matlab linmod,linmod 线性化系统

系统是用S-Function 写的，请见附件，为了使用linmod函数，故建立xls文件，包含S-Function模块，

和一个阶跃。模型是2输入2输出，linmod 之后，得到a 矩阵，但是b、c、d 矩阵显示是空集。感觉不合理。

请大神指导帮忙。

另外，对于这个系统，怎么用 trim解稳态点。谢谢各位。

matlab版本R2012b，系统64位window7.

S-Function中的代码：

function [sys,x0,str,ts,simStateCompliance] = model0402(t,x,u,flag)

switch flag,

%%%%%%%%%%%%%%%%%%

% Initialization %

%%%%%%%%%%%%%%%%%%

case 0,

[sys,x0,str,ts,simStateCompliance]=mdlInitializeSizes;

%%%%%%%%%%%%%%%

% Derivatives %

%%%%%%%%%%%%%%%

case 1,

sys=mdlDerivatives(t,x,u);

%%%%%%%%%%

% Update %

%%%%%%%%%%

case 2,

sys=mdlUpdate(t,x,u);

%%%%%%%%%%%

% Outputs %

%%%%%%%%%%%

case 3,

sys=mdlOutputs(t,x,u);

%%%%%%%%%%%%%%%%%%%%%%%

% GetTimeOfNextVarHit %

%%%%%%%%%%%%%%%%%%%%%%%

case 4,

sys=mdlGetTimeOfNextVarHit(t,x,u);

%%%%%%%%%%%%%

% Terminate %

%%%%%%%%%%%%%

case 9,

sys=mdlTerminate(t,x,u);

%%%%%%%%%%%%%%%%%%%%

% Unexpected flags %

%%%%%%%%%%%%%%%%%%%%

otherwise

DAStudio.error('Simulink:blocks:unhandledFlag', num2str(flag));

end

% end sfuntmpl

%

%=============================================================================

% mdlInitializeSizes

% Return the sizes, initial conditions, and sample times for the S-function.

%=============================================================================

%

function [sys,x0,str,ts,simStateCompliance]=mdlInitializeSizes

global CAs

global Ts

%

% call simsizes for a sizes structure, fill it in and convert it to a

% sizes array.

%

% Note that in this example, the values are hard coded.  This is not a

% recommended practice as the characteristics of the block are typically

% defined by the S-function parameters.

%

sizes = simsizes;

sizes.NumContStates  = 2;

sizes.NumDiscStates  = 0;

sizes.NumOutputs     = 2;

sizes.NumInputs      = 2;

sizes.DirFeedthrough = 0;

sizes.NumSampleTimes = 1;   % at least one sample time is needed

sys = simsizes(sizes);

%

% initialize the initial conditions

%

x0  = [2; 400];

%

% str is always an empty matrix

%

str = [];

%

% initialize the array of sample times

%

ts  = [0 0];

% Specify the block simStateCompliance. The allowed values are:

%    'UnknownSimState', < The default setting; warn and assume DefaultSimState

%    'DefaultSimState', < Same sim state as a built-in block

%    'HasNoSimState',   < No sim state

%    'DisallowSimState' < Error out when saving or restoring the model sim state

simStateCompliance = 'UnknownSimState';

% end mdlInitializeSizes

%

%=============================================================================

% mdlDerivatives

% Return the derivatives for the continuous states.

%=============================================================================

%

function sys=mdlDerivatives(t,x,u)

global CAs

global Ts

T0 = 300;

F = 5;

V = 1;

k0 = 8.46*10^6;

Cp = 0.231;

pro = 1000;

E = 5*10^4;

dH = -1.15*10^4;

R = 8.314;

CAs = 2;

Ts = 400;

n=2

sys = [F/V*(u(1)-x(1))-k0*exp(-E/(R*x(2)))*x(1)^n;...

F/V*(T0-x(2)) - dH/(pro*Cp)*k0*exp(-E/(R*x(2)))*x(1)^n + (u(2))/(V*pro*Cp)];

% end mdlDerivatives

%

%=============================================================================

% mdlUpdate

% Handle discrete state updates, sample time hits, and major time step

% requirements.

%=============================================================================

%

function sys=mdlUpdate(t,x,u)

global CAf

sys = [];

% end mdlUpdate

%

%=============================================================================

% mdlOutputs

% Return the block outputs.

%=============================================================================

%

function sys=mdlOutputs(t,x,u)

%%untitled中专门求解平衡点的 中间那一段，可以作图，平衡点有三个，应该选【2 400】

global CAs

global Ts

sys = [x(1);x(2)];       %% DMC的输入输出都必须减去平衡点的值

% end mdlOutputs

%

%=============================================================================

% mdlGetTimeOfNextVarHit

% Return the time of the next hit for this block.  Note that the result is

% absolute time.  Note that this function is only used when you specify a

% variable discrete-time sample time [-2 0] in the sample time array in

% mdlInitializeSizes.

%=============================================================================

%

function sys=mdlGetTimeOfNextVarHit(t,x,u)

global CAs

global Ts

sampleTime = 1;    % 文献中 0.01hr = 36 sec   化成 秒单位  Example, set the next hit to be one second later.

sys = t + sampleTime;

% end mdlGetTimeOfNextVarHit

%

%=============================================================================

% mdlTerminate

% Perform any end of simulation tasks.

%=============================================================================

%

function sys=mdlTerminate(t,x,u)

global CAs

global Ts

sys = [];

% end mdlTerminate

model.png

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S-Function