# CD Construct Transfer Function Model (Control Design Toolkit)

LabVIEW Control Design Toolkit 3.0 Help
August 2007

NI Part Number:
370853D-01

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Creates a transfer function representation of a system using the Sampling Time (s), Numerator, Denominator, and Delay. This VI also produces a transfer function model which specifies the data in symbolic form. You can use this polymorphic VI to create a single-input single-output (SISO), SISO Symbolic, multiple-input multiple-output (MIMO), or MIMO Symbolic transfer function model. You must manually select the polymorphic instance to use.

Use the pull-down menu to select an instance of this VI.

 Select an instance CD Construct Transfer Function Model (SISO)CD Construct Transfer Function Model (SISO Symbolic)CD Construct Transfer Function Model (MIMO)CD Construct Transfer Function Model (MIMO Symbolic)

## CD Construct Transfer Function Model (SISO)

Sampling Time (s) defines whether the model represents a continuous-time system or a discrete-time system. If the model represents a continuous-time system, Sampling Time (s) must equal zero. If the model represents a discrete-time system, Sampling Time (s) must be greater than zero and equal to the sampling rate, in seconds, of the discrete system. The default is 0.
 Note  If you use the inputs to create a continuous-time system, setting the Sampling Time (s) to a value greater than zero does not yield the discrete-time equivalent of the system. You must use the CD Convert Continuous to Discrete VI to convert the continuous-time system to the discrete-time equivalent of the system.
Numerator contains the constant coefficients, in ascending order, of a polynomial that represents the numerator of a SISO transfer function. The coefficients take the following form: b0 + b1s + ... +bmsm.
Denominator contains the constant coefficients, in ascending order, of a polynomial that represents the denominator of a SISO transfer function. The coefficients take the following form: a0 + a1s + ... +ansn.
Delay is the transport time delay that might exist in the system. Refer to the LabVIEW Control Design Toolkit User Manual for more information about delays.
error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node.
 status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE. code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
Transfer Function Model is the system model this VI creates. When the sampling time is zero (for continuous-time), the Numerator and Denominator collectively represent the mathematical model (in Laplace transformation) of a dynamic system H(s) that provides the relationship between the input U(s) and output Y(s) of the system. To access and modify the data in the model, use the Model Information VIs.
error out contains 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. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error.
 status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

## CD Construct Transfer Function Model (SISO Symbolic)

Sampling Time (s) defines whether the model represents a continuous-time system or a discrete-time system. If the model represents a continuous-time system, Sampling Time (s) must equal zero. If the model represents a discrete-time system, Sampling Time (s) must be greater than zero and equal to the sampling rate, in seconds, of the discrete system. The default is 0.
 Note  If you use the inputs to create a continuous-time system, setting the Sampling Time (s) to a value greater than zero does not yield the discrete-time equivalent of the system. You must use the CD Convert Continuous to Discrete VI to convert the continuous-time system to the discrete-time equivalent of the system.
Symbolic Numerator is the symbolic representation of the constant coefficients of a polynomial that represent the numerator of a SISO transfer function. The ith element of Symbolic Numerator is the coefficient of the ith order term of the polynomial. The index is zero-based.
Symbolic Denominator is the symbolic representation of the constant coefficients of a polynomial that represent the denominator of a SISO transfer function. The ith element of Symbolic Denominator is the coefficient of the ith order term of the polynomial. The index is zero-based.
Symbolic Delay is the symbolic representation of the transport time delay that may exist in the system. Refer to the LabVIEW Control Design Toolkit User Manual for more information about delays.
error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node.
 status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE. code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
Variables contains the name and value of each variable.
 Name is a variable name this VI uses to define the data of the system model. Variable names can be a combination of letters and numbers. A variable name that begins with a capital letter E can produce unpredictable errors if parts of the original string represent numbers like 1E–2. Avoid terms beginning with E in such cases. Value is the numeric value this VI associates with the variable. The VI uses this value to evaluate the model.
Transfer Function Model is the numeric model that this VI evaluates using data from Variables. This VI converts empty array elements into numeric zeros. To access and modify the data in the model, use the Model Information VIs.
error out contains 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. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error.
 status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

## CD Construct Transfer Function Model (MIMO)

Sampling Time (s) defines whether the model represents a continuous-time system or a discrete-time system. If the model represents a continuous-time system, Sampling Time (s) must equal zero. If the model represents a discrete-time system, Sampling Time (s) must be greater than zero and equal to the sampling rate, in seconds, of the discrete system. The default is 0.
 Note  If you use the inputs to create a continuous-time system, setting the Sampling Time (s) to a value greater than zero does not yield the discrete-time equivalent of the system. You must use the CD Convert Continuous to Discrete VI to convert the continuous-time system to the discrete-time equivalent of the system.
Transfer Function(s) is an array of transfer function models that you can use to define the dynamics of a multiple-input single-output (MISO), a single-input multiple-output (SIMO), or a multiple-input multiple-output (MIMO) system.
 Numerator contains the constant coefficients of a polynomial that represent the numerator of a transfer function. Denominator contains the constant coefficients of a polynomial that represent the denominator of a transfer function.
error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node.
 status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE. code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
Transfer Function Model is the system model this VI creates. The size of the Transfer Function(s) array determines if the system is SISO, MIMO, MISO, or SIMO. To access and modify the data in the model, use the Model Information VIs.
error out contains 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. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error.
 status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

## CD Construct Transfer Function Model (MIMO Symbolic)

Sampling Time (s) defines whether the model represents a continuous-time system or a discrete-time system. If the model represents a continuous-time system, Sampling Time (s) must equal zero. If the model represents a discrete-time system, Sampling Time (s) must be greater than zero and equal to the sampling rate, in seconds, of the discrete system. The default is 0.
 Note  If you use the inputs to create a continuous-time system, setting the Sampling Time (s) to a value greater than zero does not yield the discrete-time equivalent of the system. You must use the CD Convert Continuous to Discrete VI to convert the continuous-time system to the discrete-time equivalent of the system.
Symbolic Transfer Function(s) is the symbolic representation of the transfer functions that you can use to define the dynamics of a single-input single-output (SISO), multiple-input single-output (MISO), single-input multiple-output (SIMO), or multiple-input multiple-output (MIMO) system.
 Numerator contains the constant coefficients of a polynomial that represent the numerator of a transfer function. Denominator contains the constant coefficients of a polynomial that represent the denominator of a transfer function. delay is the symbolic representation of the transport time delay that may exist in the system. Refer to the LabVIEW Control Design Toolkit User Manual for more information about delays.
error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node.
 status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE. code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
Variables contains the name and value of each variable.
 Name is a variable name this VI uses to define the data of the system model. Variable names can be a combination of letters and numbers. A variable name that begins with a capital letter E can produce unpredictable errors if parts of the original string represent numbers like 1E–2. Avoid terms beginning with E in such cases. Value is the numeric value this VI associates with the variable. The VI uses this value to evaluate the model.
Transfer Function Model is the system model this VI creates. The size of the Transfer Function(s) array determines if the system is SISO, MIMO, MISO, or SIMO. To access and modify the data in the model, use the Model Information VIs.
error out contains 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. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error.
 status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

## CD Construct Transfer Function Model Details

Only the SISO and SISO Symbolic instances of this VI support delays. To represent a delay in the model, you must specify the delay in this VI. Refer to the LabVIEW Control Design Toolkit User Manual for more information about delays.

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