SI Transfer Function Estimation Express VI

System Identification VIs

SI Transfer Function Estimation Express VI

Owning Palette: Parametric Model Estimation VIs

Installed With: System Identification Toolkit

Estimates a discrete or continuous transfer function model for a SISO unknown system. For discrete models, this VI supports the direct, indirect, and joint input-output identification methods.

Dialog Box Options
Block Diagram Inputs
Block Diagram Outputs
 Place on the block diagram  Find on the Functions palette

Dialog Box Options

ParameterDescription
SignalsDisplays the signals used to estimate the system, including the stimulus signal, reference signal, response signal, and estimated response signal.
Data typeSpecifies the data type for the input signal(s). Contains the following options:
  • Waveform (default)
  • Array
Model typeSpecifies the type of model to estimate. Contains the following options:
  • Continuous
  • Discrete (default)
Numerator orderSpecifies the order of the numerator of the system model.
Denominator orderSpecifies the order of the denominator of the system model.
Estimation methodSpecifies the estimation method to use for discrete systems. Contains the following options:
  • Direct (default)
  • Indirect
  • Joint input-output
Controller numeratorSpecifies the numerator coefficients of the discrete, linear controller.
Controller denominatorSpecifies the denominator coefficients of the discrete, linear controller.
Controller structureSpecifies the controller position in the feedback loop. If the controller is set before the plant, select Feedforward-path. If the controller is set after the output, select Feedback-path.
Zero-Pole cancellation toleranceDetermines zero-pole cancellations. If the difference between the location of a pole and a zero is within the tolerance, this VI removes the zero-pole pair.
System diagramDisplays the system diagram of the closed-loop system.
Estimated modelDisplays the mathematical equation and sampling rate of the estimated transfer function model.

Block Diagram Inputs

ParameterDescription
stimulus signalSpecifies the input waveform or array of a stimulus signal.
reference signalSpecifies the input waveform or array of a reference signal.
response signalSpecifies the input waveform or array of a response signal.
sampling rateSpecifies the sampling frequency in hertz. For discrete models, sampling rate is the system sampling rate. For continuous models, sampling rate is used to convert the continuous model to a discrete model before simulating the output.
error in (no error)Describes error conditions that occur before this VI or function runs.

Block Diagram Outputs

ParameterDescription
system model outsystem model out returns information about the model structure, nominal or estimated parameters, identification result, and so on. Use the Model Management VIs to retrieve the information system model out contains.
Note  You can use a customized system model probe to view model information that flows through system model wires when you debug a block diagram created with the System Identification VIs. Right-click a system model wire and select Custom Probe»SI System Model from the shortcut menu to use the system model probe.
coefficientsReturns the coefficients of the transfer function (TF) model. Contains the following elements:
  • numerator—returns the estimated numerator coefficients of the transfer function.
  • denominator—returns the estimated denominator coefficients of the transfer function.
continuous delayReturns the estimated delay of the continuous system in seconds.
error outContains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces.

This Express VI operates similarly to the following VIs and functions:

SI Estimate Transfer Function Model