Can TranslationDirection5D work for a 7DOF robot?

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Can TranslationDirection5D work for a 7DOF robot?

Vivian
Is it possible to create a TranslationDirection5D IK solution for a 7 DOF robot that will work with ROS? We have successfully been able to create solutions using the Transform6D solver with the same 7DOF robot (6DOF arm on a trolley on rails) by setting the trolley as a free joint, and have been able to get it working with ROS just fine, using the following:
openrave.py --database inversekinematics \
    --robot=7DOF_Robot.dae \
    --iktype=Transform6D \
    --manipname=manipulator \
    --freejoint=trolley 
However when I tried to use the TranslationDirection5D solver I get:
  File "/usr/lib/python2.7/dist-packages/openravepy/_openravepy_0_8/databases/inversekinematics.py", line 672, in generate
    raise ValueError('number of joints to solve for is not equal to required joints %d!=%d'%(len(self.solveindices),dofexpected))
ValueError: number of joints to solve for is not equal to required joints 6!=5

The problem we are trying to solve:

We are trying to plan for a plasma cutter arm. With this tool, we need to be able to set the the 3d position and axis direction of the tool, but we don't care what the 'twist' of the tool is around it's axis. By using the Transform6D solution, plans for the robot are being unnecessarily constrained by the twist orientation given as a goal for the tool, resulting in the robot often 'reaching' with the base trolley far away from the work piece as it tries to orient the tool in a full 6DOF position. This in turn causes planning to fail if there are other obstacles around the robot that would limit the position the trolley can be in, and a TranslationDirection5D solution seems like it would work perfectly.
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Re: Can TranslationDirection5D work for a 7DOF robot?

Rosen Diankov
Administrator
hi vivian,

Because the arm is 7 DOF and you have a 5 DOF IK, you'll need 2 free joints. Therefore, just add another "--freejoint" definition. I recommend adding the joints at the very top since they'll have least effect on IK, however this might not succeed due to ikfast bugs. If that happens, add the free joints at the base.

and the application sounds exciting! is there anywhere we can read about it or find out more about our work?
best,
rosen,




2013/8/13 Vivian <[hidden email]>
Is it possible to create a TranslationDirection5D IK solution for a 7 DOF robot that will work with ROS? We have successfully been able to create solutions using the Transform6D solver with the same 7DOF robot (6DOF arm on a trolley on rails) by setting the trolley as a free joint, and have been able to get it working with ROS just fine, using the following:
openrave.py --database inversekinematics \
    --robot=7DOF_Robot.dae \
    --iktype=Transform6D \
    --manipname=manipulator \
    --freejoint=trolley 
However when I tried to use the TranslationDirection5D solver I get:
  File "/usr/lib/python2.7/dist-packages/openravepy/_openravepy_0_8/databases/inversekinematics.py", line 672, in generate
    raise ValueError('number of joints to solve for is not equal to required joints %d!=%d'%(len(self.solveindices),dofexpected))
ValueError: number of joints to solve for is not equal to required joints 6!=5

The problem we are trying to solve:

We are trying to plan for a plasma cutter arm. With this tool, we need to be able to set the the 3d position and axis direction of the tool, but we don't care what the 'twist' of the tool is around it's axis. By using the Transform6D solution, plans for the robot are being unnecessarily constrained by the twist orientation given as a goal for the tool, resulting in the robot often 'reaching' with the base trolley far away from the work piece as it tries to orient the tool in a full 6DOF position. This in turn causes planning to fail if there are other obstacles around the robot that would limit the position the trolley can be in, and a TranslationDirection5D solution seems like it would work perfectly.

View this message in context: Can TranslationDirection5D work for a 7DOF robot?
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