C153A2: Position deviates from path

Good morning,

I write here because I have one COBOT that continue to enter in protective stop because one joint is totally blocked and it is impossible to go out from the situation also in freedrive, the error is “C153A2: Position deviates from path: detected by the Elbow joint.” (I attached the picture of error).

I modified the TCP and payload settings, safety settings, I tried several times restart & shutdown of COBOT but nothing change, this joint still stay blocked. Also I upgraded polyscope to 3.15.8 version.

I don’t know what is the cause of this continue error, I have to discover, but is there a systematic way to go out from one (or more) joint totally blocked and proceed to use COBOT?

Thanks a lot.


You’re saying the joint is “totally blocked”, so it won’t move at all? I’m a little confused as to how the robot has been initialized then. But it sounds to me like the brake isn’t releasing or the gear in the joint is in very bad mechanical shape.
You can test the brake to see if it’s the brake failing by taking off the lid of the joint (elbow). You can follow the guide in the service manual here: https://s3-eu-west-1.amazonaws.com/ur-support-site/15739/UR10_Service_Manual_en.pdf
It’s section 5.2.3 on page 16. If your robot is not a UR10, you can find the corresponding service manual on UR’s download page: UR Download | Support Site | Universal Robots

No matter if it’s a defective brake or the gear, you should have a local distributor take a look at it. They can repair the joint or replace it. :slight_smile:

Hello @efn!

Thank you for your suggestion, this COBOT is an UR10 yes, I will ask to follow this suggestions to the customer.
Yes the joint is totally blocked also after remove power to COBOT, other are free to move.

The cause of this blocking could also be problem about main power supply issue at the customer net?
Maybe there is no a control of undershoot/overshoot/voltage drop of power supply and motor continue to work not in optimal power supply condition instead of block them with brakes.

Thank you so much :+1:

The other joints are able to move, when the robot is powered off? They should all have their brakes engaged when power is off.

I don’t see how the main power supply can be the issue. Then they would have other issues. :slight_smile:
The robot monitors 48V power supply during operation and boot, and it will show an error, if the voltage is wrong.

COBOT yes of course has all joint blocked after shutdown.

Ok, yes I saw on the services manual that there are a lot error handling (and fault codes) about the 48V monitoring.

I saw from the custormer’s COBOT log file that it has the error C153A2 also after the normal startup unlocking brakes cycle.
COBOT stayed 21 minutes stuck after power and then error appear in a sponetaneous manner, but maybe because COBOT arm stayed in this time in elongation position with active payload wrong (1 kg less the real), this is my opinion, the exact cause I have still to discover.

Thank you for your reply

i had a similar problem. the cobot started to drift in the points and then do a protective stop on axis 6.
turned out to be a blown condensator on the axis print .