Large error for Real-time trajectory tracking by using RTDE

Technical Questions
1

Hello everyone

I’m trying to use UR10E to achieve the real-time motion tracking by using the RTDE . What I’m doing is using the rtde_c.servoL for the real-time TCP X, Y and Z coordinates and RPY rotation angle tracking. However, it shows a significant error when the moving speed is fast. Below the figure illustrates the tracking result for the fast motion. I’ve tuned the parameters for the Gain and Lookahead time, and both the parameters (1000 gain, 0.1s Lookhead) are at the best selection for not having any jerky motion. But it still shows an error up to 12cm espically in the Y direction. My questions are:

  1. Is there any solution for solving this kind of problem by using RTDE?
  2. It seems that the inertia compensation is not working well in a high-speed situation. Is there any way that we can directly input torque to each joint in real-time, so that I can create a inertia compensation module myself?

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Thank you very much!

2

Hi, the rtde_c is a 3-rd party library? from my experience. if the offset is too large, it is hard for the robot to follow.

3

Hi tizh,

Thanks for your reply! The rtde_c is “rtde_control.RTDEControlInterface” which is not a 3rd party library. And yes I think the real-time offset could be too large under a high speed situation. And for my understanding, the error will accumulate if the motion is under a high speed for a long time because there’s a control limtation for the UR internal controller. So from your experience, it cannot be solved?

Thank you!

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