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local positionning/tracking system

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l_aventurier

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Hi,

I would like to know what options exist in terms of electronic equipment for “local positionning/tracking of moving objects”.

Let’s say we consider a 50x50m warehouse with moving objects inside. Each of those object carries some sort of sensor/transponder that are used to get their coordinates, like a "local GPS"; and a computer is able to follow in real-time the local coordinates of those moving objects to, for example, draw a map of the place with moving dots…. It’s a position tracking problem.
The accuracy is important here, like a few centimetres and the data should be refreshed at least once per second.

On the following diagram, some dogs are moving in the rooms of the building and they appear as dots on the computer screen.


67-warehousef.jpg

(https://www.electro-tech-online.com/imgcache/67-warehousef.jpg)

This problem involves many smaller problems but the one I would like to focus is the positioning part.

Do you know, from your knowledge/experience, what kind of system exists? Note there may be walls and no light so I rule out system involving “photography + image processing”.

Those components would be integrated in a bigger system so they should provide some sort of interface that can be accessed by other components driving them (to be somehow controllable programmatically from software or HDL kind of stuff).

Just some pointers to send me in the right direction would be great!

Thanks for your help!
 
Is this theoretical as for a 007 movie or to be applied and implemented in the real world ?
Can the moving object have a signal emitting tag?
Bidimensional or tridimensional ?
Is the building existing or would it be built with aids/equipment for such tracking ?
How many moving objects are to be simoultaneously tracked ?
"A few centimeters" accuracy in 25 million square centimeters for such warehouse ?

Sonar could be the technology.
 
Hi,

To answer some of your questions:

Yes, that is for the real world.

Yes, the moving objects can have tags

It is tridimensional: the ability for the monitoring computer to have the following data:

object #1:
T=0s) : X=5,15m ; Y=8,50m ; Z=1m
T=1s) : X=5,25m ; Y=8,50m ; Z=1m
T=2s) : X=5,35m ; Y=8,50m ; Z=1m


…for the 10 multiple objects to be simoultaneously tracked.


To be honest, I was expecting some kind of local GPS system, like you install 3 “antennas” around the building, moving objects receive the signals and send back their coordinates to the computer via wifi.

But couldn’t find any and there may be some alternative solutions, that’s why I’m asking 

Thanks!
 
GPS is time of flight, you'd need at least four absolutely perfectly synchronized radio transmitters and a receiver which had extremely high resolution phase detection, you then determine time of flight to the four signals and calculate out your location. What resolution do you need? The quick example you gave above is .01 meters. That's a resolution less than an inch, I'm not sure you can realize something like that practically.
 
I would not choose WiFi or any 'speed of light' propagation of mobile signals. I would prefer acoustic low speeds for that accuracy.
Signals bounce can create trouble too. Walls/objects in warehouse should be not reflective.
The warehouse ceiling, (and walls) if fitted with uniformly placed array of sonar sensors, could receive transmitted pings from the mobile units, each one with its own identifier and each sonar receiver adding its X, Y, Z location to the signature signal to the "time stamp" data of reception.
Large computing power and elaborated software could determine location of each mobile. The first sensor to receive the ping is the nearest one, and by calculation of other later time stamps determine position by triangulation.

Optically, the mobile could beam a cone of light upright to an array of photocells on the ceiling. The highest intensity received would be the one from the mobile nearly directly below, Analyzing light gradients from other surrounding photocells could calculate location with the apropiate computing power. Light modulation could identify the mobile. The cone of light would have to be very and always vertical on gymbal mount.
Or,
A really reliable wireless optical "computer mouse" under the mobile could transmit its X, Y movements related to motion across the floor. Don't know how to deal with "Z" there.

I think...
Miguel
 
Find Dr. Ivan Sutherland's Doctoral Thesis (Harvard circa 1970). He designed an 6dof ultra-sonic head tracking system as part of the Sketchpad system. Ivan was chairman of my PhD committee.
 
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