MOLE GUIDANCE SYSTEM

• US 3,589,454 A
• Filed: 12/27/1968
• Issued: 06/29/1971
• Est. Priority Date: 12/27/1968
• Status: Expired due to Term

• Current Assignee: James C. Coyne
• Original Assignee: James C. Coyne
• Inventors: Coyne, James C.
• Application Number:
  US04/792,893
• Time in Patent Office: 914 Days
• US Class Current: 340/853.5
• CPC Class Codes: E21B 7/04 Directional drilling
• CPC Class Codes: E21B 7/26 Drilling without earth removal, e.g. with self-propelled burrowing devices E21B7/30 takes precedence

Abstract

A subterranean missile is equipped with three mutually orthogonal coils in its body and a fourth suitably fixed in an articulatable steering member. The missile is guided along any desired underground trajectory defined with reference to a coordinate system including the plane of a dipole-quadrupole antenna system laid on the ground above. Voltages induced in the noncenterline body coils are used in a closed feedback loop to maintain the resultant magnetic field circularly polarized at the mole location. Heading errors are then revealed as a voltage phasor on the centerline coil. Rotation of the steering member sufficiently to bring the voltage induced in its coil into phase with the centerline coil voltage also aligns the steering member such that its articulation will reduce the heading error to zero. Any new trajectory may be defined as a suitable new voltage added to the centerline coil voltage.

Claims

1. A method for controlling the heading of a missilelike burrowing device having a longitudinal axis, within a soil bulk comprising the steps of:

generating in said bulk a rotating magnetic vector that bears a known geometric relationship to a desired trajectory with respect to which said heading is to be controlled, detecting the phase angle of said vector when it aligns with the device longitudinal axis, and manipulating a steEring member that is movably connected to the mole to an attitude of known relation to said phase angle such that the new device trajectory will include a heading direction that is perpendicular to said magnetic vector.

2. A method for controlling the heading of a missilelike burrowing device having a longitudinal axis, with respect to a desired trajectory, comprising the steps of:

generating a rotating magnetic field vector at the mole location, said vector bearing a known geometric relationship to said trajectory, detecting the phase difference between signals induced by said vector in two magnetometers whose sensitive axes lie respectively along the device longitudinal axis, and selectively fixed within a steering member that is movably connected to the mole, and manipulating said steering member until said phase difference is a specified value corresponding to a steering attitude that will bring said mole into said desired trajectory.

3. A heading control method pursuant to claims 1 or 2, wherein said vector generating step comprises generating a circularly polarized field vector.

4. A heading control method pursuant to claims 1 or 2, wherein said generating step further comprises generating a circularly polarized magnetic field;

and said method comprises the further steps of generating a substantially sinusoidal signal having a magnitude and phase proportional to polar coordinates of a specified target point, adding said phasor to the induced voltage phasor of said longitudinal magnetometer, and adjusting the resulting phasor by a factor proportional to the present device position, thereby specifying a new device trajectory.

5. A heading control system for a steerable, missilelike burrowing device operating within a soil bulk comprising:

means for generating a rotating magnetic field vector at the device location, a first magnetometer mounted with its sensitive axis substantially coincident with the device longitudinal axis, a second magnetometer having its sensitive axis mounted in a predetermined orientation within a positionable steering surface, means for detecting the phase difference between the voltages induced by said rotating field in said magnetometers, means for positioning said steering surface to reduce said phase difference to a specified value, and means for affecting a steering attitude in said steering surface such as maintains said phase difference at said specified value.

6. A heading control system pursuant to claim 5, wherein said generating means generates a circularly polarized magnetic field at the device location.

7. For a missilelike burrowing device having a centerline axis and a surface placeable into a steering attitude with respect to said axis, a guidance system comprising in combination:

means for generating and maintaining at the mole location a circularly polarized magnetic field whose rotating vector is perpendicular to a reference trajectory;

means for detecting the phase of first signals developed by said field in the direction of said centerline axis;

means for detecting the phase of second signals developed by said field in the direction of the present permissible steering attitude of said surface;

means for rotating said surface about said centerline to bring said signals into phase; and

means for thereafter placing said surface into a steering attitude such as maintains said signals in phase, whereby mole heading errors with respect to said reference trajectory are corrected.

8. For a mole having a centerline axis and a steering tail rotatable about said axis and articulatable with respect to a pivot pin perpendicular to said axis, a guidance system comprising in combination:

means for generating and maintaining at the mole location a circularly polarized magnetic field whose rotating vector is perpendicular to a reference trajectory;

means for detecting the phase of first signals developed by said field in the direction of said cEnterline axis;

means for detecting the phase of second signals developed by said field in the direction which said tail would move if then articulated;

means for rotating said tail to bring said signals into phase; and

means for articulating said tail to bring said mole into a trajectory that reduces the magnitude of said first signals to zero.

9. A mole guidance system pursuant to claims 8, 9, or 10, wherein the means for generating said circularly polarized field comprises a dipole and a quadrupole antenna loop, driven by AC currents of the same frequency but differing by a phase factor;

means for monitoring the phase and magnitude of the dipole and quadrupole fields at the mole location; and

means for adjusting the antenna driving currents and magnitudes so as to create a resultant vector at the mole location which rotates with constant magnitude and angular velocity.

10. For a mole having a cylindrical elongated body, a trio of magnetometers fixed in said body, with their sensitive axes mutually orthogonal, a first said magnetometer being axially coincident with the centerline of said body, a steering tail rotatable about said centerline and articulatable about a pivot pin normal to said centerline, and a fourth magnetometer fixed in said tail at right angles to said pivot pin, a guidance system comprising in combination:

means for generating and maintaining at the mole location a circularly polarized magnetic field whose rotating vector bears a known geometric relation to a reference trajectory;

means for detecting the phase difference between voltages developed by said field in said first and fourth magnetometers;

means for rotating said tail about said centerline to reduce said phase difference to zero; and

means for thereafter articulating said tail in a direction that places said mole into a trajectory which will reduce the magnitude of said first magnetometer voltages to zero.