Output block variables as signals during simulation
Simscape / Utilities
The Probe block lets you select variables from another block in the model and output them as Simulink® signals. The following rules apply:
The selected block must be at the same level of the model hierarchy as the Probe block.
After selecting the block, select the variables to probe. The context menu contains all the externally accessible block variables, regardless of whether they are exposed in the Initial Targets section of the block dialog box.
Externally accessible variables include: block variables declared with the
ExternalAccessattribute value of either
observe, inputs, outputs, intermediates, modecharts, and domain Across variables at each of the nodes. Essentially, these are the same variables that you can see in the simulation data log.
In case of conditional visibility, if a variable is active only in a subset of block parameterizations, such a variable is always available for probing, regardless of whether it is active in the current block configuration.
In case of conditional declaration, variables are not available for probing, regardless of whether the conditional branch is active in the current block configuration. For composite components, this limitation includes all the externally accessible variables of conditionally declared components.
Each of the selected variables is output as a separate signal.
The output signal unit matches the nominal unit of the variable. For more information, see Specify Nominal Value-Unit Pairs for a Model and Units in Simulink.
The Probe block outputs Simulink signals. Therefore, you can connect it directly to Simulink blocks, like scopes or buses.
You can attach (bind) a Probe block to only one block at a time. However, you can bind multiple Probe blocks to the same block in the model at the same time.
Working with the Block on the Model Canvas
To bind variables to a Probe block:
Add the Probe block to a model at the desired level.
Double-click the Probe block to start the binding process.
Select a Simscape™ block at the same level of the model hierarchy.
From a context menu containing all the block variables available for probing, select the variables to output. For example, if you selected a Rotational Electromechanical Converter block, the available variables include current, voltage, torque, and angular velocity, as well as voltage at each of the electrical ports and the rotational velocity at ports C and R.
To facilitate working with long lists of variables, the context menu has a Type to Filter field at the top. Type in this field to display only the variables that contain the filter string in their name or id.
To finish the binding process, click the X in the upper-right corner of the model canvas.
For each selected variable, the Probe block acquires an additional output port, with the port name matching the variable ID. (In this example, the port names are i and w.) Connect these ports to scopes or other blocks from the Simulink Sinks library to view the signal values during simulation.
To bind a Probe block to a different block in the model, or to change the selected variables, double-click the Probe block again and repeat the binding process. When binding to a different block, if the new block has variables with the same IDs as the ones previously bound, these variables are automatically selected again.
If you copy a Probe block together with the block that it is bound to, the connection is preserved and the same variables are automatically selected in the new pair.
Command Line Workflow
Instead of the interactive workflow on the model canvas, you can bind a Probe block and select variables by using these commands:
probeBlockmust be a valid full block path or a handle to a Probe block.
boundBlockmust be a valid full block path or a handle to another block at the same level of the model hierarchy as
probeBlock. The command does not check whether
boundBlockis a Simscape block or whether it has variables to probe.
simscape.probe.setBoundBlock(returns the Probe block to the unbound state. Does not affect the selected variables.
simscape.probe.setVariables(— Selects variables for the
probeBlockmust be a valid full block path or a handle to a Probe block.
variablesmust be a character vector, cell array of character vectors, or string array that specifies the variables. The character vectors or strings must be unique variable identifiers, lexicographically sorted. The command does not check whether the currently selected
boundBlockcontains these variables.
Instead of lexicographically sorting the variables, you can use this syntax:
I = simscape.probe.setVariables(probeBlock, variables, 'Sort', true)
The command then sorts the variables before applying them to
probeBlock. Variable identifiers must still be unique.
Ireturns the order in which the sorted
variablesappear as ports on the Probe block.
The programmatic equivalent of the interactive binding and variable selection shown in the example in Working with the Block on the Model Canvas is:
simscape.probe.setBoundBlock('ssc_dcmotor/DC Motor/Probe','ssc_dcmotor/DC Motor/Rotational Electromechanical Converter'); simscape.probe.setVariables('ssc_dcmotor/DC Motor/Probe',["i", "w"]);
As a result, the Probe block also has two output ports, i and w, bound to the Current : i and Angular velocity : w variables of the Rotational Electromechanical Converter block, respectively.
If you supply unsorted variables, the command returns the sorted order:
I = simscape.probe.setVariables('ssc_dcmotor/DC Motor/Probe', ["w", "i"], 'Sort', true)
I = 2 1
In this example, the second variable,
i, appears as the first port on
the Probe block, followed by the first variable,
You can use the
probeBlock is a valid full block path or a handle
to a Probe block, to return its bound block and variables,
x — Value of selected variable during simulation
scalar | vector | matrix
Outputs the values of one selected variable during simulation as a Simulink signal. The port name matches the name of selected variable.
If you select more than one variable, the block acquires additional output ports.
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Version HistoryIntroduced in R2020a
R2023a: Extended list of variables available for probing
In previous releases, when you were selecting the variables to output, the context menu contained only the variables exposed in the Initial Targets section of the block dialog box, that is, the same variables that can be used for block-level variable initialization.
Starting in R2023a, the context menu contains all the externally accessible block
variables, regardless of whether they are exposed in the Initial
Targets section of the block dialog box. Externally accessible variables
include: block variables declared with the
ExternalAccess attribute value
observe, inputs, outputs,
intermediates, modecharts, and domain Across variables at each of the nodes. Essentially,
these are the same variables that you can see in the simulation data log.
To facilitate scanning through long lists of variables, especially in composite
components, the display format of variables in the context menu has been reversed from
id:Name. For example, instead of
Current:i, the same variable now appears as
i:Current. This view is more consistent with the variable display in
the Variable Viewer, Simscape Results Explorer, and Simulation Data Inspector.
The context menu now also has a filter field at the top. Type in this field to filter the variables displayed in the context menu.