Converts PID gains in the Academic, Parallel, or Series form to the normalized Parallel form that the PID VI expects.


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Inputs/Outputs

  • cu8.png filter coefficient unit (Alpha) —

    filter coefficient unit specifies the unit that distinguishes the type of the derivative lowpass filter coefficients.

    0Alpha (default)—Specifies that the filter coefficients are expressed in Alpha.
    1N—Specifies that the filter coefficients are expressed in N.
    2Cutoff Frequency—Specifies that the filter coefficients are expressed in hertz.
    3Time Constant—Specifies that the filter coefficients are expressed in seconds.
  • csgl.png filter coefficient (NaN) —

    filter coefficient specifies the derivative lowpass filter coefficient.

    If you specify a value for filter coefficient unit, you must also specify a value for filter coefficient. When filter coefficient unit is Alpha, the valid value range of filter coefficient is [0, 1]. When filter coefficient unit is N, the valid value range of filter coefficient is [1, 1000]. The following equations explain the relationships among the available units:

    N = 1 / Alpha

    Time Constant = 1 / (2 * Pi * Cutoff Frequency)

    When you leave both filter coefficient unit and filter coefficient unwired, this VI uses 0.1 for filter coefficient.

  • cu8.png gains pattern (Parallel) —

    gains pattern specifies the form of the PD gains.

    0Academic—Specifies that the gains are in the Academic form.
    1Parallel (default)—Specifies that the gains are in the Parallel form.
    2Series—Specifies that the gains are in the Series form.
  • csgl.png proportional —

    proportional specifies the value of the proportional gain.

  • csgl.png derivative —

    derivative specifies the value of the derivative gain.

  • csgl.png sampling time —

    sampling time specifies the loop time, in seconds, at which the PID loop on the FPGA target runs.

  • cerrcodeclst.png error in (no error) —

    error in describes error conditions that occur before this node runs. This input provides standard error in functionality.

  • cu8.png proportional unit (Gain (K)) —

    proportional unit specifies the unit of the proportional gain. The relationship between the available units is K = 100 / PB.

    0Gain (K) (default)—Specifies that the proportional gain is expressed in terms of proportional gain (K).
    1Band (PB)—Specifies that the proportional gain is expressed in terms of proportional band (PB).
  • cu8.png derivative unit (s) —

    derivative unit specifies the units of the derivative gain.

    0Hz—Specifies that the derivative gain is expressed in hertz.
    1s (default)—Specifies that the derivative gain is expressed in seconds.
    2min—Specifies that the derivative gain is expressed in minutes.
  • inclst.png gains —

    gains returns the normalized PD gain parameters.

  • isgl.png proportional gain —

    proportional gain returns the normalized proportional gain. In equations that define the PID gains conversion, Kp represents proportional gain.

  • isgl.png derivative gain —

    derivative gain returns the normalized derivative gain. In equations that define the PID gains conversion, Kd represents derivative gain.

  • isgl.png filter coefficient —

    filter coefficient returns the derivative lowpass filter coefficient. In equations that define the PID controller, a represents filter coefficient.

  • ierrcodeclst.png error out —

    error out contains error information. This output provides standard error out functionality.

    • Use the following table to understand the details about the equations that the Convert PID Gains VI uses when converting the PID gains. The converted PID gains are Kp, Ki, and Kd, respectively.

    Original PID Form Original Gains: Units Conversion Equations
    Academic Kc: Gain (K)
    Ti: s
    Td: s
    Parallel Kp': Gain (K)
    Ki': Hz
    Kd': s
    Series KC': Gain (K)
    TI': s
    TD': s

    Examples

    Refer to the following example files included with LabVIEW FPGA Module.

    • labview\examples\CompactRIO\FPGA Fundamentals\FPGA Math and Analysis\Floating-point PID\Multi-Channel PID\Multi-Channel PID.lvproj
    • labview\examples\CompactRIO\FPGA Fundamentals\FPGA Math and Analysis\Floating-point PID\Multi-Rate PID\Multi-Rate PID.lvproj
    • labview\examples\R Series\FPGA Fundamentals\FPGA Math and Analysis\Floating-point PID\Multi-Channel PID\Multi-Channel PID.lvproj
    • labview\examples\R Series\FPGA Fundamentals\FPGA Math and Analysis\Floating-point PID\Multi-Rate PID\Multi-Rate PID.lvproj