i am not getting chaotic plot because of warning

function dx = compactchua(t,x)

dx=zeros(4,1);

dx(1) = -(1/(8200*47*1e-9))*x(2);

dx(2) = (((x(3)-x(2))/2000) -(x(4).^3*4.7e3+1e3))/6.8e-9;

dx(3) = ((x(2)-x(3))/2000 - x(4))/68e-9;

dx(4) = (x(3))/(22*10^-9);

end

[t,x] = ode15s(@compactchua,[0 5e-7],[0 12.24e-3 12.24e-3 1.7]);

plot(x(:,2),x(:,3));

error

Warning: Failure at t=6.943264e-08. Unable to meet integration tolerances without reducing the step size below

the smallest value allowed (2.117582e-22) at time t.

>>

[David Goodmanson]

Hi nune,

you might want to double check the equations, especially the signs, because the solution gives the impression of wanting to increase without bound.

[Walter Roberson]

Which equations are you using?

https://people.eecs.berkeley.edu/~chua/papers/Pospisil00.pdf

Answer 1

[Bhavana Ravirala]

Hi Pratyusha,

In case of sharp discontinuities in the reference input, it is possible that this warning is generated at intermediate time steps. As it tries to reduce the time step to a small amount in order to counter the abrupt change due to the discontinuity in the reference input.

For sharp discontinuities, it might not be possible to avoid this warning. However, for non-discontinuous inputs we can set relative and absolute tolerance to a higher number than the default setting.

For more information refer the below links:

Absolute and relative tolerance definitions - (mathworks.com)

https://www.mathworks.com/help/matlab/ref/odeset.html#:~:text=RelTol%20%E2%80%94%20Relative%20error%20tolerance

Hope this helps.