Update DH Parameters : UR10

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Julien_Demetra
Posts: 11
Joined: 08 Mar 2019, 08:48

Update DH Parameters : UR10

Post by Julien_Demetra » 08 Mar 2019, 10:08

Hello,

I'm simulating several UR10 robots in a VREP scene and I would like to know how I could check the DH parameters of my robots in VREP in order to make sure they are the same than my real robots.
Moreover, the real robots I'm using have been calibrated and thus the DH parameters are not the standard ones for UR10. Is there a way I can "upload" those parameters in my VREP scene ?

Thanks in advance,

Julien

coppelia
Site Admin
Posts: 7124
Joined: 14 Dec 2012, 00:25

Re: Update DH Parameters : UR10

Post by coppelia » 08 Mar 2019, 13:39

Hello,

the best would be to check this manually, one joint pair at a time, and adjust things accordingly.

Cheers

Julien_Demetra
Posts: 11
Joined: 08 Mar 2019, 08:48

Re: Update DH Parameters : UR10

Post by Julien_Demetra » 20 Mar 2019, 09:22

Hello,

Thank you for your answer. In my use case (UR10 VREP robot), the robot joints are not positioned in the DH formalism. It is impossible to see the DH parameters from one joint to another via Position and orientation Toolbox.
So if I understand your answer correctly I have to build a whole new UR10 robot by that I mean all the joint positions and orientation by hand ? If this is the case could you indicate me a good practice ?

Cheers,

Julien

coppelia
Site Admin
Posts: 7124
Joined: 14 Dec 2012, 00:25

Re: Update DH Parameters : UR10

Post by coppelia » 22 Mar 2019, 13:48

You can build this by hand, or programmatically create and position/orient joints, and create the hierarchy. You can use functions such as sim.createJoint, sim.setObjectPosition, sim.setObjectOrientation, sim.setObjectParent, sim.setJointPosition, etc.

Doing this by hand, you would do something similar to this tutorial.

Cheers

Julien_Demetra
Posts: 11
Joined: 08 Mar 2019, 08:48

Re: Update DH Parameters : UR10

Post by Julien_Demetra » 26 Mar 2019, 11:03

Thank you for your advices.
I followed the tutorial and used the tools proposed which are very relevant for my case.
However there is an inconsistency between the tool : DH joint creator.ttm and DH parameter extractor.
I created the 2 first DH joints of my UR10 with the creator tool and the DH value (theta) I read in the DH parameter tool is different ... See my screenshots below:
Image
Image

How is that possible ? Is there something I don't do well ?

Cheers,

Julien

coppelia
Site Admin
Posts: 7124
Joined: 14 Dec 2012, 00:25

Re: Update DH Parameters : UR10

Post by coppelia » 27 Mar 2019, 14:40

hum... there must be a bug in one of the models...

Julien_Demetra
Posts: 11
Joined: 08 Mar 2019, 08:48

Re: Update DH Parameters : UR10

Post by Julien_Demetra » 27 Mar 2019, 17:10

Which one should I trust ???
I think the creator is good though because I did the superposing of the UR10 with all j=0 and the DH parameters that I created and it matches.
Do you agree ?

Cheers,

Julien

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