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Discrepancy between simulated path and real path

#1
I am trying to let my robot follow the outer edges of a metal part. When simulating the path in RoboDk offline, the path (green line) is followed exactly. After connecting to the robot, the path is not followed exactly anymore. For example on this straight section:
   
   

Another example of the position of the tool not following the green line while running the program:
       

When moving the arm to a random point on the part manually and looking at its position in RoboDk, the location of the tool is correct:
       

I would think the model and calibration of the reference frame to not be the problem, since the offset is present both in RoboDk and real life, and sampling a random point while checking its position in RoboDk and real life is accurate (enough. I agree that some error can be attributed to the model and calibration of reference frame).

What could be the issue? What is causing this error between the path and the actual tool position?


Attached Files
.rdk   demo_buispad.rdk (Size: 696.21 KB / Downloads: 131)
#2
Are you generating your robot programs (offline programming) or moving the robot using the driver?

For TM specifically, instead of using the driver I recommend you to generating the program for your TM robot and uploading the ZIP file on your controller.

This is because using the driver requires updating the robot kinematic parameters in RoboDK (the communication happens using joint values), whereas generating the program will rely on the Cartesian values.
#3
Hey Albert,

Thanks for your response!

I have tried both offline programming and moving the robot using the driver.

The pictures in the original post are from an offline pathnode program uploaded as a zip. During the path, I paused the robot, captured the joint positions in RoboDk with the Modbus command and took pictures.

The standard, non-pathnode, post processor also shows the same error.
#4
The error you see could be related to robot accuracy. It is normal for robot arms that have not been calibrated to have a position accuracy around 2-10 mm.

Calibrating a robot can help improve this accuracy to 0.15 mm - 0.5 mm.
  




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