Electromagnetic target discriminator sensor system and method for detecting and identifying metal targets

• US 6,853,194 B2
• Filed: 03/20/2001
• Issued: 02/08/2005
• Est. Priority Date: 03/22/2000
• Status: Expired due to Term

• Current Assignee: Johns Hopkins University
• Original Assignee: Johns Hopkins University
• Inventors: Nelson, Carl V., Smith, Dexter G.
• Primary Examiner(s): LEDYNH, BOT L
• Application Number:
  US10/181,471
• Publication Number:
  US 20030052684A1
• Time in Patent Office: 1,421 Days
• Field of Search: 324/326, 324/329, 324/332, 324334-337
• US Class Current: 324/329
• CPC Class Codes: G01V 3/104 using several coupled or uncoupled coils G01V3/101 takes precedence
• CPC Class Codes: G01V 3/105 forming directly coupled primary and secondary coils or loops
• CPC Class Codes: G01V 3/15 specially adapted for use during transport, e.g. by a person, vehicle or boat
• CPC Class Codes: G06V 10/255 Detecting or recognising potential candidate objects based on visual cues, e.g. shapes

Abstract

A time-domain electromagnetic target discriminator (ETD) sensor system and method are provided capable of measuring a metal target'"'"'s time decay response based on the physical parameters of the metal target and its environment and for identifying the metal target. The ETD sensor system includes a pulse transmitter connected to a receiver via a data acquisition and control system. The transmitter and receiver include coil configurations for placement in proximity to a visually obscured, e.g., buried, metal target (or underground void) for inducing eddy currents within the metal target. The ETD sensor system measures the eddy current time decay response of the metal target in order to perform target recognition and classification. The identification process entails comparing the metal target'"'"'s (or, underground void or other object'"'"'s) time decay response with a library of normalized object signatures, e.g., time decay responses and other characteristics.

Claims

1. An algorithm for optimizing target characterization of a visually obscured object upon detection of said visually obscured object by a metal detector sensor system having a transmitter and a receiver, said algorithm comprising the steps of:

a. adjusting a first parameter of said metal detector sensor system and collecting a data set using the receiver;

b. analyzing the collected data set to determine at least one measurement of a time decay response corresponding to the object; and

c. adjusting a second parameter of said metal detector sensor system, collecting a data set using the receiver, and returning to step (b), if the determined at least one measurement is outside a predetermined range.

2. The algorithm according to claim 1, further comprising the steps of:

d. estimating a decay time response constant corresponding to the object; and

e. adjusting at least the first parameter based on the estimated decay time response constant.

3. The algorithm according to claim 2, wherein step (e) includes adjusting a transmitter pulse rate, a data sample window, and a digitizer sample rate of said detector based on the estimated decay time response constant, where the transmitter pulse rate is the first parameter.

4. The algorithm according to claim 2, further comprising the steps of:

f. collecting a plurality of data sets, including an object data set corresponding to the object and background data sets corresponding to non-object areas, using the receiver;

g. averaging the background data sets to obtain an average background data set; and

h. subtracting the average background data set from the object data set.

5. The algorithm according to claim 4, further comprising the steps of:

i. determining a characteristic of the object'"'"'s time decay response;

j. adjusting at least the second parameter and returning to step (f), if the characteristic is less than a predetermined threshold; and

k. adjusting at least the second parameter and returning to step (f), if the characteristic is greater than the predetermined threshold.

6. The algorithm according to claim 5, wherein the second parameter of said metal detector sensor system is a transmitter current of said sensor system.

7. The algorithm according to claim 5, wherein step (k) further includes adjusting at least the first parameter of said metal detector sensor system.

8. The algorithm according to claim 7, wherein step (k) includes adjusting a transmitter pulse rate, a data sample window, and a digitizer sample rate of said metal detector sensor system, where the transmitter pulse rate is the first parameter.

9. The algorithm according to claim 5, further comprising the step of classifying the visually obscured object, said step comprising the steps of:

l. comparing the object'"'"'s time decay response with a library of normalized time decay responses each corresponding to an object;

m. identifying a time decay response from the library approximating the object'"'"'s time decay response; and

n. determining the visually obscured object to be the object corresponding to the identified time decay response.

10. The algorithm according to claim 9, further comprising the step of appending the library by storing the object'"'"'s time decay response within the library with a corresponding description of the object.

11. The algorithm according to claim 10, wherein the library is appended in real-time.

12. The algorithm according to claim 1, wherein the first parameter of said detector is a transmitter pulse rate.

13. The algorithm according to claim 12, wherein step (a) adjusts the transmitter pulse rate to approximately 5 kHz.

14. The algorithm according to claim 1, further comprising the step of adjusting a data sample window of said detector to approximately 100 μ

s upon detection of said visually obscured object.

15. The algorithm according to claim 1, wherein the at least one measurement includes a saturation and a voltage measurement of the time decay response corresponding to the object.