21–30 of 83 posts
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.
It's kind of annoying that they don't go into specifics about why this is good. The problem with traditional accelerometers is that the error accumulates, and so even small errors accumulate. The article doesn't really address what makes this different - and in fact I don't think it is different. You're still just measuring acceleration using a sensor and that sensor will have errors that accumulate. So the question…
Don't trains run on a fixed path, meaning we can use more traditional "positioning systems" like, umm, math? Or placing passive sensors or paint a big number on the wall?
It's kind of annoying that they don't go into specifics about why this is good. The problem with traditional accelerometers is that the error accumulates, and so even small errors accumulate. The article doesn't really address what makes this different - and in fact I don't think it is different. You're still just measuring acceleration using a sensor and that sensor will have errors that accumulate. So the question…
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.
It 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 sol…
Also trains have quite a large number of axles, I'm sure you could reduce error by counting all of them.
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.
How about an RFID chip (costs nothing) on every sleeper. Little database and you know exactly where you are. Accurate a few centimeters
It's kind of annoying that they don't go into specifics about why this is good. The problem with traditional accelerometers is that the error accumulates, and so even small errors accumulate. The article doesn't really address what makes this different - and in fact I don't think it is different. You're still just measuring acceleration using a sensor and that sensor will have errors that accumulate. So the question…
the accumulation is due to integration when converting acceleration to distance, not the accelerometer itself
Don't trains run on a fixed path, meaning we can use more traditional "positioning systems" like, umm, math? Or placing passive sensors or paint a big number on the wall?
Maths isn't a sensor technology. Wheels slip, air pressure fluctuates, rotary counters misread, errors accumulate, so better raw data could get you a more precise estimate of your current position. Various position technologies are already in use (e.g. "balise") but they have their limits if you're after cm-level accuracy. That said, I'm not buying that quantum INS is required for this over more established technique…
Earlier quoted context omitted.
It 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 sol…
Engaging 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 ai…
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.