my program is not working properly
显示 更早的评论
function kk2
close all; clear all;
% accuracy
%options = odeset('RelTol',1e-9,'AbsTol', 1e-16);
[t,y]=ode45(@f,[0 100],[0.1;0.1;0.1+1;0.1;0.1;0.1] );
plot(t,y(:,2),t,y(:,4),t,y(:,6))
function dy=f(t,y)
%x=y(1);y=y(3);z=y(5)
r=28;
b=8/3;
k=10;
dy=zeros(6,1)
dy= [y(2);k^2*y(1)-k^2*y(3)-k*y(1)*y(5)+k*r*y(5)-k*y(3);y(4);b*y(1)*y(5)-y(1)^2*y(3)-k*y(1)*y(3)+k*y(3)*y(5)-r*k*y(1)+k*r*y(3)+y(1)*y(5)-r*y(1)+y(3);y(6);-y(1)^2*y(5)+r*y(1)^2-y(1)*y(3)-k*y(1)*y(3)+k*y(3)^2-b*y(1)*y(3)+b^2*y(5)]
end
end
so sir we want to plot between t,x,t,y
and we want to plot t vs second element of dy t,fourth element t,vs sixth element
1 个评论
@shiv gaur: You have been asked repeatedly to use a proper code formatting. Please read and consider this: https://www.mathworks.com/matlabcentral/answers/help/rtc#rtc_summary . Thanks.
回答（1 个）
Hi @shiv gaur
It appears that the system is highly unstable and all states blow up at around 0.35 sec except for 
. Please check the state equations again. Sometimes, the plus/minus signs can make a huge difference.
. Please check the state equations again. Sometimes, the plus/minus signs can make a huge difference.Edit: It has some similarities like the Lorenz system, because I recognized the magic values: 10, 8/3, 28.
clear all; clc
r = 28;
b = 8/3;
k = 10;
tspan = linspace(0, 0.3, 10001)';
fun = @(t, y) [y(2); ...
k^2*y(1) - k^2*y(3) - k*y(1)*y(5) + k*r*y(5) - k*y(3); ...
y(4); ...
b*y(1)*y(5) - y(1)^2*y(3) - k*y(1)*y(3) + k*y(3)*y(5) - r*k*y(1) + k*r*y(3) + y(1)*y(5) - r*y(1) + y(3); ...
y(6); ...
- y(1)^2*y(5) + r*y(1)^2 - y(1)*y(3) - k*y(1)*y(3) + k*y(3)^2 - b*y(1)*y(3) + b^2*y(5)];
[t, y] = ode45(fun, tspan, [0.1, 0.1, 1.1, 0.1, 0.1, 0.1]);
plot(t, y)
Once you have fixed the model, please ensure that all states can propagate at least until your desired final time, 
sec, and then you can choose what you want to plot.
sec, and then you can choose what you want to plot.6 个评论
shiv gaur
2022-3-11
Sam Chak
2022-3-11
Try this:
plot(t, y(:, 2), t, y(:, 4), t, y(:, 6))
shiv gaur
2022-3-11
Thought I have put my explanations above. The nature of your state equations is highly unstable. It cannot integrate the system pass 0.3541457 sec. That's why I simulated until 0.3 sec to show you the divergence of the states.
If you are very sure that your system is stable, please double check all 6 state equations, especially on the plus/minus signs. Both human error or publishing error (on the reference) can happen.
It's a very common error. So, no worries. You will find it if you look harder.
Would you tell what the system is? Is it a kind of attractor?
Sam Chak
2022-3-12
Hi @shiv gaur
Have you double checked the mathematical equations of your system? Since you didn't tell us what kind of system it is, and your supplied ODEs have been verified by the ode45 solver, there seems nothing wrong with the program itself. If you are very sure that the system is stable, then my guess is that one or more of the terms in the state equations must be the root cause of the instability.
类别
在 帮助中心 和 File Exchange 中查找有关 Assumptions 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
