function [Gc,kc,ti,td]=pid1(k,t,tor)
% pid function
% 用于確定PID控制器參數的函數

% Copyright 2001-2002 ECUST. 
%   $Revision: 1.2 $  $Date: 2002/02/11 22:21:35 $

no=nargout;
if no==2,
    delta=k*tor/t;
    Gc=tf(1/delta,1);
    kc=1/delta;
    ti=inf;
    td=0;
elseif no==3,
    delta=1.1*k*tor/t;
    ti=3.3*tor;
    Gc=tf([ti 1],[ti 0])/delta;
    td=0;
    kc=1/delta;
elseif no==4
    delta=0.85*k*tor/t;
    ti=2*tor;
    td=0.5*tor;
    kc=1/delta;
end;
    Gc1=tf([ti 1],[ti 0])/delta;
    Gc2=tf([td 1],1)/delta;
    Gc=Gc1+Gc2; 
if isinf(ti),
    Gc=1/delta;
end;