Computing DH Parameters from a KDL::Chain object

Submitted by vpradeep on Wed, 2009-10-14 00:55

Hello all,

I have a '''KDL::Chain''' object, and from this I need to extract a set of DH parameters that represents this chain.

I'm about to spend a decent amount of time to write code to compute the DH parameters from the '''Chain''' object, but before I do this, I just wanted to see if anyone else has already implemented anything like this.

If someone has an implementation (or partial implementation) of this type of functionality, that would definitely give me a much better place to start from (as opposed to starting from scratch).

Thanks a lot for your help!
Vijay Pradeep

‹ Kuka LWR OROCOS programmer wanted ›
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Computing DH Parameters from a KDL::Chain object

Submitted by bruyninc on Wed, 2009-10-14 05:55.

On Wed, 14 Oct 2009, vpradeep [..] ... wrote:

> I have a '''KDL::Chain''' object, and from this I need to extract a set of DH parameters that represents this chain.
>
> I'm about to spend a decent amount of time to write code to compute the DH parameters from the '''Chain''' object, but before I do this, I just wanted to see if anyone else has already implemented anything like this.
>
> If someone has an implementation (or partial implementation) of this type of functionality, that would definitely give me a much better place to start from (as opposed to starting from scratch).
>
I am not aware of any such implementation.

I _am_ aware of the shortcomings of DH: there are multiple DH conventions;
each one has representation singularities; each one can only represent 4
DOFs, so faithfull translation from a frame-based chain representation
to a DH-based representation cannot be guaranteed. DH stems from the time
that every extra bit in computer memory was expensive... Those times are
over, so I am very curious why so many people still want to use DH... :-)

Herman

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Ruben Smits's picture

Computing DH Parameters from a KDL::Chain object

Submitted by Ruben Smits on Wed, 2009-10-14 08:15.

On Wed, Oct 14, 2009 at 7:53 AM, Herman Bruyninckx
<Herman [dot] Bruyninckx [..] ...> wrote:
> On Wed, 14 Oct 2009, vpradeep [..] ... wrote:
>
>> I have a '''KDL::Chain''' object, and from this I need to extract a set of DH parameters that represents this chain.
>>
>> I'm about to spend a decent amount of time to write code to compute the DH parameters from the '''Chain''' object, but before I do this, I just wanted to see if anyone else has already implemented anything like this.
>>
>> If someone has an implementation (or partial implementation) of this type of functionality, that would definitely give me a much better place to start from (as opposed to starting from scratch).
>>
> I am not aware of any such implementation.

Going through google I did not find any reference of someone wanting
to do this :-s

Do you want the DH parameters of the entire Chain? Or for every
intermediate Segment? And for what purpose?

> I _am_ aware of the shortcomings of DH: there are multiple DH conventions;
> each one has representation singularities; each one can only represent 4
> DOFs, so faithfull translation from a frame-based chain representation
> to a DH-based representation cannot be guaranteed. DH stems from the time
> that every extra bit in computer memory was expensive... Those times are
> over, so I am very curious why so many people still want to use DH... :-)

Probably some kind of inertia ;)

> Herman
> --
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> Orocos-Users [..] ...
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