WO2001092817A1

WO2001092817A1 - Non-contact position sensing apparatus

Info

Publication number: WO2001092817A1
Application number: PCT/US2001/014103
Authority: WO
Inventors: Abdollah Owzar
Original assignee: The J.M. Ney Company
Priority date: 2000-06-01
Filing date: 2001-05-02
Publication date: 2001-12-06
Also published as: AU2001257479A1

Abstract

Position sensing apparatus (100) for providing a mutual inductance value corresponding to a position of a movable body (130), relative to a reference position, includes a first electrical coil (102), a second electrical coil (104) adjacent the first electrical coil, and a shielding component (106), disposed between the first and the second coils. The shielding component includes an aperture providing an unimpeded path from the first coil (102) to the second coil (104), such that a cross sectional area of the unimpeded path varies as a function of position of the shielding component (106). Position of the shielding component is a function of the movable body position. The first and second electrical coils are characterized by a mutual inductance value, which is also a function of movable body position . The apparatus may include a drive circuit (108) driving a signal through the first coil, and a detection circuit (112) detecting an induction signal associated with the second coil and producing the position signal as a function of the induction signal.

Description

NON-CONTACT POSITION SENSING APPARATUS

CROSS-REFERENCE TO RELATED APPLICATIONS Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH Not Applicable

REFERENCE TO MICROFICHE APPENDIX Not Applicable

BACKGROUND OF THE INVENTION

The present invention relates to sensors for providing information regarding the relative position of at least two objects, and more particularly, to sensors for providing information regarding the relative position of at least two objects that do not require physical contact between the objects.

An automobile is an example of a system that utilizes a significant number of relative position sensors for various control functions. For example, a relative position sensor may be used to determine the position of the accelerator pedal with respect to the floor of the automobile to control the speed of the engine. Another example of a relative position sensor is the fuel level sensor in the fuel tank. For such a prior art fuel level sensor 10 as shown in FIG. 1, a floating component 12 is typically mounted fixedly to one end 14 of an elongated member 16, and the opposite end 18 of the elongated member 16 is pivotally mounted to an anchor 20 that is fixed relative to the tank 22. As the level of the fuel 24 within the tank 22 changes, the elongated member 16 rotates about the pivot 26. Thus, the angular position of the elongated member 16 with respect to the anchor 20 is directly related to level of the fuel 24 within the tank 22.

In general, the fuel level sensor 10 transduces the above-mentioned angular position into a variable physical parameter. In one prior art system, the physical parameter is resistance; thus the member 16 and the anchor form a potentiometer, the resistance of which changes as a direct function of the angular position (and consequently, fuel level). A wiper on the member 16 typically contacts an elongated resistive component (e.g., a wire resistor or resistive track) on the anchor 20, and the effective resistance from the wiper to one end of the resistive component varies as the angular position changes. Although other forms of such transducers exist (e.g., optical encoders), the above-described resistive transducer is by far the most common due to the relative ease of manufacture and low cost.

One disadvantage to this form of a position sensor is that the vibrations typical of an automotive environment tend to cause the resistance measurement to be noisy. This is generally due to the wiper portion of the potentiometer moving randomly, under vibration, with respect to the resistive component on the anchor.

Another disadvantage to this form of a position sensor is that the friction occurring where the wiper meets the resistive component causes wear on both components; thus creating a failure mode for the sensor. The effect of the friction is magnified in light of the high- vibration environment the sensor typically experiences. A prior art device that may also function as a position sensor is a linear variable differential transformer (also referred to herein as LVDT), as shown in FIG. 1 A. In general, an LVDT 50 includes a primary coil 52, secondary coils 54 and a magnetic core 56 . A time-varying signal driven across the primary coil 52 generates a time-varying electro-magnetic field that couples the primary coil 52 to the secondary coils 54. The amount of coupling between the primary coil 52 and secondary coils 54 varies as a function of the position of the magnetic core 56 with respect to the primary coil 52 and the secondary coils 54. The magnetic core 56 tends to enhance the linkage between the primary and secondary coils when the core 56 is in close proximity to the coils, and the linkage diminishes as the core 56 is removed from the coils 52 and 54. Combinations of the signals induced in the secondary coils 54 are compared to the signal across primary coil 52. The amplitude and polarity of the secondary coil signals relative to the primary coil signal are indicative of the position of the core 56 with respect to the coils 52 and 54. In one prior art example shown in FIG. IB, a first secondary coil 62 is positioned with respect to the primary coil 64 such that a signal induced on the first secondary coil 62 is of the same polarity as the reference signal on the primary coil 64, and a second secondary coil 66 is positioned with respect to the primary coil 64 such that the polarity of a signal induced on the second secondary coil 66 is opposite the polarity of the signal on the primary coil 64. When the secondary coils are connected in series opposition as shown, the amplitude of the output voltage across the secondary coils with respect to the position of the magnetic core 68 is as shown in the corresponding graph of FIG. IB. As the graph shows, when the core 68 is in the center position, i.e., coupling the primary coil 64 to the first secondary coil 62 and the second secondary coil 66 equally, the secondary coil voltages cancel, resulting in a zero output voltage. As the core 68 moves along the translation axis AX towards the first secondary coil, the voltage increases positively. As the core 68 moves along the translation axis AX towards the second secondary coil, the voltage increases negatively.

It is an object of the present invention to substantially overcome the above-identified disadvantages and drawbacks of the prior art.

SUMMARY OF THE INVENTION

The foregoing and other objects are achieved by the invention which in one aspect comprises a position sensing apparatus for providing a mutual inductance value corresponding to a position of a movable body, relative to a reference position. The apparatus includes a first electrical coil, along with a second electrical coil disposed adjacent the first electrical coil. The apparatus further includes a shielding component, disposed between the first coil and the second coil. The shielding component includes at least one region characterized by a relatively high resistance to magnetic flux, and at least one region characterized by a relatively low resistance to magnetic flux (i.e., relative to the region or regions of high resistance). The position of the shielding component is a predetermined function of the movable body position, and the first and second electrical coils are characterized by the mutual inductance value. This mutual inductance value is also a predetermined function of the movable body position.

In another embodiment of the invention, the at least one region of low resistance includes an aperture for providing an unimpeded path from the first coil to the second coil, such that a cross sectional area of the unimpeded path varies as a predetermined function of a position of the shielding component.

In another embodiment of the invention, the position of the movable body includes angular position, such that the shielding component rotates about a pivot axis. In another embodiment of the invention, the aperture includes an arcuate slot having an inner radius and an outer radius about the pivot axis.

In another embodiment of the invention, the position of the movable body includes linear position, such that the shielding component translates along a travel axis. In another embodiment of the invention, the aperture includes a linear slot having an inner distance and an outer distance from the travel axis.

In another embodiment of the invention, the first electrical coil is fixed relative to the reference position.

In another embodiment of the invention, the first electrical coil and the second electrical coil are fixed relative to the reference position. In another embodiment of the invention, the shielding component is constructed and arranged such that the cross sectional area varies, according to the position of the movable object, within a range bounded by a minimum cross sectional area to a maximum cross sectional area.

In another embodiment of the invention, the minimum cross sectional area corresponds to a mutual inductance commensurate with an absence of a common field between the first electrical coil and the second electrical coil.

In another embodiment of the invention, the maximum cross sectional area corresponds to a mutual inductance commensurate with an absence of shielding between the coils. In another embodiment of the invention, the shielding component and the movable object are combined so as to include a single component.

In another embodiment of the invention, the shielding component is fixedly attached to the movable object, such that the shielding component position varies identically as the movable object position. In another embodiment of the invention, the shielding component is coupled to the movable object via a linkage, such that the component position varies as the first predetermined function of the movable body position.

In another embodiment of the invention, each of the first electrical coil and the second electrical coil includes a multiple winding inductor. In another embodiment of the invention, each of the first electrical coil and the second electrical coil includes an associated core.

Another embodiment of the invention further includes a third electrical coil connected in series opposition with the second electrical coil. The second and third coil form a composite coil, wherein the first coil and the composite coil are characterized by a composite mutual inductance value that is a predetermined function of the movable body position.

In another aspect, the invention comprises a position sensing system for providing a position signal corresponding to the position of a movable body, relative to a reference position. The position sensing system includes a first electrical coil, along with a second electrical coil disposed adjacent the first electrical coil. The system further includes a shielding component, disposed between the first coil and the second coil. The shielding component includes an aperture for providing an unimpeded path from the first coil to the second coil, such that a cross sectional area of the unimpeded path varies as a function of a position of the shielding component. The shielding component position is a predetermined function of the movable body position, and the first and second electrical coils are characterized by a mutual inductance value that is a second predetermined function of the movable body position. The system further includes a drive circuit for driving a stimulating signal through the first coil; and a detection circuit for detecting an induction signal associated with the second coil. The detection circuit produces the position signal as a predetermined function of the induction signal.

In another embodiment of the invention, the stimulating signal includes a sinusoid having a constant, predetermined amplitude and a constant, predetermined frequency. In another embodiment of the invention, the detection circuit receives a time varying voltage from across the second coil, measures an amplitude of the time varying voltage, and produces the position signal as a predetermined function of the amplitude. In another embodiment of the invention, the detection circuit includes a buffer circuit for providing isolation between the second inductor and a system output conveying the position signal. In another embodiment of the invention, the detection circuit includes a low pass filter for filtering noise from the induction signal.

Another embodiment of the invention further includes a third electrical coil connected in series opposition with the second electrical coil. The second and third coil form a composite coil, wherein the induction signal is associated with the composite coil. In another aspect, the invention comprises a method of providing a position signal corresponding to a position of a movable body, relative to a reference position. The method includes the steps of driving a stimulating signal through a first electrical coil, and providing a second electrical coil disposed adjacent the first electrical coil. The method further includes the step of providing a shielding component, disposed between the first coil and the second coil. The shielding component includes an aperture for providing an unimpeded path from the first coil to the second coil, such that a cross sectional area of the unimpeded path varies as a function of a position of the shielding component. The position of the shielding component is a predetermined function of the movable body position, and the first and second electrical coils are characterized by a mutual inductance value that is also a predetermined function of the movable body position. The method further includes the step of detecting an induction signal associated with the second coil, and producing the position signal as a predetermined function of the induction signal.

In another embodiment, the detection circuit further includes an inverter for inverting the stimulating signal so as to produce an inverted signal, an amplitude sealer for receiving and scaling the inverted signal by a predetermined scaling factor so as to produce a scaled signal, and a summer for summing the induction signal and the scaled signal so as to produce a bipolar position signal corresponding to the position of the movable body. In another aspect, the invention comprises a position sensing system for providing a position signal corresponding to a position of a movable body, relative to a reference position. The system includes a first electrical coil, a second electrical coil and a third coil. The second and third coils are electrically coupled in series opposition so as to form a coil pair, and are disposed adjacent the first electrical coil. The system further includes a shielding component disposed between the first coil and the coil pair. The shielding component has at least one region characterized by a relatively high resistance to magnetic flux, and at least one region characterized by a relatively low resistance to magnetic flux, relative to the at least one region characterized by relatively high resistance. The position of the shielding component is a first predetermined function of the movable body position. The system further includes a drive circuit for driving a stimulating signal through the first coil; a detection circuit for detecting an induction signal associated with the coil pair, wherein the detection circuit produces the position signal as a predetermined function of the induction signal.

In another aspect, the invention comprises a non-contact electrical connector assembly for transferring electrical signals. The assembly includes a primary coil and a secondary electrical coil disposed adjacent to the primary electrical coil, a drive circuit for driving an input electrical signal through the first coil, and a detection circuit for detecting an induced signal associated with the second electrical coil. The detection circuit further produces an output signal that is proportional to the input signal. In another aspect, the invention comprises a non-contact electrical connector assembly for transferring electrical signals. The assembly includes a plurality of primary coils and a plurality of secondary coils, wherein each primary coil is associated with a particular secondary coil, so as to form a plurality of primary/secondary coil pairs. For each of the primary/secondary coil pairs, the assembly also includes a driver circuit for driving an input electrical signal through the primary coil, and a detection circuit for detecting an induced signal associated with the second electrical coil. Each detection circuit produces an output signal, wherein the output signal is proportional to the input signal.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other objects of this invention, the various features thereof, as well as the invention itself, may be more fully understood from the following description, when read together with the accompanying drawings in which: FIG. 1 shows sectional view of a prior art fuel level sensor;

FIG. 1A shows one example of a prior art LVDT;

FIG. IB shows another example of a prior art LVDT;

FIG. 2 shows a perspective view of one preferred embodiment of a non-contact position sensing apparatus; FIG. 3 illustrates a exploded view of the housing, coil and shielding components from one preferred embodiment the sensing apparatus of FIG. 2;

FIG. 4 shows a perspective view of a shielding component for sensing linear position;

FIG. 5 shows an assembled view of the housing, coil and shielding components from the sensing apparatus of FIG. 3 ;

FIG. 6 shows a sectional view of one positional relationship between the shielding component and the anchor from the apparatus of FIG. 2;

FIG. 7 shows a sectional view of another positional relationship between the shielding component and the anchor from the apparatus of FIG. 2; FIG. 8 shows a schematic representation of one embodiment of the apparatus of

FIG. 2;

FIG. 9 illustrates a more detailed block diagram of the detection circuit shown in FIG. 2;

FIG. 10 shows a bipolar output embodiment of the apparatus shown in FIG. 2; FIG. 11 shows another embodiment of the apparatus of FIG. 10;

FIG. 12 shows a circuit for providing a bipolar output from the apparatus of FIG.

2;

FIG. 13 A shows a shielding component having a spatially variable resistance to flux; FIG. 13B shows another embodiment of the shielding component of FIG. 13 A; FIG. 14 shows another bipolar output embodiment of the apparatus shown in FIG. 2 including series connected secondary coils; and,

FIGS. 15A and 15B show schematic views of embodiments of a non-contact electrical signal connector.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 shows a perspective view of one preferred embodiment of a non-contact position sensing apparatus 100, including a first electrical coil 102 and a second electrical coil 104, separated by a shielding component 106. The first and second coils 102 and 104 are fixed with respect to one another, and the shielding component 106 is movable with respect to the coils 102 and 104. A drive circuit 108 drives a stimulating signal 110 into the first electrical coil 102, and a detection circuit 112 receives an induction signal 114 from the second electrical coil 104, and produces a position signal 116 as a predetermined function of the induction signal 114. In the absence of the shielding component 106, the first electrical coil 102 and the second electrical coil 104 are linked by a mutual inductance because of their relatively close proximity. As is well known in the art, the mutual inductance M of two coils is used to describe and quantify the electromagnetic linking of the two coils due to a common magnetic field. In the sensing apparatus 100 of the present invention, the shielding component 106 interacts with the common magnetic field so as to modify the mutual inductance.

The shielding component 106 is preferably constructed, in one or more regions, of a material characterized by a relatively high resistance to magnetic flux. The shielding component 106 also preferably includes one or more regions characterized by a low resistance to magnetic flux, relative to the remainder of the shielding component 106.

This non-homogenous nature of the shielding component 106 is such that the effect upon the common magnetic field is strongly dependent upon the position of the shielding component 106 with respect to the first and second coils 102 and 104. In one preferred embodiment, the low resistance region includes an aperture, although in other embodiments the low resistance region may include a cutout, an asymmetry or other such irregularity. In alternate embodiments, the low resistance region may include a region of high permeability material known to those in the art, such as iron, nickel, cobalt, etc. known to those in the art.

Because the first coil 102 and the second coil 104 are linked according to the mutual inductance M, a time- varying signal driven at the first coil 102 is inductively coupled to the second coil 104. The amplitude and frequency of the signal present at the second coil 104 is directly related to the amplitude and frequency, respectively, of the signal driven at the first coil 102. The relationship between the amplitude of the signal driven at the first coil 102 and the amplitude of the inductively coupled signal at the second coil 104 is governed by the mutual inductance M of the two coils. Therefore, a driving signal at the first coil 102 having a constant amplitude produces an inductively coupled signal at the second coil having an amplitude that is directly related to the mutual inductance, and thus to the position of the shielding component 106, relative to the coils 102 and 104. In a preferred embodiment of the invention, the shielding component 106 is pivotally mounted to an anchor, so as to allow a variation of the angular position of the shielding component 106 with respect to the anchor. The anchor is preferably fixed with respect to the coils 102 and 104. In other embodiments, the shielding component may be movably mounted to the anchor so as to allow a variation of the position of the shielding component 106 along a linear path with respect to the anchor. In further embodiments, the shielding component 106 may be movably mounted to the anchor so as to allow a variation of the position of the shielding component along a non-linear path, or in a random direction, with respect to the anchor.

FIG. 3 illustrates an exploded view of components from one embodiment of a position sensing apparatus 100 for sensing angular position variations. FIG. 4 illustrates a perspective view of an embodiment of a shielding component 106 that is intended to be movably mounted for linear position variation along a travel axis AX. FIG. 5 shows an assembled view of some of the components shown in FIG. 3.

FIG. 3 shows an anchor 120 including a first anchor half 120 A and a second anchor half 120B. Each anchor half is in the form of a hollow cylinder having an open end and a closed end. The anchor 120 is may also be referred to as the position sensing apparatus "housing," because in one preferred embodiment described herein, the anchor 120 houses the shielding component and the first and second coils 102 and 104. The anchor halves 120 A and 120B are arranged along an axis AX such that the cylinder walls are equidistant from the axis AX, the axis AX passes through the center of the open and closed end, and the open and closed ends are substantially normal to the axis AX. The first coil 102 is disposed upon the interior surface of the closed end of the first half 120 A, shown as a broken line on the first half 120 A in FIG. 3. The second coil 104 is disposed upon the interior surface of the closed end of the second half 120B. The coils 102 and 104 in this embodiment are preferably coils in the general shape of the aperture 124, although other coil shapes may also be used. A shielding component 106 having an aperture 124 is disposed between the first half 120A and the second half 120B. The shielding component 106 includes a first surface 121 A and a second surface 121B substantially parallel to one another, and arranged such that the axis AX is normal to the first and second surfaces. When assembled, the first and second halves 120 A and 120B of the anchor 120 fit together with the open ends facing one another so as to form two substantially hollow cylinders, separated by the shielding component 106. The first and second halves 120 A and 120B are positioned such that the first coil 102 and the second coil 104 are substantially adjacent; i.e., the angular positions of the first and second coils 102 and 104, with respect to the axis AX, are substantially identical.

One preferred embodiment of the invention includes an axle 130 disposed along the axis AX. The axle 130 is rotatably coupled to the second half 120B of the anchor 120 via a pivot hole 122 located in the center of the closed end of the second half 120B. The axle 130 is fixedly attached to the shielding component 106 via a press fit hole 123 located in the center of first and second surfaces 121 A and 121B of the shielding component 106. Methods for attaching the axle 130 to the shielding component 106 known to those in the art, other than press fitting, may also be used. The axle 130 is also rotatably coupled to the first half 120A of the anchor 120. In a preferred embodiment, the rotatable coupling to the first half 120 A does not include a pivot hole that runs completely through the closed end of the first half 120A, but rather includes a socket (or other means for accepting an end of the axle 130) located on the interior surface of the closed end of the first half 120 A of the anchor 120.

In operation, the aperture 124 functions as a movable window between the first coil 102 and the second coil 104. Positioning the aperture 124 in the shielding component 106 directly between the two coils, providing a direct unimpeded path from the first coil 102 to the second coil 104 (as shown in FIG. 6) maximizes the mutual inductance M. Rotating the shielding component 106 by approximately 180 degrees about the axle 130 from the position of maximum mutual inductance, such that the aperture is at its maximum distance from the first and second coils 102 and 104 (as shown in FIG. 7) minimizes the mutual inductance. As the shielding component rotates from the position shown in FIG. 6 to the position shown in FIG. 7, the mutual inductance varies from a maximum value to a minimum value. In general, when the aperture 124 moves such that there is no "line of sight" through the aperture from the first coil 102 to the second coil 104, the mutual inductance is approximately equal to the minimum inductance shown in FIG. 7. FIGs. 6 and 7 show the coils 102 and 104 schematically as a generic coil, although in one preferred embodiment, the coils 102 and 104 include coils each having a shape that substantially matches the shape of the aperture 124, so as to maximize the flux linkage between the coils 102 and 104. As described herein, placing a constant amplitude, time varying signal on the first electric coil 102 produces a similar signal on the second coil 104 which amplitude is related to the mutual inductance between the first and second coils 102 and 104. Thus, when the components shown in FIGs. 3, 4, 5, 6 and 7 are combined with a drive circuit 108 and a detection circuit 112 as shown in FIG. 2, the amplitude of the induction signal 114 is directly related to the absolute angular position of the shielding component 106 with respect to the anchor 120. The shielding component 106 may be attached to a movable object, such as the axle 130, in order to provide a position signal related to the absolute position of that movable object, with respect to the anchor 120. The link between the movable object and the shielding component may be rigid, e.g., as with the press fit connection to the axle 130 in the preferred embodiment, such that the movement of the shielding component is identical to the movable object. Other linkages known to those in the art, such as linkages for translating one rate of angular motion to another (e.g., a gearbox or transmission), linkages for converting linear motion to angular motion, or linkages for converting non-linear motion to angular motion, may also be used to connect the shielding component 106 to the movable object. For alternate embodiments in which the shielding component moves in a linear or other non-angular manner with respect to the anchor, similar linkages for connecting the shielding component to the movable object may also be used.

In one preferred embodiment, the drive circuit 108 resides within the anchor 120. In alternate embodiments, a drive circuit 108 that is external to the anchor 120 may convey the drive signal 110 to the first electrical coil 102 via an aperture in the anchor 120, or through some other port into the hollow cylinder provided for transmitting the drive signal 110. One example of a drive circuit 108 that is suitable for driving the first electrical coil 102 is shown in FIG. 8. In this drive circuit 108, the OPA277 device operates to produce a sinusoidal signal. The OPA 551 device buffers the sinusoidal signal between the generating OP A277 device and the first coil 102, so as to produce the stimulating signal 110. This buffering reduces the amount distortion in the sinusoidal signal from the OPA277 device, as compared to the OPA277 device directly driving the load presented by the first coil 102. FIG. 8 shows a potentiometer 133 drawn with broken lines in the circuit between the OPA277 and the OPA551. Some embodiments of the invention include this potentiometer 133 to adjust the amplitude of the signal from the OPA277 device, providing control of the stimulating signal amplitude so as to optimize the power dissipation of the first coil 102.

One preferred embodiment of the detection circuit 112 includes a signal recovery circuit 150, a low pass filter 152, and an amplitude detection circuit 154 (also referred to as 'peak detector'), as shown in FIG. 9. FIG. 8 shows a schematic representation of an exemplary embodiment of a detection circuit 112. The signal recovery circuit 150 provides a buffering layer between the second coil 104 and the system output (i.e., the position signal 116), so as to reduce or eliminate instabilities that may exist within the driver/first coil/second coil circuit. The low pass filter 152 removes noise that may be included on the inducted signal 114 in addition to the fundamental frequency of the stimulating signal 110. The amplitude detection circuit 154 provides an output whose voltage (or current) is proportional to the amplitude of the inducted signal 114. Such amplitude detection circuits are well known to those skilled in the art.

In another preferred embodiment, the present invention may include a first coil 202 separated from a second coil 204 by a first shielding component 206, and separated from a third coil 208 by a second shielding component 210, as shown in FIG. 10. The first shielding component 206 includes a first aperture 207, and the second shielding component 210 includes a second aperture 211. In this embodiment, the two shielding components 206 and 210 are mechanically coupled such that they both rotate simultaneously. The coupling between the first coil 202 and the second coil 204 is such that applying a time varying voltage across the first coil 202 produces a signal having the opposite polarity on the second coil 204. Likewise, the coupling between the first coil 202 and the third coil 208 is such that applying a time varying voltage across the first coil 202 produces a signal having the opposite polarity on the third coil 208. The second coil 204 and the third coil 208 are positioned with respect to the first coil 202, and are combined by the detector 112, so as to provide a bipolar (i.e., +/-) response with respect to the relative shield position. For example, the first and second coils may be positioned such that the second coil produces a signal of the same polarity as the signal driven on the first coil. Further, the first and third coils may be positioned such that the third coil produces a signal of the opposite polarity as the signal driven on the first coil. The detector 112 may then combine the signals from the second and third coils in series opposition so as to produce a bipolar output with respect to shield position. Other orientations of the coils and combinations of the output voltages known to those in the art may also be used to produce as similar bipolar output. Although this concept of using two shields and three inductors to produce a bipolar output has been described in detail for a pair of rotating shields for use in a rotary position sensor, the concept may also be extended to use in a linear position sensor as shown in FIG. 4 by allowing the shields 206 and 210 to translate along a linear axis, rather that rotate about a rotation axis.

The same bipolar effect achieved by the embodiment shown in FIG. 10 may also be accomplished by the system 230 shown in FIG. 11. In this embodiment, a single shielding component 232 separates a first coil 234 and a second coil 236. As with the similar embodiments described herein, a constant amplitude, time varying signal applied to the first electric coil 234 produces a similar signal on the second coil 236 which amplitude is related to the mutual inductance between the first and second coils 234 and 236. However, as shown in FIG. 11, the signal from the second coil 236 is summed, via summer 238, with an inverted and scaled version of the reference signal that is applied to the first coil 234. The scaling factor is preferably 0.5, although other scaling factors may also be incorporated so as to produce an alternative desired output. In the embodiment shown in FIG. 11, the inverted and scaled version of the reference signal is generated by modifying the reference signal via a hardware inverter and sealer, such as an amplifier and/or attenuator. FIG. 12 shows a circuit for converting a single ended output signal 114, as would result from the single shield architecture of FIG. 3 or FIG. 4, into a bipolar output. The upper portion of the circuit includes a peak detector, and the lower portion includes a level shifter. In other embodiments, the inverted and scaled version of the reference signal may be generated by a second signal generator, or by other means known to those in the art.

In other embodiments, the low resistance region in the shield between two inductors (as described herein) may include a spatially variable resistance to magnetic flux. Such a spatially variable resistance may be due to tailoring the shape of the low resistance region as shown in exemplary shield of FIG. 13 A, or it may be due to spatially varying the properties of the material within the low resistance region as shown in FIG. 13B. For the latter, the properties that may be varied include, but are not limited to, the thickness, the density, or the surface texture of the material, or by including a combination of various materials, where the combination varies spatially, or any combination of the above.

In another form of the invention shown in FIG. 14, a shield 302 having an aperture 304 separates a primary first coil 306 and series-connected pair of secondary coils 308 and 310. The position of the primary first coil 306 is fixed with respect to the secondary coils 308 and 310, and the shield 302 is disposed so as to rotate with respect to coils 306, 308 and 310 about an axis AX. In operation, a drive circuit 108 drives a stimulating signal across the primary first coil 306, which in turn produces a field that variably couples to the secondary coils as a function of the angular position of the shield 302. In one embodiment, the secondary coils 308 and 310 are connected in series opposition, such that the when the field from the primary coil 306 couples equally to the secondary coils 308 and 310 the null position), the resultant voltage across the outside terminals Tl and T2 of the secondary coils 308 and 310 is substantially zero. Being connected in "series opposition" is a term of art that means that the coils are electrically coupled in series, and that when both coils are subjected to a common magnetic field, the voltage that develops across one is the opposite of the voltage that develops across the other. As the shield 302 rotates away from the null position, the field from the primary coil 306 couples more to one of the secondary coils with respect to the other secondary coil. The resultant voltage at terminals Tl and T2 will be either positive or negative with respect to the stimulating signal, depending upon the orientation of the secondary coils with respect to the primary coil. Thus, the output voltage at the Tl and T2 terminals is a bipolar voltage indicative of the angular position of the shielding component 302.

The position sensing apparatus 100 shown in FIG. 2 is a specific application of the first coil 102 transferring information to the second coil 104 in the form of magnetic field energy. In general, this transfer of information from one coil another may be used in other applications, for example to implement a non-contact (also referred to as "contactless") circuit card connector assembly. Such a circuit card connector assembly could be used to transfer signals from a first assembly (e.g., a motherboard or backplane) to a second assembly (e.g., a circuit card or daughter card). The first coil/second coil pairing shown in FIG. 2, without the shielding component, could be miniaturized and duplicated multiple times to produce such a connector assembly 400 having multiple primary/secondary coil pairs residing in a respective one of mating connector housings 400 A and 400B, such as the exemplary architecture shown in FIG. 15 A. Individual drivers 402 associated with each of the primary coils 404 apply a unique stimulating signal to each of the primary coils 404. The stimulating signals each create a localized magnetic field which couples to the corresponding secondary coil 406 to produce a induced signal across that secondary coil 406. A corresponding detection circuit 408 receives the induced signal to produce an output signal 410 corresponding to the associated stimulating signal. Such a contactless connector assembly 400 is useful because it eliminates failures associated with contact wear, corrosion, reduction of contact pressure, contact spring fracture due to metal fatigue, and other failure mechanism of electrical contacts known to those in the art.

FIG. 15B shows an alternative form for the coils 404/406. In that form, coil 404 and 406 each are wound around a mandrel. 420/422 made of a magnetic material, such as an iron core. When the connector housings are positioned adjacent to each other as shown in FIG. 15B, the mandrels 420 and 422 are adjacent to each other, providing a well-defined high permeability flux path coupling the coils 404 and 406. Preferably, in a high density connector, mandrel has a correspondingly small diameter and the winding is made of fine wire.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of the equivalency of the claims are thus intended to be embraced therein.

Claims

What is claimed is:

1. A position sensing apparatus for providing a mutual inductance value corresponding to a position of a movable body, relative to a reference position, comprising: a first electrical coil, and a second electrical coil disposed adjacent said first electrical coil; and, a shielding component disposed between said first coil and said second coil, said shielding component having at least one region characterized by a relatively high resistance to magnetic flux, and at least one region characterized by a relatively low resistance to magnetic flux relative to said at least one region characterized by relatively high resistance, a position of said shielding component being a first predetermined function of said movable body position; wherein said first and second electrical coils are characterized by said mutual inductance value being a second predetermined function of said movable body position.

2 A position sensing apparatus according to claim 1 , wherein said at least one region of low resistance includes an aperture for providing an unimpeded path from said first coil to said second coil, such that a cross sectional area of said unimpeded path varies as a predetermined function of a position of said shielding component.

3. A position sensing apparatus according to claim 2, wherein said position of said movable body includes angular position, such that said shielding component rotates about a pivot axis.

4. A position sensing apparatus according to claim 3, wherein said aperture includes an arcuate slot characterized by an inner radius and an outer radius about said pivot axis.

5. A position sensing apparatus according to claim 2, wherein said position of said movable body includes linear position, such that said shielding component translates along a travel axis.

6. A position sensing apparatus according to claim 5, wherein said aperture includes a linear slot characterized by an inner distance and an outer distance from said travel axis.

7. A position sensing apparatus according to claim 1, wherein said first electrical coil is fixed relative to said reference position.

8. A position sensing apparatus according to claim 1, wherein said first electrical coil and said second electrical coil are fixed relative to said reference position.

9. A position sensing apparatus according to claim 2, wherein said shielding component is constructed and arranged such that said cross sectional area varies, according to said position of said movable object, within a range bounded by a minimum cross sectional area to a maximum cross sectional area.

10. A position sensing apparatus according to claim 9, wherein said minimum cross sectional area corresponds to a mutual inductance commensurate with an absence of a common field between said first electrical coil and said second electrical coil.

11. A position sensing apparatus according to claim 9, wherein said maximum cross sectional area corresponds to a mutual inductance commensurate with an absence of shielding between said coils.

12. A position sensing apparatus according to claim 1, wherein said shielding component and said movable object are combined so as to include a single component.

13. A position sensing apparatus according to claim 1, said shielding component being fixedly attached to said movable object, such that said shielding component position varies identically as said movable object position.

14. A position sensing apparatus according to claim 1, said shielding component being coupled to said movable object via a linkage, such that said component position varies as said first predetermined function of said movable body position.

15. A position sensing apparatus according to claim 1 , wherein each of said first electrical coil and said second electrical coil includes a multiple winding inductor.

16. A position sensing apparatus according to claim 1 , wherein each of said first electrical coil and said second electrical coil includes an associated core.

17. A position sensing apparatus according to claim 1 , further including: a third coil disposed such that said first coil is between said second coil and said third coil; and, a second shielding component disposed between said first coil and said third coil, said second shielding component being mechanically coupled to said first shielding component such that said first shielding component and said second shielding component exhibit substantially identical movement; wherein said second coil and said third coil are electrical coupled so as to produce a bipolar output in response to movement of said shielding components, when a time varying, constant amplitude signal is applied to said first coil.

18. A position sensing apparatus according to claim 1 , wherein said at least one region characterized by a relatively low resistance to magnetic flux includes a region characterized by a spatially variable resistance to magnetic flux.

19. A position sensing apparatus according to claim 18, wherein said region characterized by a spatially variable resistance includes an aperture having a spatially variable size.

20. A position sensing apparatus according to claim 18, wherein said region characterized by a spatially variable resistance includes a material having one or more spatially varying properties.

21 A position sensing apparatus according to claim 1, further including a third electrical coil connected in series opposition with said second electrical coil, said second and third coil forming a composite coil, wherein said first coil and said composite coil are characterized by a composite mutual inductance value being a predetermined function of said movable body position.

22. A position sensing system for providing a position signal corresponding to a position of a movable body, relative to a reference position, comprising: a first electrical coil, and a second electrical coil disposed adjacent said first electrical coil; a shielding component disposed between said first coil and said second coil, said shielding component having at least one region characterized by a relatively high resistance to magnetic flux, and at least one region characterized by a relatively low resistance to magnetic flux relative to said at least one region characterized by relatively high resistance, a position of said shielding component being a first predetermined function of said movable body position; a drive circuit for driving a stimulating signal through said first coil; and, a detection circuit for detecting an induction signal associated with said second coil, wherein said detection circuit produces said position signal as a predetermined function of said induction signal.

23. A position sensing system according to claim 22, wherein said stimulating signal includes a sinusoid having a constant, predetermined amplitude and a constant, predetermined frequency.

24. A position sensing system according to claim 22, wherein said detection circuit further includes: an inverter for inverting said stimulating signal so as to produce an inverted signal, and an amplitude sealer for receiving and scaling said inverted signal by a predetermined scaling factor so as to produce a scaled signal; and, a summer for summing said induction signal and said scaled signal so as to produce a bipolar position signal corresponding to said position of the movable body.

25. A position sensing system according to claim 22, wherein said detection circuit receives a time varying voltage from across said second coil, measures an amplitude of said time varying voltage, and produces said position signal as a predetermined function of said amplitude.

26. A position sensing system according to claim 22, wherein said detection circuit includes a buffer circuit for providing isolation between said second inductor and a system output conveying said position signal.

27. A position sensing system according to claim 22, wherein said detection circuit includes a low pass filter for filtering noise from said induction signal.

28. A position sensing system according to claim 22, further including a third electrical coil connected in series opposition with said second electrical coil, said second and third coil forming a composite coil, wherein said induction signal is associated with said composite coil.

29. A position sensing system for providing a position signal corresponding to a position of a movable body, relative to a reference position, comprising: a first electrical coil, a second electrical coil and a third coil, said second and third coils being electrically coupled in series opposition so as to form a coil pair and disposed adjacent said first electrical coil; a shielding component disposed between said first coil and said coil pair, said shielding component having at least one region characterized by a relatively high resistance to magnetic flux, and at least one region characterized by a relatively low resistance to magnetic flux relative to said at least one region characterized by relatively high resistance, a position of said shielding component being a first predetermined function of said movable body position; a drive circuit for driving a stimulating signal through said first coil; and, a detection circuit for detecting an induction signal associated with said coil pair, wherein said detection circuit produces said position signal as a predetermined function of said induction signal.

30. A method of providing a position signal corresponding to a position of a movable body, relative to a reference position, including the steps of: driving a stimulating signal through a first electrical coil; providing a second electrical coil disposed adjacent said first electrical coil; providing a shielding component disposed between said first coil and said second coil, said shielding component having at least one region characterized by a relatively high resistance to magnetic flux, and at least one region characterized by a relatively low resistance to magnetic flux relative to said at least one region characterized by relatively high resistance, a position of said shielding component being a first predetermined function of said movable body position; detecting an induction signal associated with said second coil, and producing said position signal as a predetermined function of said induction signal.

31. A non-contact electrical connector assembly for transferring electrical signals, comprising:

a primary coil and a secondary electrical coil disposed adjacent to said primary electrical coil;

a drive circuit for driving an input electrical signal through said first coil; and,

a detection circuit for detecting an induced signal associated with said second electrical coil, and for producing an output signal, wherein said output signal is proportional to said input signal.

32. A non-contact electrical connector assembly for transferring electrical signals, comprising: A. a plurality of primary coils disposed in a first connector housing, each of said primary coils extending about a respective one of a plurality of parallel axes to a point at or near a mating surface of said first connector housing, wherein said parallel axes have a predetermined spatial distribution; B. a plurality of secondary coils disposed in a second connector housing, each of said secondary coils extending about a respective one of a plurality of parallel axes to a point at or near a mating surface at said second connector housing, wherein each of said secondary coils is associated with a corresponding primary coil; wherein said mating surfaces of said first and second connector housings are adapted to be positioned to permit adjacent alignment of said associated primary coils and said secondary coils, whereby the axes of the respective primary and secondary coils are mutually parallel.

33. A non-contact electrical connector assembly according to claim 31 wherein each of said primary and secondary coils are disposed about a high magnetic permeability mandrel extending along its axis.

34. A non-contact electrical connector assembly according to claim 31 , further including for each said primary/secondary coil pairs, (i) a driver circuit for driving an, input electrical signal through said primary coil, (ii) a detection circuit for detecting an induced signal associated with said second electrical coil, and for producing an output signal, wherein said output signal is proportional to said input signal.