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How to control Maxon Motor by using ROS_CANopen

asked 2016-12-16 04:03:02 -0500

CJ.Nilson gravatar image

updated 2016-12-26 12:22:20 -0500

Hi all,

I am a newbie to ROS, I would like to use ROS_CANopen package to connect with my robot, I want to set different modes of operation for position and current control. After that, I would like to use MoveIt to control my robot. However, I checked from previous ROSAnswer about ROS_CANopen can not find more detail tutorials on how use it.

Here is my hardware configuration:

  1. A USB-to-CAN compact made by IXXAT is used to communicate between my laptop and the robot. The Linux driver called IXXAT socketcan driver.
  2. The robot uses Maxon EPOS2 with CANopen. eds file is generated from EPOS studio.

OS: Ubunutu 14.04 with indigo installed. I already tested with socketcan driver by using can-utils i.e. cansend can0 xxx. Therefore, I can just use CANopen protocol-301 and 402 with command-line to control Maxon motor, in the meantime, use sockketcan_dump to verify command and status.

How to use Ros_CANopen? could someone give me a hint to do next steps or some examples I could refer to? or any package to run roslaunch to control ROS_CANopen?

Many thanks,

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Excuse me, I now have a USB-to-CAN device (kvaser leaf light v2), a motor! I want to know how to use ROS_CANopen and socketcan_driver to control motor rotation? Can you tell me what to do? This problem has been bothering me for a long time, please!

FAN gravatar imageFAN ( 2019-08-16 07:43:45 -0500 )edit

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answered 2016-12-16 05:40:03 -0500

Mathias Lüdtke gravatar image

updated 2016-12-16 05:40:40 -0500

It should be more or less straightforward:

  1. Setup SocketCAN (you already have this running): http://wiki.ros.org/socketcan_interfa...
  2. Prepare URDF with sane limits (this is required for now, will be optional in the future): http://wiki.ros.org/urdf/Tutorials/Cr...
  3. Prepare EDS/DCF, take special care for the PDO mapping ( http://wiki.ros.org/canopen_402 ), use transmission type 1 (every sync)
  4. Prepare driver config
  5. Prepare controller config
  6. Prepare a launchfile for canopen_motor_node
    • upload driver config as private parameters
    • upload controller config into namespace
    • upload robot description
  7. rosservice call [/namespace]/driver/init ( http://wiki.ros.org/canopen_chain_nod... )
  8. start/switch the controllers (rqt_controller_manager, ontroller_manager, spawner etc.)

The EDS file parser is not really bullet proof (and EDS file format is rather flexibel) and might fail with some error indication. In addition ros_canopen enforces strict typing, some EDS files list non-standard types for some objects (e.g. signed instead of unsigned). This must be fixed as well in the EDS.

A basic driver config looks like:

bus:
  device: can0
sync:
  interval_ms: 10  # 100Hz
  overflow: 0
defaults:
  eds_pkg: my_package
  eds_file: "config/MyDescription.dcf" # the parser reads EDS and DCF
nodes:
  my_joint:
    id: 1

controller config example: https://github.com/ipa320/canopen_tes...

Fairly complex examples: https://github.com/ipa320/schunk_robots/

It would be great if you could turn this into a tutorial on ROS Wiki based on your experiences :)

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Thank you for the replies. I still have some questions regarding your replies.

  • item 2: I have created URDF to describe elements fo my robot, but why need URDF in ros_canopen
  • item 5: Why ros_canopen package need ros_control? Could you briefly introduce the main idea for using ros_control
CJ.Nilson gravatar imageCJ.Nilson ( 2016-12-19 12:19:51 -0500 )edit

I'm trying to refer "schunk_robots and canopen_test_utils" as a model for item 4, 5 and 6. Which packages do you recommend for my case? Thanks you very much.

CJ.Nilson gravatar imageCJ.Nilson ( 2016-12-19 12:30:52 -0500 )edit

The URDF is used for getting the joint limits and to verify the names of the joints.

More information on ros_control can be found in the wiki: http://wiki.ros.org/ros_control And schunk_robots contains full-fledged examples.. If in doubt have a look at both.

Mathias Lüdtke gravatar imageMathias Lüdtke ( 2016-12-19 17:19:02 -0500 )edit

When I tried to do item 7 you listed, I met the failure during initializing the lwa4d, have you ever meet this before ? Thanks for your reply

CJ.Nilson gravatar imageCJ.Nilson ( 2016-12-23 01:28:02 -0500 )edit
1

Hello CJ and Mathias, please, could you help me with a similar problem in this question: #q292882

Many thanks, Jorge

jdeleon gravatar imagejdeleon ( 2018-06-01 01:41:44 -0500 )edit

@Mathias Lüdtke , When you say use transmission type 1, that is for both RxPDO and TxPDO ?

Cyril_J gravatar imageCyril_J ( 2018-12-06 04:38:45 -0500 )edit

Yes, for both. This is how we run it with Care-O-bot. It is not mandatory, but it enforces a deterministic data flow. Otherwise the timing would be arbitrary and might result in (small) jumps.

Mathias Lüdtke gravatar imageMathias Lüdtke ( 2018-12-10 09:49:44 -0500 )edit

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Asked: 2016-12-16 03:58:20 -0500

Seen: 4,718 times

Last updated: Dec 26 '16