Personnel monitoring tag

• US 5,745,037 A
• Filed: 06/13/1996
• Issued: 04/28/1998
• Est. Priority Date: 06/13/1996
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Corporation
• Inventors: Cox, Daniel D., Guthrie, Warren E.
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): LA, ANH V
• Application Number:
  US08/663,340
• Time in Patent Office: 684 Days
• Field of Search: 340/573, 340/574, 340/539, 340/825.72, 340/825.14, 340/825.08, 340/825.2, 455/83
• US Class Current: 340/573.4
• CPC Class Codes: G08B 21/22 responsive to presence or absence of persons
• CPC Class Codes: G08B 29/18 Prevention or correction of operating errors G08B29/02, G08B29/12 take precedence

Abstract

A method for accounting for individual persons of a plurality of persons based upon random times that occur as a function of a first specified time interval, and a random interval monitoring system that operates in accordance with the method to report information regarding the presence of both desired and undesired conditions affecting a person. The method includes a first step of transmitting information signals based upon random times from individual ones of a plurality of tags each to be worn by respective persons to at least one of at least one master transceiver and at least one transceiver. The information signals transmitted from each tag correspond to whether a tag is being worn and to certain activities or a lack thereof of sensors in electrical communication with the tag including pressure and motion sensing equivocated to actually wearing the tag.

Claims

1. A method for monitoring individual persons of a plurality of persons, comprising the steps of:

transmitting information signals at random times from individual ones of a plurality of tags to at least one master transceiver, the individual ones of the plurality of tags each to be worn by a respective person, the information signals transmitted from the individual tags corresponding to whether the tag is in use, and wherein a probability that an individual one of the plurality of tags will transmit an information signal during a period of time that none of the other ones of the plurality of tags are transmitting information signals is represented by P_tx, where;

##EQU5## and where ton represents a duration of an information signal transmission;

toff represents an average time interval between chronological information signal transmissions of interest;

n represents the number of the other ones of the plurality of tags, and m represents a number of transmissions attempted during the time period;

in response to the at least one master transceiver receiving an information signal to an associated confirmation device; and

within the confirmation device, in response to receiving an information signal from the master transceiver, confirming that the person corresponding to the tag generating the information signal is accounted for.

2. A method as set forth in claim 1, wherein the random times occur as a function of a first specified time interval.

3. A method as set forth in claim 2, wherein the random times also occur as a function of a rate at which specified events are detected by at least one sensor.

4. A method as set forth in claim 1, wherein the step of transmitting is performed to transmit the information signals from individual tags to at least one of the at least one master transceiver and at least one remote transceiver.

5. A method as set forth in claim 4, wherein for a case in which the information signals are transmitted to the at least one remote transceiver, the remote transceiver receives information signals from at least one of the plurality of tags and, in response to receiving each of the information signals, relays the signal to the master transceiver.

6. A method as set forth in claim 4, wherein the remote transceiver receives information signals from the at least one of the plurality of tags depending upon, at least in part, a position of the remote transceiver relative to that of the at least one of the plurality of tags.

7. A method as set forth in claim 4, wherein whether the individual ones of the plurality of tags transmit information signals to the master transceiver or to the remote transceiver depends upon, at least in part, positions of the individual ones of the plurality of tags relative to positions of the master transceiver and the remote transceiver.

8. A method as set forth in claim 1, wherein individual ones of the random times occur randomly during respective individual ones of sequentially occurring time intervals.

9. A method as set forth in claim 1, further comprising the step of:

detecting an occurrence or non-occurrence of a specified event affecting any of the persons wearing the tags, wherein in response thereto, the tag to be worn by an affected person transmits information signals based upon random times occurring as a function of a second specified time interval.

10. A method as set forth in claim 9, wherein at least a first one and a second one of the information signals are transmitted such that they are temporarily separated as a function of the second specified time interval, thereby indicating the detection of the specified event occurring to the affected person, and wherein the step of confirming further comprises the step of:

determining that the first one and the second one of the information signals have been received and are temporarily separated as a function of the second specified time interval, and recognizing thereafter the detection of the specified event occurring to the affected person.

11. A method as set forth in claim 10, wherein the specified event or lack thereof is at least one of pressure contact with the tag, motion, ground connection, and circuit completion.

12. A method as set forth in claim 10, wherein individual ones of the random times occur randomly during respective individual ones of sequentially occurring time intervals.

13. A method as set forth in claim 4, further comprising the step of:

within at least one of the master transceivers, the at least one remote transceiver, and the confirmation device, in response to receiving an information signal originally transmitted from an individual one of the originally transmitted from an individual one of the tags, measuring a signal strength of the received information signal to obtain a measured signal strength of the received information signal; and

based upon a difference between the measured signal strength of the received information signal and a reference signal strength, determining at least one of a displacement and a location of a person wearing the tag.

14. A method as set forth in claim 1, wherein the step of transmitting is performed using a Direct Sequence Spread Spectrum (DSSS) technique.

15. A method as set forth in claim 5, wherein the step of transmitting is performed using a Direct Sequence Spread Spectrum (DSSS) technique.

16. A method as set forth in claim 1, wherein each individual one of the plurality of tags transmits information signals independently from other ones of the plurality of tags, thereby limiting a probability that the master transceiver will receive more than one information signal simultaneously.

17. A method as set forth in claim 1, further comprising the steps of:

at individual ones of the plurality of tags;

in response to transmitting a first one of the information signals, switching to a receive mode of operation for a predetermined time interval; and

in response to an expiration of the predetermined time interval, switching to a transmit mode of operation by which a second one of the information signals is transmitted.

18. A method as set forth in claim 17 wherein in response to the at least one master receiver receiving a first information signal from any one of the plurality of tags, the master receiver performs the steps of:

determining a frequency of the received first information signal; and

transmitting a response signal to the tag from which the first information signal was received such that the tag receives the response signal during the predetermined time interval.

19. A method as set forth in claim 18, wherein the response to receiving the response signal, the tag error checks the response signal, whereafter the tag transmits a signal to the master receiver indicating whether or not an error has been detected in the response signal.

20. A monitoring system having a self monitor to verify usage, the system comprising:

a housing wearable by a person;

a transmitter disposed within the housing;

a pressure sensor in electrical communication with the transmitter and disposed within the housing to extend therefrom and be in contact with the person when the housing is worn to thereby impose pressure on the sensor and create an electrical signal, said pressure sensor communicating to the transmitter a first electrical signal comprising the presence or absence of said pressure;

a motion sensor in electrical communication with the transmitter and disposed within the housing to detect motion thereof, said motion sensor detect motion thereof, said motion sensor communicating to the transmitter a second electrical signal comprising the presence or absence of said motion;

a ground connection sensor in electrical communication with the transmitter and disposed within the housing, said ground connection sensor having a ground connector leading therefrom and attachable to a ground site, said ground site having a ground connection confirmation signal transferable through the ground connector to the ground connection sensor to detect ground connection of the device and communicate to the transmitter a third electrical signal comprising the presence or absence of said ground connection; and

at least one receiver capable of receiving transmissions of pressure, motion, and ground connection information transmitted by the transmitter.

21. A monitoring system as claimed in claim 20 wherein the housing wearable by a person is adapted to be worn on a wrist.

22. A monitoring system as claimed in claim 21 wherein the housing is attachable to the person with a wrist strap.

23. A monitoring system as claimed in claim 20 wherein a plurality of receivers are respectively situated at a plurality of sites.

24. A monitoring system as claimed in claim 20 wherein the ground connector comprises two wires disposed between the ground site and the ground connection sensor.

25. A monitoring system as claimed in claim 24 wherein the ground connector has therein a resistor and the ground connection confirmation signal is resistance by the resistor of an electrical signal transferred from the ground site through the ground connector.

26. A monitoring system as claimed in claim 20 wherein the motion sensor comprises a switch normally in a closed circuit configuration and open for brief intervals during movement.

27. A personal monitor having a self monitor to verify usage, the monitor comprising:

a housing wearable by a person;

a transmitter disposed within the housing;

a pressure sensor in electrical communication with the transmitter and disposed within the housing to extend therefrom and be in contact with the person when the housing is worn to thereby impose pressure on the sensor and create an electrical signal, said pressure sensor communicating to the transmitter a first electrical signal comprising the presence or absence of said pressure;

a motion sensor in electrical communication with the transmitter and disposed within the housing to detect motion thereof, said motion sensor communicating to the transmitter a second electrical signal comprising the presence or absence of said motion; and

a ground connection sensor in electrical communication with the transmitter and disposed within the housing, said ground connection sensor having a ground connector leading therefrom and attachable to a ground site, said ground site having a ground connection confirmation signal transferable through the ground connector to the ground connection sensor to detect ground connection of the device and communicate to the transmitter a third electrical signal comprising the presence or absence of said ground connection.