3 ms·
I would have thought a simple device that counts the number of times the wheel has rotated would be vastly simpler and cheaper, and surely accurate to within a
by rwmj 10mo ago
I would have thought a simple device that counts the number of times the wheel has rotated would be vastly simpler and cheaper, and surely accurate to within a few centimeters.
- petesergeant 10mo agoBut then they couldn't use the word quantum
- TheOtherHobbes 10mo agoIt wouldn't. Wheels slip in the wet, they develop flat areas with differential friction, minor differences in wheel circumference would soon add up over long distances, and all dimensions change with temperature. But fiberoptic gyro navigation is already a thing, and has been for decades. It's not super cheap, but it's cheap enough for an industrial application like this one. So I'm not sure what problem is being solved here.
- defrost 10mo agoEngaging with the substance of the suggestion ... * What would the Central Limit Theorem give us if a significant number of wheels on loco's and carriages were instrumented and ID logged over the years. * What drift patterns and correction factors can be observed and fine tuned by passing {many} wheel streams through station to station and line end to line end "known distance" corrections. For half a century or so aircraft height was largely done with air pressure alone. To this day GPS accuracy is "improved" by logging the "drift" of fixed point stations giving us filter coefficients to correct for atmospheric wobble, acute angle uncertainty, as yet uncorrected time drift, etc.
- goodcanadian 10mo agoFor half a century or so aircraft height was largely done with air pressure alone. It still is. Flight levels (20000 feet and above in the US) are defined by air pressure without reference to current atmospheric conditions (i.e. the actual altitude of FL200 can vary based on atmospheric conditions). Below 19000 feet, altimeters are calibrated to local conditions which are given to the pilots by air traffic control.
- defrost 10mo agoStill used, sure, but not solely ( 'alone' ) - it's augmented by GPS height, feedback from ground radar, onboard radar facing down and forward, etc. See: https://en.wikipedia.org/wiki/Altimeter https://en.wikipedia.org/wiki/Altimeter that list five types (including trad. air pressure type)
- __alexs 10mo agoIf it's wet inside a tube tunnel something has usually gone very wrong surely? Also trains have quite a large number of axles, I'm sure you could reduce error by counting all of them.
- _Wintermute 10mo agoA number of the tube lines have large sections above ground.
- defrost 10mo agoTrains in tubes have a lot of suction that draws in condensation from outside air. A curious advantage of instrumenting all axles for wheel turn counting is calibration against actual known distances (end to end, etc) over time reveals slow wheel degradation that can trigger carriage maintainance. Not all operators do this, it's been done at various times for heavy rail mining operators with loooong trains and heavy daily usage.
- ulfw 10mo agoHow about an RFID chip (costs nothing) on every sleeper. Little database and you know exactly where you are. Accurate a few centimeters
- circuit10 10mo agoOr maybe a camera underneath the train? It could be the same kind of thing used in optical mice, or just count the sleepers
- defrost 10mo agoNot bad, but practically have you seen the underside of many trains? The spit up of grease, leaves, metal particulate from rail and wheel grind, etc gets pretty thick. The vision challenge is to cheaply and effectively keep a clean lens. There's a similar challenge in monitoring production conveyor belts in mineral processing - vibration, tempreture, rocks kick about, dust make for a savage environment.
- hengistbury 10mo agoUniversal Signalling are a company doing exactly this to give better train location information to signallers. https://www.universalsignalling.com/news/latest#h.12nuchpah7nq https://www.universalsignalling.com/news/latest#h.12nuchpah7...
- clickety_clack 10mo agoIt has to be for research purposes or something. They own the whole system of trains and tunnels, so there’s got to be loads of ways they can easily implement to see if a train passes a particular point.