controller_alinea(densities, flows, celldata, ts, idx)

function new_flows = controller_alinea(densities, flows, celldata, ts, idx)
% CONTROLLER_ALINEA - implementation of ALINEA controller.
%
% Call:   new_flows = controller_alinea(densities, flows, celldata, ts, idx)
%
% Parameters:
%             densities - vector of densities;
%             flows     - vector of on-ramp flows, same size as 'densities';
%             celldata  - array of freeway cell structures, whose length
%                         must be the same as size of 'densities';
%             ts        - sampling period;
%             idx       - index of the cell with our on-ramp.
%
% Returns:   new_flows - updated vector of on-ramp flows.
%
% Last modified:   10/14/2006.

%
% Alex Kurzhanskiy   <[e-mail]>
%

L = size(densities, 1);
M = size(flows, 1);
N = size(celldata, 2);

if L ~= N
  error('CONTROLLER_ALINEA: number of densities does not match number of cells.');
end

if M ~= N
  error('CONTROLLER_ALINEA: number of flows does not match number of cells.');
end

if (idx < 1) | (idx > N)
  error('CONTROLLER_ALINEA: invalid cell index.');
end

% initialize flow vector with current values
new_flows = flows;

if (celldata(idx).ORmlcontroller.upstream > 0) & (idx > 1)
  i = idx - 1;
else
  i = idx;
end
 
o_d = celldata(i).FDrhocrit;% / celldata(i).FDrhojam;  % desired occupancy
o_a = densities(i, 1);% / celldata(i).FDrhojam;  % actual occupancy
K   = celldata(idx).ORmlcontroller.K;  % control gain
f   = flows(idx, 1)  +  K * (o_d - o_a) / ts; % on-ramp flow that we can allow
f   = min([f celldata(idx).ORmlcontroller.Cmax]);
f   = max([f celldata(idx).ORmlcontroller.Cmin 0]);

% update flow vector
new_flows(idx, 1) = f;

return;