1.14.11

Don't know what's worse, having a problem or knowing that it was something incredibly stupid all along.

Changing the disturbances didn't directly change the saturation issue, although it did help lower the prediction error greatly, probably since there was actually something to predict. But I noticed that there was this persistent static wavefront that even the classical loop had no effect on. Right now I'm storing the reference centroid info in a particular file that I occasionally refresh, and it turns out that there was a duplicate in a different directory...generated about the same time I started having these problems. The result was that this file would occasionally be used in stead of the correct reference, causing a "fake" bias that the actuator's couldn't reduce. Genius.

This explains a lot. The bias was usually tilt-like, explaining why the edge actuators were the first to saturate. I suspect that the main issue was that with this shit stuck in the system the disturbance sequences weren't anywhere near zero mean, and that this possibly screwed up the predictor.

Its still early, so I guess its possible this isn't the actual problem. But things got better immediately after removing the ghost file. Here are some sweet results using (fairly strong) disturbances and 25 modes

Obviously the LTI controller is obliterating much of the disturbance. There's still some high frequency amplification, but I think that can be knocked out with some frequency weighting. Looking at the rms values basically tells the whole story

Note that now I'm multiplying each mode by the norm of the phase profiles they produce, so you can compare their rms values relative to each other.

Even with stuff "fixed" though, saturation can still happen. Here's what the commands look like when the LTI controller is switched on suddently

As you might expect there's a jump when the loop is closed. But even this brief foray into shit-town doesn't destabilize the system. At some point it might be interesting to embed the saturation in the internal plant model.

Next week its back to target measurements. There has to be something that works with this kind of reduction in the RMS wavefront. Also, some new disturbance models might be interesting, since this current one is basically the easiest case.