clear all;

%控制r1 r2两个角位移 就可改变双摆初状态

r1=0.8;

r2=0.8;

m1=1;

m2=1;

L1=1;

L2=1;

g=9.8;

Da=inline(['[x(3);x(4);',...

    'inv([(m1+m2)*L1,m2*L2*cos(x(1)-x(2));',...

    'm1*L1*cos(x(1)-x(2)),m1*L2])*'...

    '[m2*L2*x(4)^2*sin(x(2)-x(1))-(m1+m2)*g*sin(x(1));',...

    'm2*L1*x(3)^2*sin(x(1)-x(2))-m2*g*sin(x(2))]]'],'t','x',...

    'flag','m1','m2','L1','L2','g');

set(gcf,'DoubleBuffer','on');

[t,x]=ode45(Da,[0,20],[r1,r2,0,0],[],m1,m2,L1,L2,g);

axis([-(L1+L2),(L1+L2),-(L1+L2)*1.8,1]);

axis square;hold on;

gh1=plot([0,L1*exp(i*(x(1)-pi/2))],'r-');

set(gh1,'linewidth',2,'markersize',6,'marker','o');

gh2=plot([L1*exp(i*(x(1)-pi/2)),L1*exp(i*(x(1)-pi/2))+L2*exp(i*(x(2)-pi/2))],'b-');

set(gh2,'linewidth',2,'markersize',6,'marker','o');

for k=2:size(x,1);

    C1=[0,L1*exp(i*(x(k,1)-pi/2))];

    C2=[L1*exp(i*(x(k,1)-pi/2)),L1*exp(i*(x(k,1)-pi/2))+L2*exp(i*(x(k,2)-pi/2))];

    set(gh1,'xdata',real(C1),'ydata',imag(C1));

    set(gh2,'xdata',real(C2),'ydata',imag(C2));

    title(['t=',num2str(t(k))],'fontsize',12);

    pause(0.1);

end

% figure;

% subplot(2 ,3 ,1);plot(t,x(:,1));title('t-\theta_1');

% xlabel('t');ylabel('\theta_1');

% subplot(2 ,3 ,2);plot(t,x(:,2));title('t-\theta_2');

% xlabel('t');ylabel('\theta_2');

% subplot(2 ,3 ,3);plot(t,x(:,3));title('t-\omega_1');

% xlabel('t');ylabel('\omega_1');

% subplot(2,3,4);plot(t,x(:,4));title('t-\omega_2');

% xlabel('t');ylabel('\omega_2');

% subplot(2,3,5);plot(x(:,1),x(:,3));title('\theta_1-\omega_1');

% xlabel('\theta_1');ylabel('\omega_1');

% subplot(2,3,6);plot(x(:,2),x(:,4));title('\theta_2-\omega_2');