How it works - Aviation Inertial Reference System - Autonomous navigation without GPS.
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- Опубликовано: 3 авг 2024
- The Inertial Reference System - Ring lasers and using GPS to calibrate.
How it works - Aviation Inertial Reference System - Autonomous navigation, without GPS.
Autonomous navigation systems have been around before GPS.
I try to explain the concept of a ring laser at a rudimentary level. This is NOT a design class, or physics lesson, and my intent is to convey the concept of applying wave theory in a way which makes a significant difference in society.
Both the Inertial Reference System, and Inertial Navigation systems, are mostly autonomous.
These systems require an external reference during initialization, after which they operate autonomous.
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Never imagined someone could explain Ring Laser Gyros using sand and sea shells. Nice.
Well - I tried at least - lol
Just fantastic. I have flown 737's for almost 8 thousand hours and never had the curiosity to understand better the IRS system. Very well explained. Thank you!
Glad you liked it.. it's not entirely accurate, but a close approximation.
Nearly thirty years ago my wife's cousin described to me this amazing innovation being utilized in NATO Submarines, I had purchased my first LORAN at the time for my sailboat. It boggled my mind, but now I can comprehend how it works. Thank You!
Thanks for the feedback Robert - Glad you liked it. It's fascinating science.
The ring gyro was in fact developed for submarines. I worked with the inventor of the ring gyro. The project was sold to a company that used it in missiles. They had to call back the engineer who designed it because it failed in missiles. He understood the problem and was fascinated at how he found the fault
I wanted to really thank you for this video because I don't think I could break it down any easier. I was the sales and marketing manager for a company that designed and built the worlds most accurate multi axis test systems for ring laser gyros and earlier guidance systems all the way back before the Saturn program for NASA. As a matter of fact the test systems were so delicate back then they would hire ambulances to carry them all the way across the US in carefully built boxes so they wouldn't vibrate as much. I asked and they said they paid them a big fee and they charged for every mile and they had no idea what they were carrying other than it was for the US government and extremely delicate and was sworn to secrecy. True story. God Bless and stay safe.
Wow - what an amazing story! Who would imagine that this was the only means of safe transportation? Really an incredible part of history - thanks for sharing
Great video! Helicopter pilot going for my CFII and needed a good explanation of this. Appreciated from another South African living in the US
Thanks Max - glad you found it somewhat useful ...
When I was a teenager an Air Canada co-pilot explained this navigation system to me while I sat in the cockpit during a Toronto to Vancouver flight (pre 9-11 times). I never forgot his explanation and have always wondered about it ever since. This video confirms the missing pieces and details of the system I had naturally filled in from my imagination. I’m glad someone bothered to take the time to explain this sophisticated system to me. I’ve been interested in INS, GPS, GLANOSS, LORAN C, and ground based radar systems ever since.
Thats great - there;s a lot of science which makes ring laser gyros function properly, and provide precision guidance information.
I had such hard time to understand INS till I watched your video. I’ve been following you on instagram for a long time and at first I was just curious about your pictures and now you’re an inspiration. The time spent watching your contents is never a dull
Thank you Hélio - for the kind words, and feedback - glad you like the video and thanks for following along. Let me know how I can improve?
Thank you so much for the excellent explanation of ring laser gyros...it has helped me understand the IRS. Many years ago, I worked on INS on the USAF F-111A ( Litton AJQ-20) which had gyros in the stabilized platform unit (SPU). When ring lasers came out, I didn't understand how lasers could replace spinning gyros, but now I understand, thanks to you. You video was very helpful to me.
Happy New Year!!!
Glad you liked it. it's elementary with some assumptions, but the concept is close enough for understanding
i'm a pilot student, i just say thank you. That's beautiful explanation of this topic. Simply amazing
Glad you liked it... keeping it simple, helps sometimes.
At 12:55 it is not a frequency shift it is a PHASE shift. One laser is fired (pulsed) at a splitter and then into the input of each fiber optic cable. It is not one loop in each direction but precisely matched lengths to form several loops in each fiber optic cable - each looped in opposing directions. Because a single laser is fired and split into each fiber optic cable equally, the lights starts at the same phase in each cable. But if the Gryo rotates in one direction, the light will take a longer time to travel and arrive late at the far end (just a few pico seconds) in one cable. And the light will take a shorter time to travel and arrive early at the far end (just a few pico seconds) in the other cable. The two light beams are then combined as they exit the fiber optic cables. Because the two light sources are now slightly out of phase, they cancel each other out a tiny bit and thus the bightness is slighty dimmer (compared to as if it had not been rotated) and this dimming translates as to the rotation angle. The more it rotated, the more the result dims.
The arrival times are also measured but not as accurately, they are just measured to see which arrived first to determine rotation direction. Ring Gyros are very quiet, compact, light weight, more rugged, have less procession and drift, and are more accurate than spinning Gyros. Even tiny Gryos can be made on Silicon. In that case, each path is just a circular series or traces in the Silicon that act similarly to fiber optic cables but use electrons rather than photons. These chips can be the size of your pinky fingernail and contain 3 Gyros, one for each axis. Adafruit has low cost ones that you can control with an Ardunio Nano to form a tiny Gyro system. I designed one into my Model Rocket Avionics Bay, along with an Altimeter and Temperature/Humidity sensor. It records these parameters, and when it senses the rocket has stopped gaining altitude and starts to tip over, it deploys the drouge parachute, and then the final landing parachutes at 300 meters from the ground.
you've used the most simplest way to explain how it works, good job
Glad it helped a bit
This system is actually super accurate and super cool.
Thanks for watching - yes the system is very accurate
I've been trying to get my head around Ring Laser Gyros and your demonstration on the beach really helped a ton! Thanks!
Great to hear!
Yes Sir, clear to the periphery, I have to read laser and understand why laser frequency and velocity is always constant irrespective of the velocity of the object on which it is fitted.
Speed of light is a constant?
Actually that was a good basic explanation of how it works.
Obviously need some incredibly accurate computer system to be able to read it.
But it's the first time I've had an idear how it works.
Thank you.
it's a very rudimentary explanation, of very complex physics - but hopefully I conveyed the concept, without butchering the science too much ... lol
Good explaination! I used to work in the manufacturing of IRS systems based on RLG gyros. First job was with the F-T ADIRU. Basically it's the same sort of explaination I gave to alot of new techs and engineers. Have since moved onto MEMs based INS systems.
Thanks Dustin - well then you're the expert and manufacturing sure gives you some interesting insights... must have been a fun assignment
@@DeonMitton It was! Learned from alot of really smart folks. One thing I also generally added to help people understand was how rotation of the gyro caused destructive wave interference. The sensors then pick that up as pulses of light during rotation. Rate of pulses equals rate of rotations.
@@hingos2002 Yes - phase shifting causing the interference... it's fascinating science for sure.
Would you mind answering a question please? I understand the basic principle for detecting rotation (I've read about laser interferometry because I like astronomy and it's used to great effect in LIGO). What I'm not sure I grasp is how the linear component of acceleration is measured. Is this also detectable based on interference patterns? I can't quite imagine how that would work.
@@macronencer The IMUs also have 3 accelerometers install as well. They are many styles used. MEMs based, vibrating beam, hinge and pendulum. All rely on inertia moving a structure to change either a resistance or capacitance reading. Calibrate that change to a know rate and you can build a model.
Great video! I'm studying from home due to covid so it's hard to get basic questions answered. This helped me a lot in understanding my course content. Good explanation on ring laser gyros!
Glad it was helpful and thanks for watching...
in my opinion ring laser gyro technology is straight out of a sci-fi movie.it's so fascinating.OMG.
Very easy to understand. Thank you. Also great concept...teach from the beach!
Made perfect sense the first time an I am slow,So well explained , thanks . Maybe cause you are SA and i am from Pretoria
Glad the somewhat elementary explanation made some sense.. it's fascinating science for sure.
This is a great video Deon! Really informative and entertaining. Keep it up
Thanks for the feedback - glad you liked my amateur explanation
Great video thanks Deon, I really enjoyed the explanation and the fantastic scenery. Cheers Malcolm from NZ
Thanks a lot ! Glad you found it fun to watch !
Excellent explanation on the Ring Laser Gyro! Thanks.
Thanks - glad you like it
Great video, very simple way of explaining a complex system.
Thanks Joseph - it is indeed very advanced physics application here, and incredible that we are able to harness the power of nature in such a way
Very cool and informative video! Thank you
Fantastic stuff! Thank you sir! What a way to captivate and educate at the same time :)
Thanks !!
Great explanation! I was impressed , thanks a lot
Glad it was helpful!
Excellent content! Great footage and I learned something new. Thank you!
Essentially, the beams run in different, and opposite directions, they enter and exit the tubes at the exact same point, which enables an interferometer to measure the reassembled signal at the moment of the exit the tubes.
When a ring laser gyro is in motion, the beams of light will travel different distances. In this system, difference in frequency is proportional to the rotation rate of the gyro (which is mounted inside the aircraft and therefore detects the roll rate of the aircraft in each of the axis where the laser is mounted).
The frequency difference is detected and measured via an interference fringe pattern/ and which phasing contains the directional information.
Hope that a bit more info about the fascinating science of using light beams to construct a gyro.
Great video thanks I enjoyed this
This video is underrated.
Thanks for the feedback !!
Great... Well explained ,Thank you 14:55
This is so interesting! Awesome video.
Glad you enjoyed it
Fascinating tech, thanks for the explanation.
Thanks Terry - so many interesting things going on in av/tech
This is an excellent video, really good explanation.
Thanks - glad you like it !
This was simple and very helpful... Thank you...!
Thanks - very over simplified - but hope it kinda helped explain some of what was going on .
I worked with the inventor of the laser ring gyro. It was never built for aviation use. The Ring gyro is over 40 yrs old. It has been adapted for use in aviation & missile systems since its development.
The ring gyro was a triangle shape not a tubular fashion.
Thank you for the note Roy - wow - it would be fascinating to hear the story of development.
@@DeonMitton because a lot of it was company private I cant talk about a lot of thing as the company I worked for is a defense contractor. The company made submarine navigation systems, weapons control systems and the world leader in radar technology, developing doppler radar and phased array antenna panels, both military projects which are now used around the world. Dthe doppler was meant as a replacement for the EWR systems, but got cancelled due to satellites. The company sold the project to NOAA for tornado predictions as it was able to detect the tight radar echo in what as known now as the "hook" echo, detecting both inbound and outbound echos at the same time
I can say that the ring gyro project was sold to another company that made missiles and at first they had major issues getting the ring gyro to work on a missile due to the huge g-force that were involved. I also know that the ring gyro was so sensitive that the optical bench that was used in my company could detect the earths wobble
Great explanation. The subject of IRS alignment at initialization would be a great subject for another video.
That's a great idea ... I'll add that to my todo list.
Amazing video. Thanks
THanks for the feedback !
Cool explanation!!! Brilliant
Glad you liked it and glad it helped you out.
Brilliant, helped me a lot!
Glad it helped!
Very interesting Deon, baie dankie!
Thanks Peter - a pleasure - hope it's helpful - and fun to learn about
Yes, Enjoyed that. Got my subscribe !
Thanks for the feedback - glad you liked it. Hopefully you'll like the upcoming Alaska series too.
great explanation mate ! short & quick thank you so much ! if I got it right those bottom shells should'nt move as they were the light source
Correct
Oh this is lovely !!! You got my sub ! Great explanation :)
Thanks
Thanks for sending a note! Really appreciate it
Great job. Thanks
Thanks for the feedback!
wow I love this guy
That;s funny ! Glad you enjoyed watching...
Wow!
Showing how you can be productive even on a Vacation...
Indeed!
The IRS system still uses accelerometers as the ring lasers do not detect linear acceleration only rotation. There is 3 ring lasers one for each axis and accelerometers for each axis.
AMAZING!
thanks for the explanation.
Thanks - it's kinda over simplification - but hope it was fun to watch
What a nice video!! Thanksss
Thanks - glad you enjoyed it
Very nicely eplained
Laymen's terms, but hopefully the high level message comes across.
Amazing
Nice explanation
Thank you !
It was very helpful.. can you share a video regarding how the alignment takes place with help of RLGs during the aircraft start up
Willdo soon
Simple and sweet
Yip
Thank You!
You're welcome!
So you mentioned a difference in arrival time to the output detector is calculated with math. Well to some degree it is. The speed of light being 7.5 times around the earth in 1 second is hard to calculate speed differences in a enclosed 3 inch space. So it’s actually phase shift is what’s being calculated. The longer travel beam has a different phase than the shorter beam so the math is basically the Doppler Effect.
Essentially, the beams run in different, and opposite directions, they enter and exit the tubes at the exact same point, which enables an interferometer to measure the reassembled signal at the moment of the exit the tubes.
When a ring laser gyro is in motion, the beams of light will travel different distances. In this system, difference in frequency is proportional to the rotation rate of the gyro (which is mounted inside the aircraft).
The frequency difference is detected and measured via an interference fringe pattern/ and which phasing contains the directional information.
Hope that a bit more info about the fascinating science of using light beams to construct a gyro.
Beautiful location ! I thought you would start with Radio Direction Finding beacons as aircraft navigation aids. Not sure if you confused accelerometers (detecting accelerations, including gravity !) from gyroscopes (detecting angles of rotation). Yes navigation technology has undergone an amazing evolution over the last 50 years. From large mechanical systems, miniaturised, reliable laser/solid state, and now chips containing these devices with complex software providing complete navigation solutions (eg drone autopilots for $30).
There's much to say about the topic - and the purpose of this video is not as a technical classroom/lecture, but rather to create awareness to the interesting science at work, in the devices we take for granted today. I bring you these videos, in the spirit of raising curiosity about aviation and science in general. In that spirit, there are lots of other education center videos on the topic. My channel is purely for the enjoyment of aviation, and to inspire 1 x more person to take up aviation. If I achieve that, then I'll call it success.
Waves are a wonderful phenomena.
Sure are !!
Thank you sir
Welcome
Hello brother thanks for such an informative video.can you tell me please how platform calculates the direction and north of aircraft position.
There are many good sources of info online. Just google "ring lasers"
As a former engineer at AlliedSignal Aerospace/Honeywell, I can say that you roughly have the concept correct but your model of the ring laser gyro is completely wrong. First off, it’s not a ring! The path is either a triangle or a square. Secondly, there are not two laser emitters, there’s only one that goes through a beam splitter. Third, there are not two detectors, there’s only one that senses the interference pattern.
Awesome Explanation, (How Is The Laser Light Fed; To The Ring Since The Ring Moves?)
Think of it this way, a ring laser gyro is a delicate instrument. You should never drop, or subject the box to more than a few G's. The movements inside the box (The three ring laser gyros) one for pitch, one for roll and one for azimuth (Heading) are precision components. The ring movement is measured in thousands of an inch or fraction of a mm. The emitters and detectors project and receive laser light at the three apexes of an equilateral triangle simultaneously. Think of the three sides of each ring laser as A, B and C not a circle but a ring using a glass triangle. The glass is then surface coated like that of a microscope or telescope mirror. At each apex there is an opening where laser is emitted into and another for laser to exit and be detected for that side of the triangle. The three emitters and three detectors are calibrated to reference zero angle at a precise point. Any movement of the box in any direction results in the three ring lasers (When powered) results to give a precise output where the box has moved when bolted to the aircraft. The movements of the aircraft are measured in minuscule amounts instantaneously whether momentarily or, continuously. Theory being a mass remains in motion any change in the acceleration of that mass results in a change to the ring which is detected electronically by the lasers being reflected off the optical polished surfaces. The World moves around the ring laser gyro not the ring laser gyro moves around the World. This technology is only second generation inertial reference instrumentation. There are better instruments namely third and even fourth generation instruments which military uses for Nuclear defense and hyper-sonic aircraft.
Thank you
You're welcome
Deon, very interesting; what about wind drift.? Does INS/IRS account for this or would pilots have used another method without the aid of external radio signals? Cheers
For wind vector, we need heading, drift ,groundspeed, True air Speed,we have heading ,drift ,groundspeed through INS/IRS,for True Airspeed ,INS/IRS gets its True air speed through Air Data Computer,thus obtaining the wind vector..
So what about the air speed in the irs?
But In ins we have accelerometer which can tell the change in speed then in irs?
IRS is nothing else than the old chap Dead Reckoning solved by high end technology😊
How often do you fly to Alaska and do you fly bush planes predominantly? I ask cause of your Alaska Bush hat haha. I live in Alaska, love it here.
Thank you ! Yes I fly seaplanes commercially - including Alaska and the Caribbean. I made the hat myself.
@@DeonMitton You betcha! Thanks for the reply, it's a sweet hat. I bet you love your job, get to see great views constantly. Awesome video by the way, very informative and well presented.
Thankyou brother I learned something. May you always follow GOD's guidance. Keep safe
Thanks a lot!
And you use Time of Flight to sense the beam of light reaching the end point
I didn’t understand if we say the ring laser gyro is one solid-state one so when aircraft turning the whole item should turn so how does one light travels faster than the other, is it movable from inside or what. Thank you
not faster - but travels further.. and then the waves interaction can be measured
I'm just going to take a wild guess and say AHRS is a modern solid state evolution of the IRS and INS systems
Close...
IRS is an inertial platform that can detect and measure accelerations along 3 axis, as well as rotational acceleration. Therefore calculate displacement from a known position. I.e. it can be used for Navigation as well as provide attitude and heading reference.
AHARS will only give attitude and heading reference and requires another sensor to provide navigation such as a GPS system.
The video is cool. How accurate would INS be for a 4-hour flight? How much would he deviate going from airport A to airport B after 4 hours of flight? Would it be like drifting 1Nm for every hour of flight?
It's used on airliners, like inertial navigation, and is usually used to supplement other navigation systems, for long flights. You can probably find the performance specs online - so I won't elaborate here. Suffice to say, the predecessor, INS/IMU was used to land man on the moon (IRS is a FAR superior system) - I think that flight exceeded 4 hrs
@@DeonMitton Thank you very much. Do you have any FAA documentation on INS?
@@josebiscaia670 Most of their information docs are available online.
@@DeonMitton thanks
Michelson Morley Experiment turned into gyro.
Mr.Mitton how to measure coriolis with accelerometer if not a real force?
good question - I'll have to research that a little bit
There is no way that small difference in the two beams could be measured. If you study Walter Russel he said light has no speed so c is actually zero. They just use xyz accelerometers and the laser is just for show. I think JPL manufacture all the IRS units.
how is the frequency of the laser light altered by the moving "tube" ? Or did you mean the phase of the light is shifted?
Essentially, the beams run in different, and opposite directions, they enter and exit the tubes at the exact same point, which enables an interferometer to measure the reassembled signal at the moment of the exit the tubes.
When a ring laser gyro is in motion, the beams of light will travel different distances. In this system, difference in frequency is proportional to the rotation rate of the gyro (which is mounted inside the aircraft).
The frequency difference is detected and measured via an interference fringe pattern/ and which phasing contains the directional information.
Hope that a bit more info about the fascinating science of using light beams to construct a gyro.
@@DeonMitton they way you describe the change in frequency points to the Doppler effect. I think that is what's going on here. Thanks for your explanation!
@@ThomasHaberkorn checkout the Sagnac-effect : en.wikipedia.org/wiki/Sagnac_effect - I might be mis-guiding by using Frequency - but I believe the interferometer to detect phase shift also
@@DeonMitton wow, very nice derivation! No Doppler effect after all. Thanks!
With all due respect, the explanation of a RING LASER GYRO instrument is totally different.
In a ring laser gyro, the cavity, usually 3 narrow tunnels, filled with the lasing gas (a mixture of helium and neon) IS the laser. (that is why it is called a RING laser) The edges have mirrors, such that the light travels in both directions in a precise triangular path. One mirror is semi- transparent, allowing light beams to exit in two directions with additional optics, these beams are brought together where they interfere with each other creating an interference pattern of waves that can be measured.
At least one of the other mirrors is mounted on a piezzo-electric 'actuator' which moves the mirror about the distance of one light wavelength. Why? a gas laser operates only between mirrors when the path lenght is an integer multiple of the light wave lenght.
The actuator holding the mirror is called the 'path lenght servo' and is controlled and moved to maximize the laser power.
For the reasons that the presentor explained, the interference pattern will move in a direction that depends on the direction of the rotation rate component normal to the plane of the light triangle.
By counting the interference waves, this rotation rate is measured with precision.
There is one problem with ring laser gyros:
When the rotation rate is small enough the counter rotating laser beams will 'lockin' and no interference pattern will be formed.
One way to solve this problem is to mechanically 'dither' the instrument.
Injecting an external laser light into a light guide pair is another but inaccurate way to measure rotation but it is NOT CALLED A RING LASER GYRO!
It is called a fiber optic gyroscope
Thanks Herman - it's fascinating technology, and so cool that we can harness the physical world, to create precision instrumentation like this.
no way they can actually measure the tiny change in the times that the laser arrives. What is the response time of the light sensor? can they verify manufacture light sensors that react that fast? If light travels at 300000km/s and that loop is 10cm and the shift of the loop is space is 1 mm the effect on the timing of those lasers is impossible to measure.
You are right. The accelerometers do all the work and the laser is just for show. Even Michelson Morley was a contrived experiment how could they measure the small movement in the 1800's. Relativity also states you cannot measure light against light! There will always be a null result.
Well - not entirely correct. Both roll rate and acceleration in each axis are required to perform the (dead reckoning) math. Roll rate gyros, are built using ring lasers.
There are multiple good sources explaining the science behind this instrument.
Essentially, the beams run in different, and opposite directions, they enter and exit the tubes at the exact same point, which enables an interferometer to measure the reassembled signal at the moment of the exit the tubes.
When a ring laser gyro is in motion, the beams of light will travel different distances. In this system, difference in frequency is proportional to the rotation rate of the gyro (which is mounted inside the aircraft).
The frequency difference is detected and measured via an interference fringe pattern/ and which phasing contains the directional information.
Hope that a bit more info about the fascinating science of using light beams to construct a gyro.
Amazon content!
Thanks !!
The us military must have some new system to let this info out.
Its very old technology... According to Wikipedia - since 1962 - en.wikipedia.org/wiki/Ring_laser
Accelerometers are not the same as gyros -- accelerometers detect acceleration and using math can be used to determine speeds and translations. That get's you only 3 axis of information. The other 3 axis are the rotations about those 3 axis and that is provided by gyros. I know you know this and am mentioning this because you are inconsistent in usage. A small error can be ignored, but this is major and you should have redone that portion of the video.
Thank you for the feedback.
I came here because I thought the title said "Internal Revenue System"
That's a whole different ballgame ... in another arena - lol
In the future these marks on the sand will be proofs that there lives a civilisation
Thats true lol
All the comments saying “great explanation!” Got me to stick around. But you tools 10 minutes to finally get to the point and even then you did a terrible job explaining the ring laser. It is a SINGLE laser beam which is split, sent down two separate paths, then recombined at a SINGLE sensor. You have no idea what you’re talking about.
EACH LASER WOULD NEED TO BE STATIONARY, WITH THE DETECTORS BEING MOVEABLE, TO DETECT ANGULAR/LATERAL MOMENTUM.
WITHOUT BRINGING THE 'Z' ACIS INTO THE SETTING, AS ELEVATION CHANGE IS NOT DIRECTIONAL CHANGE.
PITCH AND YAW RATE MIGHT HAVE SOME EFFECT HERE, BUT NOT CERTAIN.
Detection of rotational acceleration, is actually accomplished by means of measuring the interference of the 2 x waves.
When a ring laser gyro is in motion, the beams of light will travel different distances. In this system, difference in frequency is proportional to the rotation rate of the gyro (which is mounted inside the aircraft).
The frequency difference is detected and measured via an interference fringe pattern/ and which phasing contains the directional information.
Fascinating tech, thanks for the explanation.
it's kinda like that - I probably missed a bunch of important stuff, but the concept at least is hopefully close
Thanks Terry - see ya soon in AK