IntroductiontoScientificComputingTool Scilab

ChaoChiehLanandJianHao LiouDepartmentofMechanicalEngineering

National Cheng Kung UniversityNationalChengKungUniversity

2009/09/22 1

ComputingToolsforMechanismAnalysesp g y

Lowlevel Mediumlevel HighlevelC++Fortran MathematicaMatlab

gWorkingModelADAMS

L l lLowlevel:

FastcomputationGeneralpurpose

NodirectgraphicssupportMatrixmanipulationiscumbersome

Difficulttodebug

Mediumlevel:

Directgraphicssupport EasytodebugMatrixmanipulationiseasy

Highlevel:

SlowercomputationLessgeneral

g

Graphicaluserinterface Youdontknowifthesoftwarecheatyou!2

Scilab A Free Alternative to MatlabScilab AFreeAlternativetoMatlab

Scilabisascientificsoftwarepackagefornumericalcomputations.ItwasinitiallydevelopedbyINRIAandENPCinFrance.

Scilabisanopensourcesoftware.Since1994ithasbeendistributedfreely along with the source codefreelyalongwiththesourcecodeviatheInternet.Now,thelatestedition is 5.1.1.editionis5.1.1.

ScilabsyntaxislargelybasedontheMATLAB language

OtherfreealternativestoMatlabincludeOctaveand RlabPlus.

MATLABlanguage.

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Scilab LayoutyCommandwindow:

*.sceisascriptfilethatyoucanstoreyouprogram.

*.sciisafunctionfilethatyoucanstoreyoufrequentlyusedsubroutines.

Scipad:

Youcanedit*.scefileand*.scifileshere

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BasicOperationsp Thesimplestwaytoexecutescilab codeistotypeitinattheprompt,>>,inthegraphicalcommandwindow.

Scilabdoesntneedtodeclareavariablebeforeusingit.Nopointersarerequiredeither.

Scilabisacasesensitivesoftware.ForexampleA=[12;34];butaisnotequaltoA

Use;afterthecommandtosuppressoutputtoscreen.

=%pi,imaginarynumber=%i,%e=2.71828

Linesafter// arecomments.Usetosplitalonglineintotwolines.

atan(p/q):2quadrantinversetangent;atan(p,q):4quadrantinversetangent

Cross productNo such command for Scilab You have to write it by yourself CrossproductNosuchcommandforScilab.Youhavetowriteitbyyourself.5 Scilabis1indexing,differentfromC++whichis0indexing.

MatrixManipulations(1) Therowelementsofmatrixareseparatedbyspace orcomma(,) ;thecolumn

elementsofmatrixareseparatedbysemicolon(;),forexample:

(2) Themultiplicationandproductofmatrices A=[]B=[]h l i li i f d i * *

A=[123;456]A=[]

ThemultiplicationofAandBisA*B orA*B

theproductofA B isA.*B

(3) Set A is a matrix A is the transposition matrix of A A [ ] A [ ]

(4)DenotesthesolutiontothematrixequationAX=B.

if a1*x1+a2*x2=b1 a3*x1+a4*x2=b2

(3)SetAisamatrix,AisthetranspositionmatrixofA.A=[ ]A=[]

ifa1*x1+a2*x2=b1,a3*x1+a4*x2=b2

SetA=[ ],B=[ ],x=[ ]X=A\B

(5)ColonisaveryusefultoolinScilab.

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Programming:LoopandConditionalControl

(1)forforindex=start : increment : endstatements

end

(2) while (3) if (4)breakitcanwhileexpression

statements

d

iflogicalexpressionthen

statements

else then

interruptloops.

end elsethenstatements

end

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ProgrammingTipsandUsefulCommands

Put the command clear and close in the very beginning of a * sce Putthecommand clear and close intheverybeginningofa .sce scriptfiletodeletepreviousresults.

Put a command pause in between the lines to serve as a break point.Putacommand pause inbetweenthelinestoserveasabreakpoint.Usereturntocontinueexecuting.

Usecommandwho_usertolistusersdefinedvariables.

browsevar():anembeddedfunctionwhichyoucanbrowseandeditexistingvariables.

fsolve:findazeroofasystemofnnonlinearfunctions.Itscallingsequenceis[x]=fsolve(x0,fun,tol),xistheoptimizersolution,x0istheinitialvalue

a ab es

[ ] so e( 0 , u , to ) , s t e opt e so ut o , 0 s t e t a a ue

whichyoustartingguessatthesolution,funisthefunctionthatyouwantto

solve,andtolistheprecisiontolerance.

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Programming of FunctionProgramming ofFunction(1) EditthefunctiononSciPad(2) cross is the function name You(2) cross isthefunctionname.You

cannameitbyyourself.(3) fistheoutputofthefunction.u1,

2 3 1 2 d 3 th i tu2,u3,v1,v2andv3aretheinputparametersofthefunction.

(4)Savethefileascross.sci

(5) Loadthefunctionexec(filepath)d h iandtheyoucanexecuteit

(6)Thevariablesdefinedinsidethefunctionarelocal.Theydonotaffectthevariablesoutsidethefunction.

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GraphicsPlotp(1)xinit: Openanewgraphic.Ifyoudontdothisdatawillbeplottedinthe

samegraphic.

(2)plot(x,y): Usethiscommandtoplotthecurveabouttherelationshipofxandy,wherexandyarebothvectors.

(3) l t (i 1) Fi d t th l ti f th i t ( 1 2 i)(3)locate(i,1):Findoutthelocationofthepoints(p1,p2.pi)

(a)thepointswhichyouchoose. (b)thecoordinatesofthepoints.

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GraphicsLinePropertiesp p(1) Use the commend ged() to(1) Usethecommendged() to

changethepropertiesoffigure.

(2)Choosetheitemthatyouwantto( ) ychangeitsproperties.

(3)Changetypeandwidthofthecurve.

(4)Changethecolorofthecurve.11

GraphicsAxes PropertiesGraphics AxesProperties

(1)Keyinthelabelofaxes.(2) Choose the item to adjust the properties of axes(2)Choosetheitemtoadjustthepropertiesofaxes.

(3)Changethefontsizeoflabel.

(4)Thefontsizeoftheaxes.

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GraphicsExport and PrintGraphics ExportandPrint(1) Choose

fileExport

(2)ChoosetheExporttypeitem,anddecidethefiletypethatyouwanttosave.

FilePrintPostscript

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Animationofmechanisms

Slidercrankmechanismdemo(ex4.3,p140ofCleghorn)

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Animationofcams (ex8.7,p.397ofWaldron)

Oscillating Roller FollowerOscillatingRollerFollower

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Scilab BrowseHelpandWebResources

Scilabhompagehttp://www.scilab.org/

The instruction of Scilab (1) TheinstructionofScilab(1)http://msdl.me.ncku.edu.tw/scilab/Site/Scilab_files/cintro.pdf

TheinstructionofScilab(2)h // l k d / l / b l/ b hhttp://mail.nkmu.edu.tw/~crlin/SciLab_Tutorial/SciLab_tut.htm

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