Robot shacking when reaches waypoint in 0-600mm range of TCP Z axis

Technical Questions
1

Hello everyone,

I have very strange behavior of UR10e. We are using several different waypoints in our current installation. There are certain waypoints (2-3 out of 40+) when robot starts shacking (robot has only tool attached when it starts shacking. Robot stays shacky when it reaches the waypoint.
I’ve read the related articles about robot shacking and tried to solve the problem accordingly, but they do not work in my case. I checked:

  • Payload and CoG - I measured again with UR feature, and it didn’t work,
  • I entered payload value, CoG and inertia matrix of the tool - calculated with 3D cad program simulator.
  • Decreased the acceleration and velocity at a=0.1, v=0.1 - also didn’t work,

Robot stands on the pillar and it becomes shacky especially when it crosses the TCP 0 level of Z direction and it’s shacky until from 0 to 600mm.

Can you suggest me what else I need to check? What can cause this problem?

Regards,
Giorgi

2

One more detail:
Robot starts shacking when it is about to stop, not while moving.
Most probably shacky movement comes from the Shoulder wrist. It can be stopped by additional force (e.g catching it with a hand).

3

I found the solution:
Problem was in end-effector. We use long end-effector, which is able to pick up a bin. So, rear end of the end-effector is a bit far from CoG. I changed the waypoint the way that rear part comes closer to the COG and shacky movement was eliminated.