Trying to use simplify with an equation equal to zero.

I'm sorry if this has been asked previously. I've tried searching and can't seem to find this scenario though I can't imagine I'm the first person to have this issue. Here's the code I'm working with, this is for a control systems problem...

syms s k
sys = k*(s-1)*(s-2)/(s*(s+1));
sysEqn = 1+sys ==0;
routh_func = simplify(sysEqn)

I'm getting the output I want...

Routh Function
                       2    2
  2 k + s - 3 k s + k s  + s  == 0

I want to the extract the coefficients [(1+k,1-3k,2k)] to be used with a Routh function. The problem I'm running in to is that the "== 0" needs to be removed and is stopping me from using something like this...

routh_coeffs = coeffs(routh_func)
syms epsilon
RA = routh(routh_coeffs,epsilon)

To discern the routh table. Yes I know routh isn't a built in function, credit to Author:Rivera-Santos, Edmundo J. E-mail:[e-mail]. For the routh function (downloaded from these forums!).

Any help would be greatly appreciated. Thank you!

Answer 1

[Star Strider]

The Symbolic Math Toolbox assumes zero, so it’s not necessary to state it explicitly.

This will get you the coefficients:

syms s k
sys = k*(s-1)*(s-2)/(s*(s+1));
sysEqn = 1+sys;
[routh_func,den] = numden(sysEqn)
routh_coeffs = coeffs(routh_func, s)

[ch]

This worked perfectly, thank you!!!

[Star Strider]

My pleasure!

I admire your courage in tackling classical control problems!