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.

Connecting Dashboard Blocks

Dashboard blocks do not use ports to make connections. To connect Dashboard blocks to variables and block parameters in your model, 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. If you only want to connect a single Dashboard block, you can also use the Connection table in the block dialog box to make the connection.

Tip

To facilitate understanding and debugging your model, 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 your model diagram. To connect Dashboard blocks to variables or modify variable values between opening your model and running a simulation, update your model diagram using Ctrl+D.

To enter connect mode, click the Connect button that appears above your unconnected Dashboard block when you pause on it.

In connect mode, when you select one or more signals or blocks, a list of parameters and signals available for connection appears. Select a signal or parameter from the list to connect the selected Dashboard block. To connect another Dashboard block, pause on the block and click the Connect button above it. Then, make a selection of signals and blocks in your model, and choose a signal or parameter to connect.

When you finish connecting the Dashboard blocks in your model, click the Exit button in the upper-right of the canvas to exit connect mode.

Tip

You can hide the message shown on unconnected blocks using the set_param function with the ShowInitialText block parameter.

Parameter Logging

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

Limitations

• Dashboard blocks can only connect to real scalar signals.

• You cannot use the Connection table 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 signals 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.

• Some signals are not available during accelerator mode simulations. To view such signals on a Dashboard block, mark the signal for logging.

• Parameters specified by indexing a variable array do not appear in the Connection table. For example, a block parameter defined as engine(1) using the variable engine does not appear in the table.

  To access the parameter in the Connection table, assign the indexed value to a scalar variable, such as engine_1. Then, use the scalar variable to define the block parameter.

• When you connect a Dashboard block to a variable or parameter during simulation, the data for that variable or parameter does not get 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, the Gain block displays changes made to its 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. Populate the Connection table by selecting one or more blocks in your model. Select the radio button next to the variable or parameter you want to control, and 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 control. 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 arc. The minimum must be less than the value entered for the maximum.

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 arc. The maximum must be greater than the value entered for the minimum.

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, integer, scalar value specifying the interval of major tick marks on the arc. When set to auto, the block automatically adjusts the tick interval based on the minimum and maximum values.

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 | 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.