System and method for detecting an underground object using magnetic field sensing

• US 7,038,454 B2
• Filed: 04/29/2002
• Issued: 05/02/2006
• Est. Priority Date: 12/30/1997
• Status: Expired due to Fees

• Current Assignee: Charles Machine Works Inc (Toro)
• Original Assignee: Charles Machine Works Inc (Toro)
• Inventors: Gard, Michael F., Jin, Jian
• Primary Examiner(s): PATIDAR, JAY M
• Application Number:
  US10/134,985
• Publication Number:
  US 20020190718A1
• Time in Patent Office: 1,464 Days
• Field of Search: 324/326, 324/346, 175/45
• US Class Current: 324/326
• CPC Class Codes: E21B 44/00 Automatic control systems specially adapted for drilling operations, i.e. self-operating systems which function to carry out or modify a drilling operation without intervention of a human operator, e.g. computer-controlled drilling systems; Systems specially adapted for monitoring a plurality of drilling variables or conditions
• CPC Class Codes: E21B 47/092 by detecting magnetic anomalies
• 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

Abstract

A system and method use magnetic field sensing to detect underground objects for strike avoidance. The system detects magnetic field components for both passive distortions in the magnetic field indicative of a ferromagnetic object and active magnetic fields that are impressed on an object by a signal generator. A detection module has a magnetic sensor assembly that detects the magnetic field components. The magnetic field component data is transferred through a multiplexer to an analog/digital converter to a processor. Pitch angle data from a pitch sensor and roll angle data from a roll sensor also may be transferred to the processor. The data is processed by the processor to determine the orientation of the detection module with respect to the object. The detection module may be installed in an underground boring tool or a trenching assembly.

Claims

1. A control system for use in boring comprising:

a detection module comprising;

a magnetic sensor assembly adapted to detect magnetic field components generated at a filamentary object; and

a processor adapted to receive the magnetic field components from the magnetic sensor assembly, to process the magnetic field components for amplitude and phase relationships at a single location to determine orientation of the magnetic sensor assembly relative to the object, and to communicate orientation information; and

a steering system adapted to receive the orientation information from the processor and to maneuver a boring tool in response to the orientation information from the processor.

2. The control system of claim 1 wherein the magnetic field components are representative of an alternating magnetic field.

3. The control system of claim 2 wherein the filamentary object is positioned on the surface of the ground.

4. The control system of claim 2 wherein the detection module is located in a boring tool.

5. The control system of claim 4 wherein the processor is located in a boring tool.

6. The control system of claim 5 wherein the steering system is located in a boring machine.

7. The control system of claim 6 wherein the orientation information is communicated to the steering system by telemetry.

8. The control system of claim 4 wherein the processor is located in a tracker.

9. The control system of claim 8 wherein magnetic field components are communicated to the processor by telemetry.

10. The control system of claim 2 wherein the magnetic sensor assembly is adapted to detect magnetic field components in each of three mutually orthogonal directions, representing a horizontal magnetic field component, a vertical magnetic field component, and z-axis magnetic field component.

11. The control system of claim 10 wherein the steering system maneuvers the boring tool to maintain a desired relative orientation of the boring tool with respect to the filamentary object.

12. The control system of claim 11 wherein the desired orientation comprises radial separation between the filamentary object and the boring tool.

13. The control system of claim 11 wherein the desired orientation comprises, in a plane normal to the filamentary object, a desired ratio of an amplitude of the horizontal magnetic field component to an amplitude of the vertical magnetic field component.

14. The control system of claim 11 wherein the desired orientation comprises, in a plane normal to the filamentary object, a desired phase relationship between an amplitude of the horizontal magnetic field component and an amplitude of the vertical magnetic field component.

15. The control system of claim 11 wherein a source of the alternating magnetic field at the object is connected to the processor to provide a phase reference.

16. The control system of claim 15 wherein the desired orientation comprises, in a plane normal to the filamentary object, a desired ratio of an amplitude of the horizontal magnetic field component to an amplitude of the vertical magnetic field component.

17. The control system of claim 15 wherein the desired orientation comprises, in a plane normal to the filamentary object, a desired phase relationship between an amplitude of the horizontal magnetic field component and an amplitude of the vertical magnetic field component.

18. A method for maintaining a detection module in a known orientation with an object comprising:

measuring magnetic field components from a filamentary object;

processing the magnetic field components for magnitude and phase relationships at a single location to determine an orientation of the detection module relative to the filamentary object;

communicating orientation information to a steering system; and

maneuvering a boring tool in response to the orientation information.

19. The method of claim 18 wherein the magnetic field components are representative of an alternating magnetic field.

20. The method of claim 19 wherein the magnetic field components are measured in each of three mutually orthogonal directions, representing a horizontal magnetic field component, a vertical magnetic field component, and z-axis magnetic field component.

21. The method of claim 20 wherein the boring tool is maneuvered to maintain a desired relative orientation of the boring tool with respect to the filamentary object.

22. The method of claim 21 wherein the desired orientation comprises radial separation between the filamentary object and the boring tool.

23. The method of claim 21 wherein the desired orientation comprises, in a plane normal to the filamentary object, a desired ratio of an amplitude of the horizontal magnetic field component to an amplitude of the vertical magnetic field component.

24. The method of claim 21 wherein the desired orientation comprises, in a plane normal to the filamentary object, a desired phase relationship between an amplitude of the horizontal magnetic field component and an amplitude of the vertical magnetic field component.

25. The method of claim 21 further comprising determining the phase of a source of the alternating magnetic field at the object to provide a phase reference.

26. The method of claim 25 wherein the desired orientation comprises, in a plane normal to the filamentary object, a desired ratio of an amplitude of the horizontal magnetic field component to an amplitude of the vertical magnetic field component.

27. The method of claim 25 wherein the desired orientation comprises, in a plane normal to the filamentary object, a desired phase relationship between an amplitude of the horizontal magnetic field component and an amplitude of the vertical magnetic field component.