observer, ss seems not to work

Hi.

I have to build a observer with the following form:

 x'= A^*x^ + b*u + b^*cT*x

the command ss seems not to work, can you suggest me another command?

[Andrew Newell]

Why do you say it seems not to work? What are you expecting to see and what are you getting?

Answer 1

[Paulo Silva]

ss Specifies state-space models or convert LTI models to state space, there's nothing saying that it creates observers, you got the observer formula already so you just need the values for those variables (arrays) and get x' from them, if you are using simulink you should use a matlab function block and insert that expression in a function (m file).

Here's one example of one observer (corrector in this case) function.

function estim = obs_cor(in)
global PHI GAMMA C x_ob Kzec ;
uk = in(1); %
yk = in(2); %
x_ob = PHI * x_ob + GAMMA * uk + Kzec * (yk - C * (PHI * x_ob + GAMMA * uk));
estim = x_ob;

Please read the book Computer-Controlled Systems by Astrom