close all; clear
Fs=1000; % Sampling frequency, [Hz]
t_stop=10;
a1=(2*pi*10.0)^2; %The positive stiffness, f0=10 [Hz]
a2=(2*pi*20.0)^2; % The negative stiffness
b=2; % Linear damping
sim(‘s21′, t_stop); % Simulate a Simulink model
figure(1)
plot(y,’k’);
grid on
axis tight
xlabel(‘Points, s’); ylabel(‘Displacement’);
title([‘Asymmetric free vibration, a1=’ num2str(a1) ‘, a2=’ num2str(a2)]);