System Identification

I've been using sys id for a long time now and learnt it on my own for my dissertation work, but I've hit enough walls in just being a user that I really need to start understanding what the hell is going on. I like Ljung's book "System Identification: Theory for the User", but it think the title would better be "System Identification: Theory for the Theorist" because he doesn't show you how to actually implement things computationally, which is what a "user" really needs. So I'm going to work through his book from page one and come up with the computations for the main methods in a series of IPython notebooks. I hope that my knowledge will then be sufficient to design a general system id package in Python and actually be readable (unlike the system id toolbox in Matlab).

The repo is at:

https://github.com/moorepants/ljung1999

And the computations for Chapter 1 have been started here:

http://nbviewer.ipython.org/urls/raw.github.com/moorepants/ljung1999/master/Chapter_01.ipynb

Walking System Identification

Over the weekend I implemented a method to zero out the identification of particular gains in the gain matrix (closing issue https://github.com/moorepants/DynamicistToolKit/issues/5).

The results are here for the example data:

http://nbviewer.ipython.org/urls/raw.github.com/moorepants/walking-sys-id/cfc1143c684ce0e6d1cc4daed0d96f3bc6a5f3d5/src/control_solver_example.ipynb

I'm not sure why the sum of the residuals is being returned as zero from numpu.linalg.lstsq. It seems like the A matrix becomes rank deficient once I delete columns which correspond to different feedback loops. It also seems like the gains that I don't zero out have similar profiles to the previous full gain matrix calculations.

I also found some bugs and spent a long time working on it today. Will report more tomorrow.

PYCON 2014

I submitted a PyDy tutorial and a python for human walking data analysis for PyCon 2014 in Montreal. We'll see what happens...