Talk:Inertial guidance system

The term "Brandy Snifter gyro" seems idiosyncratic. Can anyone verify this bit, and say what the general term is for this class of gyro? -- Karada 22:50, 22 Sep 2003 (UTC)

It's called a "hemispherical resonator gyro" I updated the article. User:Ray Van De Walker

General edits

I have added a comment on Dr. Robert Goddard's early works with gyroscopically stabilized guidance systems here - I hope all find it appropriate.

Also, since inertial guidance does not necessarily require "digital computers", I shortened the referenced phrase to simply "computers" (allowing the inferred inclusion of highly-tuned analog systems).

allowing the inferred inclusion of highly-tuned analog systems

Oh you Luddite! :-) Seriously, good change! There were lots of computers in the world before digital computers, and many systems still depend upon fine mechanisms.

Atlant 11:29, 27 Apr 2005 (UTC)

Copyrighted content?

This work seems to be copyrighted! See http://www.answers.com/topic/inertial-guidance-system-1 , the explanation of Inertial Guidance System is equal!

Did you notice that that page is crediting Wikipedia for this text? We appear to be the source and not the destination. Wikipedia is "open content"; you'll find lots of sites out on the web that "repackage" this content as their own (but credit Wikipedia).

Atlant 11:29, 27 Apr 2005 (UTC)

IMU vs. INS

What is the difference between INS and IMU (Inertial Measurement Unit)? As far as I can tell a INS is effectively a IMU but has more functionality? IMUs should at least be mentioned in the article.

An INS gives position, and is generally dynamic. An IMU gives orientation and maybe tracking capability, and may or may not be dynamic - data could be collected and analyzed later.

An INS includes an IMU. An IMU is an assembly of at least 3 gyros and 3 accelerometers. INS is a system. It must have a computer or processor to calculate position and velocity using IMU outputs.

An INS produces a full position/attitude solution: XYZ position and yaw,pitch and roll in some frame of reference. An IMU merely outputs inertial data: rates of acceleration and/or rates of rotation about predefined local axes. A typical modern INS is usually composed of a 6-DOF IMU, GPS, compass, and some sort of a computer that runs an estimation algorithm to combine all of the available data into a (hopefully) optimal state (position,attitude) estimate. Vectra14 11:47, 28 January 2007 (UTC)

ring inferometers

Alas, the shaker is the most accurate, because both light beams use exactly the same path. Thus laser gyros retain moving parts, but they do not move as far.

I'm guessing that a more qualitative difference is that with mechnical gyros the friction can have a significant effect on the accuracy of the system, whereas the anti-phase-locking mechanism in the optical gyro is merely required to prevent the phase-lock. The computer simply integrates out the jitter provided. This would mean that the 'shaker' only has to happen rather than have to happen precisely. njh 08:28, 2 January 2006 (UTC)

tetrahedral inertial platforms?

I happen to work with IMU's/INS's and i've never heard of such a thing. Furthermore, I can't seem to find anything about it on Google or in IEEE. Could someone provide a citation? Vectra14 03:00, 1 December 2006 (UTC)

I, too, am sceptical of 4 sensors being capable of measuring 6 independent quantities. Maybe the tetrahedral arrangement is applicable in some constrained system? It seems unlikely that a 6DOF system like a small missile can use a system like this without further constraints. 81.104.244.39 16:46, 29 December 2006 (UTC)

Well, I'm guessing that he meant 4 multi-axis accelerometers, which would produce a total of 12 measurements. Still, unless the tetrahedron is REALLY big (and the accelerometers REALLY good), this isn't really practical. And why use accelerometers to measure rates of rotation when you can get a MEMS gyro to do the same thing (though the principle is actually the same). I have to add that furthermore, especially in small missiles, there's no reason to not simply use MEMS rate gyros for rotation (supposedly with low-rate absolute attitude coming in either from gps or from low-passed accelerometers). Anyway, that section should be deleted unless someone provides a reference for an IMU that uses this "TIP" setup. Everyone (that deals with robotics-type stuff) goes through a phase where they try to figure out how to use just accelerometers to build a full IMU... it'd be a shame if they decided that it's somehow practical based on this article. Vectra14 11:40, 28 January 2007 (UTC)

removed "Accelerometer-only systems" section. If anyone can provide a link/reference to an actualy INS that uses this "tetrahedral" accelerometer-only arrangement, feel free to revert. Vectra14 06:32, 12 March 2007 (UTC)

I worked on inertial guidance systems for 10 years. (Litton systems, and Lockeed Martin.) It has been many years since, so I cannot debate intelligently on the newer technologies in this article. (All systems were spinning mechanical gyroscopes and pendulous weight acceleromters.)

I don't see anything in this article about corrections to the accelerometers for Coriolous effect.

The three forces to correct for on a gyroscope is earth movement, aircraft velocity & drift of the gyroscopes inherint flaws.

The four forces to correct for on an accelerameter aircraft acceleration, schuler effect, coliolous effect & drift of the accelerometers inherint flaws.

Have I got myself confused or forgotten something in 30 years? 68.82.133.244 18:37, 29 May 2007 (UTC)