Friction Function
Owning Palette: Nonlinear Systems Functions
Installed With: 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.
| 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 Scalar or Vector. The default value is Scalar. |
| 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. |
| offset | Specifies the offset of the friction element. |
| gain | Specifies the slope of the friction element. |
Block Diagram Inputs
| Parameter | Description |
|---|---|
| offset | Specifies the offset of the friction element. |
| gain | Specifies the slope of the friction element. |
| input | Specifies the signal to which you want to apply the function. |
Block Diagram Outputs
| Parameter | Description |
|---|---|
| output | Returns the signal that results from applying the function to the input signal. |
Friction Details
The following equations define the output of this function.
| where | u 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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