pascal.fortin's profile - activity

Maybe you could try with another Arduino if you have one nearby. I completed these tutorials a few weeks ago using indigo-ubuntu 12.04 lts with a duemilanove just for configuration informations and to confirm that it is supposed to work.

Best regards,

Pascal

Hi everyone,

we are currently working on an ERICC 1 robot (probably >30 years old) and need to update its control systems, etc. Considering that it is a 5 DOF robot, we are having a lot of difficulty with the inverse kinematics problem. It seems that KDL is able to find a solution every once in a while but it is not reliable (< 10 % of the time and not validated).

After a quick search, we found that the encouraged method for < 6 DOF robot is to use ikfast which we are currently trying to implement. We are following the tutorial.

The URDF we are using was created by us and a package containing all the meshes and the URDF can be found here: Robot_description package (sorry for the download format, I am not used to using git or anything else I hope it is not too bad)

From these files, we are able to convert the URDF to collada succesfully as explained in the tutorial using :

rosrun collada_urdf urdf_to_collada
my_robot.urdf ericc_collada.dae

then, when we visualize it using openrave, we can see the robot as in the following picture (can't upload too new on the group):

If we look at it quickly, we can see that it was imported properly (at least visually) but there is no reference frame at the tip of the end effector as I expected when reading a previous post about 5 DOF katana arm.

If I try to generate the solver, using :

python `openrave-config --python-dir`/openravepy/_openravepy_/ikfast.py --robot=ericc_collada.dae --iktype=translationdirection5d --baselink=0 --eelink=5 --savefile=ikfast_ericc

It tries various methods and end up with this error message

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/openravepy/_openravepy_/ikfast.py", line 6121, in <module>
    chaintree = solver.generateIkSolver(options.baselink,options.eelink,options.freeindices,solvefn=solvefn)
  File "/usr/lib/python2.7/dist-packages/openravepy/_openravepy_/ikfast.py", line 1639, in generateIkSolver
    chaintree = solvefn(self, LinksRaw, jointvars, isolvejointvars)
  File "/usr/lib/python2.7/dist-packages/openravepy/_openravepy_/ikfast.py", line 2055, in solveFullIK_TranslationDirection5D
    endbranchtree2 += self.solveAllEquations(AllEquations,curvars=curvars,othersolvedvars = self.freejointvars+usedvars,solsubs = solsubs,endbranchtree=endbranchtree)
  File "/usr/lib/python2.7/dist-packages/openravepy/_openravepy_/ikfast.py", line 4264, in solveAllEquations
    return self.addSolution(solutions,AllEquations,curvars,othersolvedvars,solsubs,endbranchtree,currentcases=currentcases)
  File "/usr/lib/python2.7/dist-packages/openravepy/_openravepy_/ikfast.py", line 4340, in addSolution
    return [solution[0].subs(solsubs)]+self.solveAllEquations(AllEquations,curvars=newvars,othersolvedvars=othersolvedvars+[var],solsubs=solsubs+self.Variable(var).subs,endbranchtree=endbranchtree,currentcases=currentcases)
  File "/usr/lib/python2.7/dist-packages/openravepy/_openravepy_/ikfast.py", line 4321, in solveAllEquations
    raise self.CannotSolveError('failed to find a variable to solve')
__main__.CannotSolveError: 'failed to find a variable to solve'

Any suggestions as to how I could fix this issue ?

SETUP informations: Ubuntu 12.04 LTS 64 bits, ROS hydro, Openrave 0.8

Best regards,

Pascal Fortin