Chua Oszillator in Matlab, Chaos

I have written a code to simulate the chua circuit.

the code is:

[t,y] = ode45(@chua_function,[0 150],[1 0 0]);        
subplot(2,2,1) 
plot3(y(:,1),y(:,2),y(:,3)) %3D Plot
title("Chua's circuit 3D")
xlabel('D^-^1 Region')
ylabel('D^0 Region')
zlabel('D^1 Region')
grid
..
subplot(2,2,4) 
plot(y(:,1),y(:,3)) %2D Plot (D-1/D1 Bereich)
title("Chua's circuit 2D")
xlabel('D^-^1 Region')
ylabel('D^1 Region')
grid
            

function out = chua_function(t,p)
% t = Zeit, p = Position
a = 16; % a und B sind Werte der 3 Differentialgleichungen
B = 30;
m = -1.2; % m und n sind die Steigungen der Chua-Diode
n = -0.7;

x = p(1);
y = p(2);
z = p(3);

g = n*x+0.5*(m-n)*(abs(x+1)-abs(x-1));  %St�ckweise Lineare Gleichung der Diode
xdot = a*(y-x-g);
ydot = x - y+ z;
zdot = -B*y;
% Das sind die Werte, die dargestellt werden
out = [xdot ydot zdot]';
end

In the function out i have the three dimensionsless equations (alpha, beta) for the chua circuit.

But now i want to do the same with the equations with the Parameters R, C1,C2 and L:

[t,y] = ode45(@chua_function,[0 150],[1 0 0]);        
subplot(2,2,1) 
plot3(y(:,1),y(:,2),y(:,3)) %3D Plot
title("Chua's circuit 3D")
xlabel('D^-^1 Region')
ylabel('D^0 Region')
zlabel('D^1 Region')
grid
..
subplot(2,2,4) 
plot(y(:,1),y(:,3)) %2D Plot (D-1/D1 Bereich)
title("Chua's circuit 2D")
xlabel('D^-^1 Region')
ylabel('D^1 Region')
grid
            

function out = chua_function(t,p)
% t = Zeit, p = Position
C1  = 10*10^(-9);   %10nF
C2  = 100*10^(-9);  %100nF
R = 1800;           %1.8k Ohms
G = 1/R;
L = 18*10^(-3);
m = -1.2; % m und n sind die Steigungen der Chua-Diode
n = -0.7;

x = p(1);
y = p(2);
z = p(3);

g = n*x+0.5*(m-n)*(abs(x+1)-abs(x-1));  %St�ckweise Lineare Gleichung der Diode
xdot = (1/C1)*(G*(y-x)-g);
ydot = (1/C2)*(G*(x-y)+z);
zdot  = -(1/L)*y;
% Das sind die Werte, die dargestellt werden
out = [xdot ydot zdot]';
end

But the simulation is false. in the first one, with the dimensionsless parameters alpha and beta the simullation is right, in the second one with the parameters R,C1,C2 and L the simulation is wrong ( just a stright)

anybody know whats wrong?

[Amit kumar yadav]

>> chua_function

Error: File: chua_function.m Line: 16 Column: 16

Local function name must be different from the script name.

how to resolve this error??

Answer 1

[David Goodmanson]

Hi Albin,

In your second version, the equation for xdot is dimensionally incorrect. Changing it to

xdot = (1/C1)*(G*(y-x-g));

gives a good result. And the time scale in the second version is much different, so the ode45 time limits need to be something like [0 3e-2].