How to pass values from one ode to another ode?

Question

Deepana 2013-2-10

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/62879-how-to-pass-values-from-one-ode-to-another-ode

I av to use the results of one ode(ode45) inside another ode... here is my code:

1st ode function

function dw=sd(t,w)
 va=10;
vb=0;vc=0;
%MOMENT OF INERTIA IN PRINCIPAL AXIS
I1=27;
I2=17;
I3=25;
%DIFFERENTIAL EQUATIONS 
dw(1,1)= ((I2-I3)/I1)*w(2)*w(3)+(va/I1);
dw(2,1)=((I3-I1)/I2)*w(1)*w(3)+(vb/I2);
dw(3,1)=((I1-I2)/I3)*w(1)*w(2)+(vc/I3);

function cal

[t,W]=ode45('sd',[tinit tfinal],[0;0;0]);

i av use the results of these in another ode function below

function dq=sk(t,q,w1,w2,w3)
dq(1,1)=0.5*(w3*q(2)-w2*q(3)+w1*q(4));
dq(2,1)=0.5*(-w3*q(1)+w1*q(3)+w2*q(4));
dq(3,1)=0.5*(w2*q(1)-w1*q(2)+w3*q(4));
dq(4,1)=0.5*(-w1*q(1)-w2*q(2)+w3*q(3));
end

function cal

[t,Q]=ode45('sk',[tinit tfinal],[0;1;0;0],W(:,1),W(:,2),W(:,3))

there s some error in passing as shown aabove

any suggestion pl?

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Answer 1

ChristianW 2013-2-10

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Write all equations in 1 function and make your state vector like this: 'x = [w;q]'. Tell me, if you need more details.

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Deepana 2013-2-16

Thanku so much. I got it.

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Answer 2

the cyclist 2013-2-10

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在 MATLAB Online 中打开

When you call ode45() the second time, with the function 'sk', you are calling it with 4 input arguments, but I don't think you've got the input structure correct.

If you run your code after first having done

>> dbstop if error

you will see that your W(:,1) vector is being interpreted by ode45() as the options input.