init

FOTF Toolbox/@fotf/high_order.m

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+function Ga=high_order(G0,filter,wb,wh,N,key)
+% high_order - approximate an FOTF object with high-order TFs
+%
+%   Ga=high_order(G0,filter,wb,wh,N)
+% 
+%   G0 - an FOTF object
+%   filter - can be 'ousta_fod', 'new_fod' and 'matsuda_fod'
+%   wb, wh, N - the interested frequency interval and order of the filter
+%   Ga - an equivalent TF object
+
+% Copyright (c) Dingyu Xue, Northeastern University, China
+% Last modified 28 March, 2017 
+% Last modified 18 May, 2022 
+   arguments
+      G0, filter='ousta_fod', wb(1,1){mustBeNumeric}=1e-3
+      wh(1,1) {mustBeNumeric, mustBeGreaterThan(wh,wb)}=1e3
+      N(1,1) {mustBeInteger, mustBePositive}=5, key=0
+   end
+   [n,m]=size(G0); F=filter;
+   for i=1:n, for j=1:m
+      if G0(i,j)==fotf(0), Ga(i,j)=tf(0);
+      else, G=simplify(G0(i,j)); [a,na,b,nb]=fotfdata(G);
+         G1=pseudo_poly(b,nb,F,wb,wh,N,key)/pseudo_poly(a,na,F,wb,wh,N,key);
+         Ga(i,j)=minreal(G1);
+end, end, end, end
+% 伪多项式的近似
+function p=pseudo_poly(a,na,filter,wb,wh,N,key)
+   p=0; s=tf('s');
+   for i=1:length(a), na0=na(i); n1=floor(na0); gam=na0-n1;
+      if key==1
+         g1=eval([filter '(gam,N,wb,wh)']); p=p+a(i)*g1;
+      else
+         if gam~=0, g1=eval([filter '(gam,N,wb,wh)']);
+         else, g1=1; end
+         p=p+a(i)*s^n1*g1;
+end, end, end