Below is the axis setup for the elbow joint manipulator. I am trying to workout the DH parameters for the manipulator. Green frame represents the base and frame1. Starting from there, I am able to get the correct values up to joint3 (purple frame). If I rotate the frame about Z, so the blue frame moves, it gives me incorrect values. Below is the DH parameter table.
My question is, is the DH table setup correctly? If I move the frame about q3 I am getting invalid results. You will have to set q2 to -90 to achieve the configuration in picture.
+---+-----------+-----------+-----------+-----------+-----------+
| j | theta | d | a | alpha | offset |
+---+-----------+-----------+-----------+-----------+-----------+
| 1| q1| d1| 0| -90| 0|
| 2| q2| 0| a2| 0| 0|
| 3| q3| 0| a3| -90| 0|
| 4| 0| d4| 0| 0| 0|
+---+-----------+-----------+-----------+-----------+-----------+