modstruc (System Identification Toolbox)

Define state-space structure with unknown elements.

ms = modstruc(A,B,C,D,K)
ms = modstruc(A,B,C,D,K,x0)

Description

modstruc is, like canform, a function that defines model parameterizations in state-space form, which are used in ms2th to create model structures in the theta format. The only use of the resulting matrix ms is as an input to ms2th.

The model considered is in state-space form:

The function applies both to the continuous and discrete-time cases; which one is determined only when the structure is formed with ms2th.

The input arguments A, B, C, D, K, and x0 are the matrices of the above state-space model. Numerical values in these matrices indicate fixed (known) entries, while the symbol NaN marks an element that is not known and you need to estimate.

The default value of the initial state vector x0 is the zero vector, but it may also contain parameters you need to estimate.

Examples

Define a continuous-time model structure in diagonal form with the two
(real) poles and the numerator unknown:

A = [NaN,0;0,NaN];
B = [NaN;NaN];
C = [1,1];
D = 0;
K = [0;0];
ms = modstruc(A,B,C,D,K)
th = ms2th(ms,'c');