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Knob

Change parameter or variable value using knob with customizable appearance

Since R2021a

  • Knob block

Libraries:
Simulink / Dashboard / Customizable Blocks

Description

Use the Knob block to tune the value of a variable or block parameter to during simulation. When you use the Knob block in the Customizable Blocks library, you can customize the appearance of the block so that it looks like a control in a real system. You can modify the range and tick values on the Knob block to fit the desired range for the value you want to tune. Use the Knob block with other dashboard blocks to create an interactive dashboard to control your model.

Customize Knob Blocks

When you add a Knob block to your model, the block is preconfigured with a default design. You can use the block with the default design or customize the appearance of the block.

To customize the appearance of the block, use design mode. After selecting the block, you can enter design mode in one of three ways:

  • On the block-specific tab, under Design, click Edit.

  • In the Property Inspector, on the Design tab, click Edit.

  • Pause on the ellipsis that appears over the block and click the Edit Custom Block button.

Customizable Knob block in design mode with the toolbar and the Design tab in the Property Inspector visible.

In design mode, you can:

  • Upload a handle image.

  • Upload a background image or set a solid background color.

  • Change the color and opacity of the scale, tick labels, and value bar.

  • Change the size of the scale and handle.

  • Change the arc length of the scale.

  • Reposition the scale and handle.

  • Specify the scale direction as clockwise or counterclockwise.

  • Specify the location of the origin from which the value bar grows.

  • Upload a foreground image.

You can use the toolbar above the block to upload a handle or a background image and to change the color and opacity of the scale, tick labels, and value bar. To change the color and opacity, in the second section of the toolbar from the left, select a component. Then, click the color wheel in the toolbar to change the color of the component. Move the slider to change the opacity.

To resize the scale or handle, or to change the arc length of the scale, select the component you want to change in the canvas. Then, click and drag the grab points that define its dimensions.

To reposition the scale or handle, click and drag it in the canvas. The movement of the handle is limited to the radial line that goes from the center of the block to the minimum value on the scale.

You can use the Design tab in the Property Inspector for fine control over the block design and to enter exact values for design settings.

Use the Design tab to:

  • Specify the scale direction.

  • Specify the origin.

  • Upload a foreground image.

  • Set a solid background color.

When you finish editing the design, to exit design mode, click the X in the upper right of the canvas.

Connect Dashboard Blocks

Dashboard blocks do not use ports to connect to model elements. To connect dashboard blocks to variables and block parameters, use connect mode. Connect mode facilitates the process of connecting dashboard blocks in your model, especially when you want to connect multiple blocks at once. To connect a single dashboard block, you can also use the Connection table in the block dialog box.

Tip

You can modify dashboard block connections in your model during normal and accelerator mode simulations.

Note

Dashboard blocks cannot connect to variables until you update the model diagram. To connect dashboard blocks to variables or modify variable values between opening your model and running a simulation, update the model diagram using Ctrl+D.

To enter connect mode, in the canvas, select the dashboard block to connect. On the Simulink® Toolstrip, a tab named after the type of the selected block appears. On the block tab, click Connect. In connect mode, when you select one or more blocks, a list of parameters and variables available for connection appears. Select a variable or parameter from the list to connect to the selected dashboard block.

When the value of the selected variable or block parameter is nonscalar, use the text box at the bottom of the Connection table to specify the element you want to connect to the dashboard block. To connect to an element of a vector, matrix, or array, specify the element index, for example, 3 or (1,3). To connect to an element in a bus or structure, specify the element in the context of the bus or structure hierarchy by using dots to indicate different levels in the hierarchy, and omit the top level. For example, specify a.b to connect to scalar element b of the structure or bus a nested inside the selected composite variable or parameter.

To connect another dashboard block, pause on another dashboard block and click the Connect button above it. Then, make a selection of signals and blocks in your model and choose a model element to connect.

A Knob block from the Dashboard library is in connect mode. To the right of the Knob block is a Sine Wave block that connects to a Gain block that connects to an Outport block. To the right of the Outport block is the list of parameters and variables available for connection.

When you finish connecting the dashboard blocks in your model, on the block tab, click Done Connecting.

Tip

You can hide the message shown on unconnected blocks using the set_param function with the ShowInitialText block parameter. The message also disappears when you connect the block.

Parameter Logging

Tunable parameters connected to dashboard blocks are logged to the Simulation Data Inspector, where you can view the parameter values along with logged signal data. You can access logged parameter data in the MATLAB® workspace by exporting the parameter data from the Simulation Data Inspector by using the UI or the Simulink.sdi.exportRun function. For more information about exporting data using the Simulation Data Inspector UI, see Export Data to Workspace or File. The parameter data is stored in a Simulink.SimulationData.Parameter object, accessible as an element in the exported Simulink.SimulationData.Dataset.

Limitations

  • Except for the Dashboard Scope block and the Display block, dashboard blocks can only connect to real scalar signals.

  • The toolstrip does not support blocks that are inside a panel.

  • You cannot use the Connection table in the block dialog to connect a dashboard block to a block that is commented out. When you connect a dashboard block to a commented block using connect mode, the dashboard block does not display the connected value until the you uncomment the block.

  • Dashboard blocks cannot connect to model elements inside referenced models.

  • When you simulate a model hierarchy, dashboard blocks inside referenced models do not update.

  • Dashboard blocks do not support rapid accelerator simulation.

  • When you connect a dashboard block to a variable or parameter during simulation, the data for that variable or parameter is not logged to the Simulation Data Inspector. To log variable and parameter data to the Simulation Data Inspector, connect the dashboard block to the variable or parameter prior to simulation.

  • When you simulate a model in external mode with the Default parameter behavior set to Inlined, dashboard blocks can appear to change parameter and variable values. However, the change does not propagate to the simulation. For example, Gain blocks display changes made to the Gain parameter using the dashboard blocks, but the Gain value used in the simulation does not change.

Parameters

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Use the Property Inspector and the Block Parameters dialog box to specify the values of the block parameters. To set the core parameters of the dashboard block, use the Block Parameters dialog box or the Parameters tab in the Property Inspector. To customize the block, use the Design tab in the Property Inspector. To open the Block Parameters dialog box for a block, double-click the block. To open the Property Inspector, on the Modeling tab, under Design, select Property Inspector.

Parameters

To set the core parameters of the dashboard block, open the Property Inspector and click the Parameters tab.

Connection

Use the Connection table in the Block Parameters dialog box to select or change the variable or block parameter to control. To connect the block to a variable or block parameter:

  1. If the block is not connected, in the Property Inspector, on the Parameters tab, click Connect to open the Block Parameters dialog box. If the block is already connected and you want to change the signal to which it connects, click Change.

  2. Select a block in the model.

  3. Select the variable or parameter you want to connect.

    When the value of the selected variable or block parameter is nonscalar, use the text box at the bottom of the Connection table to specify the element you want to connect to the dashboard block. To connect to an element of a vector, matrix, or array, specify the element index, for example, 3 or (1,3). To connect to an element in a bus or structure, specify the element in the context of the bus or structure hierarchy by using dots to indicate different levels in the hierarchy. Omit the top level. For example, specify a.b to connect to scalar element b of the structure or bus a nested inside the selected composite variable or parameter.

  4. Click Apply.

To help understand and debug your model, you can connect Dashboard blocks to variables and parameters in your model during simulation.

Note

To see workspace variables in the connection table, update the model diagram using Ctrl+D.

Tip

You can also use bind mode to select or change the variable or block parameter to control. To enter bind mode:

  • If you are in design mode, exit by clicking the Edit button on the Design tab of the Property Inspector.

  • Click the dashboard block in the canvas. If the dashboard block is not connected, Connect Connect button and an ellipsis appear over the dashboard block. If the dashboard block is already connected, only the ellipsis appears.

  • If the dashboard block is not connected, click Connect. If the dashboard block is connected, pause on the ellipsis. In the action menu that expands, click Connect. In either case, a list of parameters and variables available for connection appears.

The left image shows a selected dashboard block with the Connect button and the ellipsis hovering above it. The right image shows the same dashboard block with the action menu expanded above it, and the pointer hovering over the Connect button.

To connect the dashboard block in bind mode:

  • From the list, select the variable or parameter you want to connect.

  • To exit bind mode, click Done Connecting Done Connecting buttonover the dashboard block.

Programmatic Use

To programmatically connect a dashboard block to a tunable parameter or a variable, use a Simulink.HMI.ParamSourceInfo object. The Simulink.HMI.ParamSourceInfo object contains four properties. Some properties apply to connecting dashboard blocks to parameters. Some properties apply to connecting dashboard blocks to variables. Not all fields have a value for a connection because a given dashboard block connects to either a parameter or a variable.

Block Parameter: Binding
Type: Simulink.HMI.ParamSourceInfo
Default: []
Main

Finite, real, double, scalar value specifying the minimum tick mark value for the scale. The parameter value must be less than the value of the Maximum parameter.

Programmatic Use

To programmatically set the Minimum parameter, use a 1-by-3 vector containing values for the Minimum, Tick Interval, and Maximum parameters, in that order. To use the auto value for the Tick Interval, leave the Tick Interval position in the vector empty, or specify -1.

Block Parameter: Limits
Type: 1x3 vector
Default: [0 -1 100]

Finite, real, double, scalar value specifying the maximum tick mark value for the scale. The parameter value must be greater than the value of the Minimum parameter.

Programmatic Use

To programmatically set the Maximum parameter, use a 1-by-3 vector containing values for the Minimum, Tick Interval, and Maximum parameters, in that order. To use the auto value for the Tick Interval, leave the Tick Interval position in the vector empty, or specify -1.

Block Parameter: Limits
Type: 1x3 vector
Default: [0 -1 100]

Finite, real, positive, whole, scalar value specifying the interval of major tick marks on the scale. When set to auto, the block automatically adjusts the tick interval based on the values of the Maximum and Minimum parameters.

Programmatic Use

To programmatically set the Tick Interval parameter, use a 1-by-3 vector containing values for the Minimum, Tick Interval, and Maximum parameters, in that order. To use the auto value for the Tick Interval, leave the Tick Interval position in the vector empty, or specify -1.

Block Parameter: Limits
Type: 1x3 vector
Default: [0 -1 100]

Set the direction of increasing scale values.

Programmatic Use

Block Parameter: ScaleDirection
Type: character vector
Values: 'Clockwise' | 'Counterclockwise'
Default: 'Clockwise'

You can display the name of the element to which the dashboard block connects in a label positioned at the top or at the bottom of the block, or you can hide the label. If you want the label to be visible, specify the position of the block. If you do not want the label to be visible, specify Hide.

Note

When the dashboard block is not connected to an element, the label is blank.

Programmatic Use

Block Parameter: LabelPosition
Type: character vector
Values: 'Hide' | 'Bottom' | 'Top'
Default: 'Hide'

Select this parameter to maintain the aspect ratio when resizing the block in the Simulink canvas.

Tip

  • When the aspect ratio is locked, adding a new background image changes the aspect ratio of the block to match that of the background image.

  • When the aspect ratio is not locked, adding a new background image does not change the proportions of the block but instead stretches or scales the background image to fit the size of the block.

Design

To customize the dashboard block, open the Property Inspector, click the Design tab, and click Edit.

Knob

Select this parameter to maintain the aspect ratio when resizing the block in the Simulink canvas.

Tip

  • When the aspect ratio is locked, adding a new background image changes the aspect ratio of the block to match that of the background image.

  • When the aspect ratio is not locked, adding a new background image does not change the proportions of the block but instead stretches or scales the background image to fit the size of the block.

Scale

Finite, real, double, scalar value specifying the minimum tick mark value for the scale. The parameter value must be less than the value of the Maximum parameter.

Programmatic Use

To programmatically set the Minimum parameter, use a 1-by-3 vector containing values for the Minimum, Tick Interval, and Maximum parameters, in that order. To use the auto value for the Tick Interval, leave the Tick Interval position in the vector empty, or specify -1.

Block Parameter: Limits
Type: 1x3 vector
Default: [0 -1 100]

Finite, real, double, scalar value specifying the maximum tick mark value for the scale. The parameter value must be greater than the value of the Minimum parameter.

Programmatic Use

To programmatically set the Maximum parameter, use a 1-by-3 vector containing values for the Minimum, Tick Interval, and Maximum parameters, in that order. To use the auto value for the Tick Interval, leave the Tick Interval position in the vector empty, or specify -1.

Block Parameter: Limits
Type: 1x3 vector
Default: [0 -1 100]

Finite, real, positive, whole, scalar value specifying the interval of major tick marks on the scale. When set to auto, the block automatically adjusts the tick interval based on the values of the Maximum and Minimum parameters.

Programmatic Use

To programmatically set the Tick Interval parameter, use a 1-by-3 vector containing values for the Minimum, Tick Interval, and Maximum parameters, in that order. To use the auto value for the Tick Interval, leave the Tick Interval position in the vector empty, or specify -1.

Block Parameter: Limits
Type: 1x3 vector
Default: [0 -1 100]

Specify the value on the scale from which the handle moves and the value bar grows. When set to auto, the Origin is the minimum of the scale.

Example: 0

Set the direction of increasing scale values.

Programmatic Use

Block Parameter: ScaleDirection
Type: character vector
Values: 'Clockwise' | 'Counterclockwise'
Default: 'Clockwise'

Specify the arc length of the scale as a scalar value, measured in degrees.

Example: 90

Specify the angular location of the minimum scale value, measured in degrees clockwise from the horizontal axis pointing right.

Example: 0

Specify the radius of the free end of the scale tick marks as a ratio of the smaller of the two dimensions of the bounding box of the scale, width or height. The Inner Radius can be larger than the Outer Radius.

Example: 0.5

Specify the span line radius as a ratio of the smaller of the two dimensions of the bounding box of the scale, width or height. The Outer Radius can be smaller than the Inner Radius.

Example: 0.5

Specify the horizontal offset of the left edge of the bounding box of the scale from the left edge of the block as a ratio of the block width. Relative to the position of the scale when the offset is 0, an offset with a negative value moves the scale left, and an offset with a positive value moves the scale right.

Example: 1

Specify the vertical offset of the top edge of the bounding box of the scale from the top edge of the block as a ratio of the block height. Relative to the position of the scale when the offset is 0, an offset with a negative value moves the scale up, and an offset with a positive value moves the scale down.

Example: 1

Specify the width of the bounding box of the scale as a ratio of the block width.

Example: 2

Specify the height of the bounding box of the scale as a ratio of the block height.

Example: 2

Enable on this option to maintain the aspect ratio when resizing the scale using the Property Inspector.

Set the color of the scale tick marks, the span line, and the block name. Choose a color from the palette of standard colors, or specify a custom color.

Tip

You can also set the Tick Color by choosing a Foreground Color on the Format tab of the Simulink Toolstrip.

To specify the color of the block text, use the Label Color parameter.

Programmatic Use

Specify the ForegroundColor parameter for the block as a string or a character vector that defines a 1-by-3 [r g b] vector with values between 0 and 1.

Block Parameter: ForegroundColor
Type: character vector | string
Values: [r g b] vector

Choose a font color for the scale label from the palette of standard colors, or specify a custom color.

Tip

To specify the color of the scale, use the Tick Color parameter.

Specify the distance of the labels from the center of the scale as a ratio of the smaller of the two block dimensions, width or height.

Example: 0.5

Handle

Specify the width of the handle image as a ratio of the smaller of the two dimensions of the bounding box of the scale, width or length.

Example: 1

Specify the height of the handle image as a ratio of the smaller of the two dimensions of the bounding box of the scale, width or length.

Example: 1

Enable this option to maintain the aspect ratio when resizing the image using the Property Inspector.

Rotate the handle image about its center in 90 degree increments.

Example: 90

Specify the distance from the center of the handle image to the center of the scale as a ratio of the diameter of the scale.

Example: 1

Background Image

For the block background, you can provide a background image, or to select a solid color. To select a solid background color, turn Use Background Color on. To provide a background image, turn Use Background Color off.

Note

Changing the background color using the toolstrip removes the background image and enables the Use Background Color option.

When you use a solid background with the Circular Gauge block, you can design noncircular gauges. When the scale arc angle is 180° or smaller, the background shape conforms to the scale.

Knob block with noncircular orange background area

Example: on

To select a solid background color, enable the Use Background Color parameter. Then, choose a background color from the palette of standard colors, or specify a custom color.

Note

When you use a solid background with the Circular Gauge block, you can design noncircular gauges. When the scale arc angle is 180° or smaller, the background shape conforms to the scale.

Knob block with noncircular orange background area

Programmatic Use

Specify the BackgroundColor parameter for the block as a 1-by-3 [r g b] vector with values between 0 and 1 that is formatted as a string or a character vector.

Block Parameter: BackgroundColor
Type: character vector | string
Values: [r g b] vector

Specify the block background opacity as a scalar value from 0 to 1.

Example: 0.5

Set the offset of the outer edge of the area covered by the block background color from tick marks, specified as a scalar value from 0 to 1.

Example: 0.1

Foreground Image

Specify the horizontal offset of the left edge of the image from the left edge of the block as a ratio of the block width. Relative to the position of the image when the offset is 0, an offset with a negative value moves the image left, and an offset with a positive value moves the image right.

Example: 1

Specify the vertical offset of the top edge of the image from the top edge of the block as a ratio of the block height. Relative to the position of the image when the offset is 0, an offset with a negative value moves the image up, and a positive value moves the image down.

Example: 1

Specify the image width as a ratio of the block width.

Example: 0.5

Specify the image height as a ratio of the block height.

Example: 0.5

Select this parameter to maintain the aspect ratio when resizing the image using the Property Inspector.

Block Characteristics

Data Types

double | half | integer | single

Direct Feedthrough

no

Multidimensional Signals

no

Variable-Size Signals

no

Zero-Crossing Detection

no

Extended Capabilities

Version History

Introduced in R2021a

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