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CD Nyquist VI

LabVIEW 2012 Control Design and Simulation Module Help

Edition Date: June 2012

Part Number: 371894G-01

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Owning Palette: Frequency Response VIs

Requires: Control Design and Simulation Module

Produces the Nyquist plot of the input system for which this VI plots the imaginary part of the frequency response against its real part. You can display this data in the CD Nyquist Plot indicator. Wire data to the State-Space Model and Frequency Range inputs to determine the polymorphic instance to use or manually select the instance.

This VI converts state-space and zero-pole-gain models into transfer function models before determining the frequency response.

Details  Example

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

CD Nyquist (Frequency Range, State-Space)

Separate Contour?, if TRUE, produces two plots: one that represents the positive frequencies and one for negative frequencies. Otherwise, this VI produces one plot for both the positive and negative frequencies. Separating the plots allows you to verify the direction of negative frequencies.
Nyquist Graph Reference is a reference to the Nyquist Plot on an XY graph. Nyquist Graph 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 system for which this VI produces a Nyquist plot.
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)
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
Plots Index is an array of clusters of the following two elements.
input # is the index number of the specific input to the system. This VI displays the response to this input in the Nyquist Plot on an XY graph. The index is zero-based.
output # is the index number of the specific output of the system that this VI displays in the Nyquist Plot on an XY graph. The index is zero-based.
Nyquist Plot returns the imaginary part of the complex frequency response of the input system this VI plots against its real part. The Plots Index input determines which plots to display on the XY graph. Right-click this terminal on the block diagram and select Create»Indicator from the shortcut menu to display this data in a CD Nyquist Plot indicator.
Nyquist Data returns information about the Nyquist plot data. To access the Nyquist Data, use the CD Get Frequency Response Data VI.
Frequency is a 1D-array of frequency values at which this VI calculates the magnitude and phase.
Real returns data about the frequency response of the real part of the elements in the matrix H(w). The ith column in the nth page of the array is the real part of the frequency response of the transfer function between the ith output and the nth input. For example, the first two columns of the 0th page are real parts of frequency response of transfer functions between outputs y0 and y1 and the first input u0.
Imaginary returns data about the frequency response of the imaginary part of the elements in the matrix H(w). The ith column in the nth page of the array is the imaginary part of the frequency response of the transfer function between the ith output and the nth input. For example, the first two columns of the 0th page are imaginary parts of frequency response of transfer functions between outputs y0 and y1 and the first input u0.
plot type returns the type of the plot.

0bode-magnitude
1bode-phase
2nichols
3nyquist
4singular values
5step
6impulse
7initial
8simulation
error out contains error information. This output provides standard error out functionality.

CD Nyquist (Frequency Range, Transfer Function)

Separate Contour?, if TRUE, produces two plots: one that represents the positive frequencies and one for negative frequencies. Otherwise, this VI produces one plot for both the positive and negative frequencies. Separating the plots allows you to verify the direction of negative frequencies.
Nyquist Graph Reference is a reference to the Nyquist Plot on an XY graph. Nyquist Graph 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 system for which this VI produces a Nyquist plot.
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)
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
Plots Index is an array of clusters of the following two elements.
input # is the index number of the specific input to the system. This VI displays the response to this input in the Nyquist Plot on an XY graph. The index is zero-based.
output # is the index number of the specific output of the system that this VI displays in the Nyquist Plot on an XY graph. The index is zero-based.
Nyquist Plot returns the imaginary part of the complex frequency response of the input system this VI plots against its real part. The Plots Index input determines which plots to display on the XY graph. Right-click this terminal on the block diagram and select Create»Indicator from the shortcut menu to display this data in a CD Nyquist Plot indicator.
Nyquist Data returns information about the Nyquist plot data. To access the Nyquist Data, use the CD Get Frequency Response Data VI.
Frequency is a 1D-array of frequency values at which this VI calculates the magnitude and phase.
Real returns data about the frequency response of the real part of the elements in the matrix H(w). The ith column in the nth page of the array is the real part of the frequency response of the transfer function between the ith output and the nth input. For example, the first two columns of the 0th page are real parts of frequency response of transfer functions between outputs y0 and y1 and the first input u0.
Imaginary returns data about the frequency response of the imaginary part of the elements in the matrix H(w). The ith column in the nth page of the array is the imaginary part of the frequency response of the transfer function between the ith output and the nth input. For example, the first two columns of the 0th page are imaginary parts of frequency response of transfer functions between outputs y0 and y1 and the first input u0.
plot type returns the type of the plot.

0bode-magnitude
1bode-phase
2nichols
3nyquist
4singular values
5step
6impulse
7initial
8simulation
error out contains error information. This output provides standard error out functionality.

CD Nyquist (Frequency Range, Zero-Pole-Gain)

Separate Contour?, if TRUE, produces two plots: one that represents the positive frequencies and one for negative frequencies. Otherwise, this VI produces one plot for both the positive and negative frequencies. Separating the plots allows you to verify the direction of negative frequencies.
Nyquist Graph Reference is a reference to the Nyquist Plot on an XY graph. Nyquist Graph 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 system for which this VI produces a Nyquist plot.
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)
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
Plots Index is an array of clusters of the following two elements.
input # is the index number of the specific input to the system. This VI displays the response to this input in the Nyquist Plot on an XY graph. The index is zero-based.
output # is the index number of the specific output of the system that this VI displays in the Nyquist Plot on an XY graph. The index is zero-based.
Nyquist Plot returns the imaginary part of the complex frequency response of the input system this VI plots against its real part. The Plots Index input determines which plots to display on the XY graph. Right-click this terminal on the block diagram and select Create»Indicator from the shortcut menu to display this data in a CD Nyquist Plot indicator.
Nyquist Data returns information about the Nyquist plot data. To access the Nyquist Data, use the CD Get Frequency Response Data VI.
Frequency is a 1D-array of frequency values at which this VI calculates the magnitude and phase.
Real returns data about the frequency response of the real part of the elements in the matrix H(w). The ith column in the nth page of the array is the real part of the frequency response of the transfer function between the ith output and the nth input. For example, the first two columns of the 0th page are real parts of frequency response of transfer functions between outputs y0 and y1 and the first input u0.
Imaginary returns data about the frequency response of the imaginary part of the elements in the matrix H(w). The ith column in the nth page of the array is the imaginary part of the frequency response of the transfer function between the ith output and the nth input. For example, the first two columns of the 0th page are imaginary parts of frequency response of transfer functions between outputs y0 and y1 and the first input u0.
plot type returns the type of the plot.

0bode-magnitude
1bode-phase
2nichols
3nyquist
4singular values
5step
6impulse
7initial
8simulation
error out contains error information. This output provides standard error out functionality.

CD Nyquist (Frequency Vector, State-Space)

Nyquist Graph Reference is a reference to the Nyquist Plot on an XY graph. Nyquist Graph 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 system for which this VI produces a Nyquist plot.
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.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
Plots Index is an array of clusters of the following two elements.
input # is the index number of the specific input to the system. This VI displays the response to this input in the Nyquist Plot on an XY graph. The index is zero-based.
output # is the index number of the specific output of the system that this VI displays in the Nyquist Plot on an XY graph. The index is zero-based.
Nyquist Plot returns the imaginary part of the complex frequency response of the input system this VI plots against its real part. The Plots Index input determines which plots to display on the XY graph. Right-click this terminal on the block diagram and select Create»Indicator from the shortcut menu to display this data in a CD Nyquist Plot indicator.
Nyquist Data returns information about the Nyquist plot data. To access the Nyquist Data, use the CD Get Frequency Response Data VI.
Frequency is a 1D-array of frequency values at which this VI calculates the magnitude and phase.
Real returns data about the frequency response of the real part of the elements in the matrix H(w). The ith column in the nth page of the array is the real part of the frequency response of the transfer function between the ith output and the nth input. For example, the first two columns of the 0th page are real parts of frequency response of transfer functions between outputs y0 and y1 and the first input u0.
Imaginary returns data about the frequency response of the imaginary part of the elements in the matrix H(w). The ith column in the nth page of the array is the imaginary part of the frequency response of the transfer function between the ith output and the nth input. For example, the first two columns of the 0th page are imaginary parts of frequency response of transfer functions between outputs y0 and y1 and the first input u0.
plot type returns the type of the plot.

0bode-magnitude
1bode-phase
2nichols
3nyquist
4singular values
5step
6impulse
7initial
8simulation
error out contains error information. This output provides standard error out functionality.

CD Nyquist (Frequency Vector, Transfer Function)

Nyquist Graph Reference is a reference to the Nyquist Plot on an XY graph. Nyquist Graph 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 system for which this VI produces a Nyquist plot.
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.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
Plots Index is an array of clusters of the following two elements.
input # is the index number of the specific input to the system. This VI displays the response to this input in the Nyquist Plot on an XY graph. The index is zero-based.
output # is the index number of the specific output of the system that this VI displays in the Nyquist Plot on an XY graph. The index is zero-based.
Nyquist Plot returns the imaginary part of the complex frequency response of the input system this VI plots against its real part. The Plots Index input determines which plots to display on the XY graph. Right-click this terminal on the block diagram and select Create»Indicator from the shortcut menu to display this data in a CD Nyquist Plot indicator.
Nyquist Data returns information about the Nyquist plot data. To access the Nyquist Data, use the CD Get Frequency Response Data VI.
Frequency is a 1D-array of frequency values at which this VI calculates the magnitude and phase.
Real returns data about the frequency response of the real part of the elements in the matrix H(w). The ith column in the nth page of the array is the real part of the frequency response of the transfer function between the ith output and the nth input. For example, the first two columns of the 0th page are real parts of frequency response of transfer functions between outputs y0 and y1 and the first input u0.
Imaginary returns data about the frequency response of the imaginary part of the elements in the matrix H(w). The ith column in the nth page of the array is the imaginary part of the frequency response of the transfer function between the ith output and the nth input. For example, the first two columns of the 0th page are imaginary parts of frequency response of transfer functions between outputs y0 and y1 and the first input u0.
plot type returns the type of the plot.

0bode-magnitude
1bode-phase
2nichols
3nyquist
4singular values
5step
6impulse
7initial
8simulation
error out contains error information. This output provides standard error out functionality.

CD Nyquist (Frequency Vector, Zero-Pole-Gain)

Nyquist Graph Reference is a reference to the Nyquist Plot on an XY graph. Nyquist Graph 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 system for which this VI produces a Nyquist plot.
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.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
Plots Index is an array of clusters of the following two elements.
input # is the index number of the specific input to the system. This VI displays the response to this input in the Nyquist Plot on an XY graph. The index is zero-based.
output # is the index number of the specific output of the system that this VI displays in the Nyquist Plot on an XY graph. The index is zero-based.
Nyquist Plot returns the imaginary part of the complex frequency response of the input system this VI plots against its real part. The Plots Index input determines which plots to display on the XY graph. Right-click this terminal on the block diagram and select Create»Indicator from the shortcut menu to display this data in a CD Nyquist Plot indicator.
Nyquist Data returns information about the Nyquist plot data. To access the Nyquist Data, use the CD Get Frequency Response Data VI.
Frequency is a 1D-array of frequency values at which this VI calculates the magnitude and phase.
Real returns data about the frequency response of the real part of the elements in the matrix H(w). The ith column in the nth page of the array is the real part of the frequency response of the transfer function between the ith output and the nth input. For example, the first two columns of the 0th page are real parts of frequency response of transfer functions between outputs y0 and y1 and the first input u0.
Imaginary returns data about the frequency response of the imaginary part of the elements in the matrix H(w). The ith column in the nth page of the array is the imaginary part of the frequency response of the transfer function between the ith output and the nth input. For example, the first two columns of the 0th page are imaginary parts of frequency response of transfer functions between outputs y0 and y1 and the first input u0.
plot type returns the type of the plot.

0bode-magnitude
1bode-phase
2nichols
3nyquist
4singular values
5step
6impulse
7initial
8simulation
error out contains error information. This output provides standard error out functionality.

CD Nyquist Details

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

Example

Refer to the CDEx Nyquist Analysis VI in the labview\examples\Control and Simulation\Control Design\Frequency Analysis directory for an example of using the CD Nyquist VI.


 

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