GSoC Week 6

01 Jul 2016

The main theme of this week is Featherstone’s method. I have finished reading all of the text book that I feel I need to in order to finish my project. After reading I realize that I have been improper about addressing my project. Instead of saying I am introducing Featherstone’s method to SymPy, it would be more accurate to say that I am introducing one of Featherstone’s methods. The book introduced two equations of motion generation methods for open loop kinematic trees and one method for a closed loop kinematic tree (I stopped reading after chapter 8 and so there may have been even more methods). For my project I have decided to focus on the articulated body method of equation of motion generation for kinematic trees. This method is presented as being more efficient than the composite body method and the closed loop method seems rather complicated.

With this in mind I began digging deeper into the articulated body method and better learning how it works. With this mindset I went over the three passes that the method uses and looked for places where code would be needed that isn’t specifically part of the method. I compiled a list of these functions and have written docstrings and presented them in PR #11331. The support code for the method includes operations for spatial (6D) vectors and a function and library for extracing relevant joint information.

This week I reviewed PR #11333. The pull request adds docstrings to method that did not have them previously which is a big plus but the docstrings that were added were minimal and vague. I asked that the contributer add more information to the docstrings and he said he will get to it.

Future Directions

Next week I plan on furthering my work on the articulated body method. I hope to have the support functions completely written up and to begin writing the equation of motion generator itself. These plans may be set aside, however, as my most active mentor will be coming back from traveling next week and so work may resume on the base class.

PR’s and Issues

  • (Open) Added docstrings to PR #11333
  • (Open) [WIP] Featherstones EOM support PR #11331


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