Knob

Tune parameter value with dial

• Library:

• Simulink / Dashboard

• 

Description

The Knob block tunes the value of the connected block parameter to during simulation. For example, you can connect the Knob block to a Gain block in your model and adjust its value during simulation. You can modify the range of the Knob block's scale to fit your data. Use the Knob block with other Dashboard blocks to create an interactive dashboard to control your model.

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.

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 the Workspace or a 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

Connection — Select a variable or block parameter to connect

variable and parameter connection options

Select the variable or block parameter to control using the Connection table. To connect the block to a signal:

1. Make a selection in the model that includes one or more blocks.

2. 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, 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.

3. Click Apply.

To facilitate understanding and debugging 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.

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 of the properties apply to connecting dashboard blocks to parameters, and some 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: []

Scale Type — Type of scale

Linear (default) | Log

Type of scale displayed on the block. Linear specifies a linear scale, and Log specifies a logarithmic scale.

Programmatic Use

Block Parameter: ScaleType

Type: string or character vector

Values: 'Linear' | 'Log'

Default: 'Linear'

Minimum — Minimum tick mark value

0 (default) | scalar

Finite, real, double, scalar value specifying the minimum tick mark value for the scale. The minimum 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]

Maximum — Maximum tick mark value

100 (default) | scalar

Finite, real, double, scalar value specifying the maximum tick mark value for the scale. The maximum 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]

Tick Interval — Interval between major tick marks

auto (default) | scalar

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]

Label — Block label position

Top (default) | Bottom | Hide

Position of the block label. When the block is connected to an element in the model, the label is the name of the connected element.

Programmatic Use

Block Parameter: LabelPosition

Type: character vector

Values: 'Top' | 'Bottom' | 'Hide'

Default: 'Top'

Model Examples

Interactively Simulate a Thermal Model of a House

Use Dashboard blocks to configure and then interactively simulate a thermal model of a house.

Open Model

Interactively Simulate a Vehicle Climate Control System

Use a dashboard of controls and indicators to interact with the simulation of an automobile climate control system.

Open Model

Block Characteristics

Data Types	double | half | integer | single
Direct Feedthrough	no
Multidimensional Signals	no
Variable-Size Signals	no
Zero-Crossing Detection	no

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using Simulink® Coder™.

Dashboard blocks are ignored for code generation.

Version History

Introduced in R2015a