Consider the following Arm:


I looked for the DH-Parameters of this arm and I found this:


enter image description here

Although I don't think that this is correct because I think that the first Alpha should not be 0.

P.S: A clear photo of the arm: enter image description here

  • $\begingroup$ Welcome to Robotics, AchrafAhmedBelkhiria. Can you please edit your question to clarify what your problem is? Please also include a diagram of the robot with the joints clearly labeled, including the axis/frame definitions. As it stands, it's not clear how your joint diagram relates to the picture you posted. $\endgroup$ – Chuck Jul 31 '17 at 15:48
  • $\begingroup$ Sorry but I don't have a 3D concept of the arm or a labeled diagram for the joints. I thought by seeing this photo someone could help me with guessing the right DH-Parameters. I tried myself to find them on my own with the help of wikipedia but I can tell I did not succeed. Although, the DH-Paramters I posted from Github are probably wrong, because the alpha of j1 is 0 and we can clearly see that they don't have the same axis of rotation. $\endgroup$ – Achraf Ahmed Belkhiria Jul 31 '17 at 17:10
  • $\begingroup$ If you don't have a model for the robot, then I'm not sure I understand what the point of the exercise is. Why calculate DH parameters for a robot you don't have? Also, it's not clear to me what the joints are; I think I only see 5 joints in the picture - an azimuth, two elevation, an azimuth, and an elevation, for lack of more descriptive terminology. Your ASCII joint diagram shows a link 1 L1 between J1 and... what? Also, you posted a link to the GitHub page where the DH parameters were found; why not just ask the person that created them? $\endgroup$ – Chuck Jul 31 '17 at 17:45
  • $\begingroup$ I did a similar simulation using SolidWorks: youtube.com/watch?v=crJXUlzJ918 $\endgroup$ – LCarvalho Feb 19 '18 at 20:09

There are two conventions followed while deciding DH parameters. 1) Where the parameters are calculated with respect to the ith and the (i+1)th link (Excerpt from Chapter 5 of the book “Introduction to Robotics” by S.K. Saha, Tata McGraw-Hill, New Delhi, 2008)

2) Where the parameters are calculated with respect to the (i-1)th and the ith link (slide no. 38)

Cross check the methods to ensure you are using the same convention followed by the Github user.

The final answer remains the same while only the formulation of the transformation matrix changes.

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