Company Events Academic Community Support Solutions Products & Services Contact NI MyNI

SISO Controller Function

LabVIEW 2012 Control Design and Simulation Module Help

Edition Date: June 2012

Part Number: 371894G-01

»View Product Info

Owning Palette: Controllers Functions

Requires: Control Design and Simulation Module

Implements a controller for a single-input single-output (SISO) dynamic system. This function provides an interface for interactively designing and analyzing a controller that this function implements. You also can create a controller elsewhere on the block diagram and wire its model to this function to implement.

Add this function to a simulation diagram to close the loop between the setpoint and the plant with the controller you generate.

Dialog Box Options
Block Diagram Inputs
Block Diagram Outputs

Dialog Box Options

ParameterDescription
ParametersLists 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.
PreviewDisplays a graphical preview, if available, of the function output or configuration.
Parameter InformationContains 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 sourceSpecifies 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.
SetpointSpecifies the setpoint value of the process variable that you are controlling. This is the desired value for the process variable.
Initialize?Specifies whether to restart the calculation from zero. The default is FALSE.
Integral Anti-windup [s] (Ti)Specifies an integral time constant, in seconds. This input adjusts the effect of the error integral on the controller output when the output is saturated at the specified Output Range maximum and minimum values. The default value is 0, which specifies no integral action.
ManualSpecifies a value to use for the controller output if Auto? is FALSE.
Auto?If TRUE, this function uses automatic control. If FALSE, this function uses manual control by switching off the controller and using the value you specify for Manual as the controller output. In some situations, you might need to switch off the controller and operate the system in manual, or open-loop, mode.
Output RangeContains the following options that define a range to which to coerce the control output:
  • output high—Specifies the maximum value of the controller output. The default is Inf, which means the maximum output value is unlimited.
  • output low—Specifies the minimum value of the controller output. The default is –Inf, which means the minimum output value is unlimited.
Interactive DesignHosts the Interactive Control Design dialog box, in which you design and analyze a controller. When you select this parameter, the interface at the right contains the following pages and components:
  • Configuration page—Load and configure models to include in the system model. Details
  • Synthesis page—Set properties of the controller, such as gain. Details
  • Specifications page—Define constraints for the system that the controller must meet and verify the controller can meet each constraint. Details
  • Analysis page—Analyze the time or frequency response of the controller in custom graphs. Details
  • Show Analysis—Shows or hides the graphs on the Analysis tab without opening that tab. This option allows you to analyze the controller while you configure it with options on the Synthesis or Specifications tabs.
  • Stable—Is TRUE if the resulting closed-loop system with the controller you create is stable. Is FALSE and reads Unstable if the system is unstable.
  • In Spec—Is TRUE if the system meets all the constraints you set on the Specifications page. Is FALSE and reads Not in Spec if the system fails to meet one or more of the constraints.
Controller ModelProvides another way to load and edit a supported controller model. When you load or edit a model through this parameter, the model is reflected in the Interactive Control Design dialog box and vice versa.

When you select this parameter, the following options appear at the right and allow you to define a controller:
  • Load Model—Loads model information from a data file.
  • Save Model—Saves model information to a data file. This file is compatible with the Control Design VIs and functions.
  • Copy to Clipboard—Copies the current model definition to the clipboard. From the clipboard, you can paste the model on the block diagram or into another configuration dialog box of the same model form.
  • Paste from Clipboard—Pastes model information from the clipboard to the configuration dialog box.
  • Model Dimensions—Displays the following information about the controller model you load or paste:
    • Inputs—Specifies the number of model inputs.
    • Outputs—Specifies the number of model outputs.
  • Gain—Specifies the gain the controller uses in the feedback loop.
  • Controller zeros—Defines the array of zeros of the model. The zeros can be real or complex. If they are complex, they must be in complex conjugate pairs. This table automatically calculates the complex conjugate pairs when you enter the real and imaginary parts followed by the symbol, i. For example, if you type –1 + 0.5i, this table generates the complex conjugate –1 ± 0.5i, which is equivalent to (–1 + 0.5i) * (–1 – 0.5i).
  • Controller poles—Defines the array of poles of the model. The poles can be real or complex. If they are complex, they must be in complex conjugate pairs. This table automatically calculates the complex conjugate pairs when you enter the real and imaginary parts followed by the symbol, i. For example, if you type –1 + 0.5i, this table generates the complex conjugate –1 ± 0.5i, which is equivalent to (–1 + 0.5i) * (–1 – 0.5i).
Feedback SignSpecifies whether the feedback connections are positive or negative.
Execution ControlContains the following options:
  • Execution Control—Specifies the execution behavior of the subsystem. You can select from the following options:
    • Normal—(Default) Executes the subsystem without checking for an enabled state or waiting for a trigger.
    • Enable—Checks the value wired to the Enable block diagram input before executing the subsystem. The Enable block diagram input appears on the function when you select this option.
    • Trigger—Waits for a trigger from the Trigger block diagram input of the Trigger Type you specify before executing the subsystem. The Trigger block diagram input appears when you select this option.
    • Enable And Trigger—Checks the value wired to the Enable block diagram input and waits for a trigger from the Trigger block diagram input of the Trigger Type you specify before executing the subsystem. The Enable and Trigger block diagram inputs appear when you select this option.
  • Trigger Type—Specifies when to trigger the execution of the subsystem. Set Execution Control to Trigger or Enable And Trigger to enable this option. You can select from the following options:
    • Rising—Executes the subsystem when the Trigger signal crosses 0 on a positive slope.
    • Falling—Executes the subsystem when the Trigger signal crosses 0 on a negative slope.
    • Either—(Default) Executes the subsystem when the Trigger signal crosses 0 on a positive or negative slope.
    • None—Does not specify a trigger.
  • Trigger Offset—Specifies the offset from 0 that the subsystem uses when looking for a zero crossing. The default is 0. Set Execution Control to Trigger or Enable And Trigger to enable this pull-down menu.
  • Hold Previous Output—Indicates the outputs of the subsystem that hold their last known values when the subsystem does not execute. Outputs appear in this list when you set their Disabled Behavior to Hold. Select an output under Execution Control in the Parameters list to configure its Disabled Behavior.
  • Reset to Initial Output—Indicates the outputs of the subsystem that reset to their initial values when the subsystem does not execute. Outputs appear in this list when you set their Disabled Behavior to Reset. Select an output under Execution Control in the Parameters list to configure its Disabled Behavior.
OutputContains the following options:
  • Disabled Behavior—Specifies the behavior of an output of a subsystem when the subsystem does not execute. Select an output under Execution Control in the Parameters list to display this option. You can select from the following options:
    • Hold—(Default) Holds the output value to its last known value.
    • Reset—Resets the output value to its initial value.
  • Use Configured Default Value—Specifies to use the output value you specify for the value of the subsystem output value. If you set Disabled Behavior to Reset, the subsystem always outputs this value when disabled. If you set Disabled Behavior to Hold, the subsystem outputs this value only on its first execution.
  • Output—Specifies the initial value to use for the output value of the subsystem. Place a checkmark in the Use Configured Default Value checkbox to enable this option.

Block Diagram Inputs

ParameterDescription
SetpointSpecifies the setpoint value of the process variable that you are controlling. This is the desired value for the process variable.
Initialize?Specifies whether to restart the calculation from zero. The default is FALSE.
Integral Anti-windup [s] (Ti)Specifies an integral time constant, in seconds. This input adjusts the effect of the error integral on the controller output when the output is saturated at the specified Output Range maximum and minimum values. The default value is 0, which specifies no integral action.
ManualSpecifies a value to use for the controller output if Auto? is FALSE.
Auto?If TRUE, this function uses automatic control. If FALSE, this function uses manual control by switching off the controller and using the value you specify for Manual as the controller output. In some situations, you might need to switch off the controller and operate the system in manual, or open-loop, mode.
Output RangeContains the following options that define a range to which to coerce the control output:
  • output high—Specifies the maximum value of the controller output. The default is Inf, which means the maximum output value is unlimited.
  • output low—Specifies the minimum value of the controller output. The default is –Inf, which means the minimum output value is unlimited.
MeasurementAccepts the value of the reference input you want to control.
Controller ModelAccepts controller models you want this function to implement. If you do not design the controller in the Interactive Control Design dialog box, you can wire its model to this input. The controller must be in zero-pole-gain form. This value might come from the following sources:

Block Diagram Outputs

ParameterDescription
OutputReturns the result of the calculation from the controller.

 

Your Feedback! poor Poor  |  Excellent excellent   Yes No
 Document Quality? 
 Answered Your Question? 
Add Comments 1 2 3 4 5 submit