navigation stack goal problem

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navigation stack goal problem

chrisb
Hi,
I am new to ROS and am trying to use it with a MetraLabs Scitos-G5 robot, which is a differential drive non-holonomic robot. In particular, I am trying to run the navigation stack.

I have a player driver for the robot, which is a bit messy so I decided the quickest solution to get started would be to create ros nodes that connect to a player server running on the robot and republish the laser and sonar, and subscribe to cmd_vel and pass it on to player server. I made these three nodes in a package, and they seem ok. I use a static transform to publish the transformation from laser to base.

I eventually got it going enough to log data, and create a map with slam_gmapping. I then set up the navigation stack following the tutorial at http://www.ros.org/wiki/navigation/Tutorials/RobotSetup, and got rviz working to show the map, the laser, the odometry etc. The map is good, the localisation (amcl) works nicely and I can see a reasonable particle cloud using rviz.

However, when I set a goal location the robot drives to the goal but never stops. It goes past it and tries to get back to it, never reaching the finished state. Is this the normal behaviour? Is there anything that I likely missed in my player nodes - my odometry node publishes the velocities that player reports, could this be a problem? ie. Position2d::GetXSpeed(),  GetYSpeed() and GetYawSpeed() I'm not fully certain what velocity is expected here - the commanded or the actual?

Thanks in advanace!

Chris
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Re: navigation stack goal problem

Eitan Marder-Eppstein
Chris,

The navigation stack expects the actual velocities on the odometry topic. One issue could be that the acceleration limit parameters are set too high for your robot which could lead to the planner thinking that the robot can slow down and stop when it actually cannot.  See the following page for documentation on the relevant parameters: http://www.ros.org/wiki/base_local_planner#Robot_Configuration_Parameters.

If that suggestion doesn't help, could you post the configuration files that you're using for the navigation stack... that'll help give insight into what might be going on.

Also, when you say that the robot never stops, do you mean that it oscillates while trying to achieve the goal orientation? Or that it actually drives past the goal position, turns around, and attempts to achieve the position again?

Hope this helps,

Eitan

On Wed, Jul 14, 2010 at 1:12 PM, chrisb <[hidden email]> wrote:

Hi,
I am new to ROS and am trying to use it with a MetraLabs Scitos-G5 robot,
which is a differential drive non-holonomic robot. In particular, I am
trying to run the navigation stack.

I have a player driver for the robot, which is a bit messy so I decided the
quickest solution to get started would be to create ros nodes that connect
to a player server running on the robot and republish the laser and sonar,
and subscribe to cmd_vel and pass it on to player server. I made these three
nodes in a package, and they seem ok. I use a static transform to publish
the transformation from laser to base.

I eventually got it going enough to log data, and create a map with
slam_gmapping. I then set up the navigation stack following the tutorial at
http://www.ros.org/wiki/navigation/Tutorials/RobotSetup, and got rviz
working to show the map, the laser, the odometry etc. The map is good, the
localisation (amcl) works nicely and I can see a reasonable particle cloud
using rviz.

However, when I set a goal location the robot drives to the goal but never
stops. It goes past it and tries to get back to it, never reaching the
finished state. Is this the normal behaviour? Is there anything that I
likely missed in my player nodes - my odometry node publishes the velocities
that player reports, could this be a problem? ie. Position2d::GetXSpeed(),
GetYSpeed() and GetYawSpeed() I'm not fully certain what velocity is
expected here - the commanded or the actual?

Thanks in advanace!

Chris
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View this message in context: http://ros-users.122217.n3.nabble.com/navigation-stack-goal-problem-tp967590p967590.html
Sent from the ROS-Users mailing list archive at Nabble.com.

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