Check Against Reference
Check that model signal tracks reference signal during simulation
Library
Simulink Design Optimization
Description
Check that a signal remains within tolerance bounds of a reference signal during simulation:
If all bounds are satisfied, the block does nothing.
If a bound is not satisfied, the block asserts, and a warning message appears at the MATLAB® prompt. You can also specify that the block:
Evaluate a MATLAB expression.
Stop the simulation and bring that block into focus.
During simulation, the block can also output a logical assertion signal:
If all bounds are satisfied, the signal is true (
1).If a bound is not satisfied, the signal is false (
0).
You can add Check Against Reference blocks on multiple signals to check that they track reference signals.
You can also plot the reference signal on a time plot to graphically verify that the signal tracks that signal.
This block and the other blocks in the Model Verification library test that a signal remains within specified time-domain characteristic bounds. When a model does not violate any bound, you can disable the block by clearing the assertion option. If you modify the model, you can re-enable assertion to ensure that your changes do not cause the model to violate a bound.
If the signal does not satisfy the bounds, you can optimize the model parameters to satisfy the bounds. If you have Simulink® Control Design™ software, you can add frequency-domain bounds such as Bode magnitude and optimize the model response to satisfy both time- and frequency-domain requirements.
The block can be used in all simulation modes for signal monitoring
but only in Normal or Accelerator simulation
mode for response optimization.
Parameters
| Task | Parameters |
|---|---|
|
Specify a reference signal to:
| Include reference signal tracking in assertion in Bounds tab. |
| Specify assertion options (only when you specify reference to track). |
In the Assertion tab: |
| Open Response Optimization tool to optimize model response | Click Response Optimization |
| Plot reference signal | Click Show Plot. |
| Display plot window instead of Block Parameters dialog box on double-clicking the block. | Show plot on block open |
Include reference signal tracking in assertion
Check that the signal does not track the reference signal specified in Times (seconds) and Amplitudes during simulation.
The software displays a warning if the signal does not track the reference signal.
This parameter is used only if Enable assertion in the Assertion tab is selected.
The reference signal also appears on a time plot if you click Show Plot, as shown in the next figure.
If you clear Enable assertion, the bounds are not used for assertion but continue to appear on the plot.
Settings
Default: On
On Check that the signal tracks the specified reference signal during simulation.
OffDo not check that the signal tracks the specified reference signal during simulation.
Tips
Clearing this parameter disables the reference signal and the software stops checking that the signal tracks the reference during simulation.
To only view the bounds on the plot, clear Enable assertion.
Command-Line Information
Parameter: EnableReferenceBound |
| Type: character vector |
Value: 'on' | 'off' |
Default: 'on' |
Times (seconds)
Time vector for the reference signal. Specify the corresponding amplitudes in Amplitudes.
Settings
Default: linspace(0,10)
Command-Line Information
Parameter: ReferenceTimes |
| Type: character vector |
Value: linspace(0,10) | vector
of positive values of the same dimension as the amplitude vector | |
Default: linspace(0,10) |
Amplitudes
Amplitude of the reference signal corresponding to the time vector specified in Times (seconds).
Settings
Default: 1-exp(-linspace(0,10)/2)
Command-Line Information
Parameter: ReferenceAmplitudes |
| Type: character vector |
Value: 1-exp(-linspace(0,10)/2) | vector
of integers of the same dimension as the time vector |
Default: 1-exp(-linspace(0,10)/2) |
Absolute tolerance
Absolute tolerance used to determine bounds as the signal approaches the reference signal.
During simulation, the signal must remain within upper and lower limits respective to the reference signal given by:
yu = (1 + RelTol)yr + AbsTol
yl = (1 –RelTol)yr – AbsTol
where yr is the value of the reference at a certain time, yu and yl are the upper and lower tolerance bounds corresponding to that time point.
The block asserts if the signal violates these limits.
Settings
Default: eps^(1/3)
Minimum: 0
Command-Line Information
Parameter: AbsTolerance |
| Type: character vector |
Value: eps^(1/3) | positive
real scalar |
Default: eps^(1/3) |
Relative tolerance
Relative tolerance used to determine bounds as the signal approaches the reference signal.
During simulation, the signal must remain within upper and lower limits respective to the reference signal given by:
yu = (1 + RelTol)yr + AbsTol
yl = (1 — RelTol)yr— AbsTol
where yr is the value of the reference at a certain time, yu and yl are the upper and lower tolerance bounds corresponding to that time point.
The block asserts if the signal violates these limits.
Settings
Default: 0.01
Minimum: 0
Command-Line Information
Parameter: RelTolerance |
| Type: character vector |
Value: 0.01 | positive
real scalar |
Default: 0.01 |
Enable assertion
Enable the block to check that bounds specified and included for assertion in the Bounds tab are satisfied during simulation. Assertion fails if a bound is not satisfied. A warning, reporting the assertion failure, appears at the MATLAB prompt.
If the assertion fails, you can optionally specify that the block:
Execute a MATLAB expression, specified in Simulation callback when assertion fails (optional).
Stop the simulation and bring that block into focus, by selecting Stop simulation when assertion fails.
This parameter has no effect if you do not specify any bounds.
Clearing this parameter disables assertion, i.e., the block no longer checks that specified bounds are satisfied. The block icon also updates to indicate that assertion is disabled.
In the Simulink model, in the Configuration Parameters dialog box, the Model Verification block enabling parameter lets you to enable or disable all model verification blocks in a model, regardless of the setting of this option in the block.
Settings
Default: On
- On
Check that bounds included for assertion in the Bounds tab are satisfied during simulation. A warning, reporting assertion failure, is displayed at the MATLAB prompt if bounds are violated.
- Off
Do not check that bounds included for assertion are satisfied during simulation.
Dependencies
This parameter enables:
Simulation callback when assertion fails (optional)
Stop simulation when assertion fails
Command-Line Information
Parameter: enabled |
| Type: character vector |
Value: 'on' | 'off' |
Default: 'on' |
Simulation callback when assertion fails (optional)
MATLAB expression to execute when assertion fails.
Because the expression is evaluated in the MATLAB workspace, define all variables used in the expression in that workspace.
Settings
Default: []
A MATLAB expression.
Dependencies
Enable assertion enables this parameter.
Command-Line Information
Parameter: callback |
| Type: character vector |
Value: '' | MATLAB
expression |
Default: '' |
Stop simulation when assertion fails
Stop the simulation when a bound specified in the Bounds tab is violated during simulation, i.e., assertion fails.
If you run the simulation from a Simulink model window, the Simulation Diagnostics window opens to display an error message. The block where the bound violation occurs is highlighted in the model.
Settings
Default: Off
- On
Stop simulation if a bound specified in the Bounds tab is violated.
- Off
Continue simulation if a bound is violated and produce a warning message at the MATLAB prompt.
Tips
Because selecting this option stops the simulation as soon as the assertion fails, assertion failures that might occur later during the simulation are not reported. If you want all assertion failures to be reported, do not select this option.
Dependencies
Enable assertion enables this parameter.
Command-Line Information
Parameter: stopWhenAssertionFail |
| Type: character vector |
Value: 'on' | 'off' |
Default: 'off' |
Output assertion signal
Output a Boolean signal that, at each time step, is:
True (
1) if assertion succeeds, i.e., all bounds are satisfiedFalse (
0) if assertion fails, i.e., a bound is violated.
The output signal data type is Boolean only if, in the Simulink model, in the Configuration Parameters dialog box, the Implement logic signals as Boolean data parameter is selected. Otherwise, the data type of the output signal is double.
Selecting this parameter adds an output port to the block that you can connect to any block in the model.
Settings
Default:Off
- On
Output a Boolean signal to indicate assertion status. Adds a port to the block.
- Off
Do not output a Boolean signal to indicate assertion status.
Tips
Use this parameter to design complex assertion logic. For an example, see Verify Model Using Simulink Control Design and Simulink Verification Blocks (Simulink Control Design).
Command-Line Information
Parameter: export |
| Type: character vector |
Value: 'on' | 'off' |
Default: 'off' |
Show plot on block open
Open the plot window instead of the Block Parameters dialog box when you double-click the block in the Simulink model.
Use this parameter if you prefer to open and perform tasks,
such as adding or modifying bounds, in the plot window instead of
the Block Parameters dialog box. If you want to access the block parameters
from the plot window, select Edit or click 
.
For more information on the plot, see Show Plot.
Settings
Default: Off
- On
Open the plot window when you double-click the block.
- Off
Open the Block Parameters dialog box when double-clicking the block.
Command-Line Information
Parameter: LaunchViewOnOpen |
| Type: character vector |
Value: 'on' | 'off' |
Default: 'off' |
Show Plot
Open the plot window.
Use the plot to view:
System characteristics and signals computed during simulation
You must click this button before you simulate the model to view the system characteristics or signal.
You can display additional characteristics, such as the peak response time, by right-clicking the plot and selecting Characteristics.
Bounds
You can specify bounds in the Bounds tab of the Block Parameters dialog box or right-click the plot and select Bounds > New Bound. For more information on the types of bounds you can specify, see the individual reference pages.
You can modify bounds by dragging the bound segment or by right-clicking the plot and selecting Bounds > Edit Bound. Before you simulate the model, click Update Block to update the bound value in the block parameters.
Typical tasks that you perform in the plot window include:
Opening the Block Parameters dialog box by clicking
or selecting Edit.Finding the block that the plot window corresponds to by clicking
or selecting View > Highlight Simulink Block. This action makes the model window active and highlights
the block.Simulating the model by clicking
. This action also linearizes the portion of the
model between the specified linearization input and output.Adding a legend on the linear system characteristic plot by clicking
.
Response Optimization
Open the Response Optimization tool to optimize the model response to meet design requirements specified in the Bounds tab.