how to add feedback in matlab ?

hello

I want to add feedback in code, means output is feeding back to input , how should i do this ? i am plotting output by using summation,

Is the code is correct means any other suggestions ?

"sum_out = Y(:,3)+Y(:,6)"

the system is as following

code

***************

function

****************

function dz = myeqd(t,y,ti,xx)

dz = zeros(6,1);

mu = 0.3;

r= sqrt(y(1)^2 + y(2)^2);

K1=500;

K2 = 500;

F=interp1(ti,xx,t);

%osc1

dz(1)= (mu - r^2)*y(1) - y(3)*y(2) +K1.*F;

dz(2) = (mu - r^2)*y(2) + y(3)*y(1);

dz(3) = (-K1.*F) * (y(2)/sqrt(y(1)^2 + y(2)^2));

%osc2

dz(4)= (mu - r^2)*y(4) - y(6)*y(5) +K2.*F;

dz(5) = (mu- r^2)*y(5) + y(6)*y(4);

dz(6) = (-K2.*F) * (y(5)/sqrt(y(4)^2 + y(5)^2));

**************************************

main code

***************************

time = 0:0.001:20;

xx = chirp(time,100,10,400,'linear');

ti=time;

[T,Y]=ode45(@(t,y) myeqd(t,y,ti,xx),time,[5;5;90;5;5;90]);

sum_out = Y(:,3)+Y(:,6);

plot (T,sum_out)

Answer 1

[Jan]

As usual I want to stress, that ODE45 is designed for smooth function, but F=interp1(ti,xx,t); is not smooth. Here the changes are at least continuous, in opposite to many other examples you can find in this forum.

See e.g. http://www.mathworks.com/matlabcentral/answers/59582#answer_72047 for a description, why ODE45 can produce either bad or no results for such functions.

[Aniket]

thanks Jan

but instead of ODE45 , which ODE solvers are there ? which is suitable to solve this problem ?

[ChristianW]

Continuous changes, what do you mean? Smooth inputs with a converter, measurement cards, digital inputs, static friction etc?

[Jan]

There is no Matlab solver, which can handle non-smooth RHS. I've added some references at the linked page.