Remote position and orientation detection employing magnetic flux linkage

• US 4,317,078 A
• Filed: 10/15/1979
• Issued: 02/23/1982
• Est. Priority Date: 10/15/1979
• Status: Expired due to Term

• Current Assignee: The Ohio State University Research Foundation
• Original Assignee: The Ohio State University Research Foundation
• Inventors: Engira, Ram M., Weed, Herman R.
• Primary Examiner(s): Strecker, Gerard R.
• Assistant Examiner(s): Snow, Walter E.
• Application Number:
  US06/084,869
• Time in Patent Office: 862 Days
• Field of Search: 324/207, 324/208, 324/228, 324/239, 324/243, 324/244, 324/246, 340/686, 128/639-644, 128/653, 128/654
• US Class Current: 324/207.26
• CPC Class Codes: A61B 5/06 Devices, other than using radiation, for detecting or locating foreign bodies for removing same A61B17/50 ; determining position of probes within or on the body of the patient
• CPC Class Codes: A61B 5/062 using magnetic field
• CPC Class Codes: G01B 7/004 for measuring coordinates of points
• 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

The process and system for locating the position and orientation of an implement in space wherein a varying magnetic field responsive component (14) such as a coil is positioned upon the implement. A magnetic field source (12) excitable from an a.c. source derives alternating flux fields which are moved along or parallel to coordinate axes established at a reference plane. The coordinate position of the sensor is derived by determining the positions of minima and maxima flux linkage during magnetic field source movement.

Claims

1. The process for determining the location and orientation in space of a magnetic field responsive sensor having an output signal in the presence of a magnetic flux linkage comprising the steps of:

defining a plane within which are established first and second intersecting reference axes for deriving the position of said sensor with respect to said axes;

providing a magnetic field source movable with respect to said plane to derive alternating magnetic flux fields;

effectively moving said magnetic field source parallel to said first reference axis and determining, from said sensor output signal, locations representing a first null point of substantially no said flux linkage, those first and second locations on each side of said first null point representing maximum said flux linkage and the magnitudes of said sensor output signal values at said first and second locations;

effectively moving said magnetic field source parallel to said second reference axis and determining, from said sensor output signal, locations representing a second null point of substantially no said flux linkage, those third and fourth locations on each side of said second null point representing maximum said flux linkage and the magnitudes of said sensor output signal values at said third and fourth locations;

determining said sensor position geometrically most proximate said first axis as a function of said first null point location and the magnitude of the output difference between said sensor output signal values at said first and second locations;

determining said sensor position geometrically most proximate said second axis as a function of said second null point location and the magnitude of the output difference between said sensor output signal values at said third and fourth locations; and

determining the geometrically most proximate distance of said sensor from said plane as a function of the location of one of said null points, an adjacent location of maximum said flux linkage and a corresponding said difference between said magnitudes of said sensor output values associated with a given one of said first or second axes.

2. The process of claim 1 wherein said sensor component is provided as a winding configured or substantially symmetrically disposed about an orientation axis.

3. The process of claim 1 wherein said first and second axes are mutually orthogonally disposed in said plane.

4. The process of claim 1 wherein said magnetic field source is provided at said defined plane.

5. The process of claim 1 wherein said magnetic field source is effectively moved along said first axis in a manner wherein said field is substantially symmetrically disposed thereabout.

6. The process of claim 1 wherein said magnetic field source is effectively moved along a locus of travel in parallel with said second axis in a manner wherein said field is substantially symmetrically disposed thereabout.

7. The process of claim 1 wherein said magnetic field source is excitable from an alternating current source.

8. The process of claim 1 wherein said magnetic field source is provided having an axis of field orientation about which said alternating magnetic flux fields are symmetrically disposed, said field orientation axis being substantially perpendicular to said defined plane.

9. The process of claim 8 in which said sensor component is configured as a winding substantially symmetrically disposed about an orientation defining axis, said orientation defining axis being generally disposed in parallel relationship with said defined plane.

10. The process of claim 8 in which said sensor component axis of orientation is effectively oriented in generally parallel relationship with said first axis when said magnetic field source is moved therealong.

11. The process of claim 8 in which said sensor component axis of orientation is effectively oriented in generally parallel relationship with said second axis when said magnetic field source is effectively moved in parallel therewith.

12. The process of claim 8 in which said sensor component comprises:

a first magnetic field responsive winding symmetrically disposed about a first said axis of orientation; and

a second magnetic field responsive winding symmetrically disposed about a second said axis of orientation transversely disposed with respect to said first axis of orientation.

13. The process of claim 8 in which:

said sensor component is configured as a winding substantially symmetrically disposed about an orientation defining axis, said orientation defining axis being generally disposed in parallel relationship with said defined plane; and

said sensor component axis of orientation is effectively oriented in generally parallel relationship with said first axis when said magnetic field source is moved therealong.

14. The process of claim 1 in which:

said sensor component is provided as a winding configured as substantially symmetrically disposed about an orientation axis; and

wherein said first and second axes are mutually orthogonally disposed in said plane.

15. The process of claim 1 in which:

said first and second axes are mutually orthogonally disposed in said plane; and

said magnetic field source is provided at said defined plane.

16. The process of claim 1 in which:

said sensor component is provided as a winding configured as substantially symmetrically disposed about an orientation axis; and

said magnetic field source is effectively moved along said first axis in a manner wherein said field is substantially symmetrically disposed thereabout.

17. The process of claim 16 in which:

said magnetic field source is effectively moved along said first axis in a manner wherein said field is substantially symmetrically disposed thereabout; and

said magnetic field source is effectively moved along a locus of travel in parallel with said second axis in a manner wherein said field is substantially symmetrically disposed thereabout.

18. The process of claims 15, 16 or 17 in which said magnetic field source is excitable from an alternating current source.

19. The process of claim 2 wherein said step determining said sensor position geometrically most proximate said first axis is carried out by initially determining the magnitude of the difference between said sensor output values for said first and second locations representing maximum said flux linkage;

correlating said magnitude with the extent of angular deviation of said orientation axis from said first axis to derive a first error value; and

combining said first error value with said first null point location to establish said sensor position.

20. The process of claim 5 in which:

said sensor component is present as a winding substantially symmetrically disposed about an orientation axis; and

said orientation axis is disposed substantially perpendicular to said plane.

21. The process of claim 20 in which said magnetic field source is effectively moved along a locus of travel in parallel with said second axis in a manner wherein said field is substantially symmetrically disposed thereabout.

22. The process of claim 21 wherein said magnetic field source is excitable from an alternating current source.

23. The process for determining the location in space of a predetermined portion of an elongate probe comprising the steps of:

providing a sensor connected with said probe predetermined portion and effectively pivotally movable thereupon, said sensor being present as a varying magnetic field responsive winding disposed about an orientation axis and having output signals in the presence of magnetic flux linkage;

defining a reference plane within which are established first and second intersecting reference axes for deriving the position of said sensor with respect to said reference axes;

providing a magnetic field source effectively movable with respect to said reference plane, excitable from an alternating current source to derive alternating magnetic flux fields;

effectively moving said magnetic field source along a first locus in parallel with said first axis and determining, from said output signals, locations along said locus representing a first null point of substantially no said flux linkage, those first and second locations on each side of said null point representing maximum said flux linkage and the magnitudes of said sensor output signal values at said first and second locations;

effectively moving said magnetic field source along a second locus in parallel with said second axis and determining, from said sensor output signals, locations along said second axis representing a second null point of substantially no said flux linkage, those third and fourth locations on each side of said second null point representing maximum said flux linkage and the magnitudes of said sensor output signal values at said third and fourth locations;

determining said sensor position with respect to said first reference axis as a function of said first null point location and the magnitude of the output difference between said sensor output signals for said first and second locations and said sensor position with respect to said second axis as a function of said second null point location and the magnitude of the output difference between said sensor output signals for said third and fourth locations; and

determining the geometrically most proximate distance of said sensor from said reference plane as a function of the location of one of said null points and an adjacent location of maximum said flux linkage.

24. The process of claim 23 including the steps of:

moving said sensor in a first sense and repeating said effective movement of said magnetic field source along said first locus until the magnitude of said signals representing maximum said flux linkage are substantially equal to derive corrected said first null point and first and second maximum flux linkage locations following said effective movement of said source along said first locus;

moving said sensor in a second sense and repeating said effective movement of said magnetic field source along said second locus until the magnitude of said signals representing maximum said flux linkage are substantially equal to derive corrected said second null point and third and fourth maximum flux linkage locations following said effective movement along said second locus;

said determination of said sensor position with respect to said first reference axis is in correspondence with said corrected first null point location and said sensor position with respect to said second axis is in correspondence with a said corrected second null point location; and

said determination of the geometrically most proximate distance of said sensor from said reference plane is is correspondence with the location of a said corrected null point and an adjacent corrected maximum flux linkage location.

25. The process of claim 24 in which said sensor movement in said first sense is carried out by the rotation thereof.

26. The process of claim 25 in which said sensor movement in said second sense is carried out by the pivotal movement thereof upon said probe within a plane perpendicular to the axis of said rotation of said sensor.

27. The process of claim 26 wherein said magnetic field source is effectively moved along said first and second loci in a manner wherein said field is substantially symmetrically disposed thereabout.

28. The process of claim 23 wherein:

said magnetic field source is provided having an axis of field orientation about which said alternating magnetic flux fields are symmetrically disposed, said field orientation axis being substantially perpendicular to said reference plane.

29. The process for determining the location in space of an implement comprising the steps of:

providing a magnetic field source attached to said implement and excitable from an alternating current source to derive alternating magnetic flux fields;

defining a reference plane within which are established first and second intersecting axes for deriving the position of said field source with respect to said axes;

providing a sensor as a varying magnetic field responsive component having an orientation defining axis and having output signals in the presence of magnetic flux linkage therewith;

effectively moving said sensor with respect to said reference plane along a first locus parallel to said first axis and determining from said output signals, locations along said first locus representing a first null point of substantially no said flux linkage, those first and second locations on each side of said first null point representing maximum said flux linkage and the magnitudes of said sensor output signal values at said first and second locations;

effectively moving said sensor along a second locus parallel to said second axis and determining from said output signals locations along said second axis representing a second null point of substantially no said flux linkage, those third and fourth locations on each side of said second null point representing maximum said flux linkage and the magnitudes of said sensor output signal values at said third and fourth locations;

determining said magnetic field source position geometrically most proximate to said first axis as a function of said first null point location and the magnitude of the difference between said sensor output values for said first and second locations;

determining said sensor position geometrically most proximate to said second axis as a function of said second null point location and the magnitude of the difference between said sensor output signal values for said third and fourth locations; and

determining the geometrically most proximate distance of said magnetic field source from said reference plane as a function of the location of a said null point, an adjacent location of maximum said flux linkage and a corresponding said difference between said magnitudes of said sensor output signal values associated with a given one of said first or second axes.

30. A system for determining the location in space of an implement comprising:

a sensor connectable with said implement and present as a varying magnetic field responsive component substantially symmetrically disposed about an orientation axis and having output signals in the presence of magnetic flux linkage therewith;

means defining a reference plane at which are established first and second intersecting axes for deriving coordinate data representing the position of said sensor with respect to said axes;

a magnetic field source positioned at said plane and excitable from an alternating current source to derive alternating magnetic flux fields;

means for effectively moving said magnetic field source along a first locus parallel with said first axis and thence along a second locus parallel with said second axis;

output means responsive to said sensor output signals for deriving outputs dependent upon the locations of said magnetic field source at said plane, corresponding with null points of substantially no said flux linkage, and corresponding with those two locations on each side of a given said null point representing maximum said flux linkage, said outputs further being dependent on the magnitudes of said signals; and

means for determining the difference between the magnitudes of said sensor output signals at said two locations.

31. The system of claim 30 in which said sensor component is a coil, the windings of which are substantially symmetrically disposed about said orientation axis.

32. The system of claim 31 in which said sensor coil is pivotally mounted upon said implement.