porsche_circle_x3_y3_get_eq_constr.m

function eq_constr = porsche_circle_x3_y3_get_eq_constr(model)
%function eq_constr = porsche_circle_get_eq_constr(model)
%
% !!! DOKU SCHREIBEN !!!
%
% Oliver Zeeb, 01.06.2011

if isfield(model.optimization,'constraint_circle_radius')
    R=model.optimization.constraint_circle_radius;
else
    disp('field model.optimization.constraint_circle_radius does not exist!')
    disp('--> no radius for the constraint circle given! Using R=10...')
    R=10;
end

if ~isfield(model.optimization,'constraint_circle_midpoint')
    disp('field model.optimization.constraint_circle_midpoint does not exist!')
    disp('Using x_midpoint=model.pmacro(3,1), y_midpoint=model.pmacro(3,2)')
    model.optimization.constraint_circle_midpoint(1) = model.pmacro(3,1);
    model.optimization.constraint_circle_midpoint(2) = model.pmacro(3,2);
end



% n Neben-Bed: punkte aus model.mu_names auf kreis um radius r_n
x_ind=0;
y_ind=0;
for k=1:length(model.mu_names)
    position_in_pmacro = str2double(model.mu_names{k}(2));
    x_or_y = model.mu_names{k}(1);
    if x_or_y == 'x'
        x_ind = x_ind+1;
        x(x_ind) = getfield(model, model.mu_names{k});
        %x_fix(x_ind) = model.pmacro(position_in_pmacro,1);
        x_fix(x_ind) = model.optimization.constraint_circle_midpoint(1);
    elseif x_or_y == 'y'
        y_ind = y_ind+1;
        y(y_ind) = getfield(model, model.mu_names{k});
        %y_fix(y_ind) = model.pmacro(position_in_pmacro,2);
        y_fix(x_ind) = model.optimization.constraint_circle_midpoint(2);
    else
        error('unknown entry in model.mu_names');
    end
end

x_diff_sqr = (x-x_fix).^2;
y_diff_sqr = (y-y_fix).^2;
r_sqr = (R*ones(1,length(x_diff_sqr))).^2;

eq_constr = x_diff_sqr + y_diff_sqr - r_sqr;