如何编写simulink library.
由于simulink中没有非线性系统的状态空间模块，即形如
x'=f(x)+g(x)u
y=h(x)
的模块，因此对于非线性系统，使用simulink建模比较困难。
但是现在这不是问题了，因为我们有了一个第三方的simulink library：NelinSys
下载下来之后，顺便分析了这个库的实现方法，发现真的是very easy!下面介绍一下如何编写simulink library:
1.打开simulink,选择File->new->library，这样就能在里面随便添加文本，等。。东西。然后保存为.mdl文件。
2.然后就得添加一个模块，这里我没找到如何用可视化的方法进行设计，但是我发现可以直接修改.mdl文件实现。比如有一个library中的一个模块叫做Nonlinear MIMO system，它对应的代码如下：
Block 
{
BlockType SubSystem Name "Nonlinear MIMO system\n(State-Space model)" Ports [1, 2, 0, 0, 0] Position [255, 20, 385, 95] ShowPortLabels off MaskType "Nonlinear MIMO system - state-space model" MaskDescription "Nonlinear MIMO system is described by follo""wing nonlinear differential equations:\n dx/dt = f(x) +"" g(x) u\n y = h(x)\n\n states vector: x ="" [x1; x2; ; xN]\n system input: u (vector)\n syste""m output: y (vector)\n\nParameters f(x), g(x), h(x) can be specified either a""s a symbolic expression or as an identifier of a symbolic variable.\n\nFor a ""detailed description of parameters, click \"Help\" button." MaskHelp "web(fullfile(cd,'help','stavp_mimo.html'));" MaskPromptString "System order (number of states, N)|f(x) - s""ymbolic expression:|f(x) - variable identifier:|g(x) - symbolic expression:|g""(x) - variable identifier:|h(x) - symbolic expression:|h(x) - variable identi""fier:|Initial conditions (initial states):" MaskStyleString "edit,edit,edit,edit,edit,edit,edit,edit" MaskTunableValueString "on,on,on,on,on,on,on,on" MaskVariables "n=@1;F=&2;Fp=@3;G=&4;Gp=@5;H=&6;Hp=@7;pp=@8"";" MaskInitialization "% Overenie spravnosti zadania parametrov bl""oku %\nif ~isempty(F) & (Fp == 0)\n F = sym(F);\nelseif isempty(F) & (any(F""p ~= 0))\n F = sym(Fp);\nelse\n error(['Matrix f(x) unspecified or specif""ied more than once - cannot continue!']);\nend\n\nif ~isempty(G) & (Gp == 0)""\n G = sym(G);\nelseif isempty(G) & (any(Gp ~= 0))\n G = sym(Gp);\nelse\n"" error(['Matrix g(x) unspecified or specified more than once - cannot conti""nue!']);\nend\n\nif ~isempty(H) & (Hp == 0)\n H = sym(H);\nelseif isempty(H"") & (any(Hp ~= 0))\n H = sym(Hp);\nelse\n error(['Matrix h(x) unspecified"" or specified more than once - cannot continue!']);\nend\n\n% Zisti si symbol""icke premenne, ktore vystupuju vo vyrazoch %\npremF = strrep(strrep(findsym(s""ym(F)),', ',''),',',' ');\npremG = strrep(strrep(findsym(sym(G)),', ',''),','"",' ');\npremH = strrep(strrep(findsym(sym(H)),', ',''),',',' ');\n\n% Premenn""e x1, x2, , xN su korektne, preskoc ich %\nfor k = 1 : n\n premF = strre""p(premF, sprintf('x%d',k), '');\n premG = strrep(premG, sprintf('x%d',k), '""');\n premH = strrep(premH, sprintf('x%d',k), '');\nend\n\n% Ak niektory re""tazec nezostal prazdny, vyhlas chybu %\nif ~isempty(premF)\n error(['Unknow""n symbol in f(x) expression - cannot continue!']);\nend\nif ~isempty(premG)\n"" error(['Unknown symbol in g(x) expression - cannot continue!']);\nend\nif ""~isempty(premH)\n error(['Unknown symbol in h(x) expression - cannot contin""ue!']);\nend\n\n% Otestovanie spravnosti rozmerov matic F,G,H (podla \"n\") %""\nif ~all(size(F) == [n,1])\n error(['Invalid matrix dimensions: f(x) - can""not continue!']);\n return;\nend\n\nnin = size(G);\nif (nin(1,1) ~= n)\n ""error(['Invalid matrix dimensions: g(x) - cannot continue!']);\n return;\ne""nd\nnin = nin(1,2);\n\nnout = size(H);\nif (nout(1,2) ~= 1)\n error(['Inval""id matrix dimensions: h(x) - cannot continue!']);\n return;\nend\nnout = no""ut(1,1);\n\n% Kontrola vektora pociatocnych podmienok (pociatocnych stavov) %""\nif ~all(size(pp) == [n,1])\n error(['Initial conditions vector: invalid d""imensions - cannot continue!']);\n return;\nend\n\n% Nahradenie identifikat""orov \"xI\" identifikatormi \"x(I)\" %\nco_str = '{''x1'; cim_str = '{''x(1)'"";\n\nfor k = 2 : n\n co_str = sprintf('%s'',''x%d', co_str, k);\n cim_s""tr = sprintf('%s'',''x(%d)', cim_str, k);\nend\n\nco_str = strcat(co_str, '''""}'); cim_str = strcat(cim_str, '''}');\n\nF = eval(sprintf('subs(F,%s,%s)', c""o_str, cim_str));\nG = eval(sprintf('subs(G,%s,%s)', co_str, cim_str));\nH = ""eval(sprintf('subs(H,%s,%s)', co_str, cim_str));\n" MaskDisplay "disp('Nonlinear MIMO system\\n\\nx'' = f(x)"" + g(x) u\\ny = h(x)');" MaskIconFrame on MaskIconOpaque on MaskIconRotate none MaskIconUnits autoscale MaskValueString "3|[84.249*x2*x3; -165.8654*x1*x3-62.5*x2; -""15.3846*x3]|0|[0 0; 2500 0; 0 0.9799]|0|[x1; x3]|0|[0; 0; 1e-9]"
System { Name "Nonlinear MIMO system\n(State-Space model"")" Location [124, 225, 456, 399] Open off ToolBar off StatusBar off ScreenColor white PaperOrientation landscape PaperPositionMode auto PaperType usletter PaperUnits inches Block { BlockType Inport Name "Vstup" Position [15, 78, 45, 92] Port "1" PortWidth "-1" SampleTime "-1"
} Block { BlockType Demux Name "Demux" Ports [1, 2, 0, 0, 0] Position [235, 6, 240, 159] BackgroundColor black ShowName off Outputs "[nout n]" } Block { BlockType "S-Function" Name "S-funkcia realizujuca\nnelinearny syste""m" Ports [1, 1, 0, 0, 0] Position [85, 60, 195, 110] FunctionName "stavp_mimo" Parameters "n,nin,nout,F,G,H,pp" PortCounts "[]" SFunctionModules "''" } Block { BlockType Outport Name "Vystup" Position [280, 38, 310, 52] Port "1" OutputWhenDisabled held InitialOutput "0" } Block { BlockType Outport Name "Stavovy\nvektor" Position [280, 113, 310, 127] Port "2" OutputWhenDisabled held InitialOutput "[]" } Line { SrcBlock "Demux" SrcPort 2 DstBlock "Stavovy\nvektor" DstPort 1 } Line { SrcBlock "Demux" SrcPort 1 DstBlock "Vystup" DstPort 1 } Line { SrcBlock "S-funkcia realizujuca\nnelinearny syste""m" SrcPort 1 DstBlock "Demux" DstPort 1 } Line { SrcBlock "Vstup" SrcPort 1 DstBlock "S-funkcia realizujuca\nnelinearny syste""m" DstPort 1 } }
}值得注意的是其中一个s-function子模块：stavp_mimo，其实这个子模块才是最核心的地方，打开这个文件发现果然是一个标准的s-function模块:
function [sys,x0,str,ts] = stavp_mimo(t,x,u,flag,n,nin,nout,F,G,H,pp)% NelinSys - a program tool for analysis and synthesis of nonlinear control systems% based on MATLAB/Simulink 5.2%% (C) 2002-2005, Martin Ondera (eskimo@pobox.sk) (Martin.Ondera@stuba.sk)% This program is free software; you can redistribute it and/or% modify it under the terms of the GNU General Public License% as published by the Free Software Foundation; either version 2% of the License, or (at your option) any later version.%% This program is distributed in the hope that it will be useful,% but WITHOUT ANY WARRANTY; without even the implied warranty of% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the% GNU General Public License for more details.%% You should have received a copy of the GNU General Public License% along with this program; if not, write to the Free Software% Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.%% Please, see the LICENSE.TXT file to read the full license.switch flag,% =========================== Inicializacna cast s-funkcie ============================== %case 0 % Definicia stavov, vstupov a vystupov nelinearneho systemu % sizes = simsizes; sizes.NumContStates = n; sizes.NumDiscStates = 0; sizes.NumOutputs = nout+n; sizes.NumInputs = nin; sizes.DirFeedthrough = 0; sizes.NumSampleTimes = 1; sys = simsizes(sizes); % Inicializacia pociatocnych podmienok % x0 = pp; % Inicializacia "str" ako prazdna matica % str = []; % Sample times in TS % ts = [0 0];% ========================== Vypocet podla 1. stavovej rovnice ========================== %case 1 sys = eval(sym(F)) + eval(sym(G)) * u;% ========================== Vypocet podla 2. stavovej rovnice ========================== %case 3 sys(1:nout,:) = eval(sym(H)); % Ako vystup bloku sa berie nielen vystup systemu % sys(nout+1:nout+n,:) = x; % ale aj cely stavovy vektor nelinearneho systemu %% ================================= Nepouzite priznaky ================================== %case {2, 4, 9} sys = []; % ================================= Spracovanie chyby =================================== %otherwise error(['Unknown flag = ',num2str(flag)]);end