[ros-users] [Orocos-users] [release] orocos_tools 0.1.0 and orocos_controllers 0.1.0

Konrad Banachowicz konradb3 at gmail.com
Thu Nov 18 10:06:00 UTC 2010

2010/11/16 Herman Bruyninckx <Herman.Bruyninckx at mech.kuleuven.be>

> On Tue, 16 Nov 2010, Konrad Banachowicz wrote:
>  2010/11/16 Herman Bruyninckx <Herman.Bruyninckx at mech.kuleuven.be<mailto:
>> Herman.Bruyninckx at mech.kuleuven.be>>
>> On Tue, 16 Nov 2010, Konrad Banachowicz wrote:
>> 2010/11/16 Herman Bruyninckx <Herman.Bruyninckx at mech.kuleuven.be<mailto:
>> Herman.Bruyninckx at mech.kuleuven.be><mailto:
>> Herman.Bruyninckx at mech.kuleuven.be<mailto:
>> Herman.Bruyninckx at mech.kuleuven.be>>>
>> On Tue, 16 Nov 2010, Konrad Banachowicz wrote:
>> - mixing the creation of a TaskContext with a specific implementation of a
>> generic interface (trajectory generation in this case) is not a good
>> practice; these three things should be separated, in order to improve
>> modular reuse.
>> - more in particular, new trajectory generation algorithms are preferably
>> submitted to Orocos/KDL as contributions, instead of "hiding" them inside
>> a ROSified node, where they are very difficult to reuse in other
>> frameworks or stand-alone applications.
>> Trajectory generation reside in ROS stack because it is intended to be as
>> much as possible compatible with trajectory generation used in ROS.
>> I have no problem with using ROS nodes to improve interoperability, but
>> functional algorithms belong in component/node-independent source trees,
>> for maximal reusability within whatever 'component framework'.
>> Yes  you are right but look how image processing code is developed in ROS.
>> It begin as independent nodes/packages and over time move into OpenCV.
> I am not so convinced that is approach is good practice.
> Inclusion of these trajectory generation code is a way to go for me.
But from my point of view there is reason against including it directly in
Waiting on inclusion of my patches, release of KDL, update of KDL in ROS
would stop my development for a while.
I think that things can be done in parallel, i can develope my components
with embedded trajectory generation and work on inclusion in KDL.
When new KDL would be released i will swich may nodes to new implementation.

>  - I do not see much Configuration options, while this subject of
>> trajectory
>> generation, servoing etc lends itself extremely well to fine tuning and
>> customization via setting of configuration properties.
>> I have not seen any parameters that can by configured in trajectory
>> generation algorithm which i implemented.
>> Strange. Typically, I expect parameters such as maximum speeds, minimal
>> time steps, required tolerance, etc.
>> Yes but these parameters is specified for every trajectory point
>> independently through JointTrajectoryPoint message.
>> http://www.ros.org/doc/api/trajectory_msgs/html/msg/JointTrajectoryPoint.html
>> I find it better practice to separate the Communication from the
>> Configuration: the most basic, reusable approach is to provide a
>> configuration API, and only then wrap this into a message-based
>> communication.
>> I don't understand how it would be implemented.
>> Can you point my to some code implementing this approach ?
> Most of the KDL code is being designed in this way: first virtual
> interfaces (generic to a full family of kinematic chains), then various
> concrete implementations, each with its own configuration parameters, and
> only then embedding into a component model (be it RTT TaskContexts, or ROS
> nodes) with asynchronous message types.
> Herman

I would like to discuss more design of orocos robot controller than internal
design of individual components.
I think we should start from communication between hardware/sorvo component
and trajectory generation.
I created oro_servo_msgs for this purpose but i developend it with IRP6
manipulators in mind.
I imagine that it could be common way of communication with any modern
manipulator like KUKA LWR.
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