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2016-09-30 09:47:25 -0600 commented question Arduino published topics do not appear [rosserial_server]

Could you send the output of rosserial_server? You could try specifying baud rate and serial device. See this especially the serial device number changes sometimes without apparent reason... (arduino could be /dev/ttyACM1, while default is /dev/ttyACM0)

2016-09-30 09:15:49 -0600 commented question Can I run ROS jade in combination with Ubuntu snappy core?

@Mehdi: targeted at the beaglebone black (BBB) there is snappy 15.04 see here, maybe that is the best candidate, it is specifically developed for the BBB, and it should be possible to install ROS Jade from source on 15.04 ARM...

2016-09-30 09:09:14 -0600 commented question Can I run ROS jade in combination with Ubuntu snappy core?

@Mehdi: I was looking for 14.04, but I could not find it. the download page for server for ARM only lists 16.04. the alternative downloads link only lists some specific ARM targets.

2016-09-30 07:35:06 -0600 commented question Can I run ROS jade in combination with Ubuntu snappy core?

@gvdhoorn: it seems that compiling MoveIt from source is not as hard as I tought. Actually, if I understand correctly, the fact that MoveIt is allready in ros-shadow-fixed suggests that it is almost ready for release... I will definately look into this...

2016-09-30 07:30:45 -0600 commented question Can I run ROS jade in combination with Ubuntu snappy core?

@Mehdi: thanks for pointing out the server distribution, but the only available version is 16.04, which would force me to compile MoveIt from source as well (since the only ROS version compatible with 16.04 is kinetic, and MoveIt is not released for kinetic yet).

2016-09-30 05:02:44 -0600 asked a question Can I run ROS jade in combination with Ubuntu snappy core?

Hello all,

I am developing a modular robotic arm, which will consist of the following parts:

  • A PC running the motion planning (MoveIt & ros_control)
  • Embedded controllers which run the local PID loops to control the arm's joints

My idea was to use SBC's (Single Board Computers) running linux as the embedded controllers, so for communication between the main PC and the embedded controllers the standard ROS infrastructure can be used.

Most of these SBC's have some ARM processor, so my initial guess would be to run a stripped down ARM Ubuntu version on the SBC's. However, Canonical seems to have stopped distributing ARM versions of Ubuntu, apart from their new distribution for embedded systems: Ubuntu snappy core. This would not be an issue, since there is a nice plugin to create snappy-compatible packages out of ROS workspaces with the catkin plugin for snapcraft. (see also: this link). This would generate a stand-alone application that contains all ROS (and other) dependencies and is compatible with the snappy package system. (the main issue with the snappy distribution over the old ARM distributions is that you can no longer use apt-get to retrieve needed ROS packages, so the only way to get ROS on snappy is to either create a snappy package containing the ROS nodes and dependencies, or to install ROS from source)

But here is the catch:

  • MoveIt is released up to ROS jade, running on Ubuntu 15.04 (Vivid) (but not on later ubuntu versions)
  • Snapcraft is released only on Ubuntu 16.04 (Xenial), so this would correspond to ROS kinetic

As far as I know, mixing two ROS distributions is not recommended, so there would be couple options to get this working:

  • Install MoveIt from source for kinetic on Ubuntu 16.04 (Xenial) PC: Ubuntu 16.04 + Kinetic, Embedded: Ubuntu 16.04 Snappy Core
  • Install ROS jade from source on Ubuntu 16.04 (Xenial) and create snappy packages from there PC: Ubuntu 15.04 + Jade, Embedded: Ubuntu 16.04 Snappy Core, Build PC: Ubuntu 16.04 + Jade
  • Install Snapcraft from source on Ubuntu 15.04 (Vivid) and create snappy packages from there PC: Ubuntu 15.04 + Jade, Embedded: Ubuntu 16.04 Snappy Core
  • Install ROS jade from source directly onto Ubuntu 16.04 Snappy Core (circumventing the snappy package system altogether) PC: Ubuntu 15.04 + Jade, Embedded: Ubuntu 16.04 Snappy Core + Jade from source

Does any of you have any experience with this? Is this even feasible? Or would it be best to move to some other OS for the embedded controllers (one of the boards I am considering is the BeagleBone Black which can also run Debian or Angstrom for example (see also: this link) which also has some unofficial ROS support). My preferred situation would be to use as much stable software as possible, preferably in the form of binary releases.

Thanks in advance!

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2016-06-28 04:01:18 -0600 answered a question ros_control actuators and transmissions

Currently I am using the hardware abstraction layer to calculate the influence of the transmissions.

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2016-05-30 08:53:05 -0600 commented answer Unable to Locate ROS Packages?

So, are your repositories configured correctly? If you run: grep -h ^deb /etc/apt/sources.list /etc/apt/sources.list.d/* The output should at least contain: deb http://packages.ros.org/ros/ubuntu trusty main Otherwise apt-get can never find ros-indigo-desktop-full or ros-indigo-ros-tutorials

2016-05-23 07:18:03 -0600 answered a question Unable to Locate ROS Packages?

When you want to install ROS packages from the repositories, you have to add them to your sources.list first, otherwise apt-get does not now where to find the packages.

See also: http://wiki.ros.org/indigo/Installati...

Like BennyRe said: if not necessary do not install from source.

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2016-04-25 10:14:28 -0600 asked a question ros_control actuators and transmissions

I am controlling a dynamixel based SCARA arm (4 revolute joints) using ROS (MoveIt + ros_control + dynamixel_controllers). Before controlling the actual arm, I attempted to test the system with Gazebo. (up to the point where I would connect ros_control to the dynamixel motors). In my URDF I added the transmissions (in my case 1:2) between the actuators and the joints. I am using the effort_controllers/JointTrajectoryController and my joint names when spawning the controllers.

The simulation works fine, and I am able to control the arm using MoveIt pretty much as expected, however when monitoring the joint angles which are send to my controllers they map 1:1 to the joint angles set in MoveIt, where I would expect them to be double because of the transmission between my motors and my joints.

How does ros_control take the transmission into account? Should I spawn my controllers using the actuator names instead of the joint directly? Or should I implement the transmission somewhere in the hardware abstraction layer which will connect ros_control to my dynamixel_controllers?