%
% The files to simulate the distillation column are:
%    colamod.m     - model of the distillation column which 
%                    returns the derivative of the states
%                    dx/dt = f(t,x,u).
%    colas.m       - SIMULINK interface to colamod.m.
%    cola_init.mat - Binary file containig the default
%                    initial values of the states and the 
%                    controls.
%   cola_nonlin.m  - Type:
%                    cola_nonlin
%                    in the MATLAB window and the non-linear
%                    SIMULINK model of the distillation column 
%                    appears.
%   cola_lv_nonlin.m - Type:
%                    cola_lv_nonlin
%                    in the MATLAB window and the non-linear
%                    SIMULINK model of the distillation column 
%                    with LV-configuration appears.
%   cola_lin.m     - A linearized Simulink model of the 
%                    distillation column. Use the following
%                    MATLAB commands:
%                    clear all
%                    load cola_init
%                    [A,B,C,D] = linmod('colas',Xinit,Uinit); 
%                    and the linearized model of the open-loop 
%                    model appears.
%   cola_test_simulink.m - contains further description on 
%                    use of the distillation column model with 
%                    SIMULINK. 
%    

%
% States:    X    - State, the first 41 states are compositions of light
%                   component A with reboiler/bottom stage as X(1) and 
%                   condenser as X(41). State X(42)is holdup in reboiler/
%                   bottom stage and X(82) is hold-up in condenser. 
% Inputs:    U(1) - reflux L,
%            U(2) - boilup V,
%            U(3) - top or distillate product flow D,
%            U(4) - bottom product flow B,
%            U(5) - feed rate F,
%            U(6) - feed composition, zF.
%            U(7) - liquid feed fraction, qF.
%
% Outputs:   sys and x0 as described in the SIMULINK manual.
%            when flag is 0 sys contains sizes and x0 contains 
%            initial condition. 
%            when flag is 1, sys contains the derivatives,
%            and when flag is 3 sys contains outputs; 
%            y(1)    - top composition,
%            y(2)    - bottom composition,
%            y(3)    - condenser holdup,
%            y(4)    - reboiler holdup,
%            y(5:45) - tray composition, y(5) is reboiler y(45) is top.