FileName

Name of the function or MEXfile storing the model structure,
specified as a character vector (without extension) or a function
handle for computing the states and the outputs. If FileName is
a character vector, for example 'twotanks_c' , then
it must point to a MATLAB file, Pcode file, or MEXfile. For
more information about the file variables, see Specifying the Nonlinear GreyBox Model Structure.

Order

Number of outputs, inputs, and states of the model, specified
as one of the following:
Vector [Ny Nu Nx] , specifying the
number of model outputs Ny , inputs Nu ,
and states Nx . Structure with fields'Ny' , 'Nu' ,
and 'Nx' .
For time series, Nu is set to 0 ,
and for static model structures, Nx is set to 0 .

Parameters

Parameters of the model, specified as one of the following:
Np by1 structure array, where Np is
the number of parameters. The structure contains the following fields:
Field  Description  Default 

Name  Name of the parameter, specified as a character vector. For
example, 'pressure' .  'pi' , where i is an integer
in [1,Np]  Unit  Unit of the parameter, specified as a character vector.  ''  Value 
Initial value of the parameter, specified as:
  Minimum 
Minimum value of the parameter, specified as a real scalar, column vector,
or matrix of the same size as Value .
Minimum >= Value for all
components.
 Inf(size(Value))  Maximum 
Maximum value of the parameter, specified as a real scalar, column vector,
or matrix of the same size as Value .
Value <= Maximum for all
components.
 Inf(size(Value))  Fixed  Specifies whether parameter is fixed to their initial values,
specified as a boolean scalar, column vector, or matrix of the same
size as Value . 
false(size(Value))
Implies, estimate all parameters

Np by1 vector of real finite initial
values, InParameters .
The data is converted into a structure with default values for
the fields Name , Unit , Minimum , Maximum ,
and Fixed . Value is assigned the value InParameters(i) ,
where i is an integer in [1,Np]
Np by1 cell array containing finite
real scalars, finite real vectors, or finite real twodimensional
matrices of initial values.
A structure is created with default values for the fields Name , Unit , Minimum , Maximum ,
and Fixed .
Use dot notation to access the subfields of the i th
parameter. For example, for idnlgrey model M ,
the i th parameter is accessed through M.Parameters(i) and
its subfield Fixed by M.Parameters(i).Fixed .

InitialStates

Initial states of the model parameters specified as one of the
following:
Nx by1 structure array, where Nx is
the number of states. The structure contains the following fields:
Field  Description  Default 

Name  Name of the states, specified as a character vector.  'xi' , where i is an integer
in [1,Nx]  Unit  Unit of the states, specified as a character vector.  ''  Value 
Initial value of the initial states, specified as:
  Minimum 
Minimum value of the initial states, specified as a real scalar or
1byNe vector of the same size as
Value .
Minimum >= Value for all
components.
 Inf(size(Value))  Maximum 
Maximum value of the parameters, specified as a real scalar or
1byNe vector of the same size as
Value .
Value <= Maximum for all
components.
 Inf(size(Value))  Fixed  Specifies whether initial states are fixed to their initial
values, specified as boolean scalar or 1byNe vector
of the same size as Value 
true(size(Value))
Implies, do not estimate the initial states.

[] .
A structure is created with default values for the fields Name , Unit , Minimum , Maximum ,
and Fixed . Value is assigned the value 0 .
A real finite Nx byNe matrix
(InitStates ). Value of the i th structure
array element is InitStates(i,Ne) , a row vector
with Ne elements. Minimum , Maximum ,
and Fixed will be Inf , Inf and true row
vectors of the same size as InitStates(i,Ne) .
Cell array with finite real vectors of size 1byNe or {} (same
as [] ). A structure is created with default values for the fields Name , Unit , Minimum , Maximum ,
and Fixed .
Use dot notation to access the subfields of the i th
initial state. For example, for idnlgrey model M ,
the i th initial state is accessed through M.InitialStates(i) and
its subfield Fixed by M.InitialStates(i).Fixed .

FileArgument

Contains auxiliary variables passed to the ODE file (function
or MEXfile) specified in FileName , specified as
a cell array. These variables are used as extra inputs for specifying
the state and/or output equations.
Default: {} .

SimulationOptions

A structure that specifies the simulation method and related
options, containing the following fields:
Field  Description  Default 

AbsTol  Absolute error tolerance. This scalar applies to all components of the state vector.
Applicable to: Variable step solvers.
Assignable value: A positive real value.  1e6  FixedStep  Step size used by the solver.
Applicable to: Fixedstep timecontinuous
solvers.
Assignable values: 
'Auto'
Automatically chooses the initial step.
 InitialStep  Specifies the initial step at which the ODE solver starts.
Applicable to: Variablestep, timecontinuous
solvers.
Assignable values: 
'Auto'
Automatically chooses the initial step.
 MaxOrder  Specifies the order of the Numerical Differentiation Formulas (NDF).
Applicable to: ode15s.
Assignable values: 1, 2, 3, 4 or 5.  5  MaxStep  Specifies the largest time step of the ODE solver.
Applicable to: Variablestep, timecontinuous
solvers.
Assignable values: 
'Auto'
Automatically chooses the time step.
 MinStep  Specifies the smallest time step of the ODE solver.
Applicable to: Variablestep, timecontinuous
solvers.
Assignable values: 
'Auto'
Automatically chooses the time step.
 RelTol  Relative error tolerance that applies to all components of the state vector. The estimated
error in each integration step satisfies e(i)
<= max(RelTol*abs(x(i)),
AbsTol(i)) .
Applicable to: Variablestep, timecontinuous
solvers.
Assignable value: A positive real value. 
1e3
(0.1% accuracy).
 Solver  ODE (Ordinary Differential/Difference Equation) solver for solving state space
equations. Variablestep solvers for timecontinuous idnlgrey models: 'ode45' — RungeKutta (4,5)
solver for nonstiff problems.
'ode23' — RungeKutta (2,3)
solver for nonstiff problems.
'ode113' — AdamsBashforthMoulton
solver for nonstiff problems.
'ode15s' — Numerical Differential
Formula solver for stiff problems.
'ode23s' — Modified Rosenbrock
solver for stiff problems.
'ode23t' — Trapezoidal solver
for moderately stiff problems.
'ode23tb' — Implicit RungeKutta
solver for stiff problems.
Fixedstep solvers for timecontinuous idnlgrey models: 'ode5' — DormandPrince
solver.
'ode4' — Fourthorder RungeKutta
solver.
'ode3' — BogackiShampine
solver.
'ode2' — Heun or improved
Euler solver.
'ode1' — Euler solver.
Fixedstep solvers for timediscrete idnlgrey models: 'FixedStepDiscrete' General: 'Auto' — Automatically
chooses one of the previous solvers.

'Auto'
Automatically chooses one of the solvers.


Report

Summary report that contains information about the estimation
options and results when the model is estimated using the nlgreyest command.
Use Report to query a model for how it was estimated,
including:
The contents of Report are irrelevant if
the model was created by construction.
If you use nlgreyest to
estimate the model, the fields of Report contain
information on the estimation data, options, and results.
load(fullfile(matlabroot,'toolbox','ident','iddemos','data','dcmotordata'));
z = iddata(y,u,0.1,'Name','DCmotor');
nlgr = idnlgrey('dcmotor_m',[2,1,2],[1;0.28],[0;0],0,'Name','DCmotor');
nlgr = nlgreyest(z,nlgr);
nlgr.Report.OptionsUsed
Option set for the nlgreyest command:
GradientOptions: [1x1 struct]
EstCovar: 1
Display: 'off'
Regularization: [1x1 struct]
SearchMethod: 'auto'
SearchOption: [1x1 idoptions.search.lsqnonlin]
OutputWeight: []
Advanced: [1x1 struct]
Report is a readonly property.
For more information on this property and how to use it, see Output Arguments in
the nlgreyest reference page
and Estimation Report.

TimeVariable

Independent variable for the inputs, outputs, and—when
available—internal states, specified as a character vector.
Default: 't' 
NoiseVariance

Noise variance (covariance matrix) of the model innovations e.
Assignable value is an ny byny matrix.
Typically set automatically by the estimation algorithm.

Ts

Sample time. Ts is a positive scalar representing
the sampling period. This value is expressed in the unit specified
by the TimeUnit property of the model. For a continuous
time model, Ts is equal to 0 (default).
Changing this property does not discretize or resample the model.
Default: 0 
TimeUnit

Units for the time variable, the sample time Ts ,
and any time delays in the model, specified as one of the following
values: 'nanoseconds'
'microseconds'
'milliseconds'
'seconds'
'minutes'
'hours'
'days'
'weeks'
'months'
'years'
Changing this property has no effect on other properties, and
therefore changes the overall system behavior. Use chgTimeUnit to convert between time
units without modifying system behavior.
Default: 'seconds' 
InputName

Input channel names, specified as one of the following:
Character vector — For singleinput models,
for example, 'controls' . Cell array of character vectors — For multiinput
models.
Alternatively, use automatic vector expansion to assign input
names for multiinput models. For example, if sys is
a twoinput model, enter:
sys.InputName = 'controls';
The input names automatically expand to {'controls(1)';'controls(2)'} .
When you estimate a model using an iddata object, data ,
the software automatically sets InputName to data.InputName .
You can use the shorthand notation u to refer
to the InputName property. For example, sys.u is
equivalent to sys.InputName .
Input channel names have several uses, including:
Identifying channels on model display and plots Extracting subsystems of MIMO systems Specifying connection points when interconnecting
models
Default: '' for all input channels 
InputUnit

Input channel units, specified as one of the following:
Character vector — For singleinput models,
for example, 'seconds' . Cell array of character vectors — For multiinput
models.
Use InputUnit to keep track of input signal
units. InputUnit has no effect on system behavior.
Default: '' for all input channels 
InputGroup

Input channel groups. The InputGroup property
lets you assign the input channels of MIMO systems into groups and
refer to each group by name. Specify input groups as a structure.
In this structure, field names are the group names, and field values
are the input channels belonging to each group. For example:
sys.InputGroup.controls = [1 2];
sys.InputGroup.noise = [3 5];
creates input groups named controls and noise that
include input channels 1, 2 and 3, 5, respectively. You can then extract
the subsystem from the controls inputs to all outputs
using:
Default: Struct with no fields 
OutputName

Output channel names, specified as one of the following:
Character vector — For singleoutput models.
For example, 'measurements' . Cell array of character vectors — For multioutput
models.
Alternatively, use automatic vector expansion to assign output
names for multioutput models. For example, if sys is
a twooutput model, enter:
sys.OutputName = 'measurements';
The output names automatically expand to {'measurements(1)';'measurements(2)'} .
When you estimate a model using an iddata object, data ,
the software automatically sets OutputName to data.OutputName .
You can use the shorthand notation y to refer
to the OutputName property. For example, sys.y is
equivalent to sys.OutputName .
Output channel names have several uses, including:
Identifying channels on model display and plots Extracting subsystems of MIMO systems Specifying connection points when interconnecting
models
Default: '' for all output channels 
OutputUnit

Output channel units, specified as one of the following:
Character vector — For singleoutput models.
For example, 'seconds' . Cell array of character vectors — For multioutput
models.
Use OutputUnit to keep track of output signal
units. OutputUnit has no effect on system behavior.
Default: '' for all output channels 
OutputGroup

Output channel groups. The OutputGroup property
lets you assign the output channels of MIMO systems into groups and
refer to each group by name. Specify output groups as a structure.
In this structure, field names are the group names, and field values
are the output channels belonging to each group. For example:
sys.OutputGroup.temperature = [1];
sys.InputGroup.measurement = [3 5];
creates output groups named temperature and measurement that
include output channels 1, and 3, 5, respectively. You can then extract
the subsystem from all inputs to the measurement outputs
using:
Default: Struct with no fields 
Name

System name, specified as a character vector. For example, 'system_1' .
Default: '' 
Notes

Any text that you want to associate with the system, stored as a string or a cell array of
character vectors. The property stores whichever data type you
provide. For instance, if sys1 and
sys2 are dynamic system models,
you can set their Notes properties as
follows:
ans =
"sys1 has a string."
ans =
1×1 cell array
{'sys2 has a character vector.'}
Default: [0×1 string] 
UserData

Any type of data you want to associate with system, specified
as any MATLAB data type.
Default: [] 