Question

我正在寻找在满足特定条件时终止MATLAB ode的方法。我在本主题MatLab ODE start/stop conditions中找到了答案，其中讨论了“事件”的使用。但这适用于ode45，当我尝试使用ode15i的'events'时，它根本不起作用，MATLAB显示错误。

我试图用简单的例子来学习这个，并解决了一个简单的微分方程系统，如下所示。

dx / dt = 5x + 3y; dy / dt = x + 7y;我用ode45解决了它们，并尝试用ode15i做同样的事情，但它不起作用。以下是我的代码。

使用ode45

    function start_stop_test_ode45
    y0 = [5;1];
    tv = linspace(0,2,100);
    options = odeset('Events',@events);    
    f = @(t,y) [5*y(1) + 3*y(2);y(1) + 7*y(2)];
    [t,Y] = ode45(f,tv,y0,options);
    xNI = Y(:,1);
    yNI = Y(:,2);
    xCF   =  3*exp(4*t) + 2*exp(8*t);
    yCF   = -1*exp(4*t) + 2*exp(8*t);
    % Here we plot all the graphs
    figure(1)
    plot(t,xNI,'--k',t,xCF,'r','Linewidth',1.75)
    xlabel('t (s)')
    ylabel('x')
    legend('Numerical Solution','Closed Form Solution')
    figure(2)
    plot(t,yNI,'--k',t,yCF,'r','Linewidth',1.75)
    xlabel('t (s)')
    ylabel('y')
    legend('Numerical SOlution','Closed Form Solution')
    % Here we solve plot the variation of x with y
    figure(3)
    plot(xNI,yNI,'k','Linewidth',2);
    end

    function [value,isterminal,direction] = events(t,y)
    value = [y(1) - 7782;y(2) - 8863];  % Detect y = 7356
    isterminal = [1;1];
    direction = [0;0];
    end

使用ode15i

    function start_stop_test_ode15i
    clc;clear all
    t0 = 0;
    y0 = [5;1];
    Fxdy0 = [1;1];
    Fxdyp0 = [0;0];
    yp0 = [28;12];
    tRange = [0 2];
    options = odeset('Events',@events);
    [y0,yp0] = decic(@ode15ifun,t0,y0,Fxdy0,yp0,Fxdyp0);
    sol = ode15i(@ode15ifun,tRange,y0,yp0,options);
    tv = linspace(0,2,100);
    sv = deval(sol,tv);
    sv = sv';
    t = tv;
    xNI = sv(:,1);
    yNI = sv(:,2);
    xCF   =  3*exp(4*t) + 2*exp(8*t);
    yCF   = -1*exp(4*t) + 2*exp(8*t);
    % Here we plot all the graphs
    figure(4)
    plot(t,xNI,'--k',t,xCF,'r','Linewidth',1.75)
    xlabel('t (s)')
    ylabel('x')
    legend('Numerical Solution','Closed Form Solution')
    figure(5)
    plot(t,yNI,'--k',t,yCF,'r','Linewidth',1.75)
    xlabel('t (s)')
    ylabel('y')
    legend('Numerical SOlution','Closed Form Solution')
    % Here we solve plot the variation of x with y
    figure(6)
    plot(xNI,yNI,'k','Linewidth',2);
    end

    function [value,isterminal,direction] = events(t,y)
    value = [y(1) - 7782;y(2) - 8863];  % Detect y = 7356
    isterminal = [1;1];
    direction = [0;0];
    end

ode15ifun

    function res = ode15ifun(t,y,yp)
    %UNTITLED3 Summary of this function goes here
    %   Detailed explanation goes here
        res1 = yp(1) - 5*y(1)- 3*y(2);
        res2 = yp(2) - y(1) - 7*y(2);
        res  = [res1;res2];
    end

ode45工作正常但在使用ode15i时我收到错误消息。任何人都可以帮助如何使用ode15i做同样的事情？

非常感谢

（响应TroyHaskin）我正在添加错误消息的图像文件供您参考。

ode15i

0 个答案: