.. _reflexes-fall-manager:

Fall manager
============

.. toctree::
   :hidden:
   :maxdepth: 1

   reflexes-fall-manager-api

Overview | :ref:`API <reflexes-fall-manager-api>`

.. seealso::

    - :ref:`almotion`

------------

What it does
------------

Because NAO may fall, we taught him to stand up. But we went even further by establishing a system
to detect falls: it protects with her ​​arms before touching the ground. NAO can
therefore fall, he will not hurt.

By default, the fall manager is active on NAO.

How it works
------------

The basic idea is to look at both the support polygon and the Center Of Mass (COM) of NAO. If the
COM is detected out of the support polygon, the fall manager process is activated.

This process has priority over all other :ref:`motion tasks <tools-motion-task>`. The choosen
strategy is composed by an arms and pelvis joint configuration to protect the robot follow by
a **stiffness off** command to cushion the fall. The joint configuration depends on the fall angle
(back, front, right or left).

A memory event called :naoqi:event:`robotHasFallen` is raised when the fall management process is
completed.

Getting started
---------------

When the reflexe is active
++++++++++++++++++++++++++

The fall manager reflexe is only activated when at least one foot touch the ground (based on
:ref:`alfsr`).

If the robot is lift, sit or other posture than stand, the fall manager is not activated.


How to disable this reflexe
+++++++++++++++++++++++++++

As this reflexe increase a lot the life time before failure of NAO, we recommand to not disable
this reflex.

But as we know that in some situation, this reflex will disturbe your work, please follow these
two steps to disable it.

1. **Allow disactivation**

   The first step is to allow disactivation of this reflex.

   a. *With the web page*

      You can do it throw the NAO web page settings (:ref:`opennao-web-page`).

      .. image:: /medias/dev/modules/motion/motion_fallManagerCheckBox.png

      if you check the box, a popUp will ask you confirmation

      .. image:: /medias/dev/modules/motion/motion_fallManagerPopUp.png

      By clicking on the button : "I understand the risks", you will allow the disactivation of the
      fall manager.

   b. *Programmatically*

      The right of disactivation of the fall manager is managed by the ALMotion preference into the
      robot. (/home/nao/.config/naoqi/ALMotion.xml).

      So, you can edit by hand this file or use the :ref:`alpreferences` API.

      The name of the preferences in ALMotion.xml is : "ENABLE_DISACTIVATION_OF_FALL_MANAGER".

      And the preference file should have this form :

      .. code-block:: guess

         <Preference name="ENABLE_DISACTIVATION_OF_FALL_MANAGER" description="If true the
         disactivation of Fall Manager is allowed" value="true" type="bool" />

2. **Disable the reflexe**

   Once, the disactivation of the fall manager is allowed, it's possible to use the
   :cpp:func:`ALMotionProxy::setFallManagerEnabled` method to disable the fall manager for the
   current naoqi launch.

   Before this, you should have prepared your own defensive methods to protect from falls.

   .. code-block:: python

      motionProxy.setFallManagerEnabled(False)

   You can also use the ALMotion preference key "ENABLE_FALL_MANAGER_PROTECTION" with a
   value="false" for disable at every naoqi launch the fall manager reflex.

   And the preference file should have this form :

   .. code-block:: guess

      <Preference name="ENABLE_FALL_MANAGER_PROTECTION" description="If false the Fall Manager
      reflex is disable on this robot." value="false" type="bool" />