function  [sys0,sys1]=siarx(Ts,orderx)
clc;

load SIdata.mat                                     %導入用于模型辨識的數據
N=length(z);
servo=iddata(z,u,Ts);
servo.InputName='position';
servo.OutputName='distance';
ze=servo(1:N);
zv=servo(1:N);
figure,plot(ze)
%figure, plot(ze(1:1000))
%ze=dtrend(ze); 
%zv=dtrend(zv); 
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%ARX模型辨識
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NN=struc(2,2,0:100);                                %模型結構辨識
v=arxstruc(ze,zv,NN);
nn=selstruc(v,0);
nk=nn(3);                                           %確定延遲周期nk
NN=struc(1:orderx,1:orderx,0:nk+1); 
v=arxstruc(ze,zv,NN);
nn=selstruc(v,0)
m=arx(ze,nn);                                       %ARX模型辨識
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%ARX模型及降階模型分析
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disp('檢驗數據下ARX模型與實際系統的吻合程度：')       %模型檢驗
[yh1,f1]=compare(zv,m);
fit=f1   
disp('按任意鍵繼續！')
pause
mj=idmodred(m);                                     %模型降階
disp('檢驗數據下降階模型與實際系統的吻合程度：')
[yh1,f1]=compare(zv,mj);
fit=f1  
figure,compare(zv,m,mj);

my=noisecnv(m);
s=tf(my);                                           %將模型轉化為傳遞函數
sys0=s(1);                                          %ARX模型的傳遞函數                               
mjj=noisecnv(mj);
sy=tf(mjj);                                         %降階模型轉化為傳遞函數
sys1=sy(1);                                         %降階模型的傳遞函數
disp('降階后模型的傳遞函數：')
sys1
[num,den]=tfdata(sys1);
disp('傳遞函數的系數向量：')
num=num{1}
den=den{1}