[cob_collision_monitor] Investigate collision models

[fmessmer]

Apparently, with the current robot model, i.e. the collision model and meshes, as well as the current configuration of the collision matrix in the SRDF, the collision_monitor reports state_is_valid=false as reported here.

This needs further investigation before re-activating the node within bringup.
Possible reasons might be:

• collision meshes are actually colliding although they do not in hardware -> adjust collision meshes (make smaller, use "gaps")
• collisions might occur from the "dummy links" not actually having a mesh associated in real hardware (i.e. small boxes)
• wrong computation of collision matrix using moveit_setup_assistant (random, 95%) -> run several times and unify running it several times for cob4-1 always resulted in the same disable_collisions pairs
• known bugs of collision checking library fcl when using geometric primitives -> use geometric macros https://github.com/ipa320/cob_common/pull/187

@fmessmer FYI

[mathias-luedtke]

I think the ipa320/cob_robots#482 is a result of de SRDF being empty.
All adjacent links needs to be listed.
Should be done with proper SRDF file :)

However, we should check URDF for "hidden" collisions and missing collision models.

[fmessmer]

cross-referencing another collision_monitor-related issue: ipa320/cob_gazebo_plugins#16

[fmessmer]

Started to investigate this for cob4-1 with updated cob_moveit_config, i.e. collision matrix in SRDF...

In torso's home position, state_is_valid=true

In torso's front_up position; state_is_valid=false

This is due to the padded collision model for torso_3_link!
This is definitely a case where we need to update the collision mesh, i.e. the current padded model needs to be "intersected" with a semi-sphere both at the bottom ("bowl of base") as well as at the top (inverted "bowl of head") in order to "cut away the edges".....(I hope it is clear what I mean)
@ipa-tif could you please do this?

[fmessmer]

After fixing the mesh and updating the moveit_configs the collision_monitor can be used in cob_bringup again...

[fmessmer]

mesh is fixed in https://github.com/ipa320/cob_common/pull/205
moveit_configs will follow in (updated) ipa320/cob_robots#581

then testing on hw...