[ros-users] using navigation to move a robot

[Eric Perko]

Ben,

I'm at Case Western Reserve University and I recently went through
getting the navigation stack up and running on our mobile robots.
First off, after getting a joystick controller working so I could
verify that my cmd_vel was working properly, I followed these
tutorials: http://www.ros.org/wiki/navigation/Tutorials/RobotSetup and
http://www.ros.org/wiki/slam_gmapping/Tutorials/MappingFromLoggedData
in order to build a map for the nav stack to use. Have you looked at
both of those tutorials and maybe tried using launch files instead of
spawning things individually?

I can't tell you why your node isn't remapping the topics properly.
I've never had an issue with it. Have you tried having your interface
code listen to cmd_vel and see if the rest works?

The only time I've seen that error about not being able to find a
valid plan was when either there was no clear path or the robot could
not leave the obstacle space for some reason (usually a bunch of
people crowding around the LIDAR while the robot can't backup because
of a wall).

I've not used simple_navigation_goals. I have been able to
successfully command the nav stack using rviz to send goals. What sort
of results do you get when you have rviz sending goals to
move_base_simple/goal?

- Eric Perko
wisesage5001 at gmail.com
eric.perko at case.edu
mobilerobots.case.edu

On Wed, Mar 24, 2010 at 4:48 PM, Ben Reiter <bkreiter at wustl.edu> wrote:
> Dear Ros-User-Group,
> My name is Ben Reiter, I'm a student a WashU in Saint Louis. I'm trying to
> get our robot to move using the navigation stack, but I'm having some
> issues. I'll try to explain exactly what I'm doing, and what is going wrong.
> At the moment, the robot fails to move at all. In rviz, I can see that the
> transforms all are working, that it can definitely see the laser, and is
> starting to build a map.
> I run:
> Roscore
> Hokuyo_node
> rflex b21 (the interaction with our robot which sets up tf, b21/cmd_vel, and
> a host of other nodes)
> gmapping slam_mapping
> move_base move_base (which starts move_base_node)
> simple_navigation_goals (from this
> tutorial: http://www.ros.org/wiki/navigation/Tutorials/SendingSimpleGoals)
> I'm currently having 2 issues, they might or might not be related.
> First, when I run move_base I try to remap its output 'cmd_vel' to
> 'b21/cmd_vel' by writing "rosrun move_base move_base cmd_vel:=b21/cmd_vel"
> However, this seems to have no effect because move_base still creates a
> cmd_vel topic that doesn't communicate with the b21/cmd_vel.
> Second, and I think more importantly, when I run simple_navigation_goals,
> the output is as follows:
> Waiting for the move_base action server to come up
> Sending goal
> The base failed to move forward 1 meter for some reason
> And then it exits.
> Just after "sending Goal" in simple_navigation_goals, when looking at the
> output of move_base, I get this error:
> [ERROR] 1269463020.665478000: Aborting because a valid plan could not be
> found. Even after executing all recovery behaviors
> I'm not really sure how to fix this, Any help would be appreciated.
> Thanks,
> Ben Reiter
>
>
>
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