The Ramblings of the Millahtime Man

Thursday, June 10, 2004

Understand how Prognostics Works

Prognostics is actually a pretty simple concept in principal. It's the implementation that becomes the hard part.

When a failure happens to something like a transmission there are signs first. If, say, a gear were going to break then before the break there would be a change in, say, vibration. This could start happening hours or even days before the break. The vibration would be a sympton of a tiny crack in the gear that would slowly expand until the break. The idea is to detect these "small" or "incipient" faults, in this case the crack, and know what this means to the gear. Here is a little chart to show when this happens...


Prognostics Diagnostics

"small" or
"incipient" fault          Failure

|____________________|_________

          Time


If you know that the vibration means a break is going to occur then you have detected the transmission failure before it fails. The next part is knowing how long until it fails. Knowing enough about the transmission and how the vibration is that is being caused my the crack the time can be plotted until the break.

The hard part is putting all of this together on something. Knowing where to mount the sensors and what the different signals mean to a level of detail to predict when the failure will happen consistantly and accurately. But, it has been done, some universities teach about it, the DoD has invested in it and it is being done all over the world.

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