That would be more of a ROS Answers question,, e.g.
http://answers.ros.org/question/203971/how-to-compensate-gravity-in-gazebo/

2016-01-21 4:15 GMT+01:00 Yin <long188103 [..] ...>:

> Hi Juan, great thanks for your guide and recommended books.
> Is it a practicable way for me to use ROS simulate and try use KDL?
> I want to get familiar with control theory and what you have tell me from
> this.
>
>
> At 2016-01-19 18:32:41, "Juan G Victores" <jcgvicto [..] ...> wrote:
>
> Hi Yin,
> Regarding KDL, is can be used with and without ROS. The Python bindings
> are also useful.
>
> Regarding Zero-G, using only angular position sensors (e.g. encoder
> values) and without getting into control theory, you can get some decent
> results with a fast loop:
>
> getEncoders( q ); // depends on your robot API
> KDL::ChainIdSolver_RNE idsolver(chain,gravity);
> int ret = idsolver.CartToJnt(q,qdot,qdotdot,wrenches,t); // Give q
> (encoder values) and get t (torque; if you control in current you'll need
> your K). Negate qdot and qdotdot for low velocities/accelerations, negate
> wrenches too.
> setTorques( t ); // depends on your robot API
>
> That's mainly what KDL will do for you. For robot control in more depth
> look up and read everything from Bruno Siciliano (e.g.
> http://www.springer.com/gp/book/9781846286414) and/or Osama Khatib (e.g.
> http://www.springer.com/gp/book/9781846286414). For a _tiny_ introduction
> to gravity and friction compensation, you can check out
> http://dx.doi.org/10.1007/978-3-319-27149-1_5 (here's the preprint:
> http://roboticslab.uc3m.es/roboticslab/sites/default/files/morante2015fo...
> ).
>
> Cheers,
> - Juan
> ________________________________________________________
> http://roboticslab.uc3m.es/roboticslab/people/jg-victores
>
> 2016-01-18 4:50 GMT+02:00 Yin <long188103 [..] ...>:
>
>> Hello, I am new to KDL.
>> I want to control robot arm in Zero-G mode so the arm can be freely moved.
>> But I don't know how to do and have some puzzles.
>> Does the KDL can be used with ROS and also without ROS?
>> Does the control of robot arm in Zero-G mode need some extra sensors?
>> I am eager to learn about the robot control, please give me some tips.
>> Thanks in advance!
>>
>>
>>
>> --
>> -------------------end---------------------
>> --Yin
>>
>> --
>> Orocos-Users mailing list
>> Orocos-Users [..] ...
>> http://lists.mech.kuleuven.be/mailman/listinfo/orocos-users
>>
>>
>

Hi Juan, great thanks for your guide and recommended books.
Is it a practicable way for me to use ROS simulate and try use KDL?
I want to get familiar with control theory and what you have tell me from this.

At 2016-01-19 18:32:41, "Juan G Victores" <jcgvicto [..] ...> wrote:

Hi Yin,

Regarding KDL, is can be used with and without ROS. The Python bindings are also useful.

Regarding Zero-G, using only angular position sensors (e.g. encoder values) and without getting into control theory, you can get some decent results with a fast loop:

getEncoders( q ); // depends on your robot API
KDL::ChainIdSolver_RNE idsolver(chain,gravity);
int ret = idsolver.CartToJnt(q,qdot,qdotdot,wrenches,t); // Give q (encoder values) and get t (torque; if you control in current you'll need your K). Negate qdot and qdotdot for low velocities/accelerations, negate wrenches too.
setTorques( t ); // depends on your robot API

That's mainly what KDL will do for you. For robot control in more depth look up and read everything from Bruno Siciliano (e.g. http://www.springer.com/gp/book/9781846286414) and/or Osama Khatib (e.g. http://www.springer.com/gp/book/9781846286414). For a _tiny_ introduction to gravity and friction compensation, you can check out http://dx.doi.org/10.1007/978-3-319-27149-1_5 (here's the preprint: http://roboticslab.uc3m.es/roboticslab/sites/default/files/morante2015fo...).

Cheers,
- Juan
________________________________________________________
http://roboticslab.uc3m.es/roboticslab/people/jg-victores

2016-01-18 4:50 GMT+02:00 Yin <long188103 [..] ...>:

Hello, I am new to KDL.
I want to control robot arm in Zero-G mode so the arm can be freely moved.
But I don't know how to do and have some puzzles.
Does the KDL can be used with ROS and also without ROS?
Does the control of robot arm in Zero-G mode need some extra sensors?
I am eager to learn about the robot control, please give me some tips.
Thanks in advance!

--

-------------------end---------------------
--Yin

--
Orocos-Users mailing list
Orocos-Users [..] ...
http://lists.mech.kuleuven.be/mailman/listinfo/orocos-users

previously, only once, outside the loop.

PS2: Second link intended to be:
http://www.springer.com/uk/book/9783540239574

2016-01-19 12:32 GMT+02:00 Juan G Victores <jcgvicto [..] ...>:

> Hi Yin,
> Regarding KDL, is can be used with and without ROS. The Python bindings
> are also useful.
>
> Regarding Zero-G, using only angular position sensors (e.g. encoder
> values) and without getting into control theory, you can get some decent
> results with a fast loop:
>
> getEncoders( q ); // depends on your robot API
> KDL::ChainIdSolver_RNE idsolver(chain,gravity);
> int ret = idsolver.CartToJnt(q,qdot,qdotdot,wrenches,t); // Give q
> (encoder values) and get t (torque; if you control in current you'll need
> your K). Negate qdot and qdotdot for low velocities/accelerations, negate
> wrenches too.
> setTorques( t ); // depends on your robot API
>
> That's mainly what KDL will do for you. For robot control in more depth
> look up and read everything from Bruno Siciliano (e.g.
> http://www.springer.com/gp/book/9781846286414) and/or Osama Khatib (e.g.
> http://www.springer.com/gp/book/9781846286414). For a _tiny_ introduction
> to gravity and friction compensation, you can check out
> http://dx.doi.org/10.1007/978-3-319-27149-1_5 (here's the preprint:
> http://roboticslab.uc3m.es/roboticslab/sites/default/files/morante2015fo...
> ).
>
> Cheers,
> - Juan
> ________________________________________________________
> http://roboticslab.uc3m.es/roboticslab/people/jg-victores
>
> 2016-01-18 4:50 GMT+02:00 Yin <long188103 [..] ...>:
>
>> Hello, I am new to KDL.
>> I want to control robot arm in Zero-G mode so the arm can be freely moved.
>> But I don't know how to do and have some puzzles.
>> Does the KDL can be used with ROS and also without ROS?
>> Does the control of robot arm in Zero-G mode need some extra sensors?
>> I am eager to learn about the robot control, please give me some tips.
>> Thanks in advance!
>>
>>
>>
>> --
>> -------------------end---------------------
>> --Yin
>>
>> --
>> Orocos-Users mailing list
>> Orocos-Users [..] ...
>> http://lists.mech.kuleuven.be/mailman/listinfo/orocos-users
>>
>>
>