Why so much spinning in place with move_base?

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Hello,

I'm trying to tune move_base under fairly ideal circumstances so I did not think it would be this hard. I am using the arbotix_python base controller in "fake" mode which basically just moves the simulated robot exactly as it's told on /cmd_vel. So I am treating it as an "ideal" test case with no physics.

I then have a Python script that moves a simulated TurtleBot to the four corners of a 1 meter square on a blank map using the simple move_base action server.

I've run through the Navigation Tuning Guide and spent many hours of trial and error tweaking the various parameters using dynamic_reconfigure but I still can't figure out why the robot has such a tendency to spin in place before it gets to a goal even when there are no obstacles and I have the recovery and clearing behaviors disabled. The problem gets worse as I make the goal tolerances smaller--for example, setting the xy_goal_tolerance to 0.05 tends to guarantee spinning and often timing out before getting to the goal.

I'm wondering if others have figured out any secrets behind this spinning behavior. I'm also wondering if not having any real or simulated observation sources could be causing it?

I get the same results whether I use the latest Electric or Fuerte debian install under Ubuntu 11.10.

EDIT 1:

My navigation config files can be found here.

And the script that moves the robot in a square can be found here.

Thanks!
patrick