Main Content

Air-Fuel Ratio Control System with Stateflow Charts

Generate code for an air-fuel ratio control system designed with Simulink® and Stateflow®.

Figures 1, 2, and 3 show relevant portions of the sldemo_fuelsys model, a closed-loop system containing a plant and controller. The plant validates the controller in simulation early in the design cycle. In this example, you generate code for the relevant controller subsystem, "fuel_rate_control". Figure 1 shows the top-level simulation model.

Use the command rtwdemo_fuelsys to open model sldemo_fuelsys. Then, compile the model to see the signal data types.

rtwdemo_fuelsys
sldemo_fuelsys([],[],[],'compile');
sldemo_fuelsys([],[],[],'term');

Figure 1: Top-level model of the plant and controller

The air-fuel ratio control system is comprised of Simulink® and Stateflow®. The control system is the portion of the model for which you generate code.

open_system('sldemo_fuelsys/fuel_rate_control');

Figure 2: The air-fuel ratio controller subsystem

The control logic is a Stateflow® chart that specifies the different modes of operation.

open_system('sldemo_fuelsys/fuel_rate_control/control_logic');

Figure 3: Air-fuel rate controller logic

Close these windows.

close_system('sldemo_fuelsys/fuel_rate_control/airflow_calc');
close_system('sldemo_fuelsys/fuel_rate_control/fuel_calc');
close_system('sldemo_fuelsys/fuel_rate_control/control_logic');
hDemo.rt=sfroot;hDemo.m=hDemo.rt.find('-isa','Simulink.BlockDiagram');
hDemo.c=hDemo.m.find('-isa','Stateflow.Chart','-and','Name','control_logic');
hDemo.c.visible=false;
close_system('sldemo_fuelsys/fuel_rate_control');

Configure and Build the Model with Embedded Coder®

To configure and build production ANSI® C/C++ code for the model, set model configuration parameter System target file to ert.tlc (Embedded Real-Time (ERT)). You can set the System target file parameter programmatically.

rtwconfiguredemo('sldemo_fuelsys','ERT');

Generate and inspect the code. You can navigate to the relevant code segments interactively by using Previous and Next buttons. From the chart context menu (right-click the Stateflow® block), select C/C++ Code > Navigate to C/C++ Code. Programmatically, use the rtwtrace utility.

rtwbuild('sldemo_fuelsys/fuel_rate_control');
rtwtrace('sldemo_fuelsys/fuel_rate_control/control_logic')
### Starting build procedure for: fuel_rate_control
### Successful completion of build procedure for: fuel_rate_control

Build Summary

Top model targets built:

Model              Action                       Rebuild Reason                                    
==================================================================================================
fuel_rate_control  Code generated and compiled  Code generation information file does not exist.  

1 of 1 models built (0 models already up to date)
Build duration: 0h 0m 33.097s

View the air-fuel ratio control logic in the generated code.

rtwdemodbtype('fuel_rate_control_ert_rtw/fuel_rate_control.c',...
    '/* Function for Chart:','case IN_Warmup:',1,0);
/* Function for Chart: '<S1>/control_logic' */
static void Fueling_Mode(const int32_T *sfEvent)
{
  /* This state interprets the other states in the chart to directly control the fueling mode. */
  switch (rtDWork.bitsForTID0.is_Fueling_Mode) {
   case IN_Fuel_Disabled:
    rtDWork.fuel_mode = DISABLED;

    /* The fuel is completely shut off while in this state. */
    switch (rtDWork.bitsForTID0.is_Fuel_Disabled) {
     case IN_Overspeed:
      /* Inport: '<Root>/sensors' */
      /* The speed is dangerously high, so shut off the fuel. */
      if ((rtDWork.bitsForTID0.is_Speed == 2) && (rtU.sensors.speed < 603.0F)) {
        if (rtDWork.bitsForTID0.is_Fail != 1) {
          rtDWork.bitsForTID0.is_Fuel_Disabled = IN_NO_ACTIVE_CHILD;
          rtDWork.bitsForTID0.is_Fueling_Mode = IN_Running;
          switch (rtDWork.bitsForTID0.was_Running) {
           case IN_Low_Emissions:
            rtDWork.bitsForTID0.is_Running = IN_Low_Emissions;
            rtDWork.bitsForTID0.was_Running = IN_Low_Emissions;
            rtDWork.fuel_mode = LOW;
            switch (rtDWork.bitsForTID0.was_Low_Emissions) {
             case IN_Normal:
              rtDWork.bitsForTID0.is_Low_Emissions = IN_Normal;
              rtDWork.bitsForTID0.was_Low_Emissions = IN_Normal;
              break;

Close the model and code generation report.

clear hDemo;
rtwdemoclean;
close_system('sldemo_fuelsys',0);

Related Examples

For related fixed-point examples that use sldemo_fuelsys, see