Robot is in a singularity (stopl unable to generate a valid set point)

[david2]

Summary

We recently upgraded our UR10e software from 5.6.0 to 5.8.2 but shortly afterwards we started bumping into one new error:

We issue a stopl(10) command after failing to provide the next target on time during a blended motion. It is basically something like this:

movel(p1, a=2.5, v=0.3)
movel(p2, a=7.0, v=1.0, r=0.12)
movel(p3, a=7.0, v=1.0, r=0.1) 
stopl(10)

Error code

2020-06-29 14:37:08.531 :: C0A0:10 :: singularity:stopl unable to generate valid setpoint: ::  ::

The code is C0A and according to the Service Manual it is supposed to indicate No error. Also, it doesn’t seem like an actual singularity.

TCP configuration & joint limits

Reproducible with URSim

Configure the TCP position and run the broken_move.urp script. The error will always be triggered with 5.8.0 and 5.8.2 versions:

On the contrary, the error doesn’t appear with 5.6.0:

Questions

• Was there any changes in the logic behind stopl or movel?
  The Release Notes only mentions a fix in the algorithm for blended movels.

• Do you have any recommendations on how to avoid this error?
  Ex: Maximum/minimum motion profiles for UR10e, blending radii, configurations.

broken_motion.zip (2.5 MB)

[kaha]

Hello David,

I have already answered your question on Tech Support email, but for these looking for a solution: problem seems to be caused by extremely high acceleration, what in connection to blend radius and even more extreme deceleration cause given warning to occur. I have tested presented program in URSim with changed acc and dec values for few hours and problem doesn’t occur, as it was earlier (every few cycles).

[david2]

Thanks again for all the help Karol!

I will modify and validate the motion profiles before attempting to upgrade the software version again.