function [params_optim, time_out, model_E] = SLS_optimize_fixedTau_fun(exp_time,exp_strain,exp_stress, params_in)


% Optimization - Linear visco model

time_out = linspace(0,50,10000);

exp_E = exp_stress/mean(exp_strain(end-10:end));

% form of equation E(t) = Ee + E1*exp(-t/tau)

fun = @(x)sum(( (x(1) + x(2)*exp(-exp_time/0.1) + x(3)*exp(-exp_time/1) + x(4)*exp(-exp_time/10) + x(5)*exp(-exp_time/100)) - exp_E).^2);  % Weichert 4 time constant

x0 = params_in;
% x_out = fmincon(fun,x0,[],[],[],[],[0 0 0], [20000 20000 20]);
x_out = fmincon(fun,x0,[],[],[],[],[0 0 0 0 0], [40000 10000 10000 10000 10000]);
params_optim = x_out;

model_E = x_out(1) + x_out(2)*exp(-time_out/0.1) + x_out(3)*exp(-time_out/1) + x_out(4)*exp(-time_out/10) + x_out(5)*exp(-time_out/100);

end