How to make the Navigation Stack global Path not update?

Question

I am currently using the navigation stack to move around the robots in the map I created, in gazebo. I would like to apply my own algorithm for the update of the path. But in order this to happen, the navFn should stop publishing the new path when an obstacle is found. I have checked the parameters, but still I haven't made it. Does anyone know how to stop updating the global path ? Thanks a lot. I am using ros noetic. In this [google drive(https://drive.google.com/drive/folders/12kSo0-at20sOO92Nx2kuba7VNU2ruIgM?usp=drive_link). I have a video showing the code, and the source code

Answer 1

Assuming that "planner_frequency" is set to 0.0, it's not really that navFn is "publishing a new path when an obstacle is found" but rather that your local planner/controller is giving up too easily - which then causes move_base to fall back on the global planner (navFn).

Assuming the your algorithm is encapsulated in the local planner/controller you are running, then the goal should be to increase the amount of time that the controller gets before falling back to the global planner.

One approach would be to increase the "controller_patience" parameter in move_base - this is the amount of time (in seconds) that the controller is given to try and find a path. When that amount of time expires, a recovery behavior will be run (if defined) and then the controller will get another "controller_patience" amount of time to try again.

The amount of time your controller gets before navFn gets another chance to plan would be:

"controller_patience" x max("number of recovery behaviors defined", 1)

Answer 2

In move_base_params I changed the planner_frequency to 0. It doesn't update the route, but only when a collision with a dynamic object happens it is recalculated.

shutdown_costmaps: false
controller_frequency: 10.0
planner_patience: 5.0
controller_patience: 15.0
conservative_reset_dist: 3.0
planner_frequency: 0
oscillation_timeout: 10.0
oscillation_distance: 0.2

Answer 3

You can do this by selecting the Behavior Tree that let the path planner publish every X meters driven, in my case, the global path is updated every time the robot runs 100 m.

Just add in your confirmation file:

bt_navigator:
  ros__parameters:
    …
    default_nav_to_pose_bt_xml: "<your_path>/ros2_ws/src/navigation2/nav2_bt_navigator/behavior_trees/navigate_w_replanning_distance.xml" 

And in the xml file replace the 1 m set by default by the desired distance.