ode求解常微分方程如何获得某个点的数值解

Question

ma xueyi 2022-5-7

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1713815-ode

评论： Dyuman Joshi 2024-1-24

function dx = odefun(t,x)
    ki1= 13.0;
    ki2= 0.0;
    kp11= 3.70e+04;
    kp12= 673;
    kp21= 1.36e+03;
    kp22= 46;
    ktal= 2.5;
    kd= 1.0e-04;
    hp1 = 101500000;
    hp2 = 83000000;
    
dx = zeros(13,1);
dx(1) =ktal.*(x(5)+x(6)).*x(2)-ki1.*x(1).*x(3)-ki2.*x(1).*x(4);
dx(2) =ktal.*x(2).*(x(7)+x(8));
dx(3) =(ki1.*x(1)+kp11.*x(5)+kp21.*x(6)).*x(3);
dx(4) =(ki2.*x(1)+kp12.*x(5)+kp22.*x(6)).*x(4);
dx(5) =ki1.*x(1).*x(3)+kp21.*x(6).*x(3)-kp12.*x(5).*x(4)-(ktal.*x(2)+kd).*x(5);
dx(6) =ki2.*x(1).*x(4)+kp12.*x(5).*x(4)-kp21.*x(6).*x(3)-(ktal.*x(2)+kd).*x(6);
dx(7) =ki1.*x(1).*x(3)+kp11.*x(5).*x(3)+kp21.*(x(8)+x(6)).*x(3)-kp12.*x(7).*x(4)-(ktal.*x(2)+kd).*x(7);
dx(8) =ki2.*x(1).*x(4)+kp22.*x(6).*x(4)+kp12.*(x(7)+x(5)).*x(4)-kp21.*x(8).*x(3)-(ktal.*x(2)+kd).*x(8);
dx(9) =ki1.*x(1).*x(3)+kp11.*(2.*x(7)+x(5)).*x(3)+kp21.*(x(10)+2.*x(8)+x(6)).*x(3)-kp12.*x(9).*x(4)-(ktal.*x(2)+kd).*x(9);
dx(10) =ki2.*x(1).*x(4)+kp22.*(2.*x(8)+x(6)).*x(4)+kp12.*(x(9)+2.*x(7)+x(5)).*x(4)-kp21.*x(10).*x(3)-(ktal.*x(2)+kd).*x(10);
dx(11) =(ktal.*x(2)+kd).*(x(5)+x(6));
dx(12) =(ktal.*x(2)+kd).*(x(7)+x(8));
dx(13) =(ktal.*x(2)+kd).*(x(9)+x(10));
end

clear
clc
tspan=[0,1200];
y0=[2e-5,0.04,0.1524,1.0194,0,0,0,0,0,0,0,0,0];
[T,X] = ode45(@odefun,tspan,y0);
plot(T,X(:,1),'-',T,X(:,2),'-.',T,X(:,3),'.')
legend('x','y','z')
%mex(filename.c,'-compatibleArrayDims')

我的代码如上，但在点击运行后，约10分钟后报错

今天重新跑，运行二十分钟后一直没反应

我的疑问：

1.我的文件是否真的这么大，需要占用这么大数据量

2.网上查到的用例都是绘图，请问十三个未知数如何绘图

3.实际上我不关心过程，只想知道t=1200时，各自变量的数值

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Dyuman Joshi 2024-1-24

I am not sure what you are trying to solve.

Could you please share which equation (or system of equations) you are trying to solve?

I don't see a relation between the error showed and the code posted.

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Answer 1

Varun 2024-1-23

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1713815-ode#answer_1395181

Hey! Here are some things you can try out:

Go to MATLAB -> Preferences -> Workspace -> MATLAB array size limit and set it to 100%.This will help you utilize all the RAM available on your device.
Refer to the following documentation: https://www.mathworks.com/help/matlab/large-files-and-big-data.html. This will guide to a bunch of alternatives supported by MATLAB that you can employ as per your usecase.

Hope this helps!