By autonomous planning, are you referring to a frontier-exploration SLAM ? Or do you drive manually the robot during the mapping and then encounter motion planning problems after the mapping ? Your title is misleading, gmapping is the SLAM algorithm but you mention motion planning problems.

Sorry, the title should be path planning in a complex environment. I'll edit the title. But yes, I am trying to do frontier-exploration SLAM but I often get the error "aborting because a valid plan could not be found." I am wondering if this is because the complex environment confuses the robot?

Ok. Are you using an existing package for frontier-exploration SLAM or did you write your own ? If you are using the move_base library with DWA as your local planner, what is your global planner ? Are you sure that it is the local planner failing and not the global planner ?

I am using this existing package. How would I know if the global planner is failing? I do notice that the robot only plans goal nearby it and will never try to navigate across the room.

In fact, frontier exploration works at first until the robot gets caught in a corner and then I get an error that a valid plan was not found. So maybe you are on to something.

Ok then I suppose you are using the default global planner for move_base, navfn. Can you edit your post to add the exact error message that you are getting ? To help you it would help to know if it is the global or the local planner that is failing.

I edited my original post with some of the errors I get. I appreciate your help!!!

"scan matching failed using odometry" suggests that your odometry may not be properly calibrated/functioning. Have you tried building maps by driving around your turtlebot and using gmapping, instead of autonomous mapping ? Do the maps look good ? Some screenshots of the maps would help.

Also test your odometry as described in the "Odometry" section here : http://wiki.ros.org/navigation/Tutorials/Navigation%20Tuning%20Guide If gmapping cannot produce good maps because of a poor odometry, the scan matching could at some point position distant obstacles too close to the robot.

I don't have access to my robot right now so I can't give you any screenshots but Gmapping works well when I drive manually. The maps are good and I can do autonomous navigation on those maps with good performance. It's only when I'm navigating in an unknown environment

For example if I use the "set nav goal" in Rviz for a mapped environment, there are no issues but if I do it while I'm gmapping, i get errors. I also get errors when I'm using autonomous exploration such as frontier exploration. Something about the global planner perhaps?

I'm thinking it might be an odometry issue because when I'm doing another unrelated process I get an error "waiting for transform from baselink to odom"