[ros-users] Introducing A Better Inverse Kinematics Package

[Linas Vepstas]

Hi Patrick,

Not having looked at your code at all, can I make a request?  I have some
joints that are not simple chains, and thus are not handled by any IK
solver I know of ... but should be.

The joint I have is a three-legged table; one of the legs is fixed, the
other two are driven by linkages;  I need to be able to know joint angles,
given a desired table surface position and orientation.

I currently solve this using some fairly simple hand-written code,
integrated in a most awful hacky way, but it would be nice to see this
supported in an IK solver.

--linas

On Fri, Nov 6, 2015 at 6:11 AM, Patrick Beeson via ros-users <
ros-users at lists.ros.org> wrote:

> TRACLabs Inc. is glad to announce the public release of our Inverse
> Kinematics solver TRAC-IK.  TRAC-IK is a faster, significantly more
> reliable drop-in replacement for KDL's pseudoinverse Jacobian solver.
>
> Source (including a MoveIt! plugin) can be found at:
> https://bitbucket.org/traclabs/trac_ik.git
>
> TRAC-IK has a very similar API to KDL's IK solver calls, except that the
> user passes a maximum time instead of a maximum number of search
> iterations.  Additionally, TRAC-IK allows for error tolerances to be set
> independently for each Cartesian dimension (x,y,z,roll,pitch.yaw).
>
> More details:
>
> KDL's joint-limited pseudoinverse Jacobian implementation is the solver
> used by various ROS packages and MoveIt! for generic manipulation chains.
> In our research with Atlas humanoids in the DARPA Robotics Challenge and
> with NASA's Robotnaut-2 and Valkyrie humanoids, TRACLabs researchers
> experienced a high amount of solve errors when using KDL's inverse
> kinematics functions on robotic arms.  We tracked the issues down to the
> fact that theoretically-sound Newton methods fail in the face of joint
> limits.  As such, we have created TRAC-IK that concurrently runs two
> different IK methods: 1) an enhancment of KDL's solver (which detects and
> mitigates local minima that can occur when joint limits are encountered
> during gradient descent) and 2) a Sequential Quadratic Programming IK
> formulation that uses quasi-Newton methods that are known to better handle
> non-smooth search spaces.  The results have been very positive.  By combing
> the two approaches together, TRAC-IK outperforms both standalone IK methods
> with no additional overhead in runtime for small chains, and significant
> improvements in time for large chains.
>
> Details can be found here in our Humanoids 2015 paper here:
>
> <https://personal.traclabs.com/%7Epbeeson/publications/b2hd-Beeson-humanoids-15.html>
> https://personal.traclabs.com/~pbeeson/publications/b2hd-Beeson-humanoids-15.html
>
> A few high-level results are shown in the attached (low-res) figure.
>
>
> _______________________________________________
> ros-users mailing list
> ros-users at lists.ros.org
> http://lists.ros.org/mailman/listinfo/ros-users
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ros.org/pipermail/ros-users/attachments/20151106/e510705e/attachment.html>