# Revision history [back]

### Clearing costmap to unstuck robot (3.000000m)

I've been banging my head against this navigation problem for days. It occurs under both ROS Indigo and ROS Hydro (Debian installs). And it occurs with both a Kobuki and a Segway RMP 210 both in Gazebo and the real world. At the moment, both robots are using a single planar laser scanner for obstacle detection mounted about 15cm off the ground. Also, I am not using a static map--both the local and global cost maps are using the odom frame for the global frame.

The issue is that when the robot attempts to pass through a narrow gap, such as a doorway, the global planner (NavfnROS) usually plans a reasonable path through the gap. The local planner (TrajectoryPlannerROS) then speeds the robot along the path toward the gap and some times the robot makes it through but at least 50% of the time, the robot stops either just before it enters the gap or even after it has entered the gap. The robot then rotates through small angles left and right and might even back up a bit. After 10 to 15 seconds, I see the warning:

Clearing costmap to unstuck robot (3.000000m)


on the move_base terminal. I've tried a gazillion combination of parameters including increasing the planner frequency, changing the map resolution, reducing the inflation radius to as small as 0.1 and nothing seems to eliminate the problem. In addition, I don't know where the number 3.000000m in the message above is coming from. Looking at the source code for clear_costmap_recovery.cpp this parameter is defined on line 61 as:

private_nh.param("reset_distance", reset_distance_, 3.0);


However, I cannot figure out how to redefine this parameter in my yaml files. For example, neither:

conservative_clear:
reset_distance: 1.0


nor

conservative_reset_dist: 1.0


changes the value of the parameter in the warning message above. Also, the following screen shot shows a typical situation where this stuck behavior occurs:

Notice how the global plan (thin green line) passes very close to the obstacle on the right. And this is after the robot has already been stuck for 10 seconds or so even though the planner frequency in this case was 5 Hz. For some reason, the robot just remains stuck instead of replanning a path to go more centrally through the gap.

So the more general question is this: what parameter tricks are people using to get their robots to move through narrow gaps like doorways?

Thanks!
patrick