[ros-users] kinematics stack status ?

[Konrad Banachowicz]

2011/1/18 Sachin Chitta <sachinc at willowgarage.com>

> Hi Konrad,
>
> The GetKinematicSolverInfo was intended as a read-only information service
> that would provide information about the joint limits used in the solver.
> The service itself is a convenience service and not really essential since
> most of the information comes from the robot description. Note that none of
> the services impose any conditions on where the limits are sourced from.
> Currently, they are sourced from the robot description internally in the
> node but I could add an api where you can override those limits using ROS
> parameters.
>
ok so there should be corresponding for "plugins"

> RobotState is intended for complete representation of a generic robot state
> and not just an arm. I am not sure what you mean by "contains alot of
> unnecessary data". Could you please clarify which fields are unnecessary.
>
 I was thinking about multi_dof_joint_state field and vellocity and effort
fields of joint_state. Those field seem to be ignored by kinematics solvers.

> I expect the core kinematics services (GetPositionIK, GetPositionFK)
> themselves to be stable. The only possible change is to add a "group name"
> so you would not have to specify every joint to be used by the solver. The
> other possible change would be to add a new service that lets you call IK on
> a vector of poses to save the trouble of calling a service multiple times. I
> would prefer not to do a wholesale change of API but would like to get some
> of the convenience elements (like group names) in.
>
> I do have an "plugin" implementation of the kinematics in place right now
> but I have not pushed it out. It lets you configure and  call solvers using
> the plugin architecture used by other components in ROS (like the navigation
> stack). I will push it out for review in a few days after putting up more
> documentation.
>
Documentation would be very useful.

> You are welcome to send more such feedback. In fact, if anyone would like
> to step up and volunteer to help maintain the kinematics stacks and do some
> of these API changes (like Jack O'Quinn is maintaining camera drivers), that
> would be more than welcome.
>
I have created kinematics_utils package containing useful functions from
pr2_kinematics_utils and node capable of loading kinematics plugins and
providing kinematics sevices.


> Sachin
>
>
> On Sun, Jan 16, 2011 at 11:09 AM, Konrad Banachowicz <konradb3 at gmail.com>wrote:
>
>> 2011/1/16 Herman Bruyninckx <Herman.Bruyninckx at mech.kuleuven.be>
>>
>>> On Sun, 16 Jan 2011, Konrad Banachowicz wrote:
>>>
>>>  I started to move our code for our robot kinematics to ROS.
>>>> I would like to know what is the stabilization status of kinematics
>>>> stack,
>>>> because latst review happend nearly year ago.
>>>> I have some remarks and suggestions about kinematics stack :
>>>> - kinematics serwices use motion_planning_msgs/RobotState which contains
>>>> alot of
>>>> unnecessary data.
>>>> - SolverInfo contains limits field which duplicate data avalible through
>>>> robot_description.
>>>>
>>>
>>> You might want to configure a solver with tighter limits than what the
>>> robot's mechanics impose...
>>
>> ok but those data are read-only by getSolverInfo service.
>> Currently every implementation simply send data readed from
>> robot_description.
>>
>>>
>>>
>>>  - pr2_kinematics contains many useful functions in
>>>> pr2_arm_kinematics_utils.cpp
>>>> this could be moved to common package, maybe kinematics_utils.
>>>>
>>>> - common node for ik and ik_with_constraints should exist, using
>>>> kinematics
>>>> plugins.
>>>> This would simplify implementation of kinematics for new robot.
>>>>
>>>
>>> Herman
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>>>
>>
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>
>
> --
> Sachin Chitta
> Research Scientist
> Willow Garage
>
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