Re: sign of the moment of inertia in the description of the KUKA LWR dynamics in KDL

On Wed, Oct 8, 2014 at 10:57 AM, Vincent Padois <[email protected]>
wrote:

> Hello Ruben
>
> 2014-10-08 10:13 GMT+02:00 Ruben Smits <[email protected]>:
>
>>
>>
>> On Fri, Sep 19, 2014 at 2:02 PM, Vincent Padois <[email protected]>
>> wrote:
>>
>>> Hello,
>>>
>>> I am using the KUKA LWR kinematics and dynamics description that can be
>>> found in the KDL source code here:
>>> orocos_kinematics_dynamics/orocos_kdl/models/kukaLWR_DHnew.cpp
>>>
>>> and I am surprised to see that some of the  moments of inertia of the
>>> segments (joint 2 and 4 associated segments) are negative. By definition
>>> these terms should be positive. Can someone tell me more about the reason
>>> for these negative signs ?
>>>
>>
>> It has been a long time, so I don't remember exactly but it might be due
>> to the fact that those axes are not right-hand turning?
>>
>
> Then, if this information is only embedded in the moment of inertia I
> don't understand why the Jacobian would be correct (it is correct when
> compared to the one provided by KUKA). So there must be some other reason.
> Have you actually used the LWR  dynamics model from KDL to perform dynamic
> decoupling control on the real robot ?
>
>

Not that I remember, it was actually not me creating that model but Wilm
Decre


>
>>
>>> Also, how were these (I mean all of them, not just the negative ones)
>>> values identified/obtained ?
>>>
>>
>> AFAIK they were obtained using
>> http://limo.libis.be/Lirias:lirias123456789/167731 on a LWR4 (not a
>> LWR4+ IIRC)
>>
>
> I looked inside and the only data available are the one from a KUKA IR 361.
>

Yes, but think we used a similar/same approach to determine it, you should
ask Wilm for more information.

R.


>
> Best
> V
>
>
>>
>> R,
>>
>>
>>>
>>> Thanks in advance for your help,
>>> Best
>>> Vincent
>>>
>>> --
>>> Vincent Padois
>>> http://pages.isir.upmc.fr/~padois/website
>>>
>>> --
>>> Orocos-Dev mailing list
>>> [email protected]
>>> http://lists.mech.kuleuven.be/mailman/listinfo/orocos-dev
>>>
>>>
>>
>>
>> --
>> Ruben Smits, CTO
>> +32 479 511 786
>> Intermodalics - Kapeldreef 60, 3001 Heverlee - BELGIUM
>> www.intermodalics.eu
>>
>>
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>
>


-- 
Ruben Smits, CTO
+32 479 511 786
Intermodalics - Kapeldreef 60, 3001 Heverlee - BELGIUM
www.intermodalics.eu

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