move_base will send a zero-velocity message each time the local planner fails "just to be safe," so those may be the messages you are seeing. This hints you do not have a good config for the local planner. If the local planner is failing, you should be getting error messages in the logs saying so.

I find it useful to disable retries in both move_base and in the local planner while debugging issues like this - you want it to fail immediately to diagnose the problem.

In my opinion, forcing such a high min. velocity for linear.x is a bad idea - it should be 0 (or negative if your robot can go backwards.)

Thanks, Mike. Looks you are right. After "Got new map" it comes with a warning:

[ WARN] [1646066043.620563171]: DWA planner failed to produce path.

Have you any idea why? My local DWA planner yaml file is configured:

DWAPlannerROS:
  # for details see: https://wiki.ros.org/dwa_local_planner
  odom_topic: odom

# Robot Configuration Parameters
  max_vel_x: 1.0
  min_vel_x: -0.7

  max_vel_y: 0            # 0 for non-holonomic robot
  min_vel_y: 0           # 0 for non-holonomic robot

# The velocity when robot is moving in a straight line
  max_trans_vel:  1.0
  min_trans_vel:  -0.7

  max_rot_vel: 0.5
  min_rot_vel: 0.1

  acc_lim_x: 0.8
  acc_lim_y: 0.0
  acc_lim_theta: 1 

# Goal Tolerance Parametes
  xy_goal_tolerance: 0.1
  yaw_goal_tolerance: 0.17
  latch_xy_goal_tolerance: false

There are a large number of reasons that cause the local planner to fail. An obstacle inside the footprint, or very close to the robot, is one that I see a lot. Even a single pixel obstacle will put the robot in collision.

If this robot has never moved under control of move_base, you might want to experiment with a simpler planner (maybe carrot_planner?) just to make sure the data path works end-to-end. The DWAPlanner is the most complicated one in the navigation stack, and its default values are not great.

Loads of thanks, Mike. Being still new in Ros, one last question. In order to change to another planner such as the carrot_planner, is it sufficient to replace in the move_base node my parameter "DWAPlanner" by "CarrotPlanner",

<param name="base_local_planner" value="dwa_local_planner/DWAPlannerROS" />

or is it also necessary to write a transform listener as written here: http://wiki.ros.org/carrot_planner?distro=noetic

The carrot_planner isn't going to help you debug your dwa_planner config - I forgot that it is a global planner, not a local planner, so it can't replace dwa_planner.

I'm not sure where you should go from here. Have you tried to enable debug-level log messages for dwa_planner to see if it says anything helpful to you? You can use the app rqt_logger_level to change log levels for most ros nodes.