Merge signals from If Action Subsystem blocks

This example shows how to merge signals controlled by an If block. The If block selects the execution of an If Action Subsystem block from a set of subsystems. Regardless of which subsystem the If block selects, you can create a single signal with a Merge block. Open model.

All blocks in an If Action Subsystem block must execute at the same rate as the driving If block. You can satisfy this requirement by setting the sample time parameter for each block to either inherited (-1) or the same value as the If block sample time.

Support for Fixed-Point Data Type

The If block does not directly support fixed-point data types. However, you can use the Compare To Constant block to work around this limitation.

Consider the following floating-point model without fixed-point data types:

In this model, the If Action Subsystem blocks use their default configurations. The simulation parameters are set to their default values except for the parameters listed in the following table.

The block parameters are set to their default values except for the parameters listed in the following table.

For this model, when input u1 is greater than 0 or input u2 is greater than 0.5, the output is 4. Otherwise, the output is -4. The Scope block displays the output from the Merge block with inputs u1, and u2.

You can implement this block diagram as a model with fixed-point data types:

The Repeating Sequence Stair blocks output fixed-point data types.

The Compare To Constant blocks implement two parts of the If expression that is used in the If block in the floating-point version of the model, (u1 > 0) and (u2 > 0.5). The OR operation, (u1|u2), can still be implemented inside the If block. For a fixed-point model, the expression must be partially implemented outside of the If block as it is in this model.

The block and simulation parameters for the fixed-point model are the same as for the floating-point model with the following exceptions and additions: