Low frequency magnetic induction positioning system and method

• US 9,086,469 B2
• Filed: 03/11/2013
• Issued: 07/21/2015
• Est. Priority Date: 05/08/2012
• Status: Active Grant

• Current Assignee: Centrak Incorporated (Halma PLC)
• Original Assignee: Awarepoint Corporation
• Inventors: Perkins, Matthew R., Truscott, Anthony, Geng, Wei
• Primary Examiner(s): Holloway, III, Edwin
• Application Number:
  US13/792,195
• Publication Number:
  US 20140191897A1
• Time in Patent Office: 862 Days
• Field of Search: 340/8.1, 340/539.13, 324/207.15
• US Class Current: 1/1
• CPC Class Codes: G01B 11/14 for measuring distance or clearance between spaced objects or spaced apertures G01B11/26 takes precedence; rangefinders G01C3/00
• CPC Class Codes: G01S 3/02 using radio waves
• CPC Class Codes: G01S 3/80 using ultrasonic, sonic or infrasonic waves
• CPC Class Codes: G01S 5/12 by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial
• CPC Class Codes: G07C 9/28 the pass enabling tracking or indicating presence

Abstract

A method and system for determining a real-time location of an object or person in a facility using low frequency magnetic induction positioning is disclosed herein. Each of the plurality of low frequency receivers is configured to receive a signal packet from a low-frequency magnetic induction transmitter, decode the signal packet, and estimate a distance from the low-frequency magnetic induction transmitter to the low-frequency receiver based on the decoded signal packet.

Claims

1. A method for determining a real-time location of an object within a facility, the method comprising:

transmitting a signal packet from at least one low-frequency magnetic induction transmitter of a plurality of low-frequency magnetic induction transmitters, each of the plurality of low-frequency magnetic induction transmitters comprising at least one orthogonally oriented transmit coil, the signal packet comprising a unique transmitter identifier code and a coil orientation code;

receiving the signal packet at at least one low-frequency receiver;

decoding the signal packet at the at least one low-frequency receiver to generate a decoded signal packet data; and

estimating a distance from the at least one low-frequency magnetic induction transmitter to the at least one low-frequency receiver based on the decoded signal packet data.

2. The method according to claim 1 further comprising sending distance information to a processor, wherein the processor determines a location of an object.

3. The method according to claim 2 wherein the processor is a context aware location engine.

4. The method according to claim 1 wherein the distance drives a workflow.

5. The method according to claim 1 wherein the estimated distance provides context for at least one of an interaction, a workflow milestone and a departure.

6. The method according to claim 1 wherein the at least one low-frequency magnetic induction transmitter comprises at least one of a radiofrequency transmitter, an ultrasound transmitter and an infrared transmitter.

7. The method according to claim 1 wherein the at least one low-frequency magnetic induction transmitter comprises a WiFi transmitter, a BLUETOOTH transmitter and a ZIGBEE transmitter.

8. The method according to claim 1 wherein the estimating the distance comprises combining a received signal strength intensity for the signal packet and the coil orientation code to remove the effects of relative coil orientation;

and estimating a position of the at least one low-frequency receiver.

9. The method according to claim 1 wherein the estimating the distance comprises utilizing a link intensity estimate.

10. The method according to claim 1 further comprising transmitting a signal from the at least one low-frequency receiver to a mesh network, the mesh network comprising a plurality of sensors within a facility.

17. The system according to claim 1 wherein the at least one low-frequency magnetic induction transmitter comprises a WiFi transmitter, a BLUETOOTH transmitter and a ZIGBEE transmitter.

11. A system for determining a real-time location of an object within a facility, the system comprising:

a plurality of low-frequency magnetic induction transmitters, each of the plurality of low-frequency magnetic induction transmitters comprising at least one orthogonally oriented transmit coil, each of the plurality of low-frequency magnetic induction transmitters configured to transmit a signal packet comprising a unique transmitter identifier code and a coil orientation code; and

a plurality of low-frequency receivers, each of the plurality of low frequency receivers configured to receive the signal packet, decode the signal packet, and estimate a distance from the low-frequency magnetic induction transmitter to the low-frequency receiver based on the decoded signal packet.

12. The system according to claim 11 further comprising a processor, the processor configured to receive the distance information and determine a location of an object.

13. The system according to claim 12 wherein the processor is a context aware location engine.

14. The system according to claim 11 wherein the distance drives a workflow.

15. The system according to claim 11 wherein the estimated distance provides context for at least one of an interaction, a workflow milestone and a departure.

16. The system according to claim 11 wherein the at least one low-frequency magnetic induction transmitter comprises at least one of radiofrequency transmitter, an ultrasound transmitter and an infrared transmitter.

18. The system according to claim 11 wherein each of the plurality of low-frequency magnetic induction transmitters is configured to drive each coil with multiple power levels;

each plurality of low-frequency receivers is configured to determine an effective signal strength by correlating a number of signal packets received from each transmit coil with a corresponding power level of each of the plurality of low-frequency magnetic induction transmitters; and

a resulting value is a threshold for reception and is related to an effective RSSI.

19. The system according to claim 11 wherein each of the plurality of low-frequency magnetic induction transmitters is configured to encode both a unique device code and a transmit power level indication, and each plurality of low-frequency receivers is configured to estimate a link strength using the lowest power level indication code received from a particular low-frequency magnetic induction transmitter of the plurality of low-frequency magnetic induction transmitters.

20. The system according to claim 11 wherein the receiver has a variable gain amplifier and automatic gain control to automatically adjust a gain to maintain a constant output level, and an adjusted gain level is inversely proportional to the received signal strength and is used for RSSI calculation.

21. The system according to claim 11 wherein the combination of two or more signal packets received from two or more transmitter orientations located at a common point are combined in vector magnitude form to produce an orientation invariant signal strength.

22. The system according to claim 11 wherein each of the plurality of low-frequency magnetic induction transmitters synchronizes the signal packet transmissions to reduce over-the-air collisions.

23. The system according to claim 11 wherein each of the plurality of low-frequency magnetic induction transmitters uses motion activation to trigger signal packet transmissions by each of the plurality of low-frequency magnetic induction transmitters in an area.

24. The system according to claim 11 further comprising a plurality of sensors positioned within a facility.

25. The system according to claim 24 wherein the plurality of sensors forms a mesh network.

26. The system according to claim 25 further comprising at least one position engine in communication with the mesh network.