Lyapunov exponents of Chen

Chen2.m

function dX = Chen2(t,X) % % Chen吸引子，用来计算Lyapunov指数 % dx/dt=a*(y-x) % dy/dt=(c-a)*x+c*y-x*z % dz/dt=x*y-b*z global a; % 变量不放入参数表中 global b; global c; x=X(1); y=X(2); z=X(3); % Y的三个列向量为相互正交的单位向量 Y = [X(4), X(7), X(10); X(5), X(8), X(11); X(6), X(9), X(12)]; % 输出向量的初始化 dX = zeros(12,1); % Lorenz吸引子 dX(1) = a*(y-x); dX(2) = (c-a)*x+c*y-x*z; dX(3) = x*y-b*z; % Lorenz吸引子的Jacobi矩阵 Jaco = [-a a 0; c-a-z c -x; y x -b]; dX(4:12) = Jaco*Y;

Z1=[]; Z2=[]; Z3=[]; global a; global b; global c; b=3;c=28; for a=linspace(32,40,100); y=[1;1;1;1;0;0;0;1;0;0;0;1]; lp=0; for k=1:200 [T,Y] = ode45('Chen2', 1, y); y = Y(size(Y,1),:); y0 = [y(4) y(7) y(10); y(5) y(8) y(11); y(6) y(9) y(12)]; y0=GS(y0); mod(1)=norm(y0(:,1)); mod(2)=norm(y0(:,2)); mod(3)=norm(y0(:,3)); lp = lp+log(abs(mod)); y0(:,1)=y0(:,1)/mod(1); y0(:,2)=y0(:,2)/mod(2); y0(:,3)=y0(:,3)/mod(3); y(4:12) = y0'; end lp=lp/200; Z1=[Z1 lp(1)]; Z2=[Z2 lp(2)]; Z3=[Z3 lp(3)]; end a=linspace(32,40,100); plot(a,Z1,'-',a,Z2,'-',a,Z3,'-'); title('Lyapunov exponents of Chen') xlabel('b=3,c=28,parameter a'),ylabel('lyapunov exponents') grid on

Z=[]; d0=1e-8; for a=linspace(32,40,80) lsum=0; x=1;y=1;z=1; x1=1;y1=1;z1=1+d0; for i=1:100 [T1,Y1]=ode45('Chen',1,[x;y;z;a;3;28]); [T2,Y2]=ode45('Chen',1,[x1;y1;z1;a;3;28]); n1=length(Y1);n2=length(Y2); x=Y1(n1,1);y=Y1(n1,2);z=Y1(n1,3); x1=Y2(n2,1);y1=Y2(n2,2);z1=Y2(n2,3); d1=sqrt((x-x1)^2+(y-y1)^2+(z-z1)^2); x1=x+(d0/d1)*(x1-x); y1=y+(d0/d1)*(y1-y); z1=z+(d0/d1)*(z1-z); if i>50 lsum=lsum+log(d1/d0); end end Z=[Z lsum/(i-50)]; end a=linspace(32,40,80); plot(a,Z,'-'); title('Chen 系统最大lyapunov指数') xlabel('parameter a'),ylabel('lyapunov exponents')

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