Add Time-optimal Trajectory Generation tutorial (#289)

* Add Time-optimal Trajectory Generation tutorial

* Rewordings in time_parameterization tutorial

Author: henningkayser

doc/time_parameterization/time_parameterization_tutorial.rst

@@ -16,8 +16,14 @@ The speed of a parameterized kinematic trajectory can also be modified during ru
 
 Time Parameterization Algorithms
 --------------------------------
-MoveIt! can support different algorithms for post-processing a kinematic trajectory to add timestamps and velocity/acceleration values. Currently two are available by default in MoveIt!: :moveit_codedir:`Iterative Parabolic Time Parameterization<moveit_core/trajectory_processing/src/iterative_time_parameterization.cpp>`, and :moveit_codedir:`Iterative Spline Parameterization<moveit_core/trajectory_processing/src/iterative_spline_parameterization.cpp>`.
+MoveIt! can support different algorithms for post-processing a kinematic trajectory to add timestamps and velocity/acceleration values. Currently there are three available by default in MoveIt!: 
+
+* :moveit_codedir:`Iterative Parabolic Time Parameterization<moveit_core/trajectory_processing/src/iterative_time_parameterization.cpp>`
+* :moveit_codedir:`Iterative Spline Parameterization<moveit_core/trajectory_processing/src/iterative_spline_parameterization.cpp>`
+* :moveit_codedir:`Time-optimal Trajectory Generation<moveit_core/trajectory_processing/src/time_optimal_trajectory_generation.cpp>`
 
 The Iterative Parabolic Time Parameterization algorithm is used by default in the `Motion Planning Pipeline <../motion_planning_pipeline/motion_planning_pipeline_tutorial.html>`_ as a Planning Request Adapter as documented in `this tutorial <../motion_planning_pipeline/motion_planning_pipeline_tutorial.html#using-a-planning-request-adapter>`_. Although the Iterative Parabolic Time Parameterization algorithm MoveIt! uses has been used by hundreds of robots over the years, there is known `bug with it <https://github.com/ros-planning/moveit/issues/160>`_.
 
-The Iterative Spline Parameterization algorithm was recently merged into mainstream MoveIt! in `PR 382 <https://github.com/ros-planning/moveit/pull/382>`_ to deal with these issues. While preliminary experiments are very promising, we are waiting for more feedback from the community before replacing the Iterative Parabolic Time Parameterization algorithm completely.
+The Iterative Spline Parameterization algorithm was merged with `PR 382 <https://github.com/ros-planning/moveit/pull/382>`_ as an approach to deal with these issues. While preliminary experiments are very promising, we are waiting for more feedback from the community before replacing the Iterative Parabolic Time Parameterization algorithm completely.
+
+Time-optimal Trajectory Generation introduced in PRs `#809 <https://github.com/ros-planning/moveit/pull/809>`_ and `#1365 <https://github.com/ros-planning/moveit/pull/1365>`_ produces trajectories with very smooth and continuous velocity profiles. The method is based on fitting path segments to the original trajectory and then sampling new waypoints from the optimized path. This is different from strict time parameterization methods as resulting waypoints may divert from the original trajectory within a certain tolerance. As a consequence, additional collision checks might be required when using this method.