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2013-09-27 13:13:50 -0600 commented question Camera plugin broken in gazebo_ros_pkgs ver 2.3.2?

I think this is the bug I am suffering from: https://github.com/ros-simulation/gazeborospkgs/pull/120

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2013-09-25 19:26:16 -0600 asked a question Camera plugin broken in gazebo_ros_pkgs ver 2.3.2?

I am having an issue that is possibly related to this question. The problem started after I upgraded to gazebo_ros_pkgs ver 2.3.2. I am using ROS Hydro.

I have a robot that has an ros_openni_kinect sensor. Every time I subscribe to the image topic (through rviz say, or even rostopic echo) published by that sensor, gzserver crashes with the following error message:

gzserver: /usr/include/boost/smart_ptr/shared_ptr.hpp:412: boost::shared_ptr<T>::reference boost::shared_ptr<T>::operator*() const [with T = boost::mutex, boost::shared_ptr<T>::reference = boost::mutex&]: Assertion `px != 0' failed.
Aborted (core dumped)

The stacktrace on the core dump is:

#0  0x00007f0bf5a95425 in raise () from /lib/x86_64-linux-gnu/libc.so.6
#1  0x00007f0bf5a98b8b in abort () from /lib/x86_64-linux-gnu/libc.so.6
#2  0x00007f0bf5a8e0ee in ?? () from /lib/x86_64-linux-gnu/libc.so.6
#3  0x00007f0bf5a8e192 in __assert_fail () from /lib/x86_64-linux-gnu/libc.so.6
#4  0x00007f0b74dc82b9 in gazebo::GazeboRosCameraUtils::ImageConnect() () from /opt/ros/hydro/lib/libgazebo_ros_camera_utils.so
#5  0x00007f0bdf82f23e in ros::PeerConnDisconnCallback::call() () from /opt/ros/hydro/lib/libroscpp.so
#6  0x00007f0bdf8345c9 in ros::CallbackQueue::callOneCB(ros::CallbackQueue::TLS*) () from /opt/ros/hydro/lib/libroscpp.so
#7  0x00007f0bdf83608b in ros::CallbackQueue::callAvailable(ros::WallDuration) () from /opt/ros/hydro/lib/libroscpp.so
#8  0x00007f0b74dc6ae2 in gazebo::GazeboRosCameraUtils::CameraQueueThread() () from /opt/ros/hydro/lib/libgazebo_ros_camera_utils.so
#9  0x00007f0bf67a9ce9 in thread_proxy () from /usr/lib/libboost_thread.so.1.46.1
#10 0x00007f0bf75d8e9a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#11 0x00007f0bf5b52ccd in clone () from /lib/x86_64-linux-gnu/libc.so.
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2013-09-25 19:04:04 -0600 commented question roslaunch rrbot_gazebo rrbot_world.launch & rrbot_description rrbot_rviz.launch

I may be getting the same error, or something closely related. My issue is here: http://answers.gazebosim.org/question/4495/camera-plugin-broken-in-gazebo_ros_pkgs-ver-232/

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2013-08-22 11:21:23 -0600 marked best answer Problem with SDF files or robot_description parameter

So I am working my way through some of the tutorials for ROS/Gazebo. I am running into some issues with the ROS Control with Gazebo Tutorial however. In particular when I launch the robot_control package, I get an error saying

Could not find parameter robot_description on parameter server

After a little digging I added the following to my launch file:

<param name="robot_description" textfile="path/to/robot.sdf"/>

to set the robot_description parameter. However after I did that I get the error:

/opt/ros/hydro/lib/robot_state_publisher/robot_state_publisher
[ERROR] [1376891403.184690567]: Could not find the 'robot' element in the xml file
[ERROR] [1376891403.184756779]: Could not generate robot model
[ERROR] [1376891403.184774430]: Failed to extract kdl tree from xml robot description

So I am guessing that what is happening is that robot_state_publisher is looking for a URDF file while I am providing a SDF file. How do I get around this?

Thanks in advance.

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2013-08-22 11:09:48 -0600 commented question libgazebo_ros_openni_kinect.so topic values and their visualization in rviz

Done. Ros Hydro, and Gazebo 1.9.

2013-08-22 02:50:45 -0600 commented answer joint_state ROS topic from Gazebo and ros_control

Thanks. I think I have gotten to the point where I can at least proceed further. I'm getting /joint_state updates and I can publish to the controllers to move my (toy) robot.

2013-08-22 02:38:25 -0600 asked a question libgazebo_ros_openni_kinect.so topic values and their visualization in rviz

The oppenni_kinect plugin publishes data to the following topics:

  1. Image Topic (say /depth_camera/image_raw)
  2. Depth Image Topic (say /depth_camera/depth_image_raw)
  3. Point Cloud Topic (say /depth_camera/points)

I have some questions about each of these:

  1. The point cloud (/depth_camera/points) topic seems to publish a sequence of xyzrgb values (each component 4 bytes long). I can visualize this in rviz though the pointcloud2 display (the coordinates of which need to be transformed first it seems). While this places the points appropriately, it colors them all black (my guess is that it is expecting 1 byte long rgb values rather than 4?). Is there a way to get the color right?

  2. The depth image topic (/depth_camera/depth_image_raw) is a sequence of 32 bit floating points that represent distance in meters. I could not find a way to visualize this in rviz. I tried depthcloud, but that didn't work. Is there a way to visualize this data?

  3. The image topic (/depth_camera/image_raw) is an simple rgb image. So I setup a camera display reading from this topic. I was expecting it to be displayed in 2D window like how my normal image camera display shows up, but I was surprised to see that it colored my point cloud display in the 3D view. I'm happy this happened, but a little confused. How did that happen?

I am using ROS Hydro and Gazebo 1.9.

2013-08-22 02:11:55 -0600 marked best answer joint_state ROS topic from Gazebo and ros_control

I am trying to learn Gazebo/ROS from the tutorials and I am confused about a couple of things.

  1. When I run Gazebo as a ROS node, does Gazebo publish to the /joint_state topic? It does not seem like it does from looking at the topic subscriber/publisher graph. Is there a way for me to do this? It seems like necessary information to have for programming the robot from ROS. Also, I would like to view the state of the robot in rviz, which needs /tf data which in turn needs /joint_states (afaik).

  2. I do not understand ros_control and how it works with gazebo at all. ros_control is pretty much undocumented in ROS. Any suggestions on where to start looking for information? Or if somebody could give me a quick high level overview that would be incredibly helpful.

Thanks in advance.