Time Delay from laptop to robot of each data sample

m22me001 · September 26, 2023, 10:12pm

Continuing the discussion from Get current time:
Hey!! I have a question
I am using Python script to teleoperate UR5, how can I calculate the time delay from my laptop to robot?
I need to know at what time does each data sample (suppose position data) reach robot?

mry · September 27, 2023, 7:24am

The results will depend a lot of what protocol you use.

m22me001 · September 27, 2023, 11:27am

I am new to this robotics communication field, and I simply need a procedure, I exactly don’t know which protocol I am using, maybe it is UDP protocol but I am using ROS communication. UR5 and my laptop are connected to the same network ( intranet). Please guide me

mry · October 6, 2023, 12:07pm

I’m not sure it’s exactly what you’re asking for, but since you’re already using ROS, this thread from the UR-sponsored ROS driver project might be useful:

github.com/UniversalRobots/Universal_Robots_Client_Library

Reduce Delay Time of ServoJ Command ( lookahead_time ?)

opened 10:20AM - 11 Aug 21 UTC

closed 12:06PM - 13 Oct 21 UTC

yottasyno

question solution proposed

**Our Setup:** We are communicating with the UR control box via TCP/IP using th…e RTDE protocol, sending commands from a linux system with patched real-time kernel to our UR10e robot. We want to control the robot in joint space and need very fast response to follow our desired joint angles that are sent from the linux pc. On the linux pc a loop with 2ms cycle time is running and sending new desired joint angles to the robot controler. On the robot side we are using the servoj(…) command to track the desired joint angles. **Our Problem:** We are saving the desired (sent to the robot) and actual joint angles (received from robot) in the same cycle as vectors on the linux system. After performing a cross-correlation of the two vectors, we see delays of ~17 time steps (with a cycle time of 2ms this corresponds to 34ms). To test our communication we only sent joint angles to the controler and back to the linux system. (We removed the servoj() command and replaced it with a sync()). Now the delays shown by the cross-correlation are 2 or 3 time steps (corresponding to 4ms or 6ms). **Our Conclusion:** The servoj(q_des, 0, 0, 0.002, 0.03, 1200) has a time delay according to lookahead_time = 0.03s. This is a serious problem for our application. **Our Question:** Is the time delay of 30ms coming from the servoj() command with lookahead_time=0.03? Can we somehow reduce this time delay? Can we use another function than servoj() to control the joint angles? (maybe less safe but faster?) Thanks for your help!!

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Time Delay from laptop to robot of each data sample

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