Signal Processing Fine-Tuning in Progress

A project log for Peril-Sensitive Sunglasses

A version of the Peril-Sensitive Sunglasses (as described by Douglas Adams in The Hitchhiker's Guide to the Galaxy)

minimum-effective-doseMinimum Effective Dose 04/19/2014 at 06:071 Comment

No pictures this update - but some information on the process of making the whole thing work.

As seen in the last update, the prototype hardware construction is complete.  All the solder-y and nuts & bolts-y parts are done.  What's left is figuring out what exactly to do with all the data we are getting from the sensors.

This is easier said than done.  I can read the sensors just fine but deciding what to do with the data at a high level is a bit tricky.

Testing reveals that my current methods are good enough to tell the sensors are working -- but not well enough to reliably isolate anomalies. False positives (detecting Peril where there is none) and false negatives (failing to detect Peril) abound.  I need to re-evaluate my software.

It helps to define the problem.  Here is what we want:

Ignore slow and steady changes, and take action only on anomalous signals.

To do this we need to:

No matter what method or thresholds we use for sensors, the common thread is that we need to take and keep accurate measurements over time.  Only by comparing what's happening to what has already happened can we make judgments about normal vs anomalous.

The existing software does this, but as stated - not well enough.  Some software work should sort this out.  I'm reminded of why Signals Processing is an entirely separate discipline, because it's easier said than done!


andyhull wrote 04/19/2014 at 10:10 point
Hmmmm.. I think we need to integrate peril over time, the more rapid DeltaPeril/DeltaTime, the more pressing is the problem... slow increases suggest peril is at a manageable level, rapid increases suggest the beast is about to eat you.

Now... is that a logarithmic or linear relationship I wonder... good luck with finding out, and remember to keep the Wumpus at least two caves distant while testing.

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