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Friction Function

LabVIEW 2012 Control Design and Simulation Module Help

Edition Date: June 2012

Part Number: 371894G-01

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Owning Palette: Nonlinear Systems Functions

Requires: Control Design and Simulation Module

Represents friction at zero but guarantees linear behavior for nonzero inputs. You also can use this function to represent Coulomb and viscous friction.

Details  Example

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.
offsetSpecifies the offset of the friction element.
gainSpecifies the slope of the friction element.

Block Diagram Inputs

ParameterDescription
offsetSpecifies the offset of the friction element.
gainSpecifies the slope of the friction element.
inputSpecifies the signal to which you want to apply the function.

Block Diagram Outputs

ParameterDescription
outputReturns the signal that results from applying the function to the input signal.

Friction Details

The following equations define the output of this function.

whereu is the input
y is the output

Viscous and Coulomb Friction

If you set the value of the gain parameter to 0, this function models Coulomb friction.

If you set the value of the offset parameter to 0, this function models viscous friction.

Feedthrough Behavior

All input/output pairs of this function have direct feedthrough behavior.

Example

Refer to the SimEx friction VI in the labview\examples\Control and Simulation\Simulation\Nonlinear directory for an example of using the Friction VI.


 

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