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F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional What is S-Function? S-Functions is computer language description of Simulink block If written in MATLAB.

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Presentation on theme: "F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional What is S-Function? S-Functions is computer language description of Simulink block If written in MATLAB."— Presentation transcript:

1 F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional 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 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/s-function to run in real time ………..faster

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3 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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5 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: /toolbox/simulink/blocks/msfuntmpl.m Sfundemos: >>sfundemos >> is matlab workspace prompt /toolbox/simulink/simdemos User Manaul: Advantage: Easy to write and compatibility with matlab toolbox functions

6 F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional C MEX s-function Mex s-function are written in C or C++, Fortran, Adao 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 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 / 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

7 F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional 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 Have standard code representation similar to sfuntmpl_basic.c builder-name_wrapper.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

8 F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional Importing C code into Simulink for Signal Processing Applications S-function Builder C-code S-function CSimulink M-code S-function Caution: interpreted, not compiled MATLABSimulink >> sim(‘mymodel’) SimulinkMATLAB MEX ActiveX/COM & DDE CMATLAB Engine or COM [x,y,t] = sim(‘mymodel’,u0) SimulinkC MATLAB Engine ActiveX/COM & DDE MATLAB Compiler & runtime MATLABC How?Call…From…

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

10 F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional 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 //wrap_slicer.c mdlOutputs(S) { slicer(); } //slicer.c //definition // of //slicer() UNIX is a registered trademark of The Open Group t

11 F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional mdlInitializeSizes() mdlInitializeSampleTimes() mdlOutputs() mdlTerminate() y t = f(t, u t ) y = outputs, t = time u = inputs Done? n y The “S-function” DLL contains several methods

12 F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional 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” 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 always_one(void) { int y = 0; y = y + 1; return y; } int up(void) { static int y = 0; y = y + 1; return y; } int counter(int *z) { *z = *z + 1; return *z; }

13 F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional 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 states x d, w input u output y=f(t,x d,w,u)

14 F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional 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() 2) General structure or advanced needs – use full S-function –Leaf with output and update functions intermixed  Use “work vectors”, update them in mdlOutputs() 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 [x t+  t, y t ]= f(t, x t, u t )

15 F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional 1) “Output-update” function.c structure mdlInitializeSizes() mdlInitializeSampleTimes() mdlOutputs() mdlTerminate() x t+  t = g(t, x t, u t ) Done? n y mdlUpdate() y t = f(t, x t, u t ) y = outputs, t = time x = states, u = inputs “Division of labor is preferred”

16 F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional 2) General leaf structure mdlInitializeSizes() mdlInitializeSampleTimes() mdlOutputs() 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 Done? n y

17 F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional 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

18 F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional 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

19 F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional S-function compilation issue* 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% Ver 2.2.0Version 6Version 6.0 Ver Version 7 Ver 7.1 Recommended Real Time Workshop MATLAB Microsoft Visual C/C++ Windows XP or or 2000 *MATLAB TECH NOTE 1601

20 F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional s-function use with Real Time Workshop For Real Time Window Target 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

21 F. Nagi Dep. Of Mech Eng. Universiti Tenaga Nasional s-function examples using s-function builder and MSVC 6.0 Debugging slicer.c and iir_general.c Webinar /extern/examples/mex/ /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


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