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Docs: Plane: Add hint to solve 1Hz pitch oscillations #6558

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11 changes: 11 additions & 0 deletions plane/source/docs/automatic-tuning-with-autotune.rst
Original file line number Diff line number Diff line change
Expand Up @@ -153,6 +153,17 @@ This is a special level that does not change the rates or time constant (ie like
Completing the tune
===================

.. _automatic-tuning-with-autotune-completing-the-tune:

.. warning::

If you have successfully tuned your plane with Autotune and see oscillations on the pitch axis around 1 Hz,
check if :ref:`PTCH_RATE_I<PTCH_RATE_I>` far exceeds :ref:`PTCH_RATE_P<PTCH_RATE_P>`.
This is an unwanted result of Autotune for Plane and it typically becomes visible if you fly straight for
a longer distance. Autotune does blindly copy the value of :ref:`PTCH_RATE_FF<PTCH_RATE_FF>` to
:ref:`PTCH_RATE_I<PTCH_RATE_I>` due to a wrong design decision. In this case reduce the value of
:ref:`PTCH_RATE_I<PTCH_RATE_I>` to half of it's value.

Once you have learned reasonable tuning parameters with
autotune you should complete the tune by manually tuning some other key
parameters.
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Original file line number Diff line number Diff line change
Expand Up @@ -183,6 +183,9 @@ increasing the value of :ref:`TECS_TIME_CONST<TECS_TIME_CONST>` in increments of
where throttle changes cause noticeable pitch angle changes. Ideally you
should improve your pitch loop tuning first, before adjusting
:ref:`TECS_PTCH_DAMP<TECS_PTCH_DAMP>` and :ref:`TECS_TIME_CONST<TECS_TIME_CONST>` as described here.
Low frequency pitch oscillations around 1Hz are an indicator that :ref:`PTCH_RATE_I<PTCH_RATE_I>` is
too high. Refer to the warning :ref:`Completing the tune <automatic-tuning-with-autotune-completing-the-tune>`.


If using airspeed sensing, adjust the value of :ref:`TRIM_THROTTLE<TRIM_THROTTLE>` so
that it matches the average amount of throttle required by the
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