Modeling and Simulation

Transcription

1 Automation Robotics and System CONTROL Università degli Studi di Modena e Reggio Emilia Modeling and Simulation 21/03/2011 Cesare Fantuzzi University of Modena and Reggio Emilia 1

2 Course syllabus Part 1: Theory of Modeling and Simulation. Part 2: Numerical simulation. Part 3: How develop simulation projects using Matlab and Simulink. Part 4: Case studies. 21/03/2011 2

3 Part 4: Case Studies We analyze some simulation case studies. 21/03/2011 3

4 What is S-Function? S-Functions is computer language description of Simulink block If written in MATLAB programming environment it is called M-file s-function If written in C/C++ programming environment it is called C Mex s-function

5 What S-Function Do? Allows you to add your own code to simulink model or environment Code can be written for continuous, discrete or hybrid system Can be use with Real Time Workshop Real Time workshop generates code for Simulink/sfunction to run in real time..faster 21/03/2011 5

6 Automation Robotics and System CONTROL Università degli Studi di Modena e Reggio Emilia

7 How S-function Works Mathematically simulink block consist of a set of inputs u, a set of states x, and set of outputs y Simulation Stages Initialization port widths, data types, sample time, memories allocation, execution order, evaluates block parameters Simulation loop Execute block determined during initialization, computes/updates blocks states, derivatives and outputs during a sample time

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9 M-file S-function M-files s-function is a matlab function [sys,x0,str,ts] = f(t,x,u,flag,p1,p2, ) Inputs f s-function name t is the current time x is the state vector flag indicates the task to be performed p1, p2 are block parameter to be changed externally Outputs sys Output of s-function x0 [ initial value vector of states] str not used [ ] ts [sample time offset time] M-file s-function template Examples: <matlabroot>/toolbox/simulink/blocks/msfuntmpl.m Sfundemos: >>sfundemos >> is matlab workspace prompt <matlabroot>/toolbox/simulink/simdemos User Manaul: Advantage: Easy to write and compatibility with matlab toolbox functions

10 C MEX s-function Mex s-function are written in C or C++, Fortran, C Mex files can modify data structure of Simulink SimStruct which is used for housekeeping. Can handle multiple data types and matrix signals Used with Real Time Workshop, wrapper s-function

11 How to build C Mex s-function Simulink specific naming convention and housekeeping (SimStruct) standards should be followed by C Mex files Template and examples in <matlabroot> / simulink /src sfuntmpl_basic.c >> mex setup should be run a priori to setup the compiler C Mex files are compiled in MATLAB with mex command Matlab Executable (mex) creates xxx.dll, dynamically loadable file excutable for simulink S- function Builder 21/03/

12 S-Function Builder Easiest way to embed your C code in Simulink model S-function builder is a Simulink block Act as calling program (wrapper) to C source code from Simulink providing necessary interfacing options S-function builder generates its own: builder-name.c builder-name_wrapper.c Have standard code representation similar to sfuntmpl_basic.c Customized interfacing options entered in builder builder-name.tlc Permit code generated to run in accelerated and real time Workshop builder-name.dll Simulink executable dll file

13 Importing C code into Simulink for Signal Processing Applications From Call How? C C MATLAB MATLAB Simulink Simulink MATLAB Simulink C Simulink MATLAB C MATLAB Engine ActiveX/COM & DDE MATLAB Compiler & runtime Engine or COM [x,y,t] = sim( mymodel,u0) MEX ActiveX/COM & DDE >> sim( mymodel ) M-code S-function Caution: interpreted, not compiled S-function Builder C-code S-function

14 Structure of code to be imported: `main() and slicer.c test_slicer.exe //test_slicer.c main() { for(){ slicer(); } } t //slicer.c slicer() { return; }

15 Structure of code after import: `wrapped slicer.c Call your `slicer.c code from a wrapper to interface with Simulink Compile both and link.dll Simulink calls the DLL using several functions ( methods ) wrap_slicer.dll Simulink t //wrap_slicer.c mdloutputs(s) { slicer(); } //slicer.c //definition // of //slicer() UNIX is a registered trademark of The Open Group

16 The S-function DLL contains several methods mdlinitializesizes() mdlinitializesampletimes() mdloutputs() y t = f(t, u t ) y = outputs, t = time u = inputs n Done? y mdlterminate()

17 What about leaf functions with states? States preserved across time steps Independent set of states per instance FIR, IIR, coders, decoders Also known as... Computer science: Re-entrant persistent storage { Object-oriented: property C++: member variable int always_one(void) { int y = 0; y = y + 1; return y; } int up(void) static int y = 0; y = y + 1; return y; Different from static variables in C are persistent but shared, not } re-entrant If a leaf contains static data it can only be instantiated once } int counter(int *z) { *z = *z + 1; return *z;

18 Two main types of state available in Simulink Discrete states, x d Read-only (const) in the mdloutput() method + Available in S-Function Builder block and full S-function Work vectors, w + Read-write in mdloutput() Presently only accessible from full S-function API input u states x d, w output y=f(t,x d,w,u)

19 Approach depends on code structure 1) Output-update structure use S-function Builder block Leaf with separate output and update functions Use discrete states, update them in mdlupdate() y t = f(t, x t, u t ), x t+ t = g(t, x t, u t ) y = outputs,t = time, x = states, u = inputs 2) General structure or advanced needs use full S-function Leaf with output and update functions intermixed Use work vectors, update them in mdloutputs() [x t+ t, y t ]= f(t, x t, u t )

20 1) Output-update function.c structure mdlinitializesizes() mdloutputs() mdlupdate() mdlinitializesampletimes() n Done? mdlterminate() y y t = f(t, x t, u t ) y = outputs, t = time x = states, u = inputs Division of labor is preferred x t+ t = g(t, x t, u t )

21 2) General leaf structure mdlinitializesizes() mdlinitializesampletimes() mdloutputs() n Done? y mdlterminate() y t = f(t, w t, u t ) w t+ t = g(t, w t, u t ) y = outputs t = time w = work vec u = inputs

22 Demonstrations Examples of S-function builder S-function Builder block features Slicer: a memoryless block IIR Filter: a block with memory Output-update structure S-function Builder A Discrete state Output in mdloutputs()and update in mdlupdate() General structure Full S-function 1-element Work vector Output and update in mdloutputs() Using the sample code as a resource Tour of the S-function reference material

23 Debugging s-function.dll in MSVC Open sfunc_name.dll file built by S-builder for e.g. simfunc_name.mdl in MSVC Setup breakpoint in sfunction.c using Right Mouse button Click Right mouse button on sfunc_name.dll open setting dialouge box, select debug tab, under executable field enter C:\MATLAB6p5\bin\win32\matlab.exe, OK! load sfunction.c in MSVC on the desired line enabled Choose build option from main menu and select start debug and Go! MATLAB will start under debugging mode Open simfunc_name.mdl for degguer MATLAB Run the file Watch the stop sign in MSVC sfunction.c file, the program should stop with arrow Select view from main menu and select debug Windows memory, variable, registers use F11 or steps increment icons from the MSVC toolbar to step to next line in sfunction.c

24 S-function compilation issue* Microsoft Visual C/C++ Ver 7.1 Recommended Version 6.0 MATLAB Version 7 Version 6 Real Time Workshop Windows Ver XP or 2000 Ver or 2000 *MATLAB TECH NOTE 1601 Always set MATLAB Command Window directory to the directory where source files are stored >> mex setup % At matlab startup % >> rtwintgt install % At startup % >> mex g sfun_name.c % s-function debugging%

25 Real time Workshop (RTW) generates portable, customize standalone C/C++ code of simulink model which operates in Real time Target Language Compiler (TLC) transform Simulink Block into C/C++ Simulink external mode enables communication between simulink and external process Real Time Window Target (RTWT) is a component of RTW RTWT helps to connect simulink model with external actuators and sensor for control and monitoring of Physical process s-function use with Real Time Workshop For Real Time Window Target

26 s-function examples using s-function builder and MSVC 6.0 Debugging slicer.c and iir_general.c Webinar <%matlabroot>/extern/examples/mex/ <%matlabroot>/toolbox/simulink/blocks/ i) fnpointer - use pointers to pass simulink matrix data to and from external source in C. MATLAB7, RTWT compilation ii) myadd - add matrix internally using array indexes, MATLAB7 iii) disc_stsp7 Discrete state updates internally, MATLAB7 iv) fnmat use pointers and array index for internal and external codes, MATLAB7 v) ludlub Linear system equation solver, using C source code from Numerical Recipes in C ludcmp.c & lubksb.c, MATLAB 6.5 vi) mylms Least mean square, MATLAB7, RTWT

27 21/03/2011 END OF PART 4 27