getting error while using feedback

syms s d e

y=((0.005659*s^2+0.05206*s+0.004496)/(s^3+9.357*s^2+2.228*s+0.06147))*((27.5084*d)+(27.5084*(e/s)))

using feedback(y,1,-1) is giving me a error, what is wrong here

Answer 1

[Jesús Zambrano]

You need to work with model objects, they must be either continuous os discrete with identical sample times.

Here, please read the documentation about the command feedback, which also includes some examples:

https://www.mathworks.com/help/releases/R2021a/control/ref/lti.feedback.html

Hope it helps!

[bhanu kiran vandrangi]

ok, but if my input for feedback is matrix then how to use feedback in matlab

Answer 2

[Paul]

The Control System Toolbox does not support operations on sym objects. Having siad that, the error message that I'm seeing is fairly opaque, something about "not enough input arguments," which isn't very helpful.

Answer 3

[VBBV]

%if true
  K1 = tf([0.005659 0.05206 0.004496],[1 9.357 2.228 0.06147])
K2 = tf([0 0 27.5084 0],[0 0 27.5084 0])
feedback(K1,K2,1)

Try something like above. Split the function to two TF and apply feedback

[Paul]

Wow. When I read read the question, it never occured to me that e and d are signals, as opposed to unquantifed parameters. Having said that I think that K2 should be:

K2 = tf(27.5084,[1 0]);

And K2 should be in the forward path, not the feedback path? And sitll need to account for the disturbance input, d.