Update documentation for pluginized motion models (#905)

* updates to mppi configuration and migration

Signed-off-by: Alessio Parmeggiani <parmeggiani.alessio1@gmail.com>

* restored AckermannMotionModel parameter section

Signed-off-by: Alessio Parmeggiani <parmeggiani.alessio1@gmail.com>

* remove extra spaces

Signed-off-by: Alessio Parmeggiani <parmeggiani.alessio1@gmail.com>

---------

Signed-off-by: Alessio Parmeggiani <parmeggiani.alessio1@gmail.com>

Author: Alessio-Parmeggiani

configuration/packages/configuring-mppic.rst

@@ -35,11 +35,23 @@ MPPI Parameters
   ============== ===========================
   Type           Default
   -------------- ---------------------------
-  string         "DiffDrive"
+  string         "diff_drive"
   ============== ===========================
 
   Description
-    The desired motion model to use for trajectory planning. Options are ``DiffDrive``, ``Omni``, or ``Ackermann``. Differential drive robots may use forward/reverse and angular velocities; Omni add in lateral motion; and Ackermann adds minimum curvature constraints.
+    The desired motion model plugin to use for trajectory planning. The plugin type is required to be specified in the corresponding namespace.
+
+:``<motion_model>``.plugin:
+
+  ============== ===========================
+  Type           Default
+  -------------- ---------------------------
+  string         N/A
+  ============== ===========================
+
+  Description
+    The plugin to use for the motion model constraints of the MPPI planner.
+    Supported motion model plugins include "mppi::DiffDriveMotionModel", "mppi::OmniMotionModel", and "mppi::AckermannMotionModel" for differential drive, omnidirectional, and Ackermann robots respectively.
 
 :critics:
 
@@ -374,10 +386,10 @@ Trajectory Visualization
   Description
     Whether to allow QoS profiles to be overwritten with parameterized values.
 
-Ackermann Motion Model
-----------------------
+AckermannMotionModel
+--------------------
 
-:min_turning_r:
+:``<motion_model>``.min_turning_r:
 
   ============== ===========================
   Type           Default
@@ -386,7 +398,7 @@ Ackermann Motion Model
   ============== ===========================
 
   Description
-    The minimum turning radius possible for the vehicle platform (m).
+    The minimum turning radius possible for the vehicle platform (m). This is only used if ``<motion_model>``.plugin is set to "mppi::AckermannMotionModel".
 
 Default Optimal Trajectory Validator
 ------------------------------------
@@ -1085,7 +1097,9 @@ Example
           iteration_count: 1
           temperature: 0.3
           gamma: 0.015
-          motion_model: "DiffDrive"
+          motion_model: "diff_drive"
+          diff_drive:
+            plugin: "mppi::DiffDriveMotionModel"
           visualize: false
           critic_index_to_visualize: 0
           reset_period: 1.0 # (only in Humble)
@@ -1097,8 +1111,6 @@ Example
             plugin: "mppi::DefaultOptimalTrajectoryValidator"
             collision_lookahead_time: 2.0
             consider_footprint: false
-          AckermannConstraints:
-            min_turning_r: 0.2
           critics: ["ConstraintCritic", "CostCritic", "GoalCritic", "GoalAngleCritic", "PathAlignCritic", "PathFollowCritic", "PathAngleCritic", "PreferForwardCritic"]
           ConstraintCritic:
             enabled: true

migration/Kilted.rst

@@ -945,3 +945,25 @@ Global planner plugin natively accepts viapoints
 `PR #5995 <https://github.com/ros-navigation/navigation2/pull/5995>`_ updates the ``createPath`` API for the ``BaseGlobalPlanner`` to include a vector ``std::vector<geometry_msgs::msg::PoseStamped>`` argument that takes in a list of intermediate points and passes them to the planner plugin implementation.
 
 The function signature for ``createPath`` must be updated accordingly for all custom planner plugins inheriting from the ``BaseGlobalPlanner``. This change does not alter the behavior of ``ComputePathThroughPoses`` that connects consecutive segments end-to-end but does upgrade the ``ComputePathToPose`` action.
+
+MPPI motion models use plugin-based configuration
+--------------------------------------------------
+
+`PR #6076 <https://github.com/ros-navigation/navigation2/pull/6076>`_ adds support for plugin-based configuration of motion models in MPPI.
+
+Motion model now has to be set up by specifying plugin to use:
+
+.. code-block:: yaml
+
+  MPPIController:
+    plugin: "nav2_mppi_controller::MPPIController"
+    motion_model: "diff_drive"
+    diff_drive:
+      plugin: "mppi::DiffDriveMotionModel"
+
+Supported motion model plugins are:
+  - ``mppi::DiffDriveMotionModel`` : replaces ``motion_model: DiffDrive``
+  - ``mppi::OmniMotionModel`` : replaces ``motion_model: Omni``
+  - ``mppi::AckermannMotionModel`` : replaces ``motion_model: Ackermann``
+
+While "diff_drive" is the default value for ``motion_model`` parameter, it is still required to specify the plugin for it, as shown above.