Simulink.op.ModelOperatingPoint

Complete operating point of model in simulation

Description

A Simulink.op.ModelOperatingPoint object contains a complete representation of the operating point of a model in simulation. Use the Simulink.op.ModelOperatingPoint object to initialize a model to an operating point for simulation. If you do not modify the model, simulations initialized using model operating points produce the same results as an equivalent simulation with no initial state specified.

For example, when you simulate a system that has a startup phase or initialization behavior, you can:

1. Simulate the model through the end of the startup or initialization phase.

2. Save the model operating point.

3. Run a set of simulations initialized to the model operating point at the end of the startup or initialization phase.

A model operating point contains:

• Block state values, including hidden block states

• The state of the solver and execution engine

• Output values for some blocks

For more information, see Speed Up Simulation Workflows by Using Model Operating Points.

Creation

To get the operating point of a model, configure the model to save the final operating point in simulation. The software creates a Simulink.op.ModelOperatingPoint object when the simulation completes or when you pause or stop the simulation.

To configure a model to save the final operating point:

1. In the Simulink^® Toolstrip, on the Modeling tab, click Model Settings.

2. On the Data Import/Export pane, select Final states and Save final operating point.

By default, the model operating point is returned as a property of the Simulink.SimulationOutput object returned by the simulation. If you disable the Single simulation output configuration parameter, the model operating point is saved in a workspace variable when you run the simulation from a user interface, such as the Simulink Editor.

To specify the name of the Simulink.SimulationOutput property or workspace variable that contains the model operating point, enter the name in the Final States box.

You can also get the operating point of a model using either of these approaches:

• When a simulation is paused, use the get_param function to get the current operating point of the model.

  op = get_param(mdl,"CurrentOperatingPoint");

• Configure the model to log operating points to a MAT file throughout the simulation. For details, see Save Model Operating Point During Simulation.

Properties

loggedStates — States of built-in blocks

Simulink.SimulationData.Dataset object | structure

States of built-in blocks, specified as a Simulink.SimulationData.Dataset object or a structure. The software does not log the states of all built-in blocks. The loggedStates property contains only states of built-in blocks that are logged. For example, the loggedStates property does not contain the states of these blocks:

• Hidden blocks

• Blocks inside for-each subsystems

• Simscape™ blocks

• Blocks inside referenced models configured to simulate in a mode other than normal mode

The format of the states data depends on the format used to log states and outputs. To specify the format for states and outputs, use the Configuration Parameters dialog box.

1. In the Simulink Toolstrip, on the Modeling tab, click Model Settings.

2. On the Data Import/Export pane, select a value for the Save format parameter.

Once a ModelOperatingPoint is created, you cannot modify the format of the states data. The table summarizes the format of the states data for each value of the Save format parameter.

Format parameter value	Format of loggedStates property value
Dataset	Simulink.SimulationData.Dataset object
Structure with time Structure Array	Structure that contains block state values

You can modify only the values of states in the loggedStates property.

Tips

To access or modify the operating point information for a Stateflow^® chart, a MATLAB System block, or an S-function with a custom operating point implementation, use the get and set functions.

description — Operating point description

string | character vector

Operating point description, specified as a string or a character vector. The default description includes the name of the model and the simulation time at which the operating point was saved.

For example, the default description of an operating point of the model vdp saved at a simulation time of 3 seconds is Operating point of the model 'vdp' at simulation time 3.

Tips

The snapshotTime property stores the simulation time at which the model operating point was saved.

startTime — Start time of simulation that created operating point

Read-only: scalar number

This property is read-only.

Start time of simulation that created operating point, returned as a scalar number.

Data Types: double

snapshotTime — Simulation time at which operating point was created

Read-only: scalar number

This property is read-only.

Simulation time at which operating point was created, returned as a scalar number.

Data Types: double

Object Functions

get	Get operating point information for Stateflow chart, MATLAB System block, or S-function
set	Set operating point information for Stateflow chart, MATLAB System block, or S-function

Examples

Resume Simulation Using Initial Operating Point

Open the model vdp.

mdl = "vdp";
open_system(mdl);

Configure the model to save the final operating point at the end of simulation.

1. On the Modeling tab, under Setup, click Model Settings.

2. In the Configuration Parameters dialog box, select the Data Import/Export pane.

3. On the Data Import/Export tab, select Final states and Save final operating point.

4. Click OK.

Alternatively, create a Simulink.SimulationInput object to store the parameter values for the simulation. Then, use the setModelParameter function to specify the parameter values to use in the simulation.

simIn = Simulink.SimulationInput(mdl);

simIn = setModelParameter(simIn,"SaveFinalState","on");
simIn = setModelParameter(simIn,"SaveOperatingPoint","on");

Set the stop time for the simulation to 10 seconds. On the Simulation tab, under Simulate, in the Stop Time box, enter 10, or use the setModelParameter function to specify the value of the StopTime parameter for the simulation.

simIn = setModelParameter(simIn,"StopTime","10");

Simulate the model.

out = sim(simIn);

To view the simulation results, double-click the Scope block in the model. The plot in the Scope displays the values of the signals x1 and x2 over the 10-second simulation.

Resume the simulation by using the operating point you saved at the end of the first simulation as the initial operating point for the second simulation.

Get the final operating point from the first simulation from the Simulink.SimulationOutput object out.

vdpOP = out.xFinal;

Specify the operating point as the initial state for the simulation.

1. On the Modeling tab, under Setup, click Model Settings.

2. In the Configuration Parameters dialog box, on the Data Import/Export pane, select Initial state.

3. In the text box, enter vdpOP.

4. Click OK.

Alternatively, create another Simulink.SimulationInput object to configure this simulation. Then, use the setInitialState function to specify the initial state.

simIn2 = Simulink.SimulationInput(mdl);

simIn2 = setInitialState(simIn2,vdpOP);

Set the stop time for this simulation to 20. On the Simulation tab, under Simulate, in the Stop Time box, enter 20, or use the setModelParameter function to specify the value of the StopTime parameter for the simulation.

simIn2 = setModelParameter(simIn2,"StopTime","20");

Simulate the model again, resuming the prior simulation by starting this simulation from the final operating point saved in the first simulation.

out2 = sim(simIn2);

The plot in the Scope window updates to show the data from this simulation. The time axis starts at 0 and goes to the simulation stop time of 20. Because this simulation started from the initial operating point from the first simulation, which ended after 10 simulation seconds, the plot shows the values of the signals x1 and x2 only between simulation time 10 seconds and 20 seconds.

Tips

• For best results, clear the Block reduction parameter before running a simulation that saves the final operating point. When you simulate a model from an initial operating point, the software disables the Block reduction configuration parameter. You might not be able to initialize simulations using an operating point if the Block reduction parameter is enabled in the simulation that creates the operating point.

• When you specify an initial state as a model operating point:

  • The software uses the fixed step size in the operating point if the simulation uses a fixed-step solver and specifies the Fixed-step size (fundamental sample time) parameter as auto.

  • The software uses the maximum step size in the operating point if the simulation uses a variable-step solver and specifies the Max step size parameter as auto.

• To modify the operating point of a model reference in a simulation that runs from an initial operating point, specify the InitialState parameter of the Model block as a Simulink.op.ModelBlockOperatingPoint object. The Model block operating point overrides the operating point information for the block in the Simulink.op.ModelOperatingPoint object specified as the initial operating point of the top model.

• To initialize a simulation to a partial operating point, specify the initial operating point of one or more Model blocks without specifying an initial operating point for the top model.

Version History

Introduced in R2019a

R2023b: Inf state values supported

State data that you specify using the Initial state model configuration parameter can have Inf values, including when you specify the initial state for a model using a Simulink.op.ModelOperatingPoint object. In previous releases, the software issued an error when initial state data included Inf values.

R2019a: Simulink.SimState.ModelSimState is renamed to Simulink.op.ModelOperatingPoint

The Simulink.SimState.ModelSimState object, which was introduced in R2009a, is renamed and replaced with the Simulink.op.ModelOperatingPoint object. You can still use simulation snapshots from a previous release that you captured and saved as ModelSimState objects. When you load the object into the workspace or a model, the object is replaced with a ModelOperatingPoint object that contains the same data.

The ModelOperatingPoint object has the same properties as the ModelSimState object. The setBlockSimState and getBlockSimState functions continue to work but are not recommended. Instead, use the get and set functions for the ModelOperatingPoint object.