Define and initialize state-space canonical form model structures.
Syntax
th = canstart(z,orders,nu)
th = canstart(z,orders,nu,dkx)
Description
orders,nu,dkx: These arguments define the state-space model parameterization exactly as for the function canform. In the present case orders can also be taken as a scalar, giving the model order (dimension of state vector). Then a default choice of parameterization is made.
The output th is a matrix in the theta format. It defines a state-space model parameterization according to the arguments orders, nu and dkx. The values of the parameters in th are estimated from the data matrix
z = [y u]
where y is the matrix of output signals, one column for each output, and u is the matrix of input signals, again one column for each input.
Choosing the order indices for many systems is not critical in the sense that most n-th order systems can be described by any set of order (pseudo-observability) indices whose sum is n. See "Model Structure Selection and Validation" on page 3-49 in the User's Guide for more information.
The model th could be further refined by using pem.
Algorithm
The state-space model is first estimated using n4sid, and then transformed to the chosen canonical form using ss2th.
Examples
A system with two inputs and two outputs is estimated with a third order model:
th = canstart(z,3,2);
th = pem(z,th);
resid(z,th);
See Also
canform, pem
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