Use N4sid for system identification (for new data estimation)

Hi,

I am using N4sid toolbox to do a system identification problem. I used the command: "m = n4sid(z, 5,'Form','free', opt);" to create the system based on measured "input" and "output" (contains in z=z = iddata(y', u', 0.2, 'Name', 'heating/cooling load', 'TimeUnit', 's');".

However,I still want to use this model to predict some unmeasured cases. To be more specific, I have a new input measurement U2, I want to used to model to predict the output from U2. How can I realize that? What is command for this estimation using the model from N4sid?

Thanks very much.

Answer 1

[Rajiv Singh]

Computing response of a model to a given input is called simulation. Use the idParametric/sim command for that as in:

 Ud = iddata([], U2, .2);
 Yd = sim(m, Ud);
 Y2 = Yd.y; % the raw response data

See:

http://www.mathworks.com/help/ident/ref/sim.html

http://www.mathworks.com/help/ident/ref/findstatesidparametric.html

[Xiwang]

Thanks very much. Rajiv. Another questions. If I use "ident" tool, and use the "state space model" to train the model, how can I code it in my "mfile"? And how can I apply the model to simulate the new data.

Thanks again.

Xiwang Li