Unbounded Variable-Size Signal Basic Operations

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This example shows how to use unbounded variable-size signals in Simulink® modeling. For more information about the general concept of unbounded variable-size signals, see Unbounded Variable-Size Signals.

This model describes how to configure blocks to use unbounded variable-size signals. 

open_system('ex_boundedsignals')

Model with blocks that use fixed finite size signals.

The following sections describe how to configure the Inport block, MATLAB Function block, MATLAB System block, Simulink.Signal object and Simulink.Bus object to use unbounded variable-size signals.

Configure Inport Block to Generate Unbounded Variable-Size Signals

To generate unbounded variable-size signals from Inport blocks, in the block dialog box:

  • On the Signal Attributes tab, set the appropriate values of Port dimensions as Inf. Set Variable-size signal to Yes to allow variable-size signals.

  • On the Execution tab, set the Sample time to a discrete rate and clear Interpolate data check box.

In this example:

  • For the Inport1 and Inport2 blocks connected to the input ports u1 and u2, respectively, of the MATLAB System block, on the Signal Attributes tab, set the Port dimensions parameter to [Inf 6], and set Variable-size signal to Yes. On the Execution tab, set the Sample time value to 1, and clear the Interpolate data check box. Click Apply and OK.

  • For the Inport3 block connected to the input port of the Selector block, on the Signal Attributes tab, set the Port dimensions parameter to [Inf 6], and set Variable-size signal to Yes. On the Execution tab, set the Sample time value to 1, and clear the Interpolate data check box. Click Apply and OK.

Parameter settings in the Signal Attributes tab of the Inport1 block.

Parameter settings in the Execution tab of the Inport1 block.

To use an unbounded variable-size signal as index signal to the Selector block, replace the Constant block with an Inport block. Configure the Inport block to generate the index signal with dimension Inf, data type uint16 and sample time 1. Click Apply and OK.

Right-click on the signal named indexSig , and select Properties > Signal name must resolve to Simulink signal object. Click Apply and OK.

For the Selector block, in the Block Parameters dialog box, select Number of input dimensions as 2 and set Index vector (dialog) to [3 4 5]. Click Apply and OK.

Configure MATLAB Function Block for Unbounded Variable-Size Signals

Specify the size of a variable-size input/output signal associated with the MATLAB Function block. To interactively configure the MATLAB Function block, in the Simulink Editor, on the Modeling tab, from the Design gallery, select Model Explorer. From the Model Explorer window, select the MATLAB Function. Set the dimension in Size to [Inf 6] and select Variable size check box. Click Apply to apply the changes.

MATLAB Function block configuration to handle unbounded variable-size signals.

Configure MATLAB System Block and System Objects for Unbounded Variable-Size Signals

The MATLAB System block uses the System object® sigOps that adds and computes difference between two signals. While configuring the System Object® for unbounded variable-size signals, set the flag for isOutputFixedSizeImpl to false and change the output dimensions for getOutputSizeImpl to [Inf 6].

MATLAB system object named sigOps is configured for unbounded variable-size signals.

Configure Simulink.Signal Object as Unbounded Variable-Size Signal

Specify the size of a variable-size Simulink.Signal object as unbounded. To programmatically configure the signals, in the Simulink Editor, on the Modeling tab, select Model Settings > Model Properties. In the Model Properties dialog box, on the Callbacks tab, select PreLoadFcn to edit the Simulink.Signal object properties.

For the signal object:

  • Set Dimensions value to Inf.

  • Set DimensionsMode to Variable.

In the PreLoadFcn section of the Callbacks tab, the Simulink signal object is configured as an unbounded variable-size signal.

Configure Simulink.Bus Object as Unbounded Variable-Size Signals

Specify the size of a variable-size Simulink.Bus object as unbounded. To programmatically configure the bus elements, in the Simulink Editor, on the Modeling tab, select Model Settings > Model Properties. In the Model Properties dialog, on the Callbacks tab, select PreLoadFcn to edit the Simulink.BusElement object properties.

For each bus element:

  • Set appropriate dimensions to infinity by setting Dimensions value to Inf.

  • Set DimensionsMode to Variable.

Click Apply and OK.

In the PreLoadFcn section of the Callbacks tab, the Simulink bus elements are configured as unbounded variable-size signals.

Configure Data Store for Unbounded Variable-Size Signals

Check if the Data type is set to Bus:A on the Signal Attributes tab of the Data Store Memory block.

Compile the Model and Verify Signal Dimensions

Once you configure the blocks and Simulink objects, save (Ctrl+S) the model in the working folder and close it. Reopen the model for the updated properties of Simulink.BusElement and Simulink.Signal objects to be effective.

Update (Ctrl+D) the model. Verify the signal dimensions with this image.

Model after it is configured to use unbounded variable-size signals.

Set Model Configuration Parameters for Simulation

In the Simulink Editor, on the Modeling tab, select Model Settings. In the Configuration Parameters dialog box:

  • On the Solver tab, check that the solver is set to auto or discrete.

  • On the Data Import/Export tab, check that the Format is set to Dataset.

  • On the Simulation Target tab, set Language as C++. In Advanced parameters section indicated by ellipsis (...), check that Dynamic memory allocation in MATLAB functions is selected.

Set Up Data Logging

To log the output signals from the Data Store Read block, use the Outport block. In this case, the output signals sig1 and sig3 are Simulink bus elements.

See Also

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