Discretize Model

NI MAX Control Design Steps

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Discretize Model

Converts a continuous-time model to a discrete-time model, converts a discrete-time model to a continuous-time model, or changes the sampling time of a discrete-time system model.

Details  

ParameterDescription
Bode MagnitudeDisplays the decibel magnitude of the given model plotted against a set of frequencies.
Bode PhaseDisplays the phase (in degrees) of the model plotted against a set of frequencies.
Autoscale magnitudeAutomatically scales the y-axis of the magnitude on the display graph.
Autoscale phaseAutomatically scales the y-axis of the phase on the display graph.
Input DataContains the following parameter:
  • Model—Specifies the model you want to transform from continuous to discrete or discrete to continuous, or to change the sampling time.
ConfigurationContains the following options:
  • Input Model—Contains the following options:
    • Sampling time in (s)—Displays whether the system model represents a continuous-time system or a discrete-time system. If the model represents a continuous-time system, Sampling time in (s) equals zero. If the model represents a discrete-time system, Sampling time in (s) is greater than zero and equal to the sampling time, in seconds, of the discrete system.
    • Nyquist frequency in—Displays the half maximum frequency in the spectrum of the input system model.
  • Operation—Specifies the type of transformation you want to perform. If you select a continuous model from the Model pull-down menu on the Input Data tab, you can select only Discretize from this pull-down menu. If you select a discrete model from the Model pull-down menu on the Input Data tab, you can select one of the following options:
    • Discretize (default)
    • Re-discretize
    • Make Continuous
  • Method—Specifies the algorithm used to calculate the discrete equivalent of the continuous-time system model or the continuous equivalent of the discrete-time system model. You can select one of the following options:
    • Zero-Order-Hold (default)
    • Tustin (Bilinear)
    • Tustin with Prewarping
    • Forward
    • Backward
    • Z-Transform
    • First-Order-Hold
    • Matched Pole-Zero
  • Frequency unit—Specifies the frequency unit of the system model. You can select one of the following options:
    • Hz
    • rad/s (default)
  • Output Model—Contains the following options:
    • Sampling time out (s)—Defines whether the system model represents a continuous-time system or a discrete-time system. If the model represents a continuous-time system, Sampling time out (s) must equal zero. If the model represents a discrete-time system, Sampling time out (s) must be greater than zero and equal to the sampling time, in seconds, of the discrete system. The default is 100m.
    • Nyquist frequency out—Specifies the half maximum frequency in the spectrum of the output system model. The Control Design Assistant correlates the Nyquist frequency out to the Sampling time out (s) by using the following equations:

      wn=2*pi/T (rad/s) or

      fn=1/T (Hz)

      The default is 2*pi/0.1, or 31.4159.

Discretize Model Details

Refer to the LabVIEW Control Design User Manual for information about the equations this step uses for each Method.

Note  You must install the LabVIEW Control Design and Simulation Module to access this manual.

Access this manual by navigating to the labview\manuals directory and double-clicking CD_User_Manual.pdf.

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