AMCL and map_server were ported to ROS2 with minimal functional changes, but some refactoring.
- amcl -> nav2_amcl
- map_server -> nav2_map_server
In addition, move_base itself has been split into multiple components:
- nav2_simple_navigator (replaces move_base)
- nav2_dijkstra_planner (replaces global_planner)
- nav2_controller_dwb (replaces local_planner)
The nav2_simple_navigator replaces move_base at the top level, with a Task interface to call the global and local planners.
- Note: the Task interface is a temporary proxy for ROS2 Actions which are not yet implemented. When Actions become available, the planners will be called through ROS2 Actions.
The reason for the change was to make it so that global and local planners would be Action Servers and could be replaced at launch or run time with other implementations providing the same Action.
The nav2_simple_navigator itself is also a Task Server and can also be replaced with other implementations. The first such implementation is currently in progress called nav2_bt_navigator. It uses Behavior Trees to make it possible to have more complex state machines and to add in recovery behaviors as additional Task Servers. See nav2_bt_navigator for that implementation. (currently WIP in Pull request 91)
The nav2_dijkstra_planner is ported from the navfn package in ROS, but adds the Task Server interface to enable it to be strongly decoupled from the nav2_simple_navigator.
Similarly, the nav2_controller_dwb is ported from the dwb controller package, and also adds a Task Server interface to also enable it to be decoupled from the nav2_simple_navigator.
All these changes make it possible to replace any of these nodes at launch/run time with any other algorithm that implements that same interface.
See each package README.md for more details