[ros-users] reverse kinematics using robot_state_publisher ?

[Ugo Cupcic]

Dear Ruben,

Are you using KDL::TreeIkSolverPos_NR_JL for the inverse position 
kinematics ? If it is the case, would you have an example? I can't find 
any on the web :S

Cheers,

Ugo

On 07/04/10 12:08, Ruben Smits wrote:
> On Wednesday 07 April 2010 12:48:23 Sachin Chitta wrote:
>    
>> Hi Ugo,
>>
>> You can use KDL to do inverse kinematics using one of the inverse
>> kinematics solvers in the package. These are numerical solvers that
>> operate on a KDL chain. First use the kdl_parser package to create a KDL
>> chain and then initialize an inverse kinematics solver for the chain. The
>> solution tends to be dependent on the initial state you pass into the
>> solver and can sometimes get stuck in local minima. Also, I am not sure
>> about how well the solvers handle joint limits. I believe more advanced
>> solvers are in the works but I will let the orocos folks comment on that.
>>      
>
> If you need inverse velocity kinematics, which is commonly the case in
> a control application, KDL contains various implementations including
> the use of (task and/or robot space weighted)pseudo-inverses of the
> jacobian and (damped) least squares solutions of the inverse velocity
> problem.  More advanced (constraint-based) solvers are currently being
> developed, but these are still at the velocity level.
>
>
> If you need inverse position kinematics, KDL does currently not have a
> perfect solution, at the moment we only have an implementation of a
> Newton-Raphson integration on top of one of the inverse velocity
> kinematic solvers.
>
> Ruben
>
>    
>> Have a look at the api page here
>> http://orocos.org/kdl/UserManual/kinematic_solvers for more examples.
>>      
> This page (sadly) does not cover all the existing solvers :(
>
>    
>> The other option is to write your own solver (we have one for the PR2 that
>> takes in a hint for one of the joint angles and then computes the other 6
>> analytically -
>> www.ros.org/wiki/pr2_arm_kinematics<http://www.ros.org/wiki/pr2_arm_kinema
>> tics>)
>>
>> Sachin
>>
>> On Wed, Apr 7, 2010 at 3:28 AM, Ugo Cupcic
>> <ugo at shadowrobot.com<mailto:ugo at shadowrobot.com>>  wrote: Hi all,
>>
>> Is it possible to use robot_state_publisher or some other ROS stack to
>> do reverse kinematic on my urdf model?
>> Or do I need to implement my own using the "Coding a realtime Cartesian
>> controller with KDL" tutorial ?
>>
>> Cheers,
>>
>> Ugo
>>
>>
>> --
>> Ugo Cupcic         |  Shadow Robot Company |
>> ugo at shadowrobot.com<mailto:ugo at shadowrobot.com>  Software Engineer      251
>> Liverpool Road
>> need a Hand?           London  N1 1LX       | +44 20 7700 2487
>> http://www.shadowrobot.com/hand/              @shadowrobot
>>
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>>
>>
>> --
>> Sachin Chitta
>> Research Scientist
>> Willow Garage
>>      
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>    

-- 
Ugo Cupcic         |  Shadow Robot Company | ugo at shadowrobot.com
Software Engineer      251 Liverpool Road
need a Hand?           London  N1 1LX       | +44 20 7700 2487
http://www.shadowrobot.com/hand/              @shadowrobot