Pozdrawiam
Konrad Banachowicz
2010/9/18 Herman Bruyninckx <
Herman.Bruyninckx@mech.kuleuven.be>
> 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 <Herman.Bruyninckx@mech.kuleuven.be>
>> 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
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>>
>>
>>
>>
>>
> --
> K.U.Leuven, Mechanical Eng., Mechatronics & Robotics Research Group
> <http://people.mech.kuleuven.be/~bruyninc<http://people.mech.kuleuven.be/%7Ebruyninc>>
> Tel: +32 16 328056
> EURON Coordinator (European Robotics Research Network) <
> http://www.euron.org>
> Open Realtime Control Services <http://www.orocos.org>
> Associate Editor JOSER <http://www.joser.org>, IJRR <http://www.ijrr.org>
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