How can I use ODE45 output to evaluate on each time a function inside a the Odefun

Question

Juan Luis Chacon 2016-5-16

0
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https://ww2.mathworks.cn/matlabcentral/answers/284457-how-can-i-use-ode45-output-to-evaluate-on-each-time-a-function-inside-a-the-odefun

回答： Bob 2016-10-27

Hello to everybody

Actually I already have my Quarter vehicle model done using a second Order differential equation f(x, y, xdot, ydot). And it works very good. Let me show you this.

function yp=comportamiento(t,y)

x=f(t)

yp = zeros(4,1);

yp(1)=y(2);

yp(2)= (-((ks+kt)/mw)*y(1)) -((bs/mw)*y(2)) +((ks/mw)*y(3)) + ((bs/mw)*y(4)) + ((kt/mw)*x);

yp(3)=y(4);

yp(4)= ((ks/mb)*y(1)) +((bs/mb)*y(2)) - ((ks/mb)*y(3)) - ((bs/mb)*y(4));

Applying my ode45 fun

tspan=[0:0.001:10];

y0=zeros(4,1);

[t, y] = ode45('comportamiento',tspan,y0);

Results are good. But now, problem is that I need to use a new function. One that looks like f(x, y, xdot, ydot, m(xdot,ydot)). During the calculation each xdot and ydot correspond to y(i1) and y(i2) generated from ODE45, I will need to call another function m(xdot,ydot) using as input every y(i). In others words I don't know how get those y(i) and how to use the to eval my f(x, y,xdot,ydot, m(xdot,ydot)).

I am sure I will need to open a new fun

function odefun=(y(i1),y(i2))

where do I have to indicate that

y(i1)= xdot;

y(i2)=ydot;

mf=m(xdot,ydot)

end

Regards

J.L