Choosing idgrey or idnlgrey Model Object
Grey-box models require that you specify the structure of the ODE model in a file. You use
this file to create the
idnlgrey model object. You can use both the
idgrey and the
idnlgrey objects to model linear systems. However, you can only
represent nonlinear dynamics using the
idnlgrey model object.
idgrey object requires that you write a function to describe the
linear dynamics in the state-space form, such that this file returns the state-space matrices
as a function of your parameters. For more information, see Specifying the Linear Grey-Box Model Structure.
idnlgrey object requires that you write a function or MEX-file to
describe the dynamics as a set of first-order differential equations, such that this file
returns the output and state derivatives as a function of time, input, state, and parameter
values. For more information, see Specifying the Nonlinear Grey-Box Model Structure.
The following table compares
Comparison of idgrey and idnlgrey Objects
|Settings and Operations
|Supported by idgrey?
|Supported by idnlgrey?
|Set bounds on parameter values.
|Handle initial states individually.
|Perform linear analysis.
For example, use the
|Honor stability constraints.
Specify constraints using the
You can use parameter bounds to ensure stability of an
|Estimate a disturbance model.
The disturbance model is represented by
|Optimize estimation results for simulation or prediction.