CD Discrete Zero-Pole-Gain Function
Owning Palette: Implementation VIs and Functions
Installed With: Control Design and Simulation Module
Implements a system model in discrete zero-pole-gain form. You define the system model by specifying the Zeros, Poles, and Gain of the zero-pole-gain equation.
| Dialog Box Options |
| Block Diagram Inputs |
| Block Diagram Outputs |
 Place on the block diagram |
Find on the Functions palette |
Dialog Box Options
| Parameter | Description |
|---|---|
| Polymorphic instance | Specifies whether this function is single-input single-output (SISO) or multiple-input multiple-output (MIMO). The default value is SISO. |
| Feedthrough | Configures the function to be either a Direct or Indirect feedthrough function. Enable this control by selecting a parameter from the Parameters list and then selecting Terminal from the Parameter source pull-down menu. If you select Configuration Dialog Box from the Parameter source pull-down menu, LabVIEW disables this control and calculates the feedthrough behavior automatically. Refer to the Details section for a description of the parameters that determine the feedthrough behavior of this function. |
| Parameters | Lists all the parameters associated with this function. Select a parameter from this list to configure the parameter. When you select a parameter, the parameter and its associated Parameter source control appear in the Parameter Information section of the configuration dialog box. |
| Preview | Displays a graphical preview, if available, of the function output or configuration. |
| Parameter Information | Contains the parameters you can configure for this function. You must select a parameter from the Parameters list to make that parameter and its associated Parameter source control visible in the Parameter Information section of the configuration dialog box. |
| Parameter source | Specifies whether you configure this parameter using the Configuration Dialog Box or a Terminal on the simulation diagram. The default value is Configuration Dialog Box. If you select Terminal, LabVIEW displays an input for that parameter on the simulation diagram, and you can wire values to that input to configure this function programmatically. If you select Configuration Dialog Box, LabVIEW removes that input from the simulation diagram. You then must set the value for this parameter inside the configuration dialog box. |
| Zeros-Poles-Gain | Specifies the zero-pole-gain model.
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Block Diagram Inputs
| Parameter | Description |
|---|---|
| initialize | Sets the model state(s) to 0, when TRUE. |
| input u(k) | Specifies the input to the system. input u(k) must be a vector of length m, where m is the number of inputs. |
| Zeros-Poles-Gain | Specifies a zero-pole-gain model. This input accepts either a block diagram constant or a model you created using the Control Design VIs and functions. |
| 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. 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 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. |
Block Diagram Outputs
| Parameter | Description |
|---|---|
| output y(k) | Returns the current output of the system. This vector must be of length r, where r is the number of outputs. |
| 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. |
CD Discrete Zero-Pole-Gain Details
For SISO models, this function uses the following equation to calculate the output:
For MIMO models, this function calculates the output as H = [Hij].
| where | k is the gain |
| Z[m] is the array of zeros | |
| P[n] is the array of poles | |
| m is the order of the numerator | |
| n is the order of the denominator | |
| z is the z-transform variable | |
| i is the index number of the input | |
| j is the index number of the output |
The function is based on the CD Discrete Transfer Function function, which is represented in zero-pole-gain notation.
Feedthrough Behavior
The values you specify for the Zeros and Poles subparameters determine the feedthrough behavior of this function. Given Z as the Zeros subparameter and P as the Poles subparameter:
- If the order of Z = the order of P, the function has direct feedthrough behavior.
- If the order of Z < the order of P, the input u(k) input has indirect feedthrough to the output y(k) output. All other input/output pairs have direct feedthrough behavior.
- If the order of Z > the order of P, LabVIEW returns an error.
When you use the configuration dialog box to configure Z and P, LabVIEW verifies that the feedthrough behavior is correct. For example, if you set the Execution Mode parameter to Indirect, and you set the order of Z equal to the order of P, LabVIEW changes the Execution Mode parameter to Direct.
If you define the zero-pole-gain equation programmatically, LabVIEW does not adjust the feedthrough behavior for you. You must ensure that you specify the proper feedthrough behavior for the orders of Z and P you specify.