# Robot Calibration DH-Parameters mismatch

**URL:** <https://forum.universal-robots.com/t/robot-calibration-dh-parameters-mismatch/27933>\
**Category:** Technical Questions\
**Created:** [April 13, 2023, 1:06pm UTC](https://forum.universal-robots.com/t/robot-calibration-dh-parameters-mismatch/27933 "2023-04-13T13:06:23Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![robin\_gdwl](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.universal-robots.com/robin_gdwl/32/2676_2.png) [@robin\_gdwl](https://forum.universal-robots.com/u/robin_gdwl)\
**Post date:** [April 13, 2023, 1:06pm UTC](https://forum.universal-robots.com/t/robot-calibration-dh-parameters-mismatch/27933/1 "2023-04-13T13:06:23Z")

</div>

Hello, I am trying to extract the DH-Parameters from an e-series UR5e to get accurate inverse and forward kinematics in python.  
I have extracted the parameters both from the calibration.conf file and from an unzipped .urp file.  
When using the values from the calibration.conf file and adding them to the [“standard” DH-values](https://www.universal-robots.com/articles/ur/application-installation/dh-parameters-for-calculations-of-kinematics-and-dynamics/) (from urcontrol.conf.UR5) I get quite large values for d and a. :

```python
delta_a = [
-5.4451392440e-05, 
0.02412010075500, 
0.0012052715012, 
4.35400296829e-05, 
1.19843008576e-05, 0]

delta_d = [ 
0.00022243, 
-248.57141, 
252.824383, 
-4.25266815, 
-2.47625006e-05, 
-9.50598885e-05]

```

after adding the deltas these are the calibrated values:  
 ![image](https://us1.discourse-cdn.com/flex020/uploads/universal_robots/original/2X/4/4d9ff8e959455d542d29ac7791f10011ff1afe32.png)

As per [this post these large values are to be expected](https://forum.universal-robots.com/t/ur10-calibration-conf-dh-model-generation/1638/8), as they cancel each other (especially the 250 meters of d[1] and d[2].  
However, there is one value that does not seem to cancel out:  
The second **delta\_a-value (~24mm)** does not seem correct and is not cancelled by any of the **other delta\_a values**.

When creating robot targets via inverse kinematics with these values I get a discrepancy of ~50mm depending on joint configuration. My guess would be that the 24mm discrepancy of a[1] is to blame.

What am I missing here? Where does the 24mm delta come from and how can I account for it?