Grace Lee,

The best way to create joints with multiple DOF is to chain multiple 1
DOF joints together. The links between the 1 DOF joints can just be
empty placeholders that only have a name, but don't have an inertia
etc. So, for example, if you want to create a 2 DOF link between
'link1' and 'link2', you can use:

<link name="link1" />

<joint name="joint1">
  <parent link="link1"/>
  <child link="link_virtual" />
</joint>

<link name="link_virtual" />

<joint name="joint2" >
  <parent link="link_virtual" />
  <child link="link2" />
</joint>

<link name="link2" />


Wim



On Wed, Jun 23, 2010 at 5:33 PM, Yeon Grace Lee <yeongrace.lee@gmail.com> wrote:
> Hello!
>
> I am writing an urdf for a human model and I am looking for the
> cleanest way of allowing rotation along multiple axis. For example,
> human head can tilt and pan- I plan to model this by making two
> revolute joints - but only one joint is allowed between two links? I
> am considering making a new set of links for each movement but I have
> doubts as to whether this is the most optimal way. And I am not quite
> sure where to place these new links (should I hide them inside
> overlapping set of links?). Please let me know if you know a better
> way of allowing multiple movements between two links.
>
> Thank you in advance!
>
> Grace Lee
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-- 
--
Wim Meeussen
Willow Garage Inc.
<http://www.willowgarage.com)