Tunable transfer function with fixed number of poles and zeros
blk = ltiblock.tf(name,Nz,Np)
blk = ltiblock.tf(name,Nz,Np,Ts)
blk = ltiblock.tf(name,sys)
Model object for creating tunable SISO transfer function models
of fixed order. ltiblock.tf
lets you parametrize
a transfer function of a given orderfor parameter studies or for automatic
tuning with Robust Control Toolbox™ tuning commands such as systune
or looptune
.
ltiblock.tf
is part of the Control
Design Block family of parametric models. Other Control Design
Blocks includeltiblock.pid
, ltiblock.ss
, and ltiblock.gain
.
creates
the parametric SISO transfer function: blk
= ltiblock.tf(name
,Nz
,Np
)
$$blk=\frac{{a}_{m}{s}^{m}+{a}_{m1}{s}^{m1}+\dots +{a}_{1}s+{a}_{0}}{{s}^{n}+{b}_{n1}{s}^{n1}+\dots +{b}_{1}s+{b}_{0}}.$$
n =
Np
is
the maximum number of poles of blk
, and m =
Nz
is
the maximum number of zeros. The tunable parameters are the numerator
and denominator coefficients a_{0}, ..., a_{m} and b_{0}, ..., b_{n–1}.
The leading coefficient of the denominator is fixed to 1.
creates
a discretetime parametric transfer function with sample time blk
= ltiblock.tf(name
,Nz
,Np
,Ts
)Ts
.
uses
the blk
= ltiblock.tf(name
,sys
)tf
model sys
to
set the number of poles, number of zeros, sample time, and initial
parameter values.

String specifying the 

Nonnegative integer specifying the number of zeros of the parametric
transfer function 

Nonnegative integer specifying the number of poles of the parametric
transfer function 

Scalar sample time. 



Parametrization of the numerator coefficients a_{m}, ..., a_{0} and
the denominator coefficients 1,b_{n–1}, ..., b_{0} of
the tunable transfer function
The following fields of
 

Sample time. For continuoustime models, Changing this property does not discretize or resample the model.
Use Default:  

String representing the unit of the time variable. This property
specifies the units for the time variable, the sample time
Changing this property has no effect on other properties, and
therefore changes the overall system behavior. Use Default:  

Input channel names. Set Alternatively, use automatic vector expansion to assign input
names for multiinput models. For example, if sys.InputName = 'controls'; The input names automatically expand to You can use the shorthand notation Input channel names have several uses, including:
Default: Empty string  

Input channel units. Use Default: Empty string  

Input channel groups. The sys.InputGroup.controls = [1 2]; sys.InputGroup.noise = [3 5]; creates input groups named sys(:,'controls') Default: Struct with no fields  

Output channel names. Set Alternatively, use automatic vector expansion to assign output
names for multioutput models. For example, if sys.OutputName = 'measurements'; The output names automatically expand to You can use the shorthand notation Output channel names have several uses, including:
Default: Empty string  

Output channel units. Use Default: Empty string  

Output channel groups. The sys.OutputGroup.temperature = [1]; sys.InputGroup.measurement = [3 5]; creates output groups named sys('measurement',:) Default: Struct with no fields  

System name. Set Default:  

Any text that you want to associate with the system. Set Default:  

Any type of data you wish to associate with system. Set Default: 
Create a parametric SISO transfer function with two zeros, four poles, and at least one integrator.
A transfer function with an integrator includes a factor of 1/s. Therefore, to ensure that a parametrized transfer function has at least one integrator regardless of the parameter values, fix the lowestorder coeffiecient of the denominator to zero.
blk = ltiblock.tf('tfblock',2,4); % two zeros, four poles blk.den.Value(end) = 0; % set last denominator entry to zero blk.den.Free(end) = 0; % fix it to zero
Create a parametric transfer function, and assign names to the input and output.
blk = ltiblock.tf('tfblock',2,3); blk.InputName = {'error'}; % assign input name blk.OutputName = {'control'}; % assign output name
genss
 hinfstruct
 looptune
 ltiblock.pid
 ltiblock.pid2
 ltiblock.ss
 ltiblock.tf
 systune