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A pathway-based method, apparatus and system for tracking, sensing and communicating with an object, such as a carriage or vehicle moving on a pathway. The system includes a transmitter winding along the pathway that is energized by a transmitter and one or more sensing windings in which a signal is

A pathway-based method, apparatus and system for tracking, sensing and communicating with an object, such as a carriage or vehicle moving on a pathway. The system includes a transmitter winding along the pathway that is energized by a transmitter and one or more sensing windings in which a signal is induced. The vehicle contains a transducer that creates a position-indicating coupling of the transmitted signal into the sensing windings. The transducer may be a passive ferromagnetic or conductive body that locally alters coupling between the windings, or a tuned coil carried on the vehicle that couples energy received from the transmitter into a sensing winding. Absolute position may be established at regular intervals using a discrete position sensor, such as a Hall Effect magnetic field sensor, and, the signal derived from the sensing windings can be monitored, by counting cycles or determining phase, to determine a precise vehicle position. With one sensing winding it is possible to determine distance to about ⅛ of a wavelength and by using two or more phased sensing windings a wayside controller determines the position within a wavelength to a smaller fraction of a wavelength. The position sensing can be accomplished without any source of power on the vehicle, and may extract power from the transducer or position sensing system to drive an electronic communication unit on the vehicle. Modulation of the position sense signal can be used to provide two-way communication between the vehicle and the wayside controller. A typical application is to transmit a vehicle identification number to a controller, or for the controller to activate a mechanism on the vehicle.

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1. A system for determining position along a pathway, the system comprisinga magnetic flux source disposed along the pathway,at least a first sensing winding comprising a plurality of inductive loops of alternating sense disposed along the pathway in stationary proximity to the magnetic flux source,

1. A system for determining position along a pathway, the system comprisinga magnetic flux source disposed along the pathway,at least a first sensing winding comprising a plurality of inductive loops of alternating sense disposed along the pathway in stationary proximity to the magnetic flux source, where loops of alternating sense alternate in sense with respect to one another, anda moveable coupling element configured to couple energy from the flux source to the first sensing winding to induce therein a position signal that varies with a position of the coupling element along the pathway. 2. A system according to claim 1, wherein the flux source comprises a transmitter winding that includes one or more current loops of alternating sense disposed along the pathway, each current loop generating magnetic flux. 3. A system according to claim 2, wherein the transmitter winding forms at least a part of a stator motor winding of a linear motor. 4. A system according to claim 2, wherein the transmitter winding is disposed in proximity to a stator motor winding of a linear motor. 5. A system according to claim 4, wherein at least one of the transmitter winding and the first sensing winding has a period that is a multiple of a period of the stator motor winding. 6. The system of claim 1, wherein the flux source defines the pathway. 7. The system of claim 1, wherein the coupling element is arranged for movement with an object, such that the position signal varies with a position of the object along the pathway. 8. The system of claim 1, comprisinga second sensing winding, the second sensing winding comprising a plurality of inductive loops of alternating sense disposed along the pathway,the coupling element being configured to couple energy from the flux source to the second sensing winding to induce therein a position signal that varies with a position of the coupling element along the pathway. 9. The system of claim 8, wherein the inductive loops of the first sensing winding are offset from the inductive loops of the second sensing winding with respect to a direction of the pathway. 10. The system of claim 8, whereinthe inductive loops of the first sensing winding are periodically spaced along the pathway,the inductive loops of the second sensing winding are periodically spaced along the pathway, andthe inductive loops of the first sensing winding are offset in phase from the inductive loops of the second sensing winding with respect to a direction of motion along the pathway. 11. The system of claim 10, wherein the offset is substantially equal to +/−180°/n, for even values of n, and is substantially equal to +/−360°/n, for odd values of n, where n is a number of sensing windings. 12. The system of claim 8, wherein the coupling element is arranged for movement with an object, such that a position of the object along the pathway is determinable from the position signals induced in the first and second sensing windings. 13. The system of claim 12, wherein a position of the object along the pathway is determinable from a ratio of the position signals induced in the first and second sensing windings. 14. A pathway system for a carriage, the system comprisinga magnetic flux source disposed along the pathway, the flux source comprising one or more current loops that generate magnetic flux,at least a first sensing winding, the first sensing winding comprising a plurality of inductive loops of alternating sense disposed along the pathway in stationary proximity to the magnetic flux source, where loops of alternating sense alternate in sense with respect to one another, anda transducer assembly coupled to the carriage, the transducer assembly comprising a resonant current loop positioned to couple energy from the flux source to the first sensing winding to induce therein a position signal that varies with a position of the coupling element along the pathway. 15. The pathway system of claim 14, wherein the resonant cu rrent loop generates a power signal for use with respect to the carriage. 16. The pathway system of claim 15, wherein a tuning of the resonant current loop is varied in order to impose a further signal on the position-indicating signals induced in the first sensing winding and any other sensing windings that may exist. 17. The pathway system according to claim 15, wherein the further signal identifies the carriage. 18. A system for determining a position of a carriage along a pathway, the system comprisinga magnetic flux source disposed along the pathway, the flux source comprising one or more current loops that generate magnetic flux,at least a first sensing winding, the first sensing winding comprising a plurality of inductive loops of alternating sense disposed along the pathway in stationary proximity to the magnetic flux source, anda coupling element arranged for movement with the carriage, the coupling element configured to couple energy from the flux source to the first sensing winding to induce therein a position signal that varies with a position of the coupling element along the pathway. 19. The system of claim 18, wherein the coupling element comprises one or more of a conductive material, paramagnetic material, a ferromagnetic material, and a resonant loop. 20. The system of claim 19, wherein the coupling element has a dimension relative to a direction of the pathway less than twice a dimension of the inductive loops relative to that direction. 21. The system of claim 20, wherein the coupling element has a dimension relative to a direction of the pathway substantially equal to a dimension of the inductive loops relative to that direction. 22. The system of claim 18, comprisinga second sensing winding, the second sensing winding comprising a plurality of inductive loops of alternating sense disposed along the pathway,the coupling element being configured to couple energy from the flux source to the second sensing winding to induce therein a position signal that varies with a position of the coupling element along the pathway. 23. The system of claim 22, whereinthe inductive loops of the first sensing winding are periodically spaced along the pathway,the inductive loops of the second sensing winding are periodically spaced along the pathway, andthe inductive loops of the first sensing winding are offset in phase from the inductive loops of the second sensing winding with respect to a direction of motion along the pathway, the offset being substantially equal to +/−180°/n, for even values of n, and is substantially equal to +/−360°/n, for odd values of n, where n is a number of sensing windings. 24. The system of claim 18, wherein the flux source a transmitter winding, the transmitter winding comprising a plurality of current loops of alternating sense disposed along the pathway, each current loop generating magnetic flux. 25. A system for determining position along a pathway, the system comprisinga transmitter winding disposed along the pathway and defining a magnetic field along the pathway,a first sensing winding arranged along the pathway in stationary proximity to the transmitter winding, the sensing wining, the sensing winding having a plurality of inductive loops of alternating sense,the first sensing winding being positioned such that movement of a coupling element along the pathway couples energy from the transmitter winding to the first sensing winding to induce therein a position signal that varies with a position of the coupling element along the pathway. 26. The system of claim 25, wherein the transmitter winding defines a plurality of flux regions of alternating polarity disposed along the pathway. 27. The system of claim 26, whereinthe inductive loops of the first sensing winding are periodically spaced along the pathway,the flux regions are periodically spaced along the pathway, andthe inductive loops of the first sensing winding are aligned with respect to the flux regions of t he pathway. 28. The system of claim 27, wherein a period of the inductive loops is an integer multiple of a period of the flux regions. 29. The system of claim 27, wherein a period of the flux regions is a multiple of a period of the inductive loops. 30. A system for determining position of a carriage along a pathway, the system comprisinga transmitter winding comprising a plurality of current loops of alternating sense disposed along the pathway, each current loop generating magnetic flux,a first sensing winding arranged along the pathway in stationary proximity to the transmitter winding, the first sensing winding having a plurality of inductive loops of alternating sense,a second sensing winding, the second sensing winding comprising a plurality of inductive loops of alternating sense disposed along the pathway,a coupling element that is arranged for movement with the carriage,the first and second sensing windings being positioned in relation to the flux source and the pathway such that movement of the coupling element along the pathway couples energy between the flux source and the first and second sensing windings to induce therein position signals that vary with a position of the carriage along the pathway. 31. The system of claim 30, whereinthe inductive loops of the first and second sensing windings are periodically spaced along the pathway, yet, are offset in phase from one another with respect to a direction of motion along the pathway,the current loops of the transmitter winding are periodically spaced along the pathway, andthe inductive loops of the first and second sensing winding are aligned with respect to the current loops of the transmitter winding along a direction of motion along the pathway. 32. The system of claim 30, wherein a period of the inductive loops is an integer multiple of a period of the current loops. 33. The system of claim 31, wherein a period of the current loops is an integer multiple of a period of the inductive loops. 34. The system of claim 30, wherein a position of the carriage along the pathway is determinable from a ratio of the position signals induced in the first and second sensing windings. 35. A method for determining position along a pathway, wherein the method comprises the steps ofproviding a magnetic flux source disposed along the pathway,providing a sensing winding disposed along the pathway in stationary proximity to the magnetic flux source, and arranged in a plurality of inductive loops of alternating sense,wherein the step of providing the sensing winding includes positioning the winding such that movement of a coupling element along the pathway couples energy between the flux source and the sensing winding to produce a position signal in the sensing winding. 36. A method for determining position of a carriage or the like moving along a pathway in a system having a current winding fixedly extending along the pathway that constitutes a linear motor for operatively driving the carriage along the pathway, such method comprising the steps ofproviding at least one sensing winding arranged stationary and proximate to the pathway and the current winding, the sensing winding including multiple loops with each loop having a spatial period and being disposed along the pathway with alternating senseoperating the current winding as a transmitter to transmit electromagnetic energy, andmounting a transducer on the carriage to passively receive the energy in a resonant current loop, the transducer being positioned to induce a signal in the sensing winding as the transducer moves along the pathway such that the induced signal in the winding indicates transducer position. 37. A method for signaling position of a carriage or the like moving along a pathway in a system having a current winding extending along the pathway that constitutes a linear motor for operatively driving the carriage along the pathway, such method comprising the steps ofproviding a plurality of sensing windings in sta tionary proximity to the pathway, each sensing winding having a period and being offset along the pathwayoperating the current winding to generate magnetic flux, andpassively receiving flux on the carriage in a resonant current loop, the loop being positioned to induce position-indicating signals in the sensing windings as the carriage carries the transducer along the pathway. 38. A pathway system for determining position of a carriage, vehicle or the like (collectively, “carriage”) moving along a pathway, the system comprisinga coil assembly configured for extending along and being securable against movement with respect to pathway,wherein the coil assembly includes a transmitter winding, a first sensing winding and a second sensing winding, the first and second sensing windings being spatially periodic and out of phase with respect to each other and in stationary proximity with the transmitter winding,the transmitter winding being deposed for electromagnectic coupling of flux generated thereby to the first and to the second sensing windings, such that motion of a coupling element carried by a carriage on the pathway varies inductive coupling between the transmitter winding and the first and second sensing windings so as to passively generate therein signals that vary with a position of the carriage along the pathway. 39. The pathway based system of claim 38, wherein the first and second sensing windings have the same spatial period, yet, are offset in phase with respect to a direction of motion of the carriage along the pathway. 40. The system of claim 39, wherein the transmitter winding has a period that is a multiple of periods of the first and second sensing windings with respect to a direction of motion of the carriage along the pathway. 41. The system of claim 38 or 39 wherein the first and second sensing windings have periods that are integer multiples of a period of the transmitter winding with respect to a direction of motion of the carriage along the pathway. 42. A pathway system for determining position of a carriage traveling along a pathway, the system comprisinga coil assembly including first and second sensing windings proximate to each other, each sensing winding having an identical spatial period and being repetitively disposed along the pathway,a transmitter winding extending along the pathway for generating a magnetic field along the pathway, anda transducer assembly coupled to the carriage, the transducer assembly comprising a resonant current loop positioned to induce position-indicating signals in the first and second sensing windings that vary with a position of the carriage along the pathway. 43. The pathway system of claim 42, wherein the resonant current loop generates a power signal for use with respect to the carriage. 44. The pathway system of claim 42, wherein a tuning of the resonant current loop is varied, modulating the position-indicating signals induced in the first and second sensing windings. 45. The pathway system according to claim 44, wherein the further signal identifies the carriage. 46. The pathway system of claim 42, wherein the resonant current loop is lithographically formed on a circuit board. 47. A system for determining position of a carriage, vehicle or the like moving along a pathway, wherein the system comprisesa coil assembly extending along and being securable against movement with respect to the pathway, wherein the coil assembly includes a current winding that constitutes a linear motor for operatively driving a carriage along the pathwaya first and a second sensing winding being periodic and out of phase with respect to each other, the sensing windings disposed in stationary proximity to the current winding for electromagnetic signal coupling from the current winding to the sensing windingssuch that passage of a coupling element over the coil assembly varies the electromagnetic signal coupling so as to generate signals in the first and second windings that vary with position of the coupling element to indicate position along the pathway. 48. The pathway system of claim 47, further comprising a coupling element adapted for moving with a carriage along the sensing windings so that as the carriage moves signals coupled to the sensing windings indicate position of the carriage. 49. A system for determining position of a carriage or the like moving along a pathway, wherein the system comprisesa coil assembly extending along and being securable against movement with respect to the pathway, wherein the coil assembly includes a current winding that constitutes a linear motor for operatively driving a carriage along the pathwayfirst and second sensing windings proximate to each other, each sensing winding having an identical spatial period and being repetitively disposed along the pathway,a transducer assembly configured for mounting on the carriage to passively receive magnetic energy from the current winding in a resonant current loop, the loop being positioned to induce position-indicating signals in the first and second sensing windings as the carriage carries the transducer along the pathway, thereby passively providing an electrical signal indicative of position. 50. A method for determining position of a carriage, vehicle or the like moving along a pathway, such method comprising the steps ofproviding a coil assembly configured for extending along and being securable against movement with respect to the pathwaywherein the step of providing the coil assembly includes providing a transmitter winding, a first sensing winding and a second sensing winding, the transmitter winding being disposed in stationary proximity to the transmitter winding for electromagnetic coupling of a signal therein to the first and to the second sensing windings, the first and second sensing windings being periodic and out of phase with respect to each othermounting a coupling assembly to a carriage positioned such that as the carriage moves along the pathway, the coupling assembly varies coupling from the transmitter winding to the first and second sensing windings so as to passively generate signals it the first and second windings that indicate position of the carriage along the pathway without requiring an active power source on the carriage. 51. A method for determining position of a carriage or the like moving along a pathway in a system having a current winding fixedly extending along the pathway that constitutes a linear motor for operatively driving the carriage along the pathway, such method comprising the steps ofproviding a first and a second sensing winding proximate to each other, each sensing winding having an identical spatial period and being repetitively disposed along the pathwayoperating the current winding to generate magnetic flux, andmounting a transducer on the carriage to passively receive the flux in a resonant current loop, the loop being positioned to induce phased position-indicating signals in the first and second sensing windings as the carriage carries the transducer along the pathway thereby passively providing an electrical signal indicative of carriage position.