MoveIt! Issues with Shuffling Walking of a Robot

asked 2016-09-09 15:10:46 -0500

JoshMarino gravatar image

updated 2016-09-09 16:40:45 -0500

Hello ROS and MoveIt! community,

I am trying to model a 10-link robot with the first and last link both being feet, shown below (collision elements).

Edit: cannot upload image yet, so link is here.

This robot should be able to walk by the following:

  1. Link1 (foot1) and link10 (foot2) will both be in contact with the ground, with the other links in between (link2-9) will be in a U-bend (as shown in the image).
  2. Link1 (foot1) will lift off the ground and move toward link10 (foot2).
  3. Link10 (foot2) will lift off ground and move away from link1 (foot2).
  4. Repeat steps 2-3 for continuous walking.

I have created the URDF and moveit_config files for the robot, but in doing so I have come across problems when using MoveIt! for trajectory planning of steps 2-3:

  1. The URDF branches outward from link1 -> link10, so planning can be done for link10. When I want to move link1 (foot1) off the ground and toward link10 (foot2), how does this work? Do I need two URDFs, one from link1 -> link10 and the other backwards from link10 -> link1?
  2. I do not want a fixed constraint in the URDF or SRDF constraining the feet (link1 and link10) to the world frame, but I would like the foot (link1) to stay fixed to the ground if the other foot (Link10) is taking a step, and vice versa.

Any help would be appreciated, thanks!

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Update: I was able to remove the attached to world link and replace it in the SRDF with a planar virtual joint. However, this did not fix planning for link1 since MoveIt! does not recognize this as an end effector link (which I assumed). Is there a way to load 2 URDF's and switch between them?

JoshMarino gravatar image JoshMarino  ( 2016-09-10 20:35:33 -0500 )edit