function [M,poles,zeros] = smform(a,b,c,d)%SMFORM - Finds the Smith-McMillan form of a LTI MIMO SYS model along with%its poles and zeros.%% Syntax:  [M,poles,zeros] = smform(SYS)%% Inputs:%    SYS - LTI MIMO system, either in State Space or Transfer Function%    representation.%% Outputs:%    M - Smith-McMillan Matrix%    poles - Poles of the Smith-McMillan Matrix%    zeros - Zeros of the Smith-McMillan Matrix%% Example: %   g11=tf([1 0],conv(conv([1 1],[1 1]),conv([1 2],[1 2])));%   g12=tf(conv([1 0],conv([1 1],[1 1])),conv(conv([1 1],[1 1]),conv([1 2],[1 2])));%   g21=tf(-conv([1 0],conv([1 1],[1 1])),conv(conv([1 1],[1 1]),conv([1 2],[1 2])));%   g22=tf(-conv([1 0],conv([1 1],[1 1])),conv(conv([1 1],[1 1]),conv([1 2],[1 2])));%   G=[g11 g12; g21 g22];%   [M,poles,zeros]=smform(G)%% Other m-files required: tf2sym, ss2sym% Subfunctions: multiplica% Active Link required: Maple%% Author: Oskar Vivero Osornio% email: oskar.vivero@gmail.com% Created: February 2006; % Last revision: 25-March-2006;% May be distributed freely for non-commercial use, % but please leave the above info unchanged, for% credit and feedback purposes%------------- BEGIN CODE --------------% Determines Syntaxni=nargin;p=sym('p');switch ni    case 1        %Transfer Function Syntax        switch class(a)            case 'tf'                %Numeric Transfer Function Syntax                g=tf2sym(a);            case 'sym'                %Symbolic Transfer Function Syntax                g=a;        end            case 4        %State Space Syntax        g=ss2sym(a,b,c,d);end%****************************************************************% Common Denominator[n,m]=size(g);[num,den]=numden(g);d=den;d=reshape(d,1,n*m);while (length(d))>1    k=1;    d1=sym([]);     for i=2:length(d)     d1(k)=lcm(factor(d(i)),factor(d(i-1)));     k=k+1;     endd=d1;clear d1end%****************************************************************% Determines P, S, and finally M%g=factor(g);P=d*g;S=maple('smith',P,p);M=simple(S/d);%****************************************************************% Determines the poles and zerosclear num denn=size(M,1);for i=1:n    [num(i),den(i)]=numden(M(i,i));endd=prod(den);n=prod(num);n=sym2poly(n);poles=solve(d);zeros=roots(n);%------------- END OF CODE --------------