Frequency Domain Analysis

NI MAX Control Design Steps

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Frequency Domain Analysis

Analyzes the system model in the frequency domain.

Parameter	Description
Bode Magnitude	Displays the linear or decibel magnitude of the given model plotted against a set of frequencies. Bode Magnitude appears if you select Bode from the Analysis Type pull-down menu on the Configuration tab.
Bode Phase	Displays the phase (in degrees) of the model plotted against a set of frequencies. Bode Phase appears when you select Bode from the Analysis Type pull-down menu on the Configuration tab.
Nyquist Plot	Displays the Nyquist plot of the model. Nyquist Plot appears if you select Nyquist from the Analysis Type pull-down menu on the Configuration tab.
Nichols Plot	Displays the Nichols plot of the model. Nichols Plot appears if you select Nichols from the Analysis Type pull-down menu on the Configuration tab.
Input Data	Contains the following option: Model—Specifies the model you want to analyze.
Configuration	Contains the following options: Analysis Type—Specifies the type of analysis you want to perform. The default is Bode. You can select one of the following options: Bode—Produces the Bode magnitude and Bode phase plots of the system model. Nyquist—Produces the Nyquist plot of the system model in which the imaginary part of the frequency response is plotted against the real part. Nichols—Creates a Nichols plot of the system model in which the magnitude, in dB, of the frequency response is plotted against the phase. Magnitude Scale—Specifies how to scale the magnitude of the frequency response. The Magnitude Scale option appears if you select Bode from the Analysis Type pull-down menu. You can select one of the following: linear dB (default) Frequency Unit—Specifies the unit of the frequency. You can select one of the following units: Hz (default) rad/s Min Number of Points—Specifies the minimum number of points used in calculating the frequency response and producing the plots. The default is 500. Initial Frequency—Specifies the initial frequency used in calculating the frequency response and producing the plots. If you place a checkmark in the Initial Frequency checkbox, you can change the initial frequency value the step uses to calculate the maximum and minimum frequencies. If you do not place a checkmark in the Initial Frequency checkbox, the step uses an algorithm based on the system dynamics to calculate the maximum and minimum frequencies. Final Frequency—Specifies the final frequency used in calculating the frequency response and producing the plots. If you place a checkmark in the Final Frequency checkbox, you can change the final frequency value the step uses to calculate the maximum and minimum frequencies. If you do not place a checkmark in the Final Frequency checkbox, the step uses an algorithm based on the system dynamics to calculate the maximum and minimum frequencies.
Frequency Analysis	Contains the following options: Gain Margin—Displays the smallest gain margin of the system. Phase Crossover Frequency—Displays the crossover frequency that is an integer multiple of –180 degrees and that corresponds to the smallest gain margin. Phase Margin—Displays the smallest phase margin of the system. Gain Crossover Frequency—Displays the 0 dB crossover frequency that corresponds to the smallest phase margin. Bandwidth—Displays the frequency, relative to the DC gain, at which the magnitude of the frequency response of the system falls below the magnitude drop.

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