[Bug 1010] New: weighted positional solver ( ChainIkSolverPos_NR_JL_WE )


Summary: weighted positional solver ( ChainIkSolverPos_NR_JL_WE
Product: KDL
Version: unspecified
Platform: All
OS/Version: All
Status: NEW
Severity: enhancement
Priority: P3
Component: Kinematic Solvers
AssignedTo: orocos-dev [..] ...
ReportedBy: jelleferinga [..] ...
Estimated Hours: 0.0

Created attachment 842
--> http://bugs.orocos.org/attachment.cgi?id=842
pibgeus ChainIkSolverPos_NR_JL_WE implementation

An old thread on ROS [1] discussed the need for a position IK solver than takes
weighting into account.
Another thread on orocos-users [2] confirmed this need.
A preliminary version has been contributed by pibgeus, though there are issues
with this implementation, as pointed out by Erwin Aertbelien:

============ ==================
pibgeus talks about weights on xyz RPY but in the code the weights are on the
displacement twist (i.e. the result of KDL's diff(..) )

You should also be sure to use a weighted inv. vel. kin.

However, this would not completely solved the problems with the 5 dof robots,
since the weights are still
a diagonal matrix. With these type of weights you cannot specify that the
rotation along a given axes is irrelevant.
You'll need a full symmetric matrix ( or its square root) to specify such a
thing. And even with a full symmetric matrix
it will be annoying to use (because you have to construct the weighing matrix
and that requires some insight).
Better would be in this case to be able to specify the weighing matrix relative
to the end effector.

[1] http://ros-users.122217.n3.nabble.com/IK-with-KDL-td1867716.html
[2] http://www.orocos.org/forum/orocos/orocos-users/help-5-dof-arm