Tutorial would be nice

[balzer82]

Hi! Great work. Unfortunately I do not understand all details. A tutorial would be nice, where you (graphically) describe, what are the parameters to set up a robot and work with your functions. E.g. you wrote 'q+pi/2' and so on: What is q?

[cdsousa]

Thanks. You are completely right. I hope to have some time in future to do it, but I don't expect it to be soon.

q is used to represent the joint position. This symbol is commonly used for that, along the theta symbol.

Meanwhile you can take a look at the test file: https://github.com/cdsousa/SymPyBotics/blob/master/sympybotics/tests/test_results.py

[balzer82]

I implemented the basic DH formalism for my own, just to learn and understand it: https://github.com/balzer82/Robot-Kinematic

Would be nice if you could at least show a way to achieve this with SymPyBotics! Thanks

[cdsousa]

Well, its just a matter of mapping your Th, d, r, al parameters to the alpha, a, d, theta parameters I use (which are the common notation found in texbooks), and put the q joint position placeholder in the correct parameter. Usually q will appear where you have a 0.0. For revolution joints that is usually the theta parameter:

>>> import sympy
>>> import sympybotics
>>> rbtdef = sympybotics.RobotDef('Example Robot', # robot name
...                               # list of tuples with Denavit-Hartenberg parameters
...                               # (alpha, a, d, theta)
...                               [('-pi/2', 0, 0, 'q+pi/2'), 
...                                ( 'pi/2', 0, 0, 'q')], 
...                                (..., ..., ..., ...),
...                                         ...
...                                (..., ..., ..., ...), # last link
...                               dh_convention='standard' # either 'standard' or 'modified'
...                              )

[lyhbuaa]

@cdsousa I used the PUMA560 model in the test file, and I found that the result is not same with the Matlab robotics toolbox.

[phuicy]

This is worrying. @lyhbuaa can you add the code for both so I can reproduce it. thanks.