rfn123's profile - activity

Hi all,

I have a question on how to obtain tf frames in a ros node (preferrably Python). I am aware of the method tf2_ros.Buffer.lookup_transform(), however, one has to specify source and target frame for that.

Lets say I have an array of known markers, but only a subset of them are detected by the camera. I want to know which of these markers are detected by looking at the existing tf frames. Is there a more elegant way to do so instead of looping over all possible markers and try to lookup the transform in a try catch block?

Thanks in advance!

P.S I am using kinetic on Ubuntu 16.04

EDIT:
In the tutorial TfUsingPython I found the method allFramesAsString() but it seems to use tf, not tf2. would there be an equivalence in tf2? Or is it generally a bad practice to mix the use of tf and tf2?

The documentation of the URDF says: " Note: multiple instances of <collision> tags can exist for the same link. The union of the geometry they define forms the collision representation of the link."

I was wondering how the collision check (e.g. in Moveit) will be performed. Let's say I do a convex decomposition on the mesh of a link and include the convex component in seperate collision instances. Would this increase the performance compared to the case where I put the convex components in a single file and thus a single collision instance? Will the collision checker first check whether the specified mesh is convex and then check for collisions or does the collision checker first combines the convex components and then does the collision check? In the latter case the combined shape is not necessarily convex anymore and thus more computation heavy to check.

Thanks!

I've created a xacro file for my robot arm and successfully visualized it in Rviz with the display.launch launchfile from the urdf_tutorials package. However, i can't slide left or right with the slidebar to control the joint movements in the joint_state_publisher GUI window, the only thing I can click is the randomize button below the slide bars. The robot is then moving accordingly, so I think there is no problem with my xacro file.

I have to mention though that I haven't included collision and inertia tags in the xacro file yet, could this be the reason?

Can anyone tell me why I can't use those slidebars, or how I can fix this problem? Thanks a lot!! :)

So the background is that I want to use the moveit_servo package with a real UR3.

I have some questions regarding implementation of the JointGroupPositionController and the UR drivers:

1) The github page of ur_modern_driver states that the package is deprecated, and the new release is ur_robot_driver. However, I have UR software version 3.4 and the new driver only supports versions >=3.7. Is it correct that I still have to use ur_modern_driver then?

2) Is it in general possible to control the UR3 with a JointGroupPositionController? If yes, how? Do I need a hardware_interface for this or can I use the existing one in the ur_robot_driver package just with a new config file?

I am using Ubuntu 18.04 with ROS melodic.

Do multiple convex collision instances in URDF increase performance? The documentation of the URDF says: " Note: multipl

You defined cv2.waitKey() without parameter, this means it blocks the process and will wait indefinitely for a key press

Could also be because your depth image is saved in 16 bit (16UC1), thus the range is 0-65535. This would explain why you

Are you only computing the distance (I.e. Depth) to the object or the 6D pose of the object with respect to the camera f

Are you using an RGBD camera? One thing is not quite clear to me: if the point cloud gets rotated with the camera, why i

rospy.spin() is needed because without it the callbacks will never get called. Did you verify e.g. with rostopic echo th

This might be a problem of the image being float (range 0-1) or int (0-255). It looks like you have to convert the image

How do you determine that info_sub does not subscribe anything? I my opinion stopping at rospy.spin() is actually the no

ROS itself does not provide image processing capabilities, what you could do is to use OpenCV to process the image, then

EDIT: as corrected by @gvdhoorn The syntax for running a launchfile is roslaunch <package_name> <launchfil

The correct syntax for running a launchfile is roslaunch <package_name> <launchfile_name> You have to a

The correct syntax for running a launchfile is roslaunch <package_name> <launchfile_name> You have to add

I am not sure what your ROS version/ exact use case is, but maybe it is useful to keep in mind that floating joints are

EDIT: apriltag_ros requires the /camera_info topic to be published. You need a bagfile with that topic in it. ========

When looking at the ROS wiki for apriltag_ros, I see that the camera_info topic is required. You probably have to record

when you do rostopic echo /usb_cam/image_raw , is it empty while playing the rosbag?

So this did not fit into the comments section: The error in your question occurs when no image is published to the sub

Ok, then we make it the other way round: we want to change the topic name where april tag node subscribes to. Which laun

Then you can try to put it in a separate launchfile which you will launch when the rosbag plays

try adding <node ns="usb_cam" name="image_proc" pkg="image_proc" type="image_proc"/> in your camera launch file

@Davide_970 have a look at image_proc

which image topic are you publishing to? Is this consistent with the topic the april tag node is subscribing to? Are the

which image topic are you publishing to? Is this consistent with the topic the april tag node is subscribing to? Are the

Hi, checkout this tutorial. I think the easiest way to use ROS on a raspberry pi is to install ubuntu on it. Like this

Hi, checkout this tutorial. I think the easiest way to use ROS on a raspberry pi is to install ubuntu on it. Like this

Hi, checkout this tutorial. I think the easiest way to use ROS on a raspberry pi is to install ubuntu on it. Like this

can you be more specific? Like do you have a 3D or 2D laser scanner?

What exactly do you want to publish to /tf? The pose of the robot or also the robot structure? For the latter you need t

If you want object detection with point clouds maybe you should look into PCL (Point cloud library)...I found this packa

How to use UR3 with JointGroupPositionController? So the background is that I want to use the moveit_servo package with

How to use UR3 with JointGroupPositionController? So the background is that I want to use the moveit_servo package with

I am not sure if the urdf included in your link is the actual one you are using, but from the commented parts I see that