Re: [Flightgear-devel] OT: real world tilt sensor

[Marlin M. <mar...@ho...>]

>From: Martin Spott <ma...@pl...>
>If I had the money to buy a ready-to-go "Intertial Measurement Unit", then 
>I
>would not ask. But for a plane whose first prototype is in model plane 
>size,
>this would exceed the existing budget.

Ahh, but is $US 1,395 too much to spend?  Check out:
http://www.pcflightsystems.com/

I probably wouldn't use it for IFR flight though because it's based on Micro 
Electro Mechanical Systems (MEMS) Gryos which is probably better quality but 
similar to the ones used in the RC helicopters. MEMS gyros don't actually 
rotate, rather they vibrate a mass and detect changes in orientation by 
measuring rates of turn and integrating the information to an absolute 
angle. The trouble is that they drift.

The best system I've seen is at Crossbow.  Their system combines both MEMS 
gyros with the placement of GPS antenas on various parts of the aircraft and 
measuring the phase differential between the received signal wave.  This is 
accurate enough to measure your orientation within a centimeter or two.  The 
drawback of GPS only, if such a system were available, would be that it's 
update speed is slow. So Crossbow marries the two, enabling the GPS to 
update the orientation of the MEMS gyros every few seconds.  I'd definitely 
take something like that into IFR conditions.

Marlin


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