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Implicit Variable Function

LabVIEW 2012 Control Design and Simulation Module Help

Edition Date: June 2012

Part Number: 371894G-01

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Owning Palette: Implicit Systems Functions

Requires: Control Design and Simulation Module

Solves semi-explicit differential algebraic equations (DAEs). This function solves a constraint function by varying the output value, the variable λ in the constraint function, over time until the value of the constraint function equals 0. This function has indirect feedthrough behavior. You use the value output of this function as an input variable for the VIs or functions you select to compute your constraint function. You then wire the output of those VIs and functions back into the constraint input of this function.

You must select the BDF solver in the Configure Simulation Parameters dialog box to use this function.

Details  

Dialog Box Options
Block Diagram Inputs
Block Diagram Outputs

Dialog Box Options

ParameterDescription
Polymorphic instanceSpecifies whether this function is Scalar or Vector. The default value is Scalar.
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.
initial valueSpecifies the value of the output value at the simulation initial time. The default is 0.

Block Diagram Inputs

ParameterDescription
constraintSpecifies the value of a constraint function. A constraint function defines conditions, or constraints, that the solution to a DAE must satisfy. Refer to the Details section for more information about the form of the function.
initial valueSpecifies the value of the output value at the simulation initial time. The default is 0.

Block Diagram Outputs

ParameterDescription
valueReturns the value of the constraint function. The Implicit Variable function solves DAEs by varying this value over time until the constraint function equals 0.

Implicit Variable Details

The semi-explicit form of DAEs combines differential equations and algebraic equations, as in the following equations:

The algebraic equations usually describe the constraints applied to the problems.


 

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