Abstract:
An improved polar coordinates sensor comprising a pot-core half having a concentric winding window surrounded by a washer-like high conductive Lenz lens. A toroidal core stack concentrically disposed at the base end of the pot-core half, the pot-core half, Lenz lens and the toroidal core stack being disposed coaxially with aligned winding windows. X-y coordinates excitation winding distributions being shuttled through the coaxial aligned windows to encircle the cross-section of pot-core half, Lenz lens and toroidal core stack forming a series circuit. X-y excitation currents being connected to the excitation distributions to induce a hemispherical driving field. The inductive reactance of the series coupled toroidal core stack allows an increased degree of differential redistribution of driving flux in response to probe tilt. A rotating/non-rotating excitation method, of which a source of the x-y signals may include electromechanical resolver type waveforms. The sensor is further expanded by adding an outer radii auxiliary driving assembly comprising a toroid core encased by a second Lenz lens series coupled to a larger diameter toroid inductive reactance, providing the capability of two independent rotating/non-rotation concentric interacting driving fields. Further disclosed is a polar coordinates sensor having an air-core pick-up coil. Further disclosed is a “hidden metal edge mapper” for aircraft construction utilizing a tilted polar sensor indicating target by signal phase angle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This Patent application is a continuation-in-part of patent application Ser. No. 09/873,838 filed Jun. 4, 2001 now U.S. Pat. No. 6,580,267. 

   BACKGROUND OF THE INVENTION 
   All eddy current induction/detection devices are obviously governed by Lenz&#39;s reflective law. A permanent magnet floating above a superconductor (Meissner effect) illustrates a literal flux suspension system. Reciprocally, the hemispherical driving flux fringing from the polar coordinates sensor in Logue U.S. Pat. No. 5,909,118 that allowed several degrees of probe tilt, was the result of a flux suspension system provided by an annular air gap between the driving core and the pick-up core. Copending Logue et al. patent application Ser. No. 09/873,838 disclosed an integral driving/sensing pot-core half wherein the flux suspension system comprised connecting the poly-phase excitation windings in a series ring; thus providing a greater degree of differential redistribution of the H field in response to probe tilt. The present disclosure adds a high premeability ballast toroidal inductance in series with the x-y coordinates excitation turns, in effect a differential flux equalization means. 
   Remember diameterwise excitation of a toroidal core (x-y axes of permeability) is not a closed loop, therefore, high frequency response is good. 
   The mechanical equivalent is left to right differential linkage means and a longer stabilizer spring travel in an automobile suspension system. 
   Early Logue eddy current devices were called “polar coordinates” sensors e.g. Logue U.S. Pat. No. 5,939,880 comprising a pick-up core (pot-core half) and a driving core (poly-phase motor stator) i.e. a concentric arrangment being magnetically neutralized due to inherent orthogonality between driving and sensing axes of permeability. Logue et. al. U.S. Pat. No. 6,265,871 taught eddy current induction-detection by utilization of a rotating diametric dipole sensing hemisphere/s (see  FIG. 1 ) fringing from the equatorial plane of a toroidal core  55   xx . The term “polar coordinates sensor” is intended to convey more than planar geometry, by prior description i.e. “a hemispherical sensing pattern” (Logue U.S. Pat. No. 5,548,212) fringing diameter-wise from the equatorial plane of a high permeability toroidal core/s. Therefore, “polar coordinates” also includes varying degrees of Lenz latitude of eddy current depth within the workpiece. Obviously the reciprocal of polar coordinates is x-y coordinates. To avoid ambiguity, “polar coordinates sensor” will continue be the generic term used herein. 
   FIELD OF THE INVENTION 
   The generic term “toroidal” includes various closed geometric shapes e.g. pot-core halves (even a plurality of concentric poles as in Logue U.S. Pat. No. 5,404,101), bell (flared trumpet) conical shapes i.e. a television deflection yoke. Firstly, the apparatus-means of the invention comprises a high permeability ballast toroid core series-wound with a driving-sensing pot-core half, the toroid acting as an inductive reactance ballast in a passive differential flux suspension system. Secondly, the pot-core half (pick-up element) is surrounded by a high conductive (e.g. copper/silver) Lenz lens for focusing the driving flux. 
   Thirdly the method-means of the invention comprises an unsymmetrical angular resolver type of driving excitation. In addition to this, a television/radar raster/scan type of x-y axes excitation method is described as first disclosed in copending Logue et al. application Ser. No. 09/873,838. 
   Excerpt from Logue application Ser. No. 09/873,838 
   “Other Excitation Methods” 
   “Just as a toroidal deflection yoke around the neck of a TV picture tube magnetically moves the electron beam/s to any location on the screen according to a predetermined program, so also the subject method moves the eddy current on (horizonal-vertical) x-y coordinates. As part of this disclosure, an eddy current scan pattern similar to a television raster may be generated in a planar workpiece by polar coordinates probe utilizing a programable (software) method. Radar type scans e.g. plan-position indicator (PPI) is also a programable method.” 
   SUMMARY OF THE INVENTION 
   Increasing the degree of tiltability in the polar coordinates sensor is a primary object of the invention. This means the flaw signature is retained over a greater probe tilt angle. 
   A diameterwise magnetization of toroidal inductance is added in series with the x-y currents exciting the mentioned driving-sensing pot-core half. 
   A further utility of the embodiments of the invention is: a “hidden metal edge mapper” for use in aircraft splice-joint construction. In such aerospace industry, it is necessary to drill holes in a slice joint centering on hidden framework or a predetermined distance from a sub-layer edge from the blind side (see Horn U.S. Pat. No. 5,172,055 for more detail of this need). Further, coaxially aligning tool bits on opposite sides of a large thick aluminum panel, may be accomplished by x-y coordinates nulling a polar coordinates sensor over a cylindrical ferrous target from the blind side and utilizing a marking means upon each side. 
   Further, by tilting the z-axis of the polar sensor (probe/s of the invention) a few degrees toward/away from the direction of probe travel a reference azimuth-phase angle signal indicative of the hidden edge is generated, any deviation +−in phase angle may be utilized to control automatic steering of a propelling and seam marking means. 
   Alternative Conductive Materials 
   The disclosure additionally covers the use of conducting metals such as mu-metal 1020 steel, stainless steels, for forming the probe structure/s termed “Lenz-reflector”, although the example probe signals displayed herein utilized copper to form the subject Lenz-reflector. All conducting materials are included. Even further, interleaved ferrous/non-ferrous laminate may be utilized for such driving field blocking/focusing geometry. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1 , is a perspective view of concentric toroid cores  55   x , 55   xx  illustrating two concentric azimuthal hemispheres of effective flux within the driving pattern of embodiment II of the disclosure. 
       FIG. 2 , is a vectorial diagram of a prior art inductive angular resolver vectorially illustrating an excitation generator/method. 
       FIG. 3 , is a polar diagram illustrating a programable stepwise active/silent eddy current induction method. 
       FIG. 4 , is a sectional/perspective view of an improved polar coordinates sensor utilizing two sub-radii ballast toroids and a laminated Lenz lens, plus a greater-radii driving toroid series wound with a second ballast toroid and a greater-radii Lenz lens. 
       FIG. 5 , is an isometric view a pair of high permeability toroids and z-axis ferrite pick-up core to geometrically illustrate how the subject flux suspension also makes possible self-nulling in response to probe tilt. 
       FIG. 6 , is a section/perspective view of another embodiment of eddy current probe utilizing a toroidal ballast core assembly and toroid-rod driver-sensing sensing arrangement. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Remember, all cross-sectional partial views of toroidal cores, Lenz-lens, grooves, air-gaps and toroidal-windings represent a complete revolution around the z-axis. Also remember, the fragmentary method of drawing a few turns of magnet wire (with/without connecting leads) linking a toroid, pot-core and/or Lenz-reflector represent entire/complete circumferential/toroidal x-y coordinates coverage. 
   The high permeability materials utilized in the invention include all soft magnetic materials including tape materials e.g. Magnesil*, Orthonol*, Permalloy*, Supermalloy*, Supermendur* and all amorphous magnetic materials: e.g. Metglas* made by Honeywell*. Even further, powdered iron and ferrites. 
   Basics 
   Isotropic magnetically soft materials having toroidal geometry may allow several directions of effective magnetization simultaneously provided the vectorial flux density is below the saturation point. Thus a simple toroid has several “axes of permeability” as pictorially shown in  FIG. 1 : e.g. x-y-z axes, t-axis (toroidal). Let us first analyze the magnetization of outer radii toroid  55   x  excited on x-y coordinates by x-y coordinates excitation windings  062   aa  (drawn in fragmentary). Bihemispherical circle  23  represents the mean (effective) flux fringing from equatorial plane EP i.e. outer flux shell  27  of probe PSzz, this shell is formed by stepwise interposed active/silent azimuth headings (only the 30–120 diameter is shown) of hemispherical flux lines fringing from the equatorial plane EP of core  55   x . Disposed concentrically within flux shell  27  is inner flux shell  22  (only the 0–180 diameter is shown) fringing from the equatorial plane EP of toroid  55   xx , represented by hemisphere  21 . X-y excitation winding distributions  062   a  (shown in partial) are uniformly wound around  55   xx , and connected to a x-y generator (not shown) via leads Exb. Notice, excitation windings  062   aa , 062   a , are electrically isolated, thus may be individually connected to separate x-y (or poly-phase) excitation generators providing a number of independent or interlocking angular phase eddy current patterns e.g. stepwise/continuous, plus various frequency/amplitude modulation modes e.g. elliptical (Logue U.S. Pat. No. 5,793,204). 
   For correspondency with the orthogonal driving/detection elements of the disclosed embodiments, an asymmetric flux pick-up assembly  099  comprising, a high permeability rod core  88   x  wound with a pick-up coil  090  having signal leads SIG. and shunted by variable capacitor Cx, all pick-up elements are coaxial on the z-axis for a signal null. 
   Referring again to  FIG. 1 , when excitation currents flow through x-y (also includes poly-phase configurations) winding distributions  062   aa / 062   a  (shown in partial) from a current generator/s (not shown) connected to respective terminals Exa/Exb, a diameterwise dipole S N fringes from the equatorial plane EP of toroid/s  55   x / 55   xx , forming a hemispherical driving field/s  21 / 23 . Depending on the excitation program field/s  21 / 23  may have zero angular velocity (x-y stepwise) or may advance e.g. 0–360 degrees unipolar (x-y or poly-phase) constant or ramping angular velocity. Said another way, this angular advancment may be linear, ramping, or stepwise burst/silent. The term “burst” refers to a number of x-y excitation alternations centered on a given azimuth. The term “silent” refers to a predetermined number of azimuth degrees of zero amplitude x-y excitation. Pick-up coil  8  generates a signal on terminals Ta in response to an asymmetry in the sensing pattern. Hb designates the complementary fringing hemisphere. Toroid/s  55   x , 55   xx  have top and bottom sensing planes  9 ,  10 . 
   Method of Excitation 
   A non rotating (stepwise) excitation mode may be seen from the teaching of Logue U.S. Pat. No. 5,793,204 where the minor elliptical generation axis may be reduced to zero. This is where a plurality of ellipses are generated at one azimuth heading i.e. zero angular velocity. Therefore this disclosure emphasizes x-y coordinate windings and excitation. Alternately, poly-phase excitation (constant or ramping angular velocity) may be utilized to drive all disclosed devices. 
     FIG. 2  is schematic of an angular resolver AR e.g. Clifton Precision Products Co. phase shifter unsymmetrical resolver type PS-17-E-1 having rotor R and orthogonal stator windings  16  (terminals SIN) and  17  (terminals COS). Excitation current from an external signal generator (not shown) is applied to coil  15  via terminals Ex magnetizing high permeability rotor core  11 . Rotor R has two generic recoprocal induction modes i.e. angular velocity and flux level (both AC and DC are covered). Condition  1 : Rotor R rotates at a constant angular velocity and has a constant flux level. Result: Sine-cosine signals SIN, COS, produce a single frequency rotating magnetic field of constant amplitude in a 2 phase polar coordinates sensor. Condition  2 : Rotor R held stationary (static) at a given angular position and winding  15  excited at a given constant frequency. Result: A zero angular velocity (stationary) the driving dipole fringing diameter-wise across the polar coordinates sensor sensing face i.e. the annular face of a pot-core half. Driving vectors are shown at 0 and 10 degrees in  FIG. 3  i.e. the same as X-axis only excitation. Although, a mechanical resolver driven by a variable speed motor could actually be utilized as a signal generator, the disclosed stepwise exitation method ( FIG. 3 ) is preferably generated by digital computer means as taught in Logue U.S. Pat. No. 5,793,204. Ramping the poly-phase excitation frequency generates a sub-frequency flaw-signal, having an oscillatory build-up on the z-axis (Logue U.S. Pat. No. 5,909,118), resulting in a rotational additive charge between the terminals of a “tank” capacitor connected across the pick-up coil leads. 
   To avoid ambiguity between description and appended claims we must explore the available terminology to designate a field focusing means (magnetic lens/es), from the terms: high-reluctance, electromagnetic-shield, skin-depth, Lenz&#39;s law, current loop, shading-coil, magnetic-lens, etc. Even more complex, an integral Tesla-transformer-driver arranged between outer radii Lenz-reflectors (second embodiment) interacting with a layered aluminum workpiece, becomes a “compound shaded pole” combination generating-detecting a degree of “second-secondary” effects. 
   The inherent-infinite imbalance-gain of the subject sensor exhibits traveling magnetic field and wave-guide effects as a perfect null is approached, meaning: exactness of excitation turns placement and sensing-face geometry (all elements) rivals waveguide construction (exhibits exacting geometric effects as though much higher frequencies were involved). 
   Inspite of common usage of the term high-reluctance as a “skin-depth” value, the eddy current phenomenon is a shorted-turn secondary of a transformer. Transformer secondary winding/s are never referred as a high reluctance (air-gap concatenation). The term “Lenz lens” conveys the desired focusing concept more adequately. 
   Embodimemt One 
   The generic polar coordinates sensor is designated PSaa in  FIG. 4 , has an optional outer radii elements as decribed under Variant II. 
   Variant I 
   We first describe polar coordinates sensor PSa (exclusive of auxiliary outer radii field means PSx shown between 0–90 degrees) in  FIG. 4 . PSa comprises a pot-core half  188 , an improved Lenz reflector  177   a , coaxially stacked with two high permeability ballast toroids  155   a , 155   b , forming a coaxial winding window  193   aa.    
   Pot-core half  188  (the pick-up core) is formed of a high permeability ferrite having an outer cylindrical pole  186  concentrically enclosing a central tubular pole  184  forming winding window  193 . Poles  186 , 184 , are connected at a first end by a base portion  185 , leaving an annular pick-up coil space  179 . A pick-up coil  190  having many turns is wound in space  179  shunted by variable capacitor. Our prototype utilized Magnetics* pot-core half OW42318. 
   The asymmetric (flaw) flux signal appears at terminals SIG.a. Pick-up core  188  is tightly fit with an improved Lenz reflector  177   a  formed of a nonferrous material such as copper/silver being in the form of a thick washer. The improvment being a laminate of several flat washers  77  glued rigidly together reducing longitudinal eddy current, yet retaining planar (focusing) eddy currents, thus probe battery efficiency is increased. Poly-phase/stepwise driving excitation is conveyed to X-Y-axes winding distributions  162   a  by leads Exa (windings and leads are shown in partial). The plane of individual winding turns  162   aa  should align with the Z-axis and leads Exa should be twisted and dressed near the Z-axes as shown to prevent stray coupling. Respectfully, X and Y axes coil pairs are connected diameterwise in series (all leads and connections are made near the Z-axis). 
   Our prototype utilized Allied Signal* Metglas* MP3210P-4AF cores to assemble inductance  155   bb.    
   A non-metallic hollow coaxial alignment spool (not shown) may be fitted in toroidal stack window  193   aa  for correct assembly glueing, then a cylindrical plastic housing (also not shown) forms a hand grip (coaxial assembly being held together with a rigid potting compound). 
   Variant II 
   Now combining PSa with PSx (all elements shown in  FIG. 4 ) we have variant designated PSaa, and referenced as “a variable-azimuthal-concentric-hemispherical” eddy current probe. 
   An outer radii auxiliary driving assembly PSx comprises an outer high permeability driving toroid  155   aa  encased within an outer cylindrical a high conductive (copper) auxiliary Lenz lens (reflector)  177   a . The sectional cut shows  177   a  has an longitudinal rim  177   aaa  tightly fit concentric around the outer diameter of  155   aa  and a radial flange touching the backplane of  155   aa . A larger diameter high permeability high cross-section ballast toroid  155   cc  is concentrically disposed adjacent the back of  177   b . The cross-section of all three elements  155   aa , 177   b    155   cc , is encircled by poly-phase excitation winding distributions  162   b  (drawn in partial) connected by leads Exb to an auxiliary x-y-axes current amplifier driven by a programable computerized generator (not shown). Obviously all elements of eddy current probe PSaa are arranged concentrically around the Z-axis for a null signal at SIG.a. Eddy current probe PSaa may be excited by a variety of modes of current modulation: 1) Two x-y axes generators, each forming a zero angular velocity field. 2) Two x-y axes generators, individually forming a stepwise azimuthal incrementing field, including unidirectional and bidrectional active/silent azimuthal increments. 
   3) Two poly-phase generators, individually forming a rotating field. 4) Two electromechanical angular resolvers, individually generating x and y fields from the stator, with wound rotors individually excited by currents DC or modulated in e.g. frequency/amplitude. 
   Embodiment Two 
   Variant 1 
     FIG. 6 , is a sectional/perspective view of polar coordinates sensor PSq, some of the improvements are: 1) Combination driving toroid  255   aa  comprising: integrally formed longitudinal flange  255   b  and radial flange  255   ax.    
   2) A large diameter laminated Lenz reflector  277 , formed of a stack high conductive (e.g. copper) of flat washers  77   a  individually insulated and bonded together, the total thickness is such that a phase shifted potion of the hemispherical component ( 23  in  FIG. 1 ) fringing from radial flange  255   ax  passing through  277  and into a workpiece is displaced substantially in phase depending on lens thickness and x-y excitation frequency. 
   The subject “improved flux suspension system” includes a pair of high permeability stacked toroids  255   x , 255   xx , forming toroidal ballast  255   xxx , having coaxially aligned winding windows  293 . Toroidal ballast  255   xxx , is coaxially aligned an adjustable displacement La, at the rear of toroidal driving core  255   aa.    
   La represents the assembly adjustable distance between equatorial planes EPa,EPb, of cores  255   ax , 255   xxx , respectively. 
   Coaxially disposed within the winding window  293  of toroidal core  255   aax  is a high permeability ferrite rod  284 , disposed coaxially on the z-axis, having a pick-up coil  290  of many turns wound around a first end (sensing/top end) having signal out leads SIG.aa shunted by a series resonant capacitor Cx. The opposite/bottom portion of ferrite rod  284  is cocentrically surrounded by a high permeability flux gating toroid  255   aa , toroidally wound with a saturating coil  262   b  having leads EXaa, connected to a programable current controller (not shown). The equatorial plane EPaa is adjusted (axial displacement  44 ) during assembly for an optimum flux gating of the complenentary hemispherial fringing from  255   aa  (see  FIG. 1 ), and the asymmetric (flaw) flux return path to toroidal reactor core  255   xxx.    
   The complementary hemisphere (not drawn) of  255   aa  is also the return path for any asymmetric Lenz reflection in the driving pattern (not shown). A toroidal flux gating principle is disclosed in Alldredge U.S. Pat. No. 2,856,581. Eddy current probe PSq has an improved flux suspension comprising ballast stack  255   xxx , comprising a high permeability toroidal core pair  255   x , 255   xx  forming coaxial window  293 . 
   Self Nulling 
   We now explain another intrinsic self nulling action of the subject flux suspension (limited to  FIG. 6 ). 
   Lateral shifting of the flux density within stacked toroidal cores ( 255   aa , 255   xxx , in  FIG. 6 ) i.e. shifting of the driving flux centroid in which pick-up rod  284  is subsubmerged, will be the crux of this treatise. This is lateral movement of the z-axis resulting from probe tilt or rectangular (T V raster) excitation.  FIG. 5  has two high permeability toroids  0055   a , 0056   b , coaxially anigned but seperated by a distance approximately equal to the diameter of  0055   a / 0055   b . A high permeability ferrite rod  0088 , having a sensing end  13  and a rear end  12 , is coaxially disposed within the winding windows  29 ,  31  of toroids  0055   a , 0055   b , with a pick-up coil  0090   x , wound coaxially at approximately the center of rod  0088  length, having signal leads SIG.ax.  FIG. 5  also illustrates the preferred x-y excitation winding method i.e. diameterwise series connected quadrant coils  0062 , 0063 , to induce “like poles parallel” in response to current flowing via leads EXz. The illustrated magnetizations SN of  0055   a , 0055   b , are actually induced by a pair of parallel quadature coils not shown. As probe tilt or a rectangular driving flux is generated, the centroid of flux with toroids  0055   a , 0055   b , both laterally shift e.g. to the right (arrows Dispa, Dispb). Inasmuch as toroids  0055   a , 0055   b , are linked by the same excitation coils  0062 , 0063 , the resultant lateral displacement of ends  12 , 13 , are approximately the same, the desired “flaw signal retention” is improved. 
   Assembly Advice 
   To prevent cutting of magnet wire insulation; all coil-touching surfaces of the Lenz-reflector should be coated with a thin insulating means (casing) before winding.