Variant Sink - Route amongst multiple outputs using variants - Simulink (original) (raw)

Route amongst multiple outputs using variants

Libraries:
Simulink / Signal Routing

Description

The Variant Sink block enables you to include multiple implementations of a component on the destination (sink) of a signal in a single layer.

For example, suppose you want to simulate this model to control the speed of the car windshield wiper by using different rain sensors. The Variant Source block switches between different rain sensors. The control logic uses this information to output the result to the Variant Sink block. The Variant Sink then switches between the wiper motor model during simulation and the command to the sensor during code generation. The variant blocks switch between choices based on the Types of Variant Control Modes in Variant Blocks you select. For more information, see Introduction to Variant Controls.

Note

At most, one variant choice connected to output port of the Variant Sink block is active during simulation.

The Variant Sink block has only one input port and one or more output ports. You can connect the varying choices to the output port of the block so that, at most, one choice is active during model execution.

The Variant Sink block is associated with a Variant control mode and a Variant activation time. The variant control mode determines how to specify the variant control. The variant activation time determines a time to activate the choices and to decide whether to include only the active choice or both active and inactive choices in the generated code. During simulation, Simulink® connects the active choice directly to the input port of theVariant Sink block and ignores the inactive choices.

Using a Variant Sink block allows you to:

• Propagate variant conditions throughout the model.
• Visualize all possible implementations of variant choices in a single layer of your model, which improves model readability.
• Simulink eliminates inactive blocks throughout the model, which improves runtime performance. If all the variant choices are inactive, Simulink removes the variant region completely from your model.
• Variant sources and sinks provide variant component interfaces that you can use to quickly model variant choices.

The color and icon of the variant badge on the block icon changes depending on the values of the Variant activation time, Variant control mode, and Allow zero active variant controls parameters set on the block. For more information, see Variant Badges.

Examples

Limitations

The Variant Sink block works with time-based, function-call, and action signals. You cannot use SimEvents®, Simscape™ Multibody™, or other non-time-based signals with these blocks.

Ports

Input

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Input signal to be connected to the active output port.

You can auto insert inport on the Variant Sink block by hovering the mouse over the block side or by dragging the signal near the block boundary. You can delete the port by either clicking delete on the keyboard or with a mouse click.

Data Types: single | double | half | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | enumerated | bus | struct

Output

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Output signal from the first variant. The variant control that evaluates totrue determines which output port is active.

You can auto insert outport on the Variant Sink block by hovering the mouse over the block side or by dragging the signal near the block boundary. You can delete the port by either clicking delete on the keyboard or with a mouse click.

Data Types: single | double | half | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | enumerated | bus

Output signal from the _N_th variant. The variant control that evaluates to true determines which output port is active.

Data Types: single | double | half | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | enumerated | bus

Parameters

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The variant control that determines the active variant choice can be any of these types.

• expression — The software chooses the active variant based on the evaluation of the variant conditions. When a condition expression evaluates totrue, the corresponding variant choice becomes active. When a condition expression evaluates to false, the corresponding variant choice becomes inactive. See Switch Between Choices Using Condition Expressions in Variant Blocks.
• label — The software chooses the active variant based on the name of the variant. The variant control is a string and does not require you to create any variable in any workspaces. See Switch Between Choices Using Labels in Variant Blocks.
• sim codegen switching — Automatically switch between the variants for simulation and code generation workflows without creating any workspace variable. When you simulate a model, the software automatically chooses thesim branch as the active choice. Similarly, when you do a software-in-the-loop (SIL) or processor-In-Loop (PIL) simulation, generate code, or use external mode, the software automatically chooses the codegen branch. See Switch Between Choices for Simulation and Code Generation Workflows Without Using Control Variables in Variant Blocks.

For more information on variant control modes, see Introduction to Variant Controls. For a comparison between different types of variant control modes, see Compare Different Types of Variant Control Modes in Variant Blocks.

Dependencies

The availability of different variant activation times depends on the type of theVariant control mode that you specify. TheVariant activation time parameter determines the time when the software sets the active choice. The parameter also determines which variability to include in the generated code. This table explains the variant activation time supported by each variant control mode.

Programmatic Use

This parameter determines which variability to include in the simulation and code generation workflows. For more information, see Activate Variant During Different Stages of Simulation and Code Generation Workflow.

• update diagram — When you execute the model, only the active choice is included in the simulation and the code generation workflow. Generated code contains only the active choice.
• update diagram analyze all choices — When you execute the model, both active and inactive choices are analyzed for consistency across the model. However, only the active choice is included in the simulation and the code generation workflow. Generated code contains only the active choice.
• code compile — When you execute the model, both active and inactive choices are analyzed for consistency across the model, and all choices are included in the simulation and the code generation workflow. Generated code contains both the active and inactive choices enclosed in the preprocessor conditionals #if and #elif. However, the executable built from the generated code contains only active choice.
• startup — When you execute the model, both active and inactive choices are analyzed for consistency across the model, and all choices are included in the simulation and the code generation workflow. With this option, you can improve the speed of iterative simulations using fast restart. For more information, see Run Iterative Simulations Without Recompiling Model for Variant Systems Using Fast Restart. Code generated from the model contains both the active and inactive choices that are enclosed in regular if conditions. The executable built from the generated code also contains both active and inactive choices.
• inherit from Simulink.VariantControl — When you execute the model, the block inherits the activation time from its variant control variables of type Simulink.VariantControl. If a variant block has multiple variant control variables of type Simulink.VariantControl, then all those variables must have the same activation time.

Dependencies

The availability of different variant activation times depends on the type of the variant control mode that you specify. The Variant activation time parameter determines when the software sets the active choice. The parameter also determines which variability to include in the generated code. This table explains the variant activation time supported by each variant control mode.

Programmatic Use

The table has a row for each variant choice connected to the output port of the Variant Sink block. If there are no variant choices, the table is empty.

You can use buttons to the left of the Port and associated conditions table to modify the elements in the table.

To...	Click...
Add a new output port: Create a new output port as a variant choice and add an entry for the new choice in the table.
Delete selected port: Delete the selected variant choice from the block and its entry from the table.
Create/Edit selected variant object: Create or edit a Simulink.VariantExpression object for the selected variant choice in the global workspace and specify the variant condition using theSimulink.VariantExpression object parameter dialog box.NoteFor a model that uses the base workspace, this operation creates theSimulink.VariantExpression object in the base workspace, and the object is available only for the current MATLAB® session. To permanently store the data, save the object in a MAT file or MATLAB script.

Number of the output port that is connected to one variant choice upstream of the Variant Sink block. This value is read-only.

Click to add a port or to delete an existing one.

A name for a choice, specified as a string.

Dependencies

To enable this parameter, set Variant control mode to label.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Example: set_param(gcb, 'VariantControls', {'A == 1','A == 2'}), where gcb is theVariant Sink or Variant Source block.

Example: get_param(gcb, 'VariantControls'), where gcb is the Variant Sink orVariant Source block.

Specify (sim) to activate the corresponding variant choice during simulation. Specify (codegen) to activate the corresponding variant choice while performing code generation workflows such as SIL, PIL, external mode, and so on.

Dependencies

To enable this parameter, set Variant control mode to sim codegen switching.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Example: set_param(gcb, 'VariantControls', {'(sim)','(codegen)'}), where gcb is the Variant Sink or Variant Source block.

Example: get_param(gcb, 'VariantControls'), where gcb is the Variant Sink orVariant Source block.

Specify the condition expression to determine the active choice. When a condition expression evaluates to true, the software activates the corresponding variant choice. When a condition expression evaluates tofalse, the software deactivates the corresponding variant choice.

The variant controls can be:

• Boolean condition expression for rapid prototyping. For example,A == 1, A ~= B, A && B == 1, and so on.
• A Simulink.VariantExpression object that contains a condition expression for condition reuse. See Simulink.VariantExpression Objects for Variant Condition Reuse of Variant Blocks.
• Default Variant Choice if none of the choices evaluates totrue.

Here, A and B are operands called as variant control variables. ==,~=, and && are operators in the condition expression. The condition expression can contain one or more such variant control variables and operators. For information on supported types and storage location of variant control variables, see Types of Variant Control Variables (Operands) in Variant Blocks and Storage Locations for Variant Control Variables (Operands) in Variant Blocks. For information on operators, see Types of Operators in Variant Blocks for Different Activation Times.

For more information, see Switch Between Choices Using Condition Expressions in Variant Blocks.

In Variant Assembly Subsystem block, this parameter is a list of auto-generated boolean expressions with Variant control variable on the left-hand side and the members of the Variant enumeration choice are on the right-hand side of the expressions. Both the sides of the expressions are connected with ==. This parameter is read-only.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Variant Subsystem block:

Example: set_param(gcb, 'VariantControl', 'V == 3'), wheregcb is the variant choice of the Variant Subsystem block.

Example: get_param(gcb, 'VariantControl'), wheregcb is the variant choice of the Variant Subsystem block.

Variant Source and Variant Sink blocks:

Example: set_param(gcb, 'VariantControls', {'A == 1','A == 2'}), where gcb is the Variant Sink or Variant Source block.

Example: get_param(gcb, 'VariantControls'), wheregcb is the Variant Sink or Variant Source block.

This parameter is read-only.

This parameter displays the condition expression specified asSimulink.VariantExpression object. To change or edit the condition expression, use the Simulink.VariantExpression parameter dialog box that appears when you double-click the object in the workspace.

Note

The operands that you specify in a condition expression of typeSimulink.VariantExpression must be defined in the base workspace or a data dictionary. Specifying operands that are defined in the mask or model workspace is not supported.

This list contains the labels of all the variant choices. To set an active choice, select a label from the list. The corresponding choice becomes active. Alternatively, to change the active choice in label mode, you can follow the approaches described in Set Active Choices Using Variant Control Labels.

Dependencies

To enable this parameter, set Variant control mode tolabel.

Programmatic Use

• off — Simulink generates an error when there is no active variant choice.
• on — When you select this parameter and if there is no active variant choice, Simulink simulates the model without any active variant choice connected to the Variant Sink block. Simulink disconnects all the blocks connected to the input and output stream of Variant Sink block, thus removing the variant regions completely from the model execution.

Consider the car windshield wiper example in the Description section. Suppose you do not want to pass the wiper speed to either of the variant choices, wiper motor and D/A. When you simulate the model withAllow zero active variant controls set toon and if there is no active variant choice in theVariant Sink controlled by mode block, Simulink disconnects the Variant Sink controlled by mode block and all its connected blocks, which removes the variant region completely from the model.

This table shows the code that you generate with and without the Allow zero active variant controls parameter for the code compile activation time. In the code that you generate with Allow zero active variant controls set tooff, only the variant choices wiper motor and D/A are conditional, whereas theGain block is unconditional. The Gain block is unconditional, and so it executes for either of the choices. This code support only scenarios where either of the choices evaluate totrue. If none of the choices evaluate totrue, both the choices are removed from compilation. The output of the Gain remains unused and this results in an error. In the code that you generate with Allow zero active variant controls set to on, the variant choices wiper motor, D/A, and the connected Gain blocks are conditional. So, if none of the choices evaluate to true, the Gain block is also removed, thus enabling you to completely remove the variant region from code compilation.

Dependencies

This parameter is available only if you set Variant control mode to expression.

Programmatic Use

When you select this option, Simulink annotates the variant condition expression on each port of theVariant Sink block.

Programmatic Use

Block Characteristics

Extended Capabilities

Version History

Introduced in R2016a

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The Variant Source and Variant Sink blocks issue errors by displaying a red border for undefined variant control variables during model editing. To see a description of the error, pause on the highlighted block, and then click the error symbol to open the notification dialog box with predefined fixes. Select the most appropriate fix, and click theFix button. You may need to provide additional information to resolve the error. If successful, the red border disappears. If not, a failure message appears.