Pozdrawiam Konrad Banachowicz 2010/9/18 Herman Bruyninckx > On Sat, 18 Sep 2010, Konrad Banachowicz wrote: > > My solution splits the trajectory generation into two parts. >> One part is hard-RT and do interpolation between two points (with non zero >> velocity >> at both ends). It can be used with sensor feedback (servo vision). >> Second part is feeding first one with points along complex trajectory, it >> do all >> "trajectory joining", joints reordering ... >> > > Ok, that sounds ok. From the software point of view, at least. But what is > the use of the "complex trajectory" if you have to react to visual data in > realtime? > Second part would be used for interfacing with ROS node like move_arm. For reacting to visual data in realtime first component is all you need. > > Pozdrawiam >> Konrad Banachowicz >> > > Herman > > > >> 2010/9/18 Herman Bruyninckx >> On Fri, 17 Sep 2010, Konrad Banachowicz wrote: >> >> Hi, >> I'm working on integration of orocos RT-controller with ROS >> manipulation pipeline. >> I already done joint_state_publisher and oro_action_server. Next on >> my list are >> joint_trajectory_action and JointSplineTrajectoryController. >> I have some concerns about real-time behaviours of those, and way >> of implementation >> in orocos. >> >> joint_trajectory_action : >> It receive goal containing trajectory (variable size, unbounded >> size), then check >> constraints and send to JointSplineTrajectoryController. >> >> JointSplineTrajectoryController: >> It loop generating interpolated position for joint regulator. >> When it receive new trajectory it reorder joints in received >> trajectory (memory >> allocation, iterating on unknown size array) and try to compose >> current trajectory >> with newly received (memory allocation, iterating on unknown size >> array). >> It have to by done between two sequential interpolations (in my >> system 1ms). >> >> My solution : >> Data transmited between joint_trajectory_action and >> JointSplineTrajectoryController >> contains only single point (constant size). >> >> joint_trajectory_action do joint reordering and compose >> trajectories and is feeding >> JointSplineTrajectoryController with trajectory points. >> >> JointSplineTrajectoryController interpolate between two points >> (have one point >> buffer) >> >> This solution should work with trajectories when time between >> points is >> 1ms. >> >> What do you think about doing this this way ? >> What is alternative solutions ? >> What do you think about re-usability of this solution in yours >> systems ? >> >> >> I do not know whether I fully understand your approach and solution, but >> here are some comments nevertheless about what I have learned about >> trajectories the last 20 years: >> - if you have a system with hard realtime constraints to connect >> trajectories together within 1ms, it makes sense to add another level of >> trajectory generation, in the form of a "trajectory joining" component. >> That component can do the joining already before the trajectory is >> finished, in a separate thread/process. It will not be a trivial >> extension to the current approach, though. >> - do you really the kind of joint space trajectories that are currently >> being used? With 1ms latency, it seems that you are looking for >> trajectories that can be joined also at non-zero velocity, in contrast to >> our current implementations... >> If you have indeed a need for other trajectory types, please start a >> discussion on this topic, since one of our PhD students. Wilm Decré, is >> doing his research on this topic; and he has already some results, but >> they have not yet been integrated in Orocos code. >> >> Herman >> _______________________________________________ >> ros-users mailing list >> ros-users@code.ros.org >> https://code.ros.org/mailman/listinfo/ros-users >> >> >> >> >> > -- > K.U.Leuven, Mechanical Eng., Mechatronics & Robotics Research Group > > > Tel: +32 16 328056 > EURON Coordinator (European Robotics Research Network) < > http://www.euron.org> > Open Realtime Control Services > Associate Editor JOSER , IJRR > > _______________________________________________ > ros-users mailing list > ros-users@code.ros.org > https://code.ros.org/mailman/listinfo/ros-users > >