Can't use laplace transformed expression with transfer function.

When i laplace transform my expression ('r2') it becomes "sym" and i cant use it with any system or transfer function in the 's'-domain.

('r1') is numerically equivalent, but declared manually. it works fine.

Is there a way to make Laplace transforms become "tf"?

Answer 1

[Rohit Pappu]

A plausible solution is as follows

% Collect the coefficients of r2
h = collect(r2);
% Split the coefficients into numerator and denominator
[ii,jj] = numden(h);
% Convert the coefficients into numerical values
num = sym2poly(ii);
den = sym2poly(jj);
% Generate Transfer function from the above coefficients
model= tf(num,den);

[Walter Roberson]

There can be additional work needed if there is a delay on the system. That shows up as an exp() term symbolically.

[Håvard Kalliainen]

Not simple, but it did work! thanks guys!