IR/RF locator

• US 5,917,425 A
• Filed: 12/29/1997
• Issued: 06/29/1999
• Est. Priority Date: 01/22/1996
• Status: Expired due to Term

• Current Assignee: Centrak Incorporated (Halma PLC)
• Original Assignee: WIRELESS COMMUNICATIONS PRODUCTS LLC
• Inventors: Crimmins, James W., Saulnier, James L.
• Primary Examiner(s): Zimmerman, Brian
• Assistant Examiner(s): Dalencourt, Yves
• Application Number:
  US08/999,184
• Time in Patent Office: 547 Days
• Field of Search: 340/825.49, 340/825.36, 340/825.72, 340/825.34, 340/825.54, 340/539, 340/572, 340/573.1, 340/573.4, 359/145, 359/152, 359/172
• US Class Current: 340/8.1
• CPC Class Codes: G01S 1/7038 Signal details
• CPC Class Codes: G01S 2201/02 Indoor positioning, e.g. in covered car-parks, mining facilities, warehouses
• CPC Class Codes: G07C 9/28 the pass enabling tracking or indicating presence
• CPC Class Codes: G08B 3/1083 Pager locating systems

Abstract

An infrared (IR) article or person locator system is described wherein a plurality of stationary units are distributed in zones throughout an enclosure. The article or person carries a portable device so that the infrared communication link can derive local information as to where the article or person is and an RF link is used, instead of cables, to transfer the local information to a central processor or station. In one embodiment local stationary beacons generate location codes at an IR carrier frequency and IR portable devices carry transceivers made of an IR receiver and a portable RF transmitter transmits the location code and a PIN code associated with the portable device to the central station. Techniques are described for reducing electrical power demands on the portable device'"'"'s battery while enhancing the speed with which the central station can be alerted of a change in the location of the portable device.

Claims

1. A system for determining the location and the identity of a device or person in an enclosure, comprising:

a plurality of stationary infrared transmitters distributed in various zones within the enclosure, each of said transmitters including means for generating an infrared location code signal representative of the location of the associated transmitter within the enclosure;

a plurality of portable transceivers each being formed of an infrared receiver responsive to detect infrared location code signals from stationary infrared transmitters, means for generating a PIN signal representative of the person or device with which the portable transceiver is associated, and an RF transmitter to generate bursts of an RF output signal representative of the PIN code and the detected location code signal for detection by a remote RF receiver and use at a central station.

2. The system as claimed in claim 1 wherein said stationary infrared transmitters transmit said infrared code signals in the form of frequency modulation with a substantially continuously transmitted infrared carrier and wherein said infrared receiver includes an FM receiver having a sufficient capture ratio so as to enhance the FM receivers sensitivity in discriminating between infrared signals from different infrared transmitters.

3. The system as claimed in claim 1 and further including:

transmitter control means within said portable transceiver and responsive to a received location code for refraining from sending an RF transmission to the remote RF receiver when the portable transceiver has not changed its location and for sending a said RF transmission when the portable transceiver has changed its location.

4. The system as claimed in claim 3 wherein said transmitter control means in said portable transceiver comprises:

means for storing a previously received location code signal;

means for storing a subsequent received location code signal; and

means for comparing said previous and subsequent location code signals and producing a comparison signal indicative thereof, with said comparison signal being effectively coupled to said RF transmitter for the generation of a said RF transmission when the comparison signal is indicative that the subsequent location code signal is not the same as said previous location code signal.

5. The system as claimed in claim 1 and further including:

means, within said portable transceiver, for detecting when a said infrared transmission from a stationary transmitter has not been received within a predetermined time period and producing a second code signal indicative thereof; and

means for RF transmitting said second code signal with said PIN code to said remote RF receiver.

6. The system as claimed in claim 1 wherein said RF transmitters at the portable transceivers generating said bursts of RF output signals at a common carrier frequency.

7. The system as claimed in claim 1 wherein the plurality of infrared transmitters generate respective location code signals at regular intervals and wherein said RF transmitters include means for generating said RF output signals at intervals selected to reduce Interferences between RF output signal bursts from different RF transmitters at the remote RF receiver.

8. The system as claimed in claim 1 wherein said portable transceivers each comprise an infrared detector for producing an electrical location code signal representative of the infrared code signal from a stationary infrared transmitter, storage means for storing a said pin signal, means for combining said electrical location code signal and said stored pin signal into a modulation signal, and means for modulating an RF carrier with said modulation signal.

9. The system as claimed in claim 1 wherein said RF transmitters include means for generating said RF output signals at a common carrier signal at repetition rates that are different for respective RF transmitters.

10. A method for determining the location and identity of a person or equipment within a facility comprising the steps of:

transmitting infrared location signals respectively associated with predetermined zones within the facility;

detecting the infrared location signals at portable devices associated with a person or equipment and re-transmitting the detected location signals from the portable devices in RF signal bursts;

combining the RF re-transmission of location signals with personal identification code signals respectively associated with individual ones of the portable devices;

whereby a determination can be made at a remote location in which zone of the facility the person or equipment is located.

11. The method as claimed in claim 10 and further including the step of

delaying said RF transmission until a subsequently detected location signal is indicative of a change of the position of said portable device relative to a previously detected location signal for the portable device.

12. The method as claimed in claim 11 wherein said delaying step further includes the step of delaying said RF transmission until a said IR location signal has not been received for a predetermined interval.

13. The method as claimed in claim 10 and further comprising the steps of:

storing a previously received location signal in the portable device;

comparing a subsequently received location signal with the stored previous location signal; and

RF transmitting the subsequently received location signal with the personal identification code signals when the comparing step indicates that the subsequently received location signal is different from the previous location signal while refraining from said RF transmitting step when the comparing step indicates that the subsequent and first location signals represent the same zone.

14. The method as claimed in claim 11 and further including the steps of:

determining within a said portable device when an IR location signal has not been detected for a predetermined interval and generating a first code signal indicative thereof; and

RF transmitting said first code signal and the personal identification code signal, associated with the portable device for which a first code signal has been generated, to s aid remote location.

15. A system for generating a signal representative of the location and identity of a device or person in an enclosure, comprising:

a plurality of portable infrared transmitters distributed in the enclosure, each of said infrared transmitters including means for generating a PIN signal representative of the person or device with which the portable infrared transmitter is associated so that the infrared transmitter produces an infrared PIN code signal indicative thereof in common IR carrier frequency bursts;

a plurality of stationary transceivers distributed in various zones within the enclosure, each transceiver being formed of an infrared receiver to detect an infrared PIN code signal from a portable infrared transmitter, means for measuring and storing the signal strength of each such received IR carrier frequency bursts, means for generating a location code signal representative of the zone in which the associated stationary transceiver is located within the enclosure, and an RF transmitter to generate RF output signal bursts and representative of the detected infrared PIN signal from an infrared transmitter and the location code signal for detection by a remote RF receiver.

16. The system as claimed in claim 15 wherein said portable infrared transmitters transmit said infrared PIN signals in the form of frequency modulation with short bursts of transmitted modulated infrared carrier.

17. The system as claimed in claim 15 and further including:

transmitter control means within said stationary transceiver and responsive to a received PIN code for not sending an RF transmission to the remote RF receiver when the portable transmitter has not changed its zone location and for sending a said RF transmission when the portable transmitter has changed its zone location.

18. The system as claimed in claim 15 wherein said RF output signal bursts from the RF transmitters are at a common carrier frequency and means in said RF transmitters for generating said RF output signals at intervals selected to reduce interferences between RF output signal bursts at the remote RF receiver from different RF transmitters.

19. A system for providing a signal representative of the location and identity of a device or person in an enclosure to a central processor, comprising:

a plurality of stationary infrared transmitters distributed in the enclosure, each of said transmitters including means for repeatedly generating an infrared location code signal which is FM modulated onto an IR carrier and is representative of the location of the associated transmitter within the enclosure;

a plurality of portable transceivers each being formed of an infrared receiver having an FM receiver section so as to detect an infrared location code signal from a stationary infrared transmitter, means for generating a PIN signal representative of the person or device with which the portable transceivers are associated, means for repeatedly producing a modulation signal representative of said infrared code and said PIN signal, and an RF transmitter having means for generating an RF carrier signal and means for applying said modulation signal to modulate said RF carrier for detection by a remote RF receiver of said infrared code and said PIN signal, whereby location and identification information is remotely collected with infrared communication and transferred via RF to the central processor.

20. A system for providing a signal representative of the location and identity of a device or person in an enclosed area to a central processor, comprising:

a plurality of portable infrared transmitters distributed in the enclosure, each of said infrared transmitters including a PIN signal generator representative of the person or device with which the portable transmitter is associated so that the infrared transmitter produces an infrared PIN code signal indicative thereof;

a plurality of stationary selectively placed transceivers, each being formed of an infrared receiver responsive to detect an infrared PIN code signal from a portable infrared transmitter, means for generating a location code signal representative of the location of the associated stationary transceiver and an RF transmitter having means for generating an RF carrier signal, means for producing a modulation signal representative of the detected infrared PIN signal from an infrared transmitter and the location code signal, and means for modulating the RF carrier signal with the modulation signal for detection by a remote RF receiver, whereby location and identification information is remotely collected with infrared communication and transferred via RF to the central processor.

21. A system for determining the location and the identity of a device or person in an enclosure, comprising:

a plurality of stationary infrared transmitters distributed in various zones within the enclosure, each of said transmitters including means for generating an infrared location code packet representative of the location of the associated transmitter within the enclosure;

each of said infrared transmitters transmitting infrared location code packets in the form of frequency modulation with a substantially continuously transmitted infrared carrier and continuously repeated location code;

a plurality of portable transceivers each being formed of an infrared receiver responsive to detect infrared location code packets from stationary infrared transmitters, and wherein said infrared receiver includes an FM receiver having a sufficient capture ratio so as to enhance the receiver'"'"'s capability in isolating and selecting the stronger of incident infrared signals from different infrared transmitters;

means within the portable transceiver to enter a sleep mode during which battery current drain is significantly reduced;

an internal timer for leaving the sleep mode so as to enable the portable transceiver to receive a subsequently available infrared code packet,

means for generating a PIN code signal representative of the person or device with which the portable transceiver is associated, and an RF transmitter to generate bursts of an RF output signal representative of the PIN code and the detected location code signal for detection by a remote RF receiver and use at a central station; and

an RF transmission controller responsive to detected location code signals for determining whether an RF portable device remains in place or has changed its location;

so as to delay sending an RF transmission burst to the remote RF receiver when the portable remains in place and for sending a said RF transmission burst when the portable device has changed its location.

22. A method for determining the location and identity of a person or equipment within a facility comprising the steps of:

transmitting infrared location signals as repeated FM packets respectively associated with predetermined zones within the facility;

placing portable devices having infrared receivers periodically in idle and awakened modes during which the infrared receivers can detect location codes in incident FM location packets;

determining whether the detected location signal in an FM packet represents a change in location of the portable device;

transmitting the detected location signals from the portable devices in RF signal bursts together with personal identification code signals respectively associated with individual ones of the portable devices when a change in location of a portable device has been determined;

whereby a determination can be made at a remote location in which zone of the facility the person or equipment is located with battery powered infrared portable devices requiring low battery power drain.