[jesse.as]

Hello,

I just stumbled upon the C-Track video about how to utilize RoboDK to do an absolute accuracy calibration. I was just curious as to how the robot calibration feature works in RoboDK. Does the calibration actually modify the parameters in the robot to so all future programs made (with or without) RoboDK will use these new calibration values? Or are these values only used by RoboDK to generate more accurate positions? 

Thanks!

[Jeremy]

Hi Jesse,

The answer is both.
You can use RoboDK to "filter" your program to account for the robot imprecisions.
This is the most accurate option as it's optimized for the workspace and the stiffness of the robot arm can be accounted for.

You can also redefine your robot kinematics and modify your controller DH parameters.
This method will impact all programs run on the controller.
We recommend this method for the more advanced users. Modifying the wrong data in the controller can have a weird effect.

Jeremy

[colinb83]

What would be the steps involved in editing the controller on a Kuka with the calibration?

[Jeremy]

Hi Colinb,

We will provide the DH parameters.
You can then enter them on the controller.
I don't know where to change those on a Kuka controller, as all the projects I did involving them used the "filter" method.
Not all controllers give you direct access to it. But we think it's possible with the Kuka. You should look for the mechanical configuration of the robot. What you will do is refine the real length of each section of the arm to improve the controller Forward and Inverse Kinematics.
You should be able to find this info on your teach pendant. I don't have one with me to look it up. You can also ask your Kuka representative.

Jeremy

[colinb83]

Oh ok, so when i get the calibration license from you, if i want to put the calibrations directly onto the robot i would need to send you the calibrated station file and you could give me the DH values from that?

Also i did send Albert a question regarding Laser vs optical trackers, i know the laser is more accurate, but realistically how much difference does that make it terms of the actual calibration and results that the robot itself would gain? the reason I ask is that the C track does have the advantage that when not being used to calibrate robots it can also run a nice laser scanner giving it more potential uses than a laser tracker alone.

Or would it be better to perhaps purchase a cheaper used Faro ion tracker ?

[Jeremy]

Regarding the DH, you don't need to send us anything, RoboDK will generate the DH and DHM table automatically.
You can look those up in the "Robot panel"->"Parameters"

Regarding the Laser vs optical, I don't think you will see a huge difference there. One of the main differences is that the optical tracker generally has a smaller workspace compared to a laser tracker.
Both systems are more accurate than the robot will ever be even after calibration.

Jeremy

[colinb83]

Thanks Jeremy, I had the guys come demo the Ctrack, the 7m workspace seems like it's more than adequate, and as long as the reference plane is in view you can always move it around without issue

Colin

[Jeremy]

Hi Colin,

Yeah, in most cases the workspace of the CTrack is enough. But we have customers calibrating linear rail over 25m long, at this point you really need a laser.

Jeremy