[ros-users] [Discourse.ros.org] [ROS-Industrial] Path planning with external axis

[Jeroen]

I'm currently working actively on a very similar problem, but not within ROS-I at the moment.
My goal is to plan trajectories for 6 or 7 DOF welding robots, mounted on rails, creating up to 3 additional axes.

Last year we did some experimenting [1] with the descartes [2] package of ROS-I. Because of my lacking C++ skill's and there being no interface for highly redundant robots in MoveIt!, I started experimenting from scratch in 2D. [3]

For your problem, my initial guess (based on the approach I'm trying now) would be:
- Create a kinematic chain from the workpiece to the robot tool (therefore ignoring the dynamics).
- Create some kind of wrapper for the inverse kinematics of this chain that can return a sampled set of all possible solutions. The sampled space is very big, but I think it could be manageable for off-line planning. (If the ranges of the positioner are not to big. Like, smaller than 30 degrees or something, sampling at 1 degree intervals, and not to much freedom on the end-effector to keep to total solution space manageable.)
- Add a custom cost function to descrates that not only minimizes joint motion, but also takes into account the priority of avoiding orientation changes. (We already experimented with adding tool orientation to the cost function, but the approach was quite hacky [4].)
- Hope for the best. Descartes seems to be in active development at the moment. In the indigo version, we often encountered a lack of memory. Computation time was never really an issue when using the IKFast solver.

Feel free to contact me. I'm open to collaboration, as far as I can contribute something.
(Coincidently, we even have a Kuka robot with a two-axis positioner in our lab [5] :slight_smile:, but I never used it.)

[[1] https://github.com/JeroenDM/descartes_tutorials](https://github.com/JeroenDM/descartes_tutorials)
[[2] http://wiki.ros.org/descartes](http://wiki.ros.org/descartes)
[[3] https://gitlab.mech.kuleuven.be/u0100037/planar_python_robotics/blob/master/example_redundant_kinematics.ipynb](https://gitlab.mech.kuleuven.be/u0100037/planar_python_robotics/blob/master/example_redundant_kinematics.ipynb)
[[4 https://github.com/JeroenDM/descartes]](https://github.com/JeroenDM/descartes)
[[5 https://iiw.kuleuven.be/onderzoek/acro]](https://iiw.kuleuven.be/onderzoek/acro)





---
[Visit Topic](https://discourse.ros.org/t/path-planning-with-external-axis/4451/4) or reply to this email to respond.