Ikfast with 3DOF leg

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Ikfast with 3DOF leg

Fabien R
Hello,

I'm using OpenRAVE 0.9 on debian-amd64/stable.

I successfully applied forward kinematics to my robot.
Now, I'd like to generate a translation3d solver.
The leg is attached to the base via a joint rotating about the z-axis.
Two additional joints are used as articulations, both rotating about the
y-axis.

The XML description file is:
<robot file="../robots/spider.dae">
<Manipulator name="left_leg">
   <!-- tip -->
   <effector>left_dummy_gripper</effector>
   <!-- origin -->
   <base>base_link</base>
   <!-- target approaching direction -->
   <direction>0 0 1</direction>
   <!-- no additional info is required since it is a leg -->
</Manipulator>
</robot>

The list of the links is:
name                     index parents
---------------------------------------------
base_footprint           0
base_link                1       base_footprint
left_ax1                 2     base_link
left_f2                  3     left_ax1
left_f1                  4     left_f2
left_ax3                 5     left_f1
left_f3                  6     left_ax3
left_ax5                 7     left_f3
left_f4                  8     left_ax5
left_dummy_gripper       9     left_f4

To generate the solver, I use:
python `openrave-config --python-dir`/openravepy/_openravepy_/ikfast.py
--robot=robots/myrobot.robot.xml --baselink=2 --eelink=8
--iktype=translation3d  --savefile=spider_leg_ik.cpp --lang=cpp --debug=0

But it fails with this error:
File
"/usr/local/lib/python2.7/dist-packages/openravepy/_openravepy_/ikfast.py",
line 4503, in solveAllEquations
     raise self.CannotSolveError('solveAllEquations failed to find a
variable to solve')
__main__.CannotSolveError: 'solveAllEquations failed to find a variable
to solve'

There's maybe something obvious I forgot.

Thanks in advance,
Fabien

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Re: Ikfast with 3DOF leg

Fabien R
On 19/01/14 17:31, Fabien R wrote:
<...>
>  
> Two additional joints are used as articulations, both rotating about the
> y-axis.

A typo: These joints are rotating about the x-axis.
-
Fabien


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Re: Ikfast with 3DOF leg

Fabien R
I found this archive
http://openrave-users-list.185357.n3.nabble.com/Translation3D-failed-to-find-a-variable-to-solve-td4026518.html#a4026527.
I also solved the problem by using:
  openrave.py --database inversekinematics
--robot=robots/myrobot.robot.xml --iktype=translation3d --iktests=100
This allowed me to grab the cpp file in ~/.openrave
-
Fabien

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