Jim,
On 02/15/2013 03:56 PM, Jim Lux wrote:
On 2/15/13 6:21 AM, Bob Camp wrote:
The timing does relate to multiple valves, so it's not quite as simple
as a single rate. The time delta's for the other stuff are all pretty
short, so you may or may not be planing to randomly drive them as well.
It all depends on how fanatic you get about the timing ...
Not very..
The physical device being driven has one solenoid valve that fills and
drains the "heart bladder". The radar looks at the gross surface
movement of the thorax (on the order of 1mm), and we want something that
isn't perfectly regular and that has some variability (so that the
algorithms used to detect the heartbeat don't wind up relying on heart
rate being zero bandwidth).
Rather than just implement something like
interval = 60/bpm + 0.1*rand
I figured if there was an easy way to generate something from a
"realistic" distribution, it would be nice.
There is several ways to produce 1/f noise. It seems like the option
that best fits your needs is the lead/lag filtering option, which is
covered in a few articles from NIST. A fellow JPL colleague of yours
then worked on it to set it up properly, so the starting state is good.
I'm sure you want to convert the BASIC code into something somewhat more
modern, but if worse comes to worse, I could probably do that in C for
you, as I have been thinking about doing it anyways. It's fairly trivial
stuff.
The key design issue is that you will need to decide how wide range of
frequencies needs to fit the 1/f slope.
Turns out that the need to simulate this both in digital and analogue
domain have been a topic since the early 60thies at NBS (now NIST) and
Jim Barnes did his PhD on it. They then improved on it further. Much of
that was then used in musical designs for "pink noise" filtering.
Let me know if you can't find the articles, and I will dig them up for
you. I should be able to find them for you before I get to LA.
Cheers,
Magnus
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