Adaptive multichannel locator system for multiple proximity detection

• US 7,741,848 B1
• Filed: 09/13/2007
• Issued: 06/22/2010
• Est. Priority Date: 09/18/2006
• Status: Active Grant

• Current Assignee: Seescan, Inc.
• Original Assignee: Seektech Inc.
• Inventors: Merewether, Ray, Olsson, Mark S., Martin, Michael J., Stuart, Paul G.
• Primary Examiner(s): WHITTINGTON, KENNETH
• Application Number:
  US11/854,694
• Time in Patent Office: 1,013 Days
• Field of Search: 324/67, 324/326, 324/327, 324/329, 340/551, 702/65, 702/75, 702/76
• US Class Current: 324/326
• CPC Class Codes: G01V 3/08 operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices with electromagnetic waves G01V3/12
• CPC Class Codes: G01V 3/081 the magnetic field is produced by the objects or geological structures characterised by the method of magnetic field measurement G01R33/00
• CPC Class Codes: G01V 3/10 using induction coils
• CPC Class Codes: G01V 3/101 by measuring the impedance of the search coil; by measuring features of a resonant circuit comprising the search coil measuring impedance or characteristics derived therefrom G01R27/00, e.g. quality factor G01R27/26
• CPC Class Codes: G01V 3/102 by measuring amplitude
• 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 3/107 using compensating coil or loop arrangements
• CPC Class Codes: G01V 3/15 specially adapted for use during transport, e.g. by a person, vehicle or boat
• CPC Class Codes: G01V 3/16 specially adapted for use from aircraft G01V3/165 - G01V3/175 take precedence

Abstract

A man-portable locator system for locating buried or otherwise inaccessible pipes, conduits, cables, wires and inserted transmitters using detector arrays and stochastic signal processing and similar techniques to analyze and display multiple target objects at differing frequencies in a layered user interface (UI). For example, the locator UI may be adapted to present a target plurality sorted by proximity of target conductor to the locator operator together with other useful information specifying the multiple objects, frequencies and changes in the subterranean landscape by means of a useful combination of graphical, numeric and acoustic representations.

Claims

1. A man-portable locator system for locating hidden objects each characterized by an electromagnetic (EM) field emission, the system comprising:

a first EM sensor assembly for detecting three orthogonal EM field emission components and producing a set of three time-varying sensor signals {S_x(t), S_y(t), S_z(t)}, including three substantially-identical EM field sensors each having a radial centroid defining a sensing axis, and a structure for supporting the three substantially-identical EM field sensors such that the corresponding sensing axes are disposed in substantial mutual orthogonality;

a second EM sensor assembly, coupled to and spaced apart from the first EM sensor assembly, for detecting the three orthogonal EM field emission components and producing a second set of three time-varying sensor signals {S′

_x(t), S′

_y(t), S′

_z(t)};

an analog-to-digital converter (ADC) coupled to the EM sensor assemblies for producing a sequence of digital samples {D(t)} corresponding to time-varying sensor signals;

a processor coupled to the sequence of digital samples {D(t)} for producing a spectrum signal {P(f)} representing the sensor signal energy within each of a first plurality B of predetermined frequency intervals responsive to the sequence of digital samples {D(t)};

at least one adaptive filter coupled to the processor for producing a filter output signal F(t) representing the sensor signal energy within each of a second plurality N<

B of predetermined frequency intervals selected responsive to the spectrum signal {P(f)};

a proximity detector coupled to the processor for producing a proximity signal d(f) for each of a third plurality B′

≦

B of predetermined frequency intervals representing the hidden object proximity to one of the EM sensor assemblies; and

a user interface (UI) coupled to the processor for indicating the presence of one or more hidden objects responsive to the filter output signal F(t).

2. The locator system of claim 1 wherein:

the spectrum signal {P(f)} represents the Fast Fourier Transform (FFT) of digital samples {D(t)}; and

each predetermined frequency interval corresponds to a FFT frequency bin.

3. The locator system of claim 1 and further comprising:

in the UI, a Graphical UI (GUI) image processor for generating a target image representing an EM field emission signal; and

a display for displaying a plurality of target images in a layered stack, wherein the image representing the EM field emission signal having the highest proximity signal value is automatically moved to the uppermost layer in the layered stack.

4. The locator system of claim 1 and further comprising:

a second filter coupled to the processor for producing a filter output signal F′

(t) representing the sensor signal energy within each of a preselected third plurality M<

B of the predetermined frequency intervals disposed at frequencies substantially different from the frequencies of the second plurality N<

B of the predetermined frequency intervals.

5. The locator system of claim 1 and further comprising:

a notch filter having a stop-band for producing a filter output signal F_N(t) representing the sensor signal S(t) after attenuation of one or more predetermined frequency components;

a cross-correlator coupled to the filter output signal F_N(t) for producing a filtered data signal representing a filtered B-field vector at the sensor assembly; and

in the UI, means for indicating the presence of the hidden object responsive to the filtered data signal.

6. The locator system of claim 5 and further comprising:

in the cross-correlator, means for processing a plurality K of the time-varying sensor signals {S_k(t)}, including a matrix accumulator for producing a data signal representing a K by K covariance matrix A_T corresponding to the covariances of the time-varying sensor signals {S_k(t)} over a selected time interval, wherein covariance matrix A_T is characterized by a plurality K of eigenvalues {λ

_k} and associated eigenvectors {V_k}; and

calculating means for producing a data signal representing a B-field vector at the sensor assembly, wherein the B-field vector corresponds to the eigenvector V₁ associated with the largest λ

₁ of the eigenvalues {λ

_k}.

7. The locator system of claim 1 and further comprising:

a first bandpass filter for producing a filter output signal F_S(t) representing a sensor signal S(t) component at a predetermined sonde frequency;

a second bandpass filter for producing a filter output signal F_T(t) representing a sensor signal S(t) component at a first predetermined utility line tracing frequency; and

in the UI, means responsive to the filter output signals F_S(t) and F_T(t) for indicating the presence of at least one selected from a group consisting essentially of a sonde and a utility line.

8. The locator system of claim 7 and further comprising:

a third bandpass filter for producing a filter output signal F_U(t) representing a sensor signal S(t) component at a selectable utility line tracing frequency; and

in the UI, means responsive to the filter output signals F_S(t), F_T(t) and F_U(t) for simultaneously indicating the presence of a sonde and two different utility lines.

9. The locator system of claim 1 and further comprising:

a cross-correlator for processing a plurality K of the time-varying sensor signals {S_k(t)}, including

a matrix accumulator for producing a data signal representing a K by K covariance matrix A_T corresponding to the covariances of the time-varying sensor signals {S_k(t)} over a selected time interval, wherein covariance matrix A_T is characterized by a plurality K of eigenvalues {λ

_k} and associated eigenvectors {V_k} and

calculating means for producing a data signal representing a B-field vector at the sensor assembly, wherein the B-field vector corresponds to the eigenvector V₁ associated with the largest λ

₁ of the eigenvalues {λ

_k}; and

in the UI, means for indicating the presence of the hidden object responsive to the data signal.

10. The locator system of claim 1 and further comprising:

in the UI, a Graphical UI (GUI) image processor for generating a target image representing an EM field emission signal; and

a display for displaying a plurality of target images in a layered stack.

11. The locator system of claim 1 and further comprising:

a variable time-constant filter coupled to the processor for producing a filter output signal F(t) and having means for increasing the filter bandwidth to decrease the response time and for decreasing the filter bandwidth to increase the response time;

signal processor coupled to the filter output signal F(t) for producing a quality signal Q(t) representing the signal-to-noise (SNR) of filter output signal F(t); and

means for adjusting the filter time constant responsive to the quality signal Q(t).

12. The locator system of claim 1 wherein the filter has a time constant, the system further comprising:

a sampling clock for producing an ADC clock signal having a clock rate; and

wherein the filter time constant is adjusted by changing the ADC clock rate.

13. The locator system of claim 1 and further comprising:

a first bandpass filter for producing a filter output signal F₁(t) representing a first harmonic of the sensor signal S(t);

a second bandpass filter for producing a filter output signal F₂(t) representing a second harmonic of the sensor signal S(t);

a signal combiner for producing a composite signal F_C(t) representing the first and second filter output signals F₁(t) and F₂(t); and

in the UI, means for indicating the presence of the hidden object responsive to the composite signal F_C(t).

14. The locator system of claim 1 and further comprising:

a notch filter having a stop-band for producing a filter output signal F_N(t) representing the sensor signal S(t) after attenuation of one or more predetermined frequency components;

a broadband filter having a pass-band overlapping the notch filter stop-band for producing a filter output signal F_B(t) representing the sensor signal S(t) frequency components in a predetermined frequency band;

a signal combiner for producing a composite signal F_N(t) representing the notch and broadband filter output signals F_N(t) and F_B(t); and

in the UI, means for indicating the presence of the hidden object responsive to the composite signal F_N(t).

15. A man-portable locator system for locating hidden objects each characterized by an electromagnetic (EM) field emission, the system comprising:

at least one EM sensor assembly for detecting an EM field emission and producing a time-varying sensor signal S(t);

an analog-to-digital converter (ADC) coupled to the EM sensor assembly for producing a sequence of digital samples {D(t)} corresponding to the time-varying sensor signal S(t);

a processor coupled to the sequence of digital samples {D(t)} for producing a spectrum signal {P(f)} representing the sensor signal S(t) energy within each of a first plurality B of predetermined frequency intervals responsive to the sequence of digital samples {D(t)};

a first bandpass filter for producing a filter output signal F_S(t) representing a sensor signal S(t) component at a predetermined sonde frequency;

a second bandpass filter for producing a filter output signal F_T(t) representing a sensor signal S(t) component at a first predetermined utility line tracing frequency; and

a third bandpass filter for producing a filter output signal F_U(t) representing a sensor signal S(t) component at a selectable utility line tracing frequency;

an adaptive filter processor coupled to at least one filter for producing at least one filter output signal F(t) representing the sensor signal energy within each of a second plurality N<

B of predetermined frequency intervals selected responsive to the spectrum signal {P(f)};

a proximity detector coupled to the processor for producing a proximity signal d(f) for each of a third plurality B′

≦

B of predetermined frequency intervals representing the EM field emission proximity to one of the EM sensor assemblies; and

a user interface (UI) including

a Graphical UI (GUI) image processor for generating a target image representing an EM field emission signal, and

a GUI display for displaying a plurality of target images in a layered stack including first means responsive to the filter output signals F_S(t), F_T(t) and F_U(t) for simultaneously indicating the presence of a sonde and two different utility lines.

16. The locator system of claim 15 further comprising:

in the GUI display, second means for automatically switching from a line-tracing target image display to a sonde target image display responsive to detection of a predetermined sonde frequency.

17. The locator system of claim 15 further comprising:

in the GUI display, a third means for automatically moving the image representing the EM field emission signal having the highest proximity signal value to the uppermost layer of the layered stack.

18. A man-portable locator system for locating hidden objects each characterized by an electromagnetic (EM) field emission, the system comprising:

at least one EM sensor assembly for detecting an EM field emission and producing a time-varying sensor signal S(t);

an analog-to-digital converter (ADC) coupled to the EM sensor assembly for producing a sequence of digital samples {D(t)} corresponding to time-varying sensor signal S(t);

a processor coupled to the sequence of digital samples {D(t)} for producing a spectrum signal {P(f)} representing the sensor signal S(t) energy within each of a first plurality B of predetermined frequency intervals responsive to the sequence of digital samples {D(t)};

at least one adaptive filter coupled to the processor for producing a filter output signal F(t) representing the sensor signal energy within each of a second plurality N<

B of predetermined frequency intervals selected responsive to the spectrum signal {P(f)};

a user interface (UI) coupled to the processor for indicating the presence of one or more hidden objects responsive to the filter output signal F(t)m;

a notch filter having a stop-band for producing a filter output signal F_N(t) representing the sensor signal S(t) after attenuation of one or more predetermined frequency components;

a cross-correlator coupled to the filter output signal F_N(t) for producing a filtered data signal representing a filtered B-field vector at the sensor assembly; and

in the UI, means for indicating the presence of the hidden object responsive to the filtered data signal.

19. A man-portable locator system for locating hidden objects each characterized by an electromagnetic (EM) field emission, the system comprising:

at least one EM sensor assembly for detecting an EM field emission and producing a time-varying sensor signal S(t);

an analog-to-digital converter (ADC) coupled to the EM sensor assembly for producing a sequence of digital samples {D(t)} corresponding to time-varying sensor signal S(t);

a processor coupled to the sequence of digital samples {D(t)} for producing a spectrum signal {P(f)} representing the sensor signal S(t) energy within each of a first plurality B of predetermined frequency intervals responsive to the sequence of digital samples {D(t)};

at least one adaptive filter coupled to the processor for producing a filter output signal F(t) representing the sensor signal energy within each of a second plurality N<

B of predetermined frequency intervals selected responsive to the spectrum signal {P(f)};

a user interface (UI) coupled to the processor for indicating the presence of one or more hidden objects responsive to the filter output signal F(t)m;

a first bandpass filter for producing a filter output signal F_S(t) representing a sensor signal S(t) component at a predetermined sonde frequency;

a second bandpass filter for producing a filter output signal F_T(t) representing a sensor signal S(t) component at a first predetermined utility line tracing frequency; and

in the UI, means responsive to the filter output signals F_S(t) and F_T(t) for indicating the presence of at least one selected from a group consisting essentially of a sonde and a utility line.

20. A man-portable locator system for locating hidden objects each characterized by an electromagnetic (EM) field emission, the system comprising:

at least one EM sensor assembly for detecting an EM field emission and producing a time-varying sensor signal S(t);

an analog-to-digital converter (ADC) coupled to the EM sensor assembly for producing a sequence of digital samples {D(t)} corresponding to time-varying sensor signal S(t);

a processor coupled to the sequence of digital samples {D(t)} for producing a spectrum signal {P(f)} representing the sensor signal S(t) energy within each of a first plurality B of predetermined frequency intervals responsive to the sequence of digital samples {D(t)};

at least one adaptive filter coupled to the processor for producing a filter output signal F(t) representing the sensor signal energy within each of a second plurality N<

B of predetermined frequency intervals selected responsive to the spectrum signal {P(f)};

a user interface (UI) coupled to the processor for indicating the presence of one or more hidden objects responsive to the filter output signal F(t)m;

a first bandpass filter for producing a filter output signal F₁(t) representing a first harmonic of the sensor signal S(t);

a second bandpass filter for producing a filter output signal F₂(t) representing a second harmonic of the sensor signal S(t);

a signal combiner for producing a composite signal F_C(t) representing the first and second filter output signals F₁(t) and F₂(t); and

in the UI, means for indicating the presence of the hidden object responsive to the composite signal F_C(t).

21. A man-portable locator system for locating hidden objects each characterized by an electromagnetic (EM) field emission, the system comprising:

at least one EM sensor assembly for detecting an EM field emission and producing a time-varying sensor signal S(t);

an analog-to-digital converter (ADC) coupled to the EM sensor assembly for producing a sequence of digital samples {D(t)} corresponding to time-varying sensor signal S(t);

a processor coupled to the sequence of digital samples {D(t)} for producing a spectrum signal {P(f)} representing the sensor signal S(t) energy within each of a first plurality B of predetermined frequency intervals responsive to the sequence of digital samples {D(t)};

at least one adaptive filter coupled to the processor for producing a filter output signal F(t) representing the sensor signal energy within each of a second plurality N<

B of predetermined frequency intervals selected responsive to the spectrum signal {P(f)};

a user interface (UI) coupled to the processor for indicating the presence of one or more hidden objects responsive to the filter output signal F(t)m;

a notch filter having a stop-band for producing a filter output signal F_N(t) representing the sensor signal S(t) after attenuation of one or more predetermined frequency components;

a broadband filter having a pass-band overlapping the notch filter stop-band for producing a filter output signal F_B(t) representing the sensor signal S(t) frequency components in a predetermined frequency band;

a signal combiner for producing a composite signal F_N(t) representing the notch and broadband filter output signals F_N(t) and F_B(t); and

in the UI, means for indicating the presence of the hidden object responsive to the composite signal F_N(t).