ur5 robot wrist splits with collision

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See the response of raequi link text to similar question.

The cause behind this unrealistic interaction (that is, this lack of friction) is the use of PositionJointInterface for the UR10 joints. Here's a decent explanation of the phenomenon:

... using 'set position' or 'set velocity' in gazebo forces the physics simulation to try and accomplish this, which results in strange behavior. It's actually preferable, according to the Gazebo team members I'm working with, to always use 'set force' in Gazebo because that allows a more normal interaction when the commanded force of an arm joint puts the arm in contact with the environment.

Following an example, I made local changes to the universal_robot package to use EffortJointInterface instead. Some gain values from ARIAC provide decent performance. Thanks to everyone who contributed suggestions!