README.md

ControlSystemIdentification

System identification for ControlSystems.jl, implemented in Julia.

This package estimates linear statespace models with inputs on the form

$$\begin{aligned} x^+ &= Ax + Bu + Ke\\\ y &= Cx + Du + e \end{aligned}$$

using methods such as N4SID or the prediction-error method, transfer functions on the form

$$G(z) = \dfrac{B(z)}{A(z)} = \dfrac{b_m z^m + \dots + b_0}{z^n + a_{n-1} z^{n-1} + \dots + a_0}$$

as well as generic nonlinear graybox models

$$x^+ = f(x, u)$$

See the documentation for help.

Examples in the form of jupyter notebooks are provided here.

Quick example:

using ControlSystemIdentification, ControlSystemsBase
Ts = 0.1
G  = c2d(DemoSystems.resonant(), Ts) # A true system to generate data from
u  = randn(1,1000)                   # A random input
y  = lsim(G,u).y                     # Simulated output
y .+= 0.01 .* randn.()               # add measurement noise
d  = iddata(y, u, Ts)                # package data in iddata object
sys = subspaceid(d, :auto)           # estimate state-space model using subspace-based identification
bodeplot([G, sys.sys], lab=["True" "" "n4sid" ""])