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As title, I can't find out how main system of this linear actuators knows each carriage absolute position. This system is iTRACK from Rockwell, but there are some other brands that do this.

Here an image of the system: https://motionanalyzer.rockwellautomation.com/Images/library/itrak/Rectangle.png

As it's possible to read from their system description, each carriage have just a magnet on internal side of the linear.

I never read about "reverse" linear encoders where stator is actually the sensor and mover is passive.

I've tough about Capacitive and Inductive PCBs on each module, but as I know this system are not very fast (and in some case precise). On system description there's +/-0.5mm and some +/-0.15mm at speed of 2meters/s to 5meters/s.

Maybe there's also possibility to place a lot of hall sensors and interpolate their results, but the complexity and price of components will be incredibly high.

Someone can explain me how this is possible and how this system works? (or references) Is this position technology something that is largely applied and commercial?

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    \$\begingroup\$ "but the complexity and price of components will be incredibly high" Having a lot of experience with Rockwell products, they are not concerned with high price or complexity. They have a PLC (just the processor module) that costs over $20,000 and has a grand total of 32Mb of memory. \$\endgroup\$ – Ron Beyer Oct 18 '19 at 15:43
  • \$\begingroup\$ @Ron Beyer Thanks for your tip. But my was a consideration. Is really possible that they have applied this kind of system? \$\endgroup\$ – Singed Oct 18 '19 at 15:59
  • \$\begingroup\$ Sure it is. I've used linear positioning systems that used a long (2+ meter) PCB with hall-effect sensors that detected a magnet running along it to give a very precise position measurement. The sensor was exceedingly expensive, but was exactly what the application required. \$\endgroup\$ – Ron Beyer Oct 18 '19 at 16:01
  • \$\begingroup\$ @Ron Beyer About your experience, it's very similar to what I'm looking for. Did you used simple linear hall sensor? How did you solve the high number of outputs and relative required ADCs? If you can also share something or references (if used) I'll appreciate (of course it's not a problem if it's a NDA) \$\endgroup\$ – Singed Oct 18 '19 at 22:03
  • \$\begingroup\$ I didn't design the sensor, I bought it and used it. That particular one was a number of years ago so I can't remember the exact model, but it was something like this which provided an analog output to the PLC that correlated to the linear position measured in 24-bit resolution over 2 meters. It was a very expensive sensor so I didn't take it apart to see how it works... \$\endgroup\$ – Ron Beyer Oct 18 '19 at 22:30

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