How To Make New Components

1. Overview

• In the How To Add Components tutorial, we have added existing components to the simulation scenario.
• This tutorial explains how to make a new component into the s2e-user directory.
  • Note: You can move the source files for the new component into the s2e-core repository if the component is useful for all S2E users.
• The supported version of this document
  • Please confirm that the version of the documents and s2e-core is compatible.

2. Overview of component expression in S2E

• Source codes emulating components are stored in the s2e-core/src/components directory.
• All components need to inherit the base class Component for general functions of components, and most of the components also inherit the base class ILoggable for the log output function.
• Component class
  • The base class has an important virtual function MainRoutine, and subclasses need to define it in their codes.
    • When an instance of the component class is created, the MainRoutine function is registered in the TickToComponent, and it will be automatically executed in the Spacecraft class.
    • The main features of the components such as observation, generate force, noise addition, communication, etc... should be written in this function.
  • PowerOffRoutine is also important especially for actuators. This function is called when the component power line is turned off. Users can stop force and torque generation and initialize the component states.
• Power related functions
  • SetPowerState and GetCurrent are power related functions. If you want to emulate power consumption and switch control, you need to use the functions.
• ILoggable class
  • This base class has two important virtual functions GetLogHeader and GetLogValue, for CSV log output.
  • These functions are registered into the log output list when the components are added in UserComponents::LogSetUp
• Communication with OBC
  • If users want to emulate the communication(telemetry and command) between the components and the OBC, they can use the base class UartCommunicationWithObc or I2cTargetCommunicationWithObc.
  • These base classes also support a feature to execute HILS function.

3. Make a simple clock sensor without initialize file

• This chapter explains how to make a simple clock sensor, which observes the simulation elapsed time with a bias noise.
• Users can find the sample codes in s2e-user-example/sample/how-to-make-new-components.
  • The sample codes already including the initialize file for the ClockSensor. Please edit the code a bit to learn the procedure step by step.

1. The clock_sensor.cpp, .hpp are created in the components directory.

   • The ClockSensor class counts clock with a constant bias noise.
   • The class inherits the Component and the ILoggable base classes as explained above.

2. The user_components.hpp and user_components.cpp are edit similar procedure with the How To Add Components

   • The constructor of the ClockSensor requires arguments as prescaler, clock_generator, simulation_time, and bias_s.
   • prescaler and bias_s are user setting parameters for the sensor, and you can freely set these values.
   • clock_generator is an argument for the Component base class.
   • simulation_time is a specific argument for the ClockSensor to get true time information. The SimulationTime class is managed in the GlobalEnvironment, and the GlobalEnvironment is instantiated in the SimulationCase class.
   • We need to add the following codes to user_components.cpp.
     • Instantiate the ClockSensor in the constructor.

     clock_sensor_ = new ClockSensor(10, clock_generator, global_environment->GetSimulationTime(), 0.001);
     

     • Delete the clock_sensor_ in the destructor.

     delete clock_sensor_;
     

     • Add log set up into the LogSetUp function.

     logger.AddLogList(clock_sensor_);
     

3. Build s2e-user and execute it

4. Check the log file to confirm the output of the clock_sensor_observed_time[sec]

   • The output of the clock sensor has an offset error defined by the bias_s value, and the update frequency is decided by the prescaler and the component_update_period_s in the base ini file.

4. Make an initialize file for the clock sensor

• Usually, we want to change the parameters of components such as noise properties, mounting coordinates, and others without rebuilding. So this section explains how to make an initialize file for the ClockSensor.

1. The initialize function InitClockSensor is defined in the clock_sensor.hpp.

   • The initialize function requires arguments as clock_generator, simulation_time, and file_name.
   • clock_generator and simulation_time are same argument with the constructor of the ClockGenerator.
   • file_name is the file path to the initialize file for the ClockSensor.

2. Edit the user_components.hpp and user_components.cpp as follows

   • user_components.cpp
     • Edit making instance of the clock_sensor at the constructor

       // Clock Sensor
       std::string file_name = iniAccess.ReadString("COMPONENT_FILES", "clock_sensor_file");
       configuration_->main_logger_->CopyFileToLogDirectory(file_name);
       clock_sensor_ = new ClockSensor(InitClockSensor(clock_generator, global_environment->GetSimulationTime(), file_name));
       

       • The first line get the file path of the initialize file of the clock sensor.
       • The second line copy the initialize file to the log output directory to save the simulation setting.
       • The third line make the instance of the ClockSensor.

3. Make clock_sensor.ini into s2e-user/data/initialize_files/components from ./Tutorial/SampleCodes/clock_sensor

4. Edit user_satellite.ini to add the following line at the [COMPONENT_FILES] section of the file

   clock_sensor_file = INI_FILE_DIR_FROM_EXE/components/clock_sensor.ini
   

   • The keyword INI_FILE_DIR_FROM_EXE is defined in the CMakeList.txt to handle the relative path to the initialize files.

5. Build s2e-user and execute it

6. Check the log file

7. Edit the clock_sensor.ini and rerun the s2e-user to confirm the initialize file can affect the result.