Pr4oblem with an ODE 45 " not enough input arguments"

1 次查看（过去 30 天）
Francesco Renzulli
评论： Francesco Renzulli 2021-1-7
I have problem withis system of ode , this is onlya part of the code
N.B I have the latest version of MatLab.
Thanks for your help
Nt=150
m_ox=0.7;
m_ox=m_ox.*ones(1,Nt);
r_dot=0.0006
m_dot_pr=1.7 ;
v_cham=1*10^(3);
m_fuel= 15.*ones(1,Nt);
burn_time=50;
t=linspace(0,burn_time,Nt)
C=((m_dot_fuel+m_ox-m_dot_pr)./(v_cham)) ;
A=((4*r_dot)./Dp_t);
y1_0=zeros(Nt,1);
y1_0=y1_0(:);
t=t(:);
y2_0=rho_ox_0.*ones(1,Nt);
y2_0=y2_0(:);
y_0=[y1_0,y2_0];
[t_sol,y_sol]=ode45(@(t,y1,y2)zero_dmodelcc(C,A,y1,y2,t,v_cham,m_dot_pr,m_ox),t,y_0);
function dy=zero_dmodelcc(C,A,y1,y2,t,v_cham,m_dot_pr,m_ox)
y=[y1;y2];
v_cham=v_cham(:);
m_ox=m_ox(:);
C=C(:);
A=A(:);
dy1 =C-(y1.*A);
dy1=dy1(:);
dy2=((y1.*m_ox)./(v_cham))+y2.*(A-m_dot_pr);
dy2=dy2(:);
dy=[dy1,dy2];
end

请先登录，再回答此问题。

采纳的回答

Bjorn Gustavsson
Bjorn Gustavsson 2021-1-7
Your definition of the ODEs is unconventional. I've always used to define coupled ODEs such that the dependent variables are in one array in the input, not as two separate ones. So, according to my understanding you should modify the zero_dmodelcc function like this:
function dy=zero_dmodelcc(C,A,y1y2,t,v_cham,m_dot_pr,m_ox)
y1 = y1y2(1); % or perhaps y1 = y1y2(1:end/2);
y2 = y1y2(2); % and if so y2 = y1y2(end/2+1:end);
v_cham=v_cham(:);
m_ox=m_ox(:);
C=C(:);
A=A(:);
dy1 =C-(y1.*A);
dy1=dy1(:);
dy2=((y1.*m_ox)./(v_cham))+y2.*(A-m_dot_pr);
dy2=dy2(:);
dy=[dy1(:);dy2(:)]; % Should be a column-vector IIRC
end
Further you somehow define the initial conditions to be of the same size as the time-variable. That doesn't make sense. Something is likely off.

更多回答（1 个）

Cris LaPierre
Cris LaPierre 2021-1-7
The ode solver expects the first two inputs to your odefun should be t and y (you can use any variable name you want, but this is what they represent). They are not defined in the code. Any additional input parameters come after that. Have a look at this example on the ode45 documentation page.
I agree your setup is unconventional. I would add that you use t incorrectly - both as the tspan input, and the odefun t input. Here's how you can modify the code to fix those issues at least.
ts = ts=linspace(0,burn_time,Nt);
y_0=[0,0];
[t_sol,y_sol]=ode45(@(t,y) zero_dmodelcc(t,y,C,A,v_cham,m_dot_pr,m_ox),ts,y_0);
function dy=zero_dmodelcc(t,y,C,A,v_cham,m_dot_pr,m_ox)
y1 = y(1);
y2 = y(2);

类别

在 Help Center 和 File Exchange 中查找有关 Ordinary Differential Equations 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by