function res= f_model(optim_params)   

    k2=optim_params(1);
    d2=optim_params(2);
    load('Ref.mat');
    
    opts = simset('DstWorkspace','current','SrcWorkspace','current');
    sim('Test_2.slx',[], opts);
    res = sum((Out_F-Out_F2).^2);
end