CD Gain and Phase Margin VI

Control Design VI and Function

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CD Gain and Phase Margin VI

Owning Palette: Frequency Response VIs

Installed With: Control Design and Simulation Module

Calculates the gain and phase margins. If a system has multiple crossover frequencies, the CD Gain and Phase Margin VI returns the smallest gain and phase margins. You can use the CD Gain and Phase Margin VI only with single-input single-output (SISO) systems. The data types you wire to the State-Space Model and Frequency Info inputs determine the polymorphic instance to use.

This VI converts state-space and zero-pole-gain models into transfer function models before calculating the margins.

Details  

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

 Place on the block diagram  Find on the Functions palette

CD Gain and Phase Margin (State-Space)

Phase Plot Reference is a reference to the Phase Plot. Phase Plot Reference configures the x-scale, y-scale, and legend properties. If you want to use the default settings or customize the settings for these properties, do not wire a value to this input.
Magnitude Plot Reference is a reference to the Magnitude Plot. Magnitude Plot Reference configures the x-scale, y-scale, and legend properties. If you want to use the default settings or customize the settings for these properties, do not wire a value to this input.
State-Space Model contains a mathematical representation of and information about the SISO system for which this VI determines gain and phase margins.
Frequency Range contains the frequency information of the model.
Initial frequency is the minimum frequency this VI uses in calculating the frequency response and producing the plots. The default is –1.
Final frequency is the maximum frequency this VI uses in calculating the frequency response and producing the plots. The default is –1.
Minimum number of points is the minimum number of points this VI uses in calculating the frequency response and producing the plots. The default is 100 points.
Frequency Unit specifies the units of frequency, either in Hertz or radians/seconds, to use in calculating the frequency response and producing the plots.

0Hz
1rad/s (default)
Magnitude Scale specifies how to scale the magnitude of the frequency response.

0linear—Does not convert the magnitude of the frequency response to decibels.
1db (default)—Converts the magnitude of the frequency response to decibels.
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 exception control to treat what is normally an error as no error or to treat a warning as an error. 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.
Magnitude Plot shows the magnitude of the frequency response of the system this VI plots against the frequency.
Phase Plot shows the phase of the frequency response of the system in degrees this VI plots against the frequency.
Gain and Phase Margins returns information about the gain and phase margins. To access the Gain and Phase Margins, use the CD Get Frequency Response Data VI.
P.M. Frequency is the 0 decibels crossover frequency that corresponds to the smallest phase margin.
Gain Margin is the smallest gain margin of the system.
G.M. Frequency is the –180 degrees crossover frequency that corresponds to the smallest gain margin.
Phase Margin is the smallest phase margin of the system.
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 Gain and Phase Margin (Transfer Function)

Phase Plot Reference is a reference to the Phase Plot. Phase Plot Reference configures the x-scale, y-scale, and legend properties. If you want to use the default settings or customize the settings for these properties, do not wire a value to this input.
Magnitude Plot Reference is a reference to the Magnitude Plot. Magnitude Plot Reference configures the x-scale, y-scale, and legend properties. If you want to use the default settings or customize the settings for these properties, do not wire a value to this input.
Transfer Function Model contains a mathematical representation of and information about the SISO system for which this VI determines gain and phase margins.
Frequency Range contains the frequency information of the model.
Initial frequency is the minimum frequency this VI uses in calculating the frequency response and producing the plots. The default is –1.
Final frequency is the maximum frequency this VI uses in calculating the frequency response and producing the plots. The default is –1.
Minimum number of points is the minimum number of points this VI uses in calculating the frequency response and producing the plots. The default is 100 points.
Frequency Unit specifies the units of frequency, either in Hertz or radians/seconds, to use in calculating the frequency response and producing the plots.

0Hz
1rad/s (default)
Magnitude Scale specifies how to scale the magnitude of the frequency response.

0linear—Does not convert the magnitude of the frequency response to decibels.
1db (default)—Converts the magnitude of the frequency response to decibels.
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 exception control to treat what is normally an error as no error or to treat a warning as an error. 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.
Magnitude Plot shows the magnitude of the frequency response of the system this VI plots against the frequency.
Phase Plot shows the phase of the frequency response of the system in degrees this VI plots against the frequency.
Gain and Phase Margins returns information about the gain and phase margins. To access the Gain and Phase Margins, use the CD Get Frequency Response Data VI.
P.M. Frequency is the 0 decibels crossover frequency that corresponds to the smallest phase margin.
Gain Margin is the smallest gain margin of the system.
G.M. Frequency is the –180 degrees crossover frequency that corresponds to the smallest gain margin.
Phase Margin is the smallest phase margin of the system.
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 Gain and Phase Margin (Zero-Pole-Gain)

Phase Plot Reference is a reference to the Phase Plot. Phase Plot Reference configures the x-scale, y-scale, and legend properties. If you want to use the default settings or customize the settings for these properties, do not wire a value to this input.
Magnitude Plot Reference is a reference to the Magnitude Plot. Magnitude Plot Reference configures the x-scale, y-scale, and legend properties. If you want to use the default settings or customize the settings for these properties, do not wire a value to this input.
Zero-Pole-Gain Model contains a mathematical representation of and information about the SISO system for which this VI determines gain and phase margins.
Frequency Range contains the frequency information of the model.
Initial frequency is the minimum frequency this VI uses in calculating the frequency response and producing the plots. The default is –1.
Final frequency is the maximum frequency this VI uses in calculating the frequency response and producing the plots. The default is –1.
Minimum number of points is the minimum number of points this VI uses in calculating the frequency response and producing the plots. The default is 100 points.
Frequency Unit specifies the units of frequency, either in Hertz or radians/seconds, to use in calculating the frequency response and producing the plots.

0Hz
1rad/s (default)
Magnitude Scale specifies how to scale the magnitude of the frequency response.

0linear—Does not convert the magnitude of the frequency response to decibels.
1db (default)—Converts the magnitude of the frequency response to decibels.
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 exception control to treat what is normally an error as no error or to treat a warning as an error. 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.
Magnitude Plot shows the magnitude of the frequency response of the system this VI plots against the frequency.
Phase Plot shows the phase of the frequency response of the system in degrees this VI plots against the frequency.
Gain and Phase Margins returns information about the gain and phase margins. To access the Gain and Phase Margins, use the CD Get Frequency Response Data VI.
P.M. Frequency is the 0 decibels crossover frequency that corresponds to the smallest phase margin.
Gain Margin is the smallest gain margin of the system.
G.M. Frequency is the –180 degrees crossover frequency that corresponds to the smallest gain margin.
Phase Margin is the smallest phase margin of the system.
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 Gain and Phase Margin (Frequency Response Data)

Phase Plot Reference is a reference to the Phase Plot. Phase Plot Reference configures the x-scale, y-scale, and legend properties. If you want to use the default settings or customize the settings for these properties, do not wire a value to this input.
Magnitude Plot Reference is a reference to the Magnitude Plot. Magnitude Plot Reference configures the x-scale, y-scale, and legend properties. If you want to use the default settings or customize the settings for these properties, do not wire a value to this input.
Frequency Response specifies the frequency response for which this VI calculates the margins.
Magnitude specifies the magnitude component of the frequency response. The Magnitude Scale parameter defines the units of the Magnitude array.
Phase specifies the phase component, in degrees, of the frequency response.
Frequency Vector specifies information about the frequencies this VI uses to excite the model.
Frequency specifies the frequencies this VI uses to excite the model.
Frequency Unit specifies the unit of measurement of the Frequency array.

0Hz—Specifies that the frequency is measured in hertz.
1rad/s (default)—Specifies that the frequency is measured in radians per second.
Magnitude Scale specifies how to scale the magnitude of the frequency response.

0linear—Does not convert the magnitude of the frequency response to decibels.
1db (default)—Converts the magnitude of the frequency response to decibels.
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 exception control to treat what is normally an error as no error or to treat a warning as an error. 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.
Magnitude Plot shows the magnitude of the frequency response of the system this VI plots against the frequency.
Phase Plot shows the phase of the frequency response of the system in degrees this VI plots against the frequency.
Gain and Phase Margins returns information about the gain and phase margins. To access the Gain and Phase Margins, use the CD Get Frequency Response Data VI.
P.M. Frequency is the 0 decibels crossover frequency that corresponds to the smallest phase margin.
Gain Margin is the smallest gain margin of the system.
G.M. Frequency is the –180 degrees crossover frequency that corresponds to the smallest gain margin.
Phase Margin is the smallest phase margin of the system.
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 Gain and Phase Margin Details

This VI supports delays. Refer to the LabVIEW Control Design User Manual for more information about delays.

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