MATLAB: Is there a way to initialize the output of a Truth Table block in Stateflow 6.4.1 (R2006a+)

initializestateflowtabletruth

I have a Stateflow chart containing an output variable. In the Model Explorer, I can set the initial value of the variable.

However, if I have a Truth Table block in my model, I cannot set the initial value in the same manner.

Best Answer

The output of the Truth Table is initially set to zero. However, during the first time step it is determined by passing the initial value of the input signal through the truth table equation. The attached screen shots show this in the debugger.

initial_1.jpg shows at time = 0, the data Y1 (i.e. the output of the truth table) is equal to 0. It is declared to this value in the internal initialization code for the truth table. (The image shows that the Scope.Start method is executed because it comes after the StateflowChart.Start method, which contains the initial values of the truth table input and output).

initial_2.jpg shows the results of StateflowChart.Outputs.Major at time = 0. The input has been passed through the truth table and the output has been set to the appropriate value.

There is no way for the user to set the initial value of the output because it is calculated by running the initial value of the truth table input through the truth table.

Related Solutions

MATLAB: Do I receive a syntax error message if I assign a vector to an output in the ‘Action’ section under ‘Action Table’ of the truth table in Stateflow 7.2 (R2008b)

The ability to accept array/vector values in the 'Action' field of the truth table is not available in Stateflow 7.2(R2008b). It can accept only scalars and variables.

As a possible workaround, define variables (data objects) in the chart inside Model Explorer, assign these vectors to them and set their scope to 'Local'.

In addition, specify the corresponding values for 'Size' of the vector and 'Initial Value (Expression)' under the 'General' and 'Value Attributes' tabs respectively in the Model Explorer.

MATLAB: How to profile block or mask initialization times in Simulink 6.4.1 (R2006a+)

Currently there is no direct way to view initialization time costs in Simulink.

As a workaround, you can utilize the MATLAB Profiler along with the Simulink update diagram to obtain this information. An example is attached.

The attached profile_model.mdl has two masked subsystems. The first one, profile_model/Subsystem, has a mask initialization command that calls the mywrapperfunction.m:

mywrapperfunction(1)

This MATLAB file executes a simple PAUSE command. This command is one second long, so it will stand out from the rest of the update calculations. profile_script.m contains:

clear all
open_system('profile_model')
profile on
set_param('profile_model','SimulationCommand','update')
profile off
profile viewer

These are the steps to update the model and profile via the command line. This utilizes MATLAB to open the model, update the model, and profile the update action. The results will show mywrapperfunction as the most expensive calculation in the update diagram call (see attached profile_screenshot.jpg).

Note the first run of profile_script.m may produce a slightly different run than the screen shot. In any case, mywrapperfunction should be the most expensive calculation.

Also note that currently there is no way to map the MATLAB functions back to a particular block mask initialization.

Best Answer

Related Solutions

MATLAB: Do I receive a syntax error message if I assign a vector to an output in the ‘Action’ section under ‘Action Table’ of the truth table in Stateflow 7.2 (R2008b)

MATLAB: How to profile block or mask initialization times in Simulink 6.4.1 (R2006a+)

Related Question