I don't understand what is going wrong with my code!!, I get error of a matrix singular

1 次查看（过去 30 天）

ouahid lakhal 2018-12-30

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/437701-i-don-t-understand-what-is-going-wrong-with-my-code-i-get-error-of-a-matrix-singular

评论： Stephan 2019-1-2

function  dy = rocketequat( t,y )
%UNTITLED6 Summary of this function goes here
g=9.81; % constant of gravity m/s^2
Ve=2800;%celerity of inject gas m/s
m0=500000;%initial mass =500000kg
dmdt=-2300;%kg/s
dy(1)= -g*sin(y(2)) - Ve * dmdt/( m0 - dmdt*t );%dy(1)=dvdt acceleration
dy(2)= ( g/y(1) )*cos( y(2) ); %dy(2)=dbetadt variation in angle of inclination
end
%in a script i wrote
[t,y]=ode23s(@rocketequat,[0 160],[0 pi/2]);
% i gut this message:
In rocket (line 1) 
Warning: Matrix is singular, close to singular or badly scaled. Results may be inaccurate. RCOND = NaN. 

3 个评论
显示 1更早的评论隐藏 1更早的评论

Stephan 2018-12-30

Please accept useful answers.

ouahid lakhal 2018-12-30

capture 2.PNG

sorry i tried .

请先登录，再进行评论。

请先登录，再回答此问题。

回答（1 个）

Stephan 2018-12-30

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/437701-i-don-t-understand-what-is-going-wrong-with-my-code-i-get-error-of-a-matrix-singular#answer_354441

编辑：Stephan 2018-12-30

在 MATLAB Online 中打开

Hi,

you do a divide by zero at the initial point - use another x0 for y(1) - for example try:

[t,y]=ode45(@rocketequat,[0 160],[0.0001 pi/2]);
plot(t,y(:,1),t,y(:,2))
function  dy = rocketequat(t,y)
%UNTITLED6 Summary of this function goes here
g=9.81; % constant of gravity m/s^2
Ve=2800;%celerity of inject gas m/s
m0=500000;%initial mass =500000kg
dmdt=-2300;%kg/s
dy(1)= -g.*sin(y(2)) - Ve .* dmdt./( m0 - dmdt*t );%dy(1)=dvdt acceleration
dy(2)= ( g./y(1) ).*cos( y(2) ); %dy(2)=dbetadt variation in angle of inclination
dy=dy';
end