.. date: 27/03/2026
   author: Andre' Neto
   copyright: Copyright 2017 F4E | European Joint Undertaking for ITER and
   the Development of Fusion Energy ('Fusion for Energy').
   Licensed under the EUPL, Version 1.1 or - as soon as they will be approved
   by the European Commission - subsequent versions of the EUPL (the "Licence")
   You may not use this work except in compliance with the Licence.
   You may obtain a copy of the Licence at: http://ec.europa.eu/idabc/eupl
   warning: Unless required by applicable law or agreed to in writing, 
   software distributed under the Licence is distributed on an "AS IS"
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Filters and type conversion
===========================

The last exercise in the previous section introduced a disturbance to the system.

In this section, we will add a filter before the controller to mitigate the effect of the disturbance.

The filter is implemented using the :vcisdoxygenmccl:`FilterGAM`, and is configured as a notch filter centred at 10 Hz.

.. literalinclude:: /_static/tutorial/Configurations/MassSpring/RTApp-MassSpring-14.cfg
    :language: c++
    :lines: 80-101
    :caption: FilterGAM configuration.
    :linenos:
    :emphasize-lines: 3-4

Running the application
-----------------------

Start the application with:

.. code-block:: bash

    ./MARTeApp.sh -f ../Configurations/MassSpring/RTApp-MassSpring-14.cfg -l RealTimeLoader -s State1

Once the application is running, inspect the ``screen`` output and verify that the log shows the ``Position`` converging to the ``ReferencePosition`` value despite the ``PositionDisturbed`` signal (which is the input to the filter) varying over time. The log should show entries similar to the following:

.. code-block:: console

   $ [Information - LoggerBroker.cpp:152]: Time [0:0]:151070000
   $ [Information - LoggerBroker.cpp:152]: ReferencePosition [0:0]:2.000000
   $ [Information - LoggerBroker.cpp:152]: Position [0:0]:2.000000
   $ [Information - LoggerBroker.cpp:152]: PositionDisturbed [0:0]:1.990489
   $ [Information - LoggerBroker.cpp:152]: PositionFiltered [0:0]:2.000000

Exercises
---------

Ex. 1: Simple statistics 
------------------------

1. Edit the file ``../Configurations/MassSpring/RTApp-MassSpring-15.cfg`` and add a ``FilterGAM`` to implement a moving average of the ``Thread1CycleTime`` and compare it with the one being computed by the ``StatisticsGAM``. The moving average should be computed over a window of 100 ms.
2. Given that the ``FilterGAM`` does not accept ``uint32`` signals, use a :vcisdoxygenmccl:`ConversionGAM` to convert the ``Thread1CycleTime`` signal to a ``float32`` before feeding it to the ``FilterGAM``.

.. dropdown:: Solution
   :icon: key

   The solution is to add a ``ConversionGAM`` to convert the signal.

   .. literalinclude:: /_static/tutorial/Configurations/MassSpring/RTApp-MassSpring-15-solution.cfg
      :language: c++
      :lines: 444-458
      :caption: Type conversion.
      :linenos:
      :emphasize-lines: 6,12

   And to add a ``FilterGAM`` to compute the moving average.

   .. literalinclude:: /_static/tutorial/Configurations/MassSpring/RTApp-MassSpring-15-solution.cfg
      :language: c++
      :lines: 459-478
      :caption: Moving average filter.
      :linenos:
      :emphasize-lines: 3-4

   Finally, add the output signal of the ``FilterGAM`` to the ``GAMDisplay`` and the GAMs to the execution list.