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<body class='hmmessage'><div dir='ltr'>Hi guys,<br><br>Willing to reopen this thread... And I have 2 remarks to start with:<br><br><ul><li>Should we consider that <a href="https://github.com/ros-industrial/rep/blob/master/rep-I0003.rst">REP-i0003</a> is a direct answer to <a href="http://wiki.ros.org/trajectory_msgs/Reviews/Cartesian%20Trajectories_API_Review_2013_06_05">last year's API review</a> on cartesian trajectories?</li><li>I really believe that the trajectory definition and the way this trajectory is achieved (e.g. via impedance control) are 2 different subjects which should be treated in isolation: let us first make the cartesian trajectory definition good and then later we can build on it for impedance control. But really cartesian trajectory is path and impedance is control: complementary but different subjects.</li></ul><br><BR>Thanks,<BR><br><BR>Antoine.<br><BR><br><div><hr id="stopSpelling">From: konradb3@gmail.com<br>Date: Fri, 7 Jun 2013 09:12:37 +0200<br>To: ros-users@code.ros.org<br>CC: ros-sig-robot-control@googlegroups.com<br>Subject: Re: [ros-users] cartesian trajectories<br><br><div dir="ltr">After considering some of possible use-cases i came up with yet another proposal (more detailed) :<br>[1] <a href="http://ros.org/wiki/trajectory_msgs/Reviews/Cartesian%20Trajectories_API_Review_2013_06_05" target="_blank">http://ros.org/wiki/trajectory_msgs/Reviews/Cartesian%20Trajectories_API_Review_2013_06_05</a><br>
</div><div class="ecxgmail_extra"><br clear="all"><div>Pozdrawiam<br>Konrad Banachowicz</div>
<br><br><div class="ecxgmail_quote">2013/6/6 Konrad Banachowicz <span dir="ltr"><<a href="mailto:konradb3@gmail.com" target="_blank">konradb3@gmail.com</a>></span><br><blockquote class="ecxgmail_quote" style="border-left:1px #ccc solid;padding-left:1ex;">
<div dir="ltr">Yes it is definitely out of scope of simple cartesian trajectory but it contains sub-message CartesianTrajectory which is simple and quiet self contained. I think that such complex goal message gives us <span lang="en"><span>good basis for discussion on it's building blocks like : </span></span>CartesianTrajectory, CartesianImpedance ....<br>
</div><div class="ecxgmail_extra"><br clear="all"><div>Pozdrawiam<span class="ecxHOEnZb"><font color="#888888"><br>Konrad Banachowicz</font></span></div><div><div class="h5">
<br><br><div class="ecxgmail_quote">2013/6/6 Georg Bartels <span dir="ltr"><<a href="mailto:georg.bartels@cs.uni-bremen.de" target="_blank">georg.bartels@cs.uni-bremen.de</a>></span><br><blockquote class="ecxgmail_quote" style="border-left:1px #ccc solid;padding-left:1ex;">
<div><div>
<div>On 06/05/2013 09:40 PM, Jonathan Bohren
wrote:<br>
</div>
<blockquote>
<div dir="ltr">
<div class="ecxgmail_extra"><br>
<div class="ecxgmail_quote">On Wed, Jun 5, 2013 at 1:18 PM,
Konrad Banachowicz <span dir="ltr"><<a href="mailto:konradb3@gmail.com" target="_blank">konradb3@gmail.com</a>></span> wrote:<br>
<blockquote class="ecxgmail_quote" style="border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex;">
<pre>[CartesianTrajectoryGoal]
Header header # A stamp of 0 means "execute now"
string[] effector_names
<span></span>CartesianTrajectory[] trajectory
PoseStamped tool # The frame which is being controlled
<span></span> CartesianTrajectoryPoint[] points
<span></span> duration time_from_start
<span></span> Pose pose
<span></span> Twist twist
CartesianImpedance[] impedance
TBD stiffness % cartesian stiffness
TBD damping % damping ratio
CartesianTolerance[] path_tolerance # Tolerance for aborting the path
<span></span> float64 position
<span></span> float64 orientation # Permitted angular error
<span></span> float64 velocity
<span></span> float64 angular_velocity
<span></span>CartesianTolerance[] goal_tolerance # Tolerance for when reaching the goal is considered successful
JointTrajectory posture # For determining the redundancy
JointImpedance nullspace_impedance # TBD
</pre>
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<div class="ecxgmail_extra">I like where this version is
going!</div>
</div>
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Konrad's proposition looks indeed promising. However, I'd like to
point out that this is more than a Cartesian Trajectory. This looks
more like a goal message to a very sophisticated controller, e.g.
whole-body motion framework or iTaSC. Shouldn't the Cartesian
Trajectory msg be somewhat smaller in scope and then be reused?
Maybe more like in the spirit of std_msgs which are mainly used as
building blocks for bigger and semantically annotated messages?<div><br>
<blockquote>
<div dir="ltr">
<div class="ecxgmail_extra"><br>
</div>
<div class="ecxgmail_extra">Meanwhile, between comments in
different mailing lists, and comments on the wiki in the old
robot_mechanism_controllers, it'd be great if we could
aggregate this discussion. Really it seems like this is an
extension to the trajectory_msgs package, so maybe we can do
an online review where people can propose and comment on
different options and subjects. I've started one [1] with the
initial proposal from the old wg review, and added Konrad's
proposal above (feel free to remove/edit that, Konrad). I
think we can use the robot control SIG to coordinate, and ping
ros-users for high-level notices. Then when we've at least
gotten the scope down, we can initiate an REP request. How
does that sound?</div>
<div class="ecxgmail_extra"><br>
</div>
<div class="ecxgmail_extra">[1] <a href="http://ros.org/wiki/trajectory_msgs/Reviews/Cartesian%20Trajectories_API_Review_2013_06_05" target="_blank">http://ros.org/wiki/trajectory_msgs/Reviews/Cartesian%20Trajectories_API_Review_2013_06_05</a></div>
</div>
</blockquote></div>
Good idea. From now on moving to the REP?<br>
<blockquote><div>
<div dir="ltr">
<div class="ecxgmail_extra"><br>
</div>
<div class="ecxgmail_extra">-j<br>
<br clear="all">
<div><br>
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-- <br>
Jonathan Bohren<br>
Laboratory for Computational Sensing and Robotics<br>
<a href="http://dscl.lcsr.jhu.edu/People/JonathanBohren" target="_blank">http://dscl.lcsr.jhu.edu/People/JonathanBohren</a><br>
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