of char– Variable length strings using Cell– String functions and Regular Expressions• Cell Array– Allows to contain any type– Useful for arrays of strings• Structure– Allows to contain structured data– a = []– a.field– a.(name)– fieldnames(a)• Dictionary– Not Native but based on Java Class java.util.Hashtable– x.put(key,value) x.get(key) x.contains(x)– key can be string/number and value can be anythingTypesValueTypeReferenceTypeMatrixStructCellHandle(number)ObjectJavaObjectFunctionHandle

Functions• Every file has a name as the main functionfunction r1,r2,r3 = name (p1, p2, p3)% commentreturn• Sub-functions allowed• Variable arguments– nargin nargout

Function Handles• Handles to functions (callbacks)– functions are full types– references to named functions using @ operator– See Plot• Passing Parameters to Callback{@fx, e1, e2, e3}When fx is called with p1 and p2 it receives also e1,e2,e3> ODE – lesson1_exode

Differential Equations• Set of differential Equations can be solved inside MATLAB• Useful for offline computation or design setup• Subset of Simulink power• Define Options with odeset• Run passing Derivative function, time and inputsFor interaction during ODE computationSet OutputFcn callbackopts = odeset('OutputFcn', @solverOutputFcn);Inside solverOutputFcn call “drawnow”and stop simulation returning 1

MATLAB Scope• Workspaces– assignin(workspace,name,value)– evalin(workspace,expression)• Global to Functions– global• Persistent to Functions (C static)– persistent name

Publishing Results• Cell-mode development in M-file– Mark Cells using %%– Evaluate (CTRL+ENTER)– Up/Down (CLTR+UP CTRL+DN)• Publishing results• Editing inside Word– Notebook feature– Define Block (ALT+D)– Evaluation of code by blocks (ALT+ENTER)

Storing Data• MAT files are the fundamental way of storing data– Binary compressed copy of variables in the workspace– Accessible from C using libmat• Variety of data formats supported– Image from Image Toolbox (imread)– CSV (importdata) and XLS (xlsread)– HF5D hierarchical data format• Example of custom format– fopen frlead fwrite– loadbin> Storing Data – lesson1_exdata

Basics of plotting• MATLAB provides 2D and 3D plotting• Plots concepts– Handle to entity (get / set functions)– Axis (limits vs auto-limit)– Subplots (subplot)– Exporting plots for publishing (EMF)– Default Entities: gca (get axis) gcf (get figure)• 3D Plot– surf– Also mesh based plots• Important for Papers/Thesis– Always put labels and units of measures in axis (xlabel,ylabel)– Sometime adjust default font size– xlabel,ylabel,title,legend• Save Plots– print -f1 -dFORMAT myfile.FORMAT (es. eps emf png jpg)• Animation> Plot Data – lesson1_explot

MATLAB 2D Plots

User Interfaces• Create User Interface for Presenting Data• Run guide for Visual Editor• GUI made of a figure-file and an associated m-file• Alternative• EasyGUI package available for R2008a• Automatic placement of entities• Loop or Callback designmygui = gui.autogui;num = gui.slider(„Points:‟,[5 50]);txt = gui.textmenu(„Color‟,{„r‟,‟b‟});while mygui.waitForInput()plot (num.Value,txt.Value)end

Major Toolboxes• MATLAB Toolboxes provide aggregate of functions• Example of useful ones:– Imaging Toolbox– Control Toolbox– Symbolic Toolbox– Signal Processing– Neural Network Toolbox

Symbolic Toolbox• Manipulation of symbolic expressions• Definition of symbols– sym(„name‟)– syms name1 name2 .. „real‟• Analysis operations– diff• Resolution– solve– dsolve• Replacing variables• Plotting– subs(expr, x, x+2)– subs(expr, {x,t},{5,2})– ezplot(fx,[-1,1])– ezsurf• Printing– pretty• Note: a symbolic variable is of a special type that overloads all the typical operators allowing toperform all the operations as if it is effectively one of the fundamental matrix types

MATLAB Resources• File Exchange– http://www.mathworks.com/matlabcentral/fileexchange/• MATLAB/Simulink Books (SSSA)