% function [Ki,K] = area2PI (A0,A1,A2,A3,Kmax);
%
% Function araa2PI calculates parameters of the PI controller:
%
% u = (Ki/s + K) * e
%
% from the measured areas of the process A0 to A3 (A0 is the process steady-state gain)
% The parameter Kmax represents the highest allowed open-loop gain K*A0 


function [Ki,K] = area2PI (A0,A1,A2,A3,Kmax);

Num = A3;							% Numerator
Den = 2*(A1*A2-A0*A3);			% Denominator

if (Num == 0)
   K = 0;
elseif (Den == 0)
   if (A0 ~= 0)
      K = Kmax/A0;
   else
      K = Kmax;
   end;
else
   K = Num/Den;
end;

Tmp = K*A0;							% Nominal gain

if (Tmp > Kmax) | (Tmp < 0)
   K = Kmax/A0;
end;

Ki = (K*A0 + 0.5)/A1;