Tasks

• [x] Validate the identified walking control model on different data
• [x] Send out latest walking ID results
• [x] Learn C the hard way: Exercise 13

Walking System Identification

Over the weekend I setup the SimpleControlSolver to validate the identified model against different data than that used for the identification. Right now if you pass in a data set it will use the first half of the steps for identification and the second half for validation. You can also pass in a separate data set for the validation data if desired. The latest version of the control solver example shows the results.

The picture hasn't gotten a whole lot clearer, but here are some observations:

• There are no apparent patterns in the gains as a function of percent of gait cycle. In a few of the gains there may be less activity in the swing phase, but it isn't clear.
• The variance in the identified gains with respect to the fit seem to be quite large. This may imply that the cost function has a large flat bottom where a variety of gain combinations will give pretty good fits.
• The VAF for the validations range between 45% and 80% for the different controls. The hip moments are better identified than the knee moments. And on average 10-20 Nm is error.
• The control contribution plots show that there is a nominal moment generated and the controller compensates for the remaining error in the sensors.
• The line charts for the control contribution plots which show the mean controls and give some idea in how much compensation is needed at each time step in the gait cycle. I'm not sure if this give much insight.
• Very oddly, the VAF is better if we use a "diagonal" gain matrix for the same data set. I have a hard time believing that is correct. There still isn't any apparent pattern in the gains either.
• The second data set gives similar results to the first in terms of gain magnitudes and VAF.
• There is one wild gain at about 60% in the model from the second data set.