What is a Variant Configuration?

Using variant elements in Simulink, you can represent all design alternatives of a system component in a single model. Each variant of a system component is depicted as a variant choice in the model. A variant control associated with each variant choice allows you to activate or deactivate the choice in the model.

For example, consider a model for a system with a plant and a controller. The controller component has three variant choices, Linear, NonLinear, and Smart. The plant component has two choices, External and Internal. This model uses Variant Subsystem blocks to represent these components and their choices. Combinations of these variant choices represents different modes or different configurations of the system, for example, a linear controller with an internal plant with no noise or a nonlinear controller with an external low fidelity plant. The latter configuration is shown in this figure.

A variant configuration represents a combination of variant choices across the model hierarchy. It contains a set of variant control variables and their values, which you can use to activate a specific variant in the model hierarchy. It helps you to easily define and manage variation points in a model.

The number of variant configurations for a model can be high depending on the number of variant choices. Configuring the choices and switching between them manually can be complicated and can introduce errors. You can use Variant Manager to define, apply, and manage variant configurations for the model.

Variant Manager enables you to:

Types of Variant Configurations

You can automatically generate all possible variant configurations for a model using Variant Manager. See Generate Variant Configurations Automatically.

Constraints on Variant Configurations

A constraint is a user defined check that you can use to prevent invalid variant combinations in a model. The constraint must be satisfied by all variant configurations created for the model. It is represented as a condition expression created using variant control variables. The expression must evaluate to true to satisfy the constraint.

For example, this constraint checks that a Linear controller in a system does not have an External plant.

~((Ctrl == ControllerType.Linear) && (PlantLoc == PlantLocation.External))

When a model is associated with a VariantConfigurationObject that has constraints, Simulink validates the variant configurations against these constraints during Variant Manager activation, update diagram, simulation, and code generation workflows.

Variant Configuration Data Object

You can use a variant configuration data object of type Simulink.VariantConfigurationData to manage and reuse variant configurations for a model. The object stores all the variant configurations and constraints created for a model. You can define the object in the base workspace or in the Configurations section of a data dictionary. If the model is not associated with a variant configuration data object, Variant Manager helps you to setup a new variant configuration data object.

From the Manage tab in Variant Manager, you can:

For an example that shows how to perform these actions from Variant Manager, see Save and Reuse Variant Configurations Using Variant Configuration Data Object.

The Simulink.VariantConfigurationData class has methods that enable you to add or remove variant configurations, constraints, and control variables.

vcdo = Simulink.VariantManager.getConfigurationData('model');

get_param('model','VariantConfigurationObject');

% Associate vcdo
set_param('model','VariantConfigurationObject','name_of_vcdo');
% Disassociate vcdo
set_param('model','VariantConfigurationObject','');
% Save the model
save_system('model');

Activate a Variant Configuration

Activating a variant configuration using Variant Manager validates that the variant elements in the model and the variant configuration are set up correctly and applies the configuration to the model. It also validates the configuration against applicable constraints. You can then compile, simulate, or generate code from the model for this configuration.

You can activate these configurations from Variant Manager:

For detailed steps to create and activate a variant configuration, see Create and Activate Variant Configurations. To activate a variant configuration programmatically, use the Simulink.VariantManager.activateModel method.

Differences Between Variant Manager Activation and Update Diagram Process

Activation of a variant configuration using Variant Manager or using the Simulink.VariantManager.activateModel method differs from the update diagram process that Simulink performs before simulation or when you update the diagram while editing the model (Ctrl+D).

Activation using Variant Manager analyzes variant elements such as variant blocks, variant parameters, or variant transitions in the model individually. The process validates that the variant elements and the variant configuration are set up correctly and then activates the configuration for the model. For example, for a variant block with Variant control mode set to expression, the process evaluates the variant controls on the block and checks if the control variables used by the block are present in the variant configuration. Variant Manager does not analyze activeness information based on block connectivity and variant condition propagation.

Referenced Component Configurations

The variant configurations for a top-level model must also define the variant control variables used by any referenced components in the model hierarchy, such as referenced models. This approach helps to maintain a single consistent definition for a variant control across the hierarchy.

If the referenced component has existing named variant configurations of its own, you can use them to set up the corresponding variant control variables in the top-level model configuration. For more information, see Compose Variant Configurations for Top Model Using Referenced Model Configurations.

Preferred Configuration

You can set any of the named configurations defined for a model as the preferred variant configuration. You can use this property to indicate the configuration that is suited for the model for common workflows.

To programmatically apply the PreferredConfiguration on your model before compiling or simulating the model, use the applyConfiguration method:

% Get the variant configuration data object for your model
vcd = Simulink.VariantManager.getConfigurationData(model);
% Apply the preferred configuration on the model
Simulink.VariantManager.applyConfiguration ...
(model, 'Configuration', vcd.getPreferredConfigurationName());

Simulink.VariantManager.applyConfiguration ...
 (model, 'Configuration', Simulink.VariantManager.getPreferredConfigurationName(model));

Variant Manager View of Variant Configurations

Open the slexVariantManagement model using the following command.

openExample('simulink_variants/VariantConfigurationObjectForAModelRefPageExample');
open_system('slexVariantManagement');

View the Configurations tab in Variant Manager.

Limitations