Nathan,
Very useful plot - thanks for posting it! If I get a chance, I'll
compare it to some test specs (EIA 364-28 and MIL-STD-202-204). One
product I'm looking at (a 2TC2 circuit breaker) is tested at 10g, 50-500
Hz. If I'm reading your plot correctly, that's slightly more than the
highest value you observed, not counting the transient events.
I'm using a similar part (ADIS16364) and if you don't mind, I have some
questions:
Do you remember which filter tap setting you used?
Where did you mount the IMU? Did you bother locating the origin along
the centerline of your vehicle or did you just apply the appropriate
transformations?
Did your IMU mount have any shock isolation?
I originally was going to reuse the IMU breakout board it came with but
it's not convenient to mount anything to the male header pins. A ribbon
cable maybe? Plus the breakout board is somewhat space inefficient. I
was planning to mount it on a PCB along with some other sensors but I'm
trying to decide where to put it, near the edge or in the center.
Thanks,
-Bob
On 01/03/2016 03:08 PM, Nathan Bergey wrote:
On Tue, Dec 22, 2015 at 3:55 PM, Monroe L. King Jr.
<monroe@xxxxxxxxxxxxxxxxxx> wrote:
Vibration does matter when your using an IMU. A test flight of theSo I managed to take a look at this from PSAS's Launch-12 data. (~35
rocket should give good vibration data. 3 axis data from similar rockets
should be useful.
kg launch vehicle, CTI N2501 motor)
Attached spectrogram suggests that most the vibration we saw was wind
noise(!) It correlates well with velocity, and there is no big band of
noise during the motor burn like I expected.
My analysis:
Most of the motor vibration is well above nyquist for our IMU rate
(819.2 Hz). A lot of that should be aliased down into the chart
somewhere, but we had a really nice IMU (Analog devices ADIS16405)
that likely low-pass filtered it before we ever even saw it.
The bright horizontal bands are broad-spectum noise i.e. 'bangs', from
the motor ignition transient and from the recovery device firing.
I did the same thing for Launch-11 (same vehicle and motor) and got an
almost identical chart! So at least results are consistent.
-Nathan
PSAS
