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Pi Robot
12-14-2010, 09:18 AM
Hey Fergs,

I was wondering what your rough projections are concerning version 0.5.0 of your ArbotiX ROS package (a.k.a. http://code.google.com/p/vanadium-ros-pkg/wiki/RoadMap)? I see you have logged an issue for speed control (/cmd_joint) and feedback (/joint_states). I wonder if you could also include effort control (/cmd_joint) and feedback (/joint_states). I was thinking that setting an effort might be interpreted as setting the torque_limit for a servo. That way, the servo stops pushing at that value. Does that make sense?

I've also been experimenting with the UA AX-12 Controller and I like their enhanced joint state message as defined at: http://www.ros.org/doc/api/ua_controller_msgs/html/msg/JointState.html. In particular, I find the is_moving and error fields quite useful. So what do you think of adding a similar message type to the ArbotiX ROS package? (I realize you can get the is_moving value from services but I understand this has more overhead than just publishing it as part of the joint state).

Thanks!
patrick

lnxfergy
12-14-2010, 09:29 AM
Hey Fergs,

I was wondering what your rough projections are concerning version 0.5.0 of your ArbotiX ROS package (a.k.a. http://code.google.com/p/vanadium-ros-pkg/wiki/RoadMap)? I see you have logged an issue for speed control (/cmd_joint) and feedback (/joint_states). I wonder if you could also include effort control (/cmd_joint) and feedback (/joint_states). I was thinking that setting an effort might be interpreted as setting the torque_limit for a servo. That way, the servo stops pushing at that value. Does that make sense?

I've also been experimenting with the UA AX-12 Controller and I like their enhanced joint state message as defined at: http://www.ros.org/doc/api/ua_controller_msgs/html/msg/JointState.html. In particular, I find the is_moving and error fields quite useful. So what do you think of adding a similar message type to the ArbotiX ROS package? (I realize you can get the is_moving value from services but I understand this has more overhead than just publishing it as part of the joint state).

Thanks!
patrick

I"ll have to investigate effort -- on an AX-12 I don't know that this makes much sense, but definitely on the larger servos.

As for a "custom JointStates" -- that's really not ideal, because the MD5 checksums won't match and so you can't use that custom joint states message with other tools developed for joint_states.

-Fergs

Pi Robot
12-14-2010, 12:13 PM
As for a "custom JointStates" -- that's really not ideal, because the MD5 checksums won't match and so you can't use that custom joint states message with other tools developed for joint_states.
-Fergs

Yeah, that makes sense. For my own experimentation a few weeks ago, I added a JointStateExtras message type to my copy of the ArbotiX 0.3.2 release and stuck the is_moving field in there while using the standard JointState message type for everything else.

--patrick

lnxfergy
12-14-2010, 12:23 PM
Yeah, that makes sense. For my own experimentation a few weeks ago, I added a JointStateExtras message type to my copy of the ArbotiX 0.3.2 release and stuck the is_moving field in there while using the standard JointState message type for everything else.

--patrick

Patrick -- I think it's a bit redundant. isMoving will really be incorporated into the jointstates message already -- basically, if the current velocity != 0 then we are moving.

The improvement for 0.5.0 is that we actually will put velocity into the joint_states publication -- currently, only position is set (which is a lame oversight).

-Fergs

Pi Robot
12-14-2010, 12:29 PM
Ah yes, I see what you mean!

--patrick