Method and system for position and track determination

• US 8,525,725 B2
• Filed: 03/08/2011
• Issued: 09/03/2013
• Est. Priority Date: 03/09/2010
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Libby, Vibeke, Wenski, Troy E., Lorenz, Allen R.
• Primary Examiner(s): GREGORY, BERNARR E
• Application Number:
  US13/043,436
• Publication Number:
  US 20110221634A1
• Time in Patent Office: 910 Days
• Field of Search: 342/27, 342/28, 342/59, 342/118, 342/126, 342/146, 342/147, 342/175, 342/195, 342450-465, 342/350, 455/403, 455/422.1, 4554561-457
• US Class Current: 342/59
• CPC Class Codes: G01S 5/02 using radio waves using satellite radio beacon systems for determining position G01S19/00

Abstract

The present disclosure describes a method and system for detecting and determining the position of a target or intruder using a plurality of sensors positioned throughout a secured perimeter and a single antenna. The system of the present disclosure detects and determines the position of a target by first analyzing the return signal strength values of each of the sensors. Next, Z_values for each of the sensors are calculated. Based on the Z_values, certain sensors are selected to compute a signal strength center-of-mass location, which is then used to determine the position of the target.

Claims

1. A method for determining a target location, the method comprising:

transmitting a plurality of radio signals from a single antenna;

receiving a plurality of return signal strength indicator (RSSI) values from a plurality of sensors;

selecting one or more sensors from the plurality of sensors having certain RSSI values;

computing a signal strength center-of-mass location of the selected one or more sensors; and

determining a direction vector of the target based on the computed signal strength center-of-mass location.

2. The method of claim 1, further comprising determining a location of the target based on the direction vector of the target.

3. The method of claim 2, further comprising determining whether the target is located inside or outside of a sensor field.

4. The method of claim 2, wherein the target vector is determined based on the computed signal strength center-of-mass location, wherein the selecting one or more sensor comprises selecting two sensors with highest computed Z_values, wherein the determining the location of the target comprises determining the location of the target along the computed target vector.

5. The method of claim 2, wherein the determining the location of the target comprises determining the location of the target along using signal strength center-of-mass location of three or more sensors with highest positive Z_value.

6. The method of claim 2, further comprising:

selecting a first sensor from the plurality of sensors with a largest negative z-value;

determining a target vector between the antenna and the first sensor, wherein the selecting one or more sensors comprises selecting at least three sensors with largest positive Z_value, wherein the computing signal strength center-of-mass location comprises computing signal strength center-of-mass location of the selected at least three sensors; and

projecting the computed signal strength center-of-mass location onto the determined target vector to determine the location of the target.

7. The method of claim 1, further comprising:

computing a Z_value for each of the plurality of sensors;

wherein the _Zvalue comprises an average RSSI value of a respective sensor from the plurality of sensors minus a current RSSI value of the respective sensor divided by a standard deviation of RSSI values of the respective sensor, wherein the selecting one or more sensor comprises selecting one or more sensors based on the computed Z_value of each sensor;

determining whether the target is present based on the computed Z_value.

8. The method of claim 7, wherein determining whether the target is present further comprises:

determining whether the target is present based on a plurality of Z_values of a single sensor from the selected one or more sensors.

9. The method of claim 7, wherein determining whether the target is present further comprises:

determining whether the target is present based on Z_values of first and second sensors from the selected one or more sensors.

10. The method of claim 9, further comprising determining whether the target is located inside or outside of a sensor field by comparing the calculated Z_values of the first and second sensors with a positive Z_value threshold and a negative positive Z_value threshold.

11. A system for determining a target location, the system comprising:

a plurality of electromagnetic sensors;

an antenna configured to transmit a plurality of electromagnetic signals and to receive a plurality of return signals from a plurality of sensors; and

a processor configured to;

determine a return signal indicator (RSSI) value for each of the received plurality of return signals;

select one or more sensors from the plurality of sensors having certain RSSI values;

compute a signal strength center-of-mass location of the selected one or more sensors; and

determine a direction vector of the target based on the computed signal strength center-of-mass location.

12. The system of claim 11, wherein the processor is further configured to determine a location of the target based on the direction vector of the target.

13. The system of claim 12, wherein the processor is further configured to determine whether the target is located inside or outside of a sensor field.

14. The system of claim 12, wherein the processor is further configured to determine whether the target is present based on a plurality of Z_values of a single sensor from the selected one or more sensors.

15. The system of claim 12, wherein the processor is further configured to determine whether the target is present based on Z_values of first and second sensors from the selected one or more sensors.

16. The system of claim 15, wherein the processor is further configured to determine whether the target is located inside or outside of a sensor field by comparing the calculated Z_values of the first and second sensors with a positive Z_value threshold and a negative Z_value threshold.

17. The system of claim 12, wherein the processor is further configured to determine a target vector based on the computed signal strength center-of-mass location, select two sensors with highest computed Z_values, and determine the location of the target along the computed target vector.

18. The system of claim 12, wherein the processor is further configured to determine the location of the target along using signal strength center-of-mass location of three or more sensors with highest positive Z_value.

19. The system of claim 12, wherein the processor is further configured to:

select a first sensor from the plurality of sensors with a largest negative z-value;

determine a target vector between the antenna and the first sensor, wherein the selected one or more sensors comprises at least three sensors with largest positive Z_value, wherein the signal strength center-of-mass location is computed using locations of the selected at least three sensors; and

project the computed signal strength center-of-mass location onto the determined target vector to determine the location of the target.

20. The system of claim 11, wherein the processor is further configured to:

compute a Z_value for each of the plurality of sensors;

wherein the Z_value comprises an average RSSI value of a respective sensor from the plurality of sensors minus a current RSSI value of the respective sensor divided by a standard deviation of RSSI values of the respective sensor, wherein the one or more sensors are selected based on the computed Z_value of each sensor; and

determine whether the target is present based on the computed Z_value.

21. A computer executable program code on a non-transitory computer readable medium configured to cause a computer to:

determine a return signal strength indicator (RSSI) value for each of a plurality of return signals received at an antenna from a plurality of sensors;

select one or more sensors from the plurality of sensors having certain RSSI values;

compute a signal strength center-of-mass location of the selected one or more sensors; and

determine a location of the target based on the computed signal strength center-of-mass location.

22. The computer executable program code of claim 21, wherein the code is further configured to cause the computer to:

compute a Z_value for each of the plurality of sensors;

wherein the Z_value comprises an average RSSI value of a respective sensor from the plurality of sensors minus a current RSSI value of the respective sensor divided by a standard deviation of RSSI values of the respective sensor, wherein the one or more sensors are selected based on the computed _Zvalue of each sensor;

determine whether the target is present based on the computed Z_value.

23. The computer executable program code of claim 21, wherein the code is further configured to cause the computer to determine whether the target is located inside or outside of a sensor field.

24. The computer executable program code of claim 21, wherein the code is further configured to cause the computer to determine whether the target is present based on a plurality of Z_values of a single sensor from the selected one or more sensors.

25. The computer executable program code of claim 21, wherein the code is further configured to cause the computer to determine whether the target is present based on Z_values of first and second sensors from the selected one or more sensors.

26. The computer executable program code of claim 25, wherein the code is further configured to cause the computer to determine whether the target is located inside or outside of a sensor field by comparing the calculated Z_values of the first and second sensors with a positive Z_value threshold and a negative positive Z_value threshold.

27. The computer executable program code of claim 21, wherein the code is further configured to cause the computer to determine a target vector based on the computed signal strength center-of-mass location, select two sensors with highest computed Z_values, and determine the location of the target along the computed target vector.

28. The computer executable program code of claim 21, wherein the code is further configured to cause the computer to determine the location of the target along using the signal strength center-of-mass location of three or more sensors with highest positive Z_value.

29. The computer executable program code of claim 21, wherein the code is further configured to cause the computer to:

select a first sensor from the plurality of sensors with a largest negative z-value;

determine a target vector between the antenna and the first sensor, wherein the selected one or more sensors comprises at least three sensors with largest positive Z_value, wherein the signal strength center-of-mass location is computed using locations of the selected at least three sensors; and

project the computed signal strength center-of-mass location onto the determined target vector to determine the location of the target.