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Repository for the DRC project.
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Specified joint limits for electric joints in the Atlas V5 models are incorrect #493

Open osrf-migration opened 9 years ago

osrf-migration commented 9 years ago

Original report (archived issue) by DouglasS (Bitbucket: DouglasS).

On the electric forearm joints of Atlas it is important not to command a position that is outside of the range of motion. If you do, it will saturate the current and rapidly overheat the motor. We measured the joint limits of the forearm and found some of the actual joint limits to be less than the URDF model.

The table below summarizes the joint limits from the URDF and then as measured on our Atlas robot. The numbers marked with asterisks indicate limits that are less than the URDF.

Joint Model File Lower Limit Model File Upper Limit Measured, Left, Lower Measured, Left, Upper Measured, Right, Lower Measured, Right, Upper
wry -3.011 +3.011 -2.999* +2.990* -2.979* +2.982*
wrx -1.763 +1.768 -1.746 +1.767* -1.765 +1.762*
wry2 -2.967 +2.967 -2.903* +2.900* -2.885* +2.881*
osrf-migration commented 9 years ago

Original comment by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

@dljsjr thanks for sharing this data. I wonder how much these joint limits vary across robots? Should the joint limits be retracted even further as a safety factor? Food for thought.

I've made these changes to atlas_v5_simple_shapes.urdf in branch issue_493 (7db63eacf4a3b86a1e4065b75567cd7ae3607b79). I based this branch off of 456dd5d0b84d6a75026af5f8f7357c3770e34973 (the xacrogenization of atlas_v5_simple_shapes.urdf), so it doesn't have @tkoolen 's fixes to the arm kinematics. The branches will easily merge with each other though.