hector exploration error msgs

Question

Hi, All,

A while ago I asked a question on using move base and hector exploration together here. Now, I get some error messages when I run SLAM, hector exploration, movebase together

[ INFO] [1385448000.186189169]: Exploration Service called [ INFO] [1385448000.186304532]: [hector_exploration_planner] exploration: starting exploration [ INFO] [1385448000.669314882]: [hector_exploration_planner] exploration: found 4802 frontiers! [ WARN] [1385448000.799343886]: [hector_exploration_planner] No path to the goal could be found by following gradient! [ INFO] [1385448000.799741182]: [hector_exploration_planner] exploration: could not plan to frontier, starting inner-exploration [ INFO] [1385448000.799854087]: [hector_exploration_planner] inner-exploration: starting exploration [ WARN] [1385448000.952170236]: [hector_exploration_planner] inner-exploration: no inner-frontiers have been found! exploration failed! [INFO] [WallTime: 1385448000.952932] No frontiers left.

The strange thing is that these warnings and error messages only appear when I start my robot, they will remain there as long as the robot is not moving (teleoped, my robot can be teleoped and explore by itself ). Once I teleop my robot for a while (a few seconds), the error messages disappeared and the robot starts to explore by itself. I am really curious what do these messages mean and how can I get rid of them. Thanks!

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Originally posted by BenMa on ROS Answers with karma: 76 on 2013-11-25

Post score: 0

Answer 1

When the system does not find any frontiers reachable from the pose of the robot, it switches to inner exploration mode, which requests the robot trajectory from hector_trajectory_server. It then tries to go to locations in the map that are far away from the trajectory of the robot (e.g. go to places not visited yet). Switching into inner exploration really shouldn´t happen at startup though, so something is going wrong. Can you provide a screenshot of the situation (e.g. map and robot pose visible) by editing your post? Won´t be able to make any changes before Xmas though, as DRC Trials are looming ;)

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Originally posted by Stefan Kohlbrecher with karma: 24361 on 2013-11-26

This answer was ACCEPTED on the original site

Post score: 0

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Original comments

Comment by BenMa on 2013-11-27:
I know what went wrong. In the costmap file of the hector explore, there is one parameter called update frequency. The default is set to 0.5. When I use 0.5 HZ, I always get a warning : Map update loop missed its desired rate of 0.5000Hz... the loop actually took 3.6498 seconds That's why I changed to 0.2 and the robot can't start to explore (above mentioned error messages). When I change to back to 0.5, the robot can start to explore, but with this warning message.