Inductive sensor device and method for operating such a sensor device

Abstract

An inductive sensor device (10) for determining the longitudinal position (P) of an object (11) along a sensitive axis (S1) of the sensor device (10), the object (11) moving at a distance from an end face (12) of the sensor device (10) and being at least partially electrically conductive and / or magnetically polarizable; and having a coil arrangement (14) with a substantially planar excitation coil (16) and sensor electronics (30) by means of which an alternating magnetic field is generated in order to induce eddy currents and / or magnetic polarization in the object (11); a first substantially planar receiving coil (18; 18a-18b) arranged substantially parallel to the excitation line The invention relates to a sensor device (10) and a sensor electronic device (30) for determining at least one parameter (DSS) of the electric signal of the excitation coil (16) which can be changed due to the reverse effect of the inductance of the object (11); determining at least one parameter (PSS) of the voltage induced in at least the first receiving coil (18; 18a-18b; 68) based on the reverse effect; and determining the longitudinal position (P) according to the electric signal parameter (DSS) of the excitation coil (16) and the induced voltage parameter (PSS) of the first receiving coil (18; 18a-18b).

Description

Technical Field

[0001] The invention relates to an inductive sensor device for determining the longitudinal position of a movable object along a sensitive axis of the sensor device, a method for operating the sensor device and a program for a data processing device. Background Art

[0002] It is known from practice that in the case of inductive position sensors, the magnetic field of an excitation coil acts on a metal object, which in turn generates a magnetic field, which induces a voltage in one or more receiving coils. The position between the sensor device and the object can be determined from the induced voltage. Usually, the excitation coil is oriented along a longitudinal axis, which at the same time corresponds to the sensitive axis of the sensor device. The receiving coil should be designed in such a way that the voltage induced in the receiving coil is zero if there is no object in the vicinity.

[0003] The inductive position sensor device BIPCD2-T017-04-BP02 from Balluff of Neuhausen auf den Fildern is configured with a series of essentially identical wound coils with a ferrite core. Each coil is in turn connected in parallel with a capacitor and operates as an LC oscillator. The oscillation amplitude of each coil is changed depending on the approach of a metal object, and the longitudinal position of the object is calculated from the change in the oscillation amplitude.

[0004] The inductive position sensor device BIPED2-B133-03-S75 from Balluff of Neuhausen auf den Fildern is an inductive sensor device having a coil system as a series sensor, which is formed in printed circuit board technology. The sensor device has an excitation coil and several receiving coils connected in series, which have crossed windings and non-crossed windings. The position of an object relative to the sensor device is determined using the vertical component of the object's magnetic field. The relative voltage and the absolute voltage as well as the phase of the induced voltage in the receiving coil depend on the object position corresponding to the sine and cosine functions. The sensor device can be operated at a fixed excitation frequency. The longitudinal measuring range is about 130 millimeters (mm).

[0005] The coil system of the inductive sensor device described in WO 2019 / 063679 A1 has an excitation coil and two receiving coils. The excitation coil can be excited by an oscillating circuit as an LC circuit element. The first receiving coil has two sections arranged continuously in the longitudinal direction, and the two sections are oriented relative to each other. The second receiving coil has three sections arranged symmetrically in the longitudinal direction. The area of ​​the middle section is as large as the area of ​​the total area of ​​the other two sections arranged in the longitudinal direction at the ends of the coil system. The excitation coil surrounds the two receiving coils. Based on the signals of the two receiving coils, the longitudinal position of the conductive or metal object is identifiable, and a switching signal can be output accordingly.

[0006] It is particularly difficult to miniaturize the above-mentioned sensor device to, for example, a total length of 15 mm with a measuring range of at least 10 mm. On the one hand, it is difficult to operate the miniaturized sensor device at a constant excitation frequency, because in the case of smaller sensor devices the complex impedance of the excitation coil varies significantly in the vicinity of the object, which in resonant operation leads to a lowering of the resonant frequency. On the other hand, when miniaturizing the coil arrangement with a constant number of coils, it is difficult to provide wires, openings through printed circuit boards, etc. in a very substantially reduced space. Furthermore, it is also problematic to appropriately reduce the insensitive or nonlinear blind areas at the ends of the sensor device and produce an acceptable sensing range.

[0007] Therefore, new concepts and new operating modes of small sensor devices with dimensions roughly corresponding to their measuring range are needed. Summary of the invention

[0008] The problem underlying the present invention is to provide a compact sensor device having dimensions which roughly correspond to its measuring range.

[0009] According to a first aspect, an inductive sensor device is provided for determining a longitudinal position of an object along a sensitive axis of the sensor device, the object being movable at a distance from an end face of the sensor device and being at least partially electrically conductive and / or magnetically polarizable, wherein the sensor device has a coil arrangement and sensor electronics, wherein the coil arrangement has: a substantially planar excitation coil, by means of which an alternating magnetic field for inducing eddy currents and / or magnetic polarization can be generated in the object; and a first substantially planar receiving coil, which is arranged substantially parallel to the excitation coil and overlaps the excitation coil, wherein the excitation coil and the first receiving coil are arranged substantially parallel to the end face of the sensor device, wherein the sensor electronics are arranged to: determine at least one parameter of an electrical signal of the excitation coil, which parameter can vary due to a back effect of the object, and at least one parameter of a voltage induced in the first receiving coil due to the back effect of the object; and determine the longitudinal position as a function of the at least one determined parameter of the induced electrical signal of the excitation coil and the at least one determined parameter of the induced voltage of the first receiving coil.

[0010] In the excitation coil of the coil arrangement of the inductive sensor device, a time-alternating magnetic field may be generated, which in turn may generate eddy currents in a movable object which may be at least partially electrically conductive and / or may generate a magnetic polarization of the object which may be at least partially magnetically polarizable. The time-alternating eddy currents and / or magnetic polarization in turn generate an alternating magnetic field, so that the object may exert an inductive back-effect both on the excitation coil of the coil arrangement and on the first receiving coil. In this context, a "back-effect" may be understood as an electrical effect on a coil located in the vicinity of the object due to eddy currents generated in the object and / or magnetic polarization of the object. Thus, due to the presence of the object in the vicinity of the coil arrangement, an oscillation parameter of the electrical signal of the excitation coil (e.g. current or voltage amplitude, oscillation frequency) may be variable and a voltage may be induced in the receiving coil. The oscillation parameter of the excitation coil may be used together with the parameter obtained from the induced voltage of the first receiving coil to determine the longitudinal position of the object along the sensitive axis, in particular relative to a reference point (e.g. midpoint) of the sensor device.

[0011] The coil arrangement can in particular have only one excitation coil.

[0012] The first receiving coil can advantageously be configured such that a determined parameter of the induced voltage of the first receiving coil depends monotonically on the longitudinal position of the object at least near the midpoint of the sensor device. For example, at least one parameter can be a monotonically increasing or monotonically decreasing function of the longitudinal position.

[0013] The sensitive axis may correspond to a direction along which at least one parameter of the electrical signal of the excitation coil and / or at least one parameter of the induced voltage of the first receiving coil may change. The coil arrangement may be arranged on a side of an end face of a sensor housing, which is remote from the object, in which the coil arrangement may be accommodated. The object may move or be movable along a trajectory, which is at a certain distance from the sensor housing, for example from the end face of the sensor housing. The distance may in particular be measured vertically between the end face of the sensor housing and the surface of the object. Both the change of the electrical signal parameter of the excitation coil and the change of the induced voltage of the first receiving coil compared to a state without an object are determined by the three-dimensional arrangement of the object relative to the coil system, in particular by the longitudinal position and the distance. As long as the object moves along a constant longitudinal trajectory, for example at a fixed distance from the end face, the longitudinal position may be determined within a monotonic region of the parameter of the induced voltage in the receiving coil. In the case of a variable distance, the relationship between the longitudinal position of the object and the parameter of the induced voltage in the receiving coil may no longer be clear. In other words, in this case, each longitudinal position of the object may also depend on the distance. For example, the amplitude of the induced voltage of the first receiving coil is generally smaller at a greater distance than at a smaller distance.

[0014] The inductive sensor device can have a particularly small configuration, since the sensor device can utilize the inductive back effect of an object, the at least partially electrically conductive and / or magnetizable object can be applied to the entire coil arrangement of the sensor device and in particular to the excitation coil, so that the excitation coil itself can also be regarded as an additional sensor coil and can be used for evaluation. For each longitudinal position of the object, the change of the electrical signal parameter of the excitation coil is generally smaller at a long distance than at a smaller distance. Therefore, by using the excitation coil as a sensor coil, the distance dependency of the signal parameter of the induced voltage of the receiving coil can be compensated, without having to use an additional receiving coil in the coil arrangement.

[0015] Furthermore, the sensor device can have a particularly small configuration, since it can have few components and the coil arrangement can have a planar configuration so that the three-dimensional space required for the coil can be small. In particular, the sensor device can be made in such a way that it can be configured to have a dimension (e.g. housing dimension) of less than or equal to about 15 mm along the sensitive axis and less than or equal to about 10 mm in the transverse direction, wherein the longitudinal measuring range is greater than or equal to about 10 mm. The depth of the sensor device measured perpendicular to the end face of the sensor device can be about 12 mm for miniaturized sensor electronics (e.g. application specific integrated circuits (ASICs)).

[0016] Due to the size of the sensor device, this can be used in various ways, for example in gripping systems for determining the position of grippers, etc., and can then be integrated in existing equipment in a simple manner. The sensor device can also be suitable for determining the position of rotating objects (e.g. rotating spindles) with rotation speeds of, for example, more than 40,000 revolutions per minute, since the sensor device can have a short response time due to the joint evaluation of the signal of the excitation coil and the first receiving coil and thus a high output transmission rate for position determination. The sensor device can be mounted flush with a surface, for example, due to its size.

[0017] The first receiving coil can be arranged with its surface extending in the plane of its coil parallel to the extension of the surface of the excitation coil and facing the end face of the sensor device and thus the object. Alternatively, the excitation coil can also be arranged facing the end face of the sensor device and thus the object, while the first receiving coil can be arranged on the side of the excitation coil facing away from the end face. Alternatively, the excitation coil can surround the first receiving coil substantially in the plane of its own coil, or both coils can be wound on the same coil former.

[0018] In one embodiment, the sensor electronics can be configured to determine the vertical distance of the object between the end face of the sensor device and the object based on the determined at least one parameter of the electrical signal of the excitation coil and the determined at least one parameter of the induced voltage of the first receiving coil. Thus, a multifunctional use of the sensor device is possible.

[0019] In one embodiment, the first receiving coil may have an anti-symmetric polarizable configuration. For example, the voltage induced in the first receiving coil may have substantially the same amplitude and opposite phase in different directions along the sensitive axis, at equal distances of the object from the midpoint of the measurement range and at equal longitudinal distances, which may be defined by the midpoint of the receiving coil. Thus, position determination and optionally distance determination may be performed based on the phase and amplitude of the induced voltage.

[0020] The sensitive axis may then be defined by the antisymmetric polarization of the first receiving coil, wherein the sensitive axis may extend in the plane of the coil and along the centerline of the first receiving coil, whereby viewed along the sensitive axis one half coil may have a first polarization and the second half coil may have the opposite polarization.

[0021] In one embodiment, the coil arrangement may have a second substantially planar and optionally also antisymmetrically polarizable receiving coil, which may be arranged substantially parallel to and overlapping the excitation coil, wherein the second receiving coil may (in particular only) overlap the first receiving coil in one or more of its end regions and may be electrically connected in series with the first receiving coil. In other words, viewed along the sensitive axis, the winding of the second receiving coil may be arranged to overlap one or both end regions of the winding of the first coil. Thus, an increased induced voltage may be provided in both end regions of the coil system, so that the longitudinal measuring range may be extended.

[0022] Both the first receiving coil and the second receiving coil may consist of several partial coils, and the partial coils of the receiving coils may be connected in series in any order of correct polarization.

[0023] Furthermore, the second receiving coil can be arranged between the excitation coil and the first receiving coil or adjacent to the first receiving coil, facing the end face of the sensor device.

[0024] In one embodiment, the coil arrangement may have a third substantially planar receiving coil, which may be arranged substantially parallel to and overlap the excitation coil and may define an additional sensitive axis of the sensor device, which additional sensitive axis may extend substantially perpendicularly to the sensitive axis of the first receiving coil, wherein the sensor electronics may be configured to determine at least one parameter of the voltage induced in the third receiving coil due to the inductive back effect of the object, and to determine the lateral position and optionally the vertical distance of the object along the additional sensitive axis from the already determined at least one parameter of the electrical signal of the excitation coil and the already determined at least one parameter of the induced voltage of the third receiving coil. The third receiving coil may also have an anti-symmetric polarizable configuration. The sensitive axis and the additional sensitive axis may in particular extend in a plane parallel to the end face. In other words, the first receiving coil and the third receiving coil may be rotated 90 degrees relative to each other in their respective coil planes. In this way, a two-dimensional movement of the object in a plane parallel to the end face of the sensor device may be detected.

[0025] The additional sensitive axis may correspond to an additional direction like the sensitive axis, along which at least one parameter of the electrical signal of the excitation coil and / or at least one parameter of the induced voltage of the third receiving coil may vary. The additional sensitive axis may be defined by an antisymmetric polarization of the third receiving coil, wherein the additional sensitive axis may extend in the plane of the coil and along the center line of the third receiving coil, so that half of the coil of the third receiving coil may have a first polarization and a second half of the coil of the third receiving coil may have an opposite polarization, viewed along the sensitive axis.

[0026] The determination of the transverse position may be performed similarly to the determination of the longitudinal position. Furthermore, at least one parameter of the induced voltage of the first receiving coil may be replaced by at least one parameter of the induced voltage of the third receiving coil in the possible signal processing.

[0027] In one embodiment, the coil arrangement may have a fourth substantially planar and optionally also anti-symmetrically polarizable receiving coil, which may be arranged substantially parallel to and overlapping the excitation coil, wherein the fourth receiving coil may (in particular only) overlap the third receiving coil in one or more of its end regions and may be electrically connected in series with the second receiving coil. In other words, viewed along the additional sensitive axis, the windings of the fourth receiving coil may be arranged to overlap one end region or both end regions of the third receiving coil. Thus, an increased induced voltage may be provided in both end regions of the coil system, so that the lateral measuring range may be extended.

[0028] In one embodiment, the excitation coil, the first receiving coil, the second receiving coil, the third receiving coil and / or the fourth receiving coil can be arranged on or in one or more layers of a printed circuit board. Manufacturing the sensor device (particularly exclusively) based on printed circuit board technology can be particularly economical.

[0029] In one embodiment, the excitation coil, the first receiving coil, the second receiving coil, the third receiving coil and / or the fourth receiving coil can be made by a winding technique. Winding the coil into a wire loop can make it possible to simply miniaturize the sensor device.

[0030] Preferably, all receiving coils can be manufactured in one and the same way.

[0031] The wound coil can be made on a coil former or without a coil former. The coil former can be produced by 3D printing technology.

[0032] In one embodiment, the windings of the coil sections (e.g., half coils) of the first, second, third, and / or fourth receiving coils, viewed along their respective sensitive axes, may be oriented relative to each other. Thus, the receiving coils may have an anti-symmetric polarizable configuration, such that by the presence of an object in one or the other half of the coil, a voltage with opposite polarity may be induced, while for a central longitudinal or transverse position of the object, the induced voltage may be almost zero.

[0033] In one embodiment, the first receiving coil, the second receiving coil, the third receiving coil and / or the fourth receiving coil, viewed along their respective sensitive axes, may have windings that are substantially centrally crossed. This measure may also have the effect that the corresponding receiving coils may have an anti-symmetrical polarizable configuration, so that by the presence of an object in one or the other half of the coil, a voltage with opposite polarity may be induced, while for a central longitudinal position of the object the induced voltage may be almost zero.

[0034] In the case where the first, second and / or third receiving coil can be wound, this coil can be in the form of a butterfly coil with crossed windings or with oppositely wound coil sections connected to one another by means of electrical wires.

[0035] The two types of anti-symmetric polarizable receiving coils described may also allow the sensor device to be mounted in a metallic environment, since due to their mounting only a small background signal, if any, may be present in the receiving coils compared to receiving coils with non-anti-symmetric properties.

[0036] In one embodiment, the sensor device may further comprise a first electrically conductive shielding element, which may be arranged transversely, in particular completely, around the coil. The shielding element may be formed as a strip, in particular as a continuous strip. The first shielding element may be configured as one or more metal foils or a metal coating on a housing wall of the sensor device housing or an edge metallization of a multilayer printed circuit board and / or extend substantially perpendicularly to the end face of the sensor device. The sensor device may thus be flush mounted in a metallic environment with only very small or no metal-free areas around the sensor device.

[0037] In one embodiment, the sensor device may further comprise a second conductive planar shielding element, which may be arranged on a side of the coil arrangement facing away from the object. The second shielding element may be formed as a metal plate or, if the coil is arranged in a layer of a printed circuit board, on a separate layer of the printed circuit board. The sensor electronics may also be arranged on a side of the second shielding element facing away from the excitation coil.

[0038] The coil arrangement and the sensor electronics and optionally the first shielding element and / or the second shielding element (if present) may be accommodated in one housing.

[0039] In one embodiment, viewed in a direction perpendicular to the sensitive axis, symmetrically and on either side of the coil arrangement, in each case a coil-free region having a width of at least 10% of the (in particular inner) opening width of the first shielding element can be provided adjacent to the first shielding element. Without said distance or if the distance is too small, the shielding element will significantly reduce the excitation efficiency and the induced voltage of the receiving coil. In particular, the same or similar spacing to the first shielding element can be provided on all sides of the coil arrangement.

[0040] In one embodiment, the excitation coil can be excited substantially with a periodic, in particular substantially sinusoidal current or a periodic, in particular substantially sinusoidal voltage, so that an alternating magnetic field can be generated in the excitation coil, which can act on the object. The excitation of the excitation coil can be performed with the aid of an oscillating circuit, in particular an LC oscillating circuit, of the sensor electronics. In other words, in one embodiment, the excitation coil can be part of the oscillating circuit. In one embodiment, the excitation coil as an inductive element of the LC circuit can be part of a self-oscillating LC oscillating circuit, so that the excitation coil together with a capacitor can form a resonant circuit, which capacitor can act as a capacitive element of the LC circuit.

[0041] In one embodiment, at least one parameter determined from at least one electrical signal (e.g., from current or voltage) of the excitation coil may be, for example but not exclusively, the frequency or amplitude of the corresponding electrical signal. These types of parameters may be sensitive to distance, so that the excitation coil may be used as part of a distance sensor.

[0042] In one embodiment, the sensor electronics may be configured to calculate a (particularly dimensionless) proximity signal from the change of a determinable parameter of the electrical signal of the excitation coil caused by the presence of the object, which is indicative of the change of at least one parameter caused by the presence of the object. The proximity signal may be specifically defined as a*(U D0 -U D ) or b*(f OSC0 -f OSC ) or a*(U D0 -U D )+b*(f OSC0 -f OSC ). In the foregoing, a, b may represent scaling factors and U D0 and f OSC0 It can be expressed as the amplitude of the demodulated voltage U D Or oscillation frequency f OSC The no-object value of .

[0043] Furthermore, the proximity signal may also be dependent on the longitudinal or lateral position.

[0044] In one embodiment, the sensor device may be configured to determine at least one reference signal from the electrical signal of the excitation coil, and a phase of the at least one reference signal may have a predetermined ratio to a phase of the electrical signal of the excitation coil.

[0045] In a first option, the sensor electronics may be configured to determine at least one parameter of the induced voltage by means of synchronous demodulation from the induced voltage using a reference signal. The at least one parameter may then be the amplitude of the phase-sensitive demodulated induced voltage, and the phase of the phase-dependent phase reference signal may have a predetermined relationship to the phase of the electrical signal of the excitation coil.

[0046] In a second option, the sensor electronics may be configured to determine at least one parameter of the induced voltage by quadrature demodulating the induced voltage using the reference signal.The at least one parameter of the induced voltage may then be a phase-dependent amplitude of the quadrature demodulated induced voltage.

[0047] These embodiments of signal processing for obtaining at least one parameter allow for continuous demodulation of the induced voltage using conventional techniques and can contribute to a fast response time of the sensor device.

[0048] In one embodiment, the sensor electronics can be configured to determine a (particularly dimensionless) longitudinal position signal as a function of at least one parameter of the induced voltage and optionally the lateral position and optionally the distance. The longitudinal position signal can then be based on at least one parameter of the induced voltage of the receiving coil. In this regard, the at least one parameter can be the phase-dependent amplitude of the quadrature-demodulated induced voltage, in particular if synchronous demodulation can be used to determine the at least one parameter. The at least one parameter can also be the in-phase component and the quadrature-phase component of the amplified induced voltage, in particular if quadrature demodulation can be used to determine the at least one parameter. The longitudinal position signal can in particular be defined as S P =c*U I , S P =d*U Q , S P =c*U I +d*U Q , S P =e*U φ , and a, b, c, d, and e represent scaling factors. φ It represents the phase-dependent amplitude of the orthogonal demodulated induced voltage. I represents the in-phase component of the amplified induced voltage, and U Q represents the quadrature phase component.

[0049] In one embodiment, the sensor electronics may be configured to determine the reduced longitudinal position signal as a ratio of the longitudinal position signal and the proximity signal in order to determine the longitudinal position from the reduced longitudinal position signal. M It can be calculated as V M =S P / S N .

[0050] In one embodiment, the sensor device may be configured to determine the longitudinal position from the reduced longitudinal position signal by means of a linearization function to ensure a more accurate position determination.

[0051] A first variant of the evaluation method in which the reduced longitudinal position signal is determined can therefore be based on dividing the synchronously demodulated or quadrature demodulated voltage by the proximity signal so that the resultant signal can be less dependent on the distance of the object than the corresponding voltage. The resultant signal can additionally depend on the longitudinal or transverse position of the object and can be converted into a longitudinal or transverse position by linearization and scaling.

[0052] In one embodiment, in a second variant of the evaluation method, the sensor device can be configured to determine the mechanical phase as arctan2 from the reduced longitudinal position signal and the proximity signal multiplied by a scaling factor determined in a previous learning process, so as to determine the longitudinal position and optionally the lateral position and optionally the distance from the mechanical phase. In particular, arctan2(V M ,B*S N ). In the foregoing, B represents a scaling factor.

[0053] The scaling factor can ensure that the arctan2 function can represent the monotonicity of the object moving within a certain range. If it is known at what vertical distance the object will likely move with what predetermined properties, the scaling factor can be established in advance, for example at the factory. Alternatively or additionally, the scaling factor can be determined with the help of a learning process, in which the object can at least move, for example, through the middle of the sensing range of the sensor device, so that the magnitude or order of magnitude of the proximity signal can be determined for the current time and from this point in time at a constant vertical distance of the object. For the calculation, it can be assumed that the two parameters of the arctan2 function can be provided as dimensionless values. Since the current or voltage signal is digitized by an A / D converter, the oscillation frequency can be measured by a microcontroller and no special measures are required to provide a dimensionless value.

[0054] In one embodiment, the sensor device may be configured to linearize the mechanical phase (eg by means of a linearization function) and then determine the longitudinal position based on the linearized mechanical phase, thereby ensuring a more accurate position determination.

[0055] In addition, the proximity signal can be used to determine the distance. It should be noted that the proximity signal depends not only on the distance, but also on the material properties and geometric properties (such as width) of the object. For example, in the presence of a small object, a smaller proximity signal may be generated under the same conditions compared to the presence of a large object.

[0056] In an alternative embodiment, linearization may be performed based on the material type of the object.

[0057] In an alternative embodiment, the sensor electronics can be configured to determine the material type of the object based on at least one parameter of the electrical signal of the excitation coil or at least one parameter of the induced voltage. In particular, the sensor electronics can be configured to determine the material type of the object based on the typical phase of the voltage induced by the object in the receiving coil relative to the phase of the electrical signal of the excitation coil. The typical phase can be defined as the phase value (or average value) at which the induced voltage occurs most often over a period of time. In addition, it can be assumed that a too narrow amplitude does not prevent the determination of the phase. It may be necessary to take into account that the sign of the induced voltage also depends on the object position and the corresponding phase shift can be corrected before determining the average value. Alternatively or additionally, the sensor electronics can be configured to determine the type of object material of the object based on the typical relationship between the amplitude change caused by the presence of the object and the frequency change of the oscillator voltage. For a known object material, one of the two evaluation variants described above and an optional, suitable linearization method can then be used for a possible very accurate position determination. For example, in contrast to the demodulation voltage change, the use of the oscillation frequency change can have the following advantages: aluminum-containing objects can be detected particularly well, because such objects may cause slight changes in the demodulation voltage. The object material can also be identified, since for different materials typical values ​​of the relation between the amplitude change and the frequency change of the oscillator voltage are known and can be compared with the measured values. It can be assumed that this value is constant and known regardless of the position. Since the characteristic of the corresponding position-dependent relation of the reduced longitudinal position signal can be non-linear, a material-dependent linearization can be performed. This can be obtained by using an inverse function of the characteristic and can be defined, for example, by an interpolable lookup table, a polynomial or some other analytical approximation function, whose content, coefficients or parameters can be parameters of the evaluation algorithm.

[0058] Before determining one or more positions and optionally distances, a learning process for the object movement may be performed in a certain movement range (eg reference travel or installation travel).The sensor device may acquire, store and / or process measurement data for determining the material of the object.

[0059] Instead of the two variants of the above evaluation method, a multivariable nonlinear function (e.g. an artificial neural network) can be used. The training of the neural network may require a previous learning process, which may be specific to the type of sensor and / or the environment of the sensor. The training can be performed in the factory during the sensor design phase and / or during sensor production. The input variables of the function can be at least one parameter of the electrical signal of the excitation coil and at least one parameter of the induced voltage, and the output variables of the function can be the longitudinal position and optionally the distance and optionally the lateral position of the object.

[0060] In one embodiment, the sensor electronics may implement a self-parameterizing evaluation algorithm.

[0061] In one embodiment, the sensor electronics may be configured to adaptively parameterize the evaluation algorithm, adaptively determine the type of object material of the object and / or adaptively identify changes in the measurement arrangement.

[0062] In one embodiment, the sensor electronics may be configured to determine and temporarily or permanently store one or more values ​​of at least one parameter for use in adaptive parameterization of the evaluation algorithm.

[0063] By all these measures, the processing time of the position determination and optionally the distance determination can be reduced.

[0064] The object can be moved at one or more fixed vertical distances relative to the sensor device, and a (self)calibration of the sensor device with respect to a combination of vertical distance and associated longitudinal position of the object can be performed. Thus, position determination can be simplified, the accuracy of position determination can be improved and / or faults of the sensor device can be compensated.

[0065] Calibration can be performed before the actual distance is determined. For example, a movement of an object along a fixed trajectory can be determined, for example a movement at a fixed object distance or a fixed longitudinal position, which is observed over an extended period depending on the application, for example between two maintenance time points or also over the life of the sensor. In this case, the sensor device can perform its self-calibration, wherein the trajectory of the object can be determined as a combination of vertical distance and longitudinal position. All combinations of vertical distance and longitudinal position determined for the trajectory of the object can be described by a position-dependent, for example linear function, which can be determined during the calibration process. In the case of actual position determination, the joint determination of vertical distance and longitudinal position can be reduced to the determination of one of the two quantities, in particular the longitudinal position. Furthermore, if there is a significant deviation from the trajectory, a maintenance signal can be issued or the calibration function can be returned.

[0066] Alternatively or additionally, the calibration can be performed when commissioning the sensor device and when performing the actual position determination. A function determined during operation can be used, which may depend on a combination of vertical distance and longitudinal position, in order to improve the accuracy of the position determination, wherein the function is used to re-determine the position and the determined position is compared with the value of the function and, if there is a deviation, the position can be determined again optionally based on the acquired measurement signals.

[0067] According to a second aspect, a method for operating an inductive sensor device for determining a longitudinal position of an object along a sensitive axis of the sensor device, the object being movable at a distance from an end face of the sensor device and being at least partially electrically conductive and / or magnetically polarizable, is provided, wherein the method comprises: generating an alternating magnetic field of a substantially planar excitation coil of a coil arrangement of the sensor device for inducing eddy currents and / or magnetic polarization in the object; determining by means of sensor electronics of the sensor device: at least one parameter of an electrical signal of the excitation coil, which parameter is modified by an inductive back effect of the object; and at least one parameter of a voltage induced in a first receiving coil of the coil arrangement due to the inductive back effect of the object, wherein the first receiving coil is of a substantially planar configuration and is arranged substantially parallel to and overlapping the excitation coil, wherein the excitation coil and the first receiving coil are arranged substantially parallel to the end face of the sensor device; and determining the longitudinal position by means of the sensor electronics based on the at least one parameter of the electrical signal of the excitation coil and the at least one parameter of the induced voltage of the first receiving coil.

[0068] According to a third aspect, there is provided a program for a data processing device, in particular a program for a sensor electronics device of a sensor device according to the first aspect, the program being configured to, if executed by the data processing device, perform the steps of the method according to the second aspect. The program may have instructions and form a control code, the control code comprising an algorithm for performing the method.

[0069] The sensor electronics may comprise at least one programmable component, such as a microcontroller and at least one non-volatile memory, in which a program for executing an algorithm of the method according to the second aspect and optionally parameters of the algorithm are stored. The program may for example be a program according to the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Embodiment examples of the invention are depicted in the drawings and explained in more detail in the following description. The drawings show:

[0071] Figure 1 schematically illustrates a sensor device and an object according to an example embodiment;

[0072] FIG. 2A to FIG. 2C Shown in exploded, perspective and cross-sectional views Figure 1 Embodiment examples of coil systems and shielding elements of sensor devices in;

[0073] Figure 3A , Figure 3B Shown in exploded and cross-sectional views Figure 1 Another embodiment example of the sensor device in;

[0074] FIG. 4A to FIG. 4D Show Figure 3A , Figure 3B The implementation method of the excitation coil and the first receiving coil of the sensor device;

[0075] Figure 5 Schematically shows Figure 1 An arrangement in which the coil of the sensor device 10 is arranged inside a first shielding element of the sensor device;

[0076] Fig. 6A , Figure 6B Shown in exploded, perspective and top views Figure 1 A coil arrangement of another embodiment of the sensor device;

[0077] Figure 7 Show Figure 1 Schematic diagram of a sensor electronics device of the sensor device in FIG. 2 , wherein the sensor electronics device is electrically connected to the excitation coil and the receiving coil of the sensor device in FIG. 2 , FIG. 3 or FIG. 6 ;

[0078] Figure 8 Show Figure 7 An example embodiment of a sensor electronics device in;

[0079] Fig. 9 Show Figure 7 Another embodiment example of the sensor electronics in;

[0080] Fig.10 schematically illustrating the correlation between the quadrature phase component and the in-phase component of the voltage induced in the receiving coil; and

[0081] FIG. 11A to FIG. 11E Graphs are shown showing the demodulated voltage, the proximity signal, the quadrature phase component of the voltage induced in the receiving coil, the relationship between the quadrature phase component and the proximity signal, and the mechanical phase as a function of the longitudinal object position for different object distances. DETAILED DESCRIPTION

[0082] The same or similar parts or elements are denoted by the same reference symbols.

[0083] Figure 1 A sensor device 10 according to an embodiment example is shown, which is configured for determining a longitudinal position of a movable object 11 along a first sensitive axis S1 of the sensor device 10. The object 11 can be moved along a trajectory at a vertical distance from an end face 12 of the sensor device 10. A distance D is measured between the end face 12 of the sensor device 10 and a surface 13 of the object 11 facing the sensor device 10. The sensor device 10 can also optionally be configured for determining a position L along a second sensitive axis S2, which extends perpendicularly to the first sensitive axis S1. The first sensitive axis S1 and the second sensitive axis S2 are oriented perpendicularly to each other. The sensor device 10 can further optionally be configured for determining the distance D.

[0084] The sensor device 10 is made of a coil arrangement and optionally a shield made of a conductive material, such as metal, which is FIG. 2A to FIG. 6B The coil arrangement and the shield are arranged on the side of the end face of the sensor device 10 facing away from the object 11 .

[0085] like FIG. 2A to FIG. 2C As shown, in a first embodiment example, the sensor device 10 has a coil arrangement 14, which has a planar rectangular excitation coil 16 and a planar butterfly receiving coil 18, both of which are configured as wound conductor loops and overlap. The opposite winding sections 20a, 20b of the receiving coil 18 oriented along the sensitive axis S1 cross in the middle of the coil, so that the receiving coil 18 is configured as a butterfly coil and the coil sections 21a, 21b (i.e., the half coils 21a, 21b) are anti-symmetrically polarizable. The first shielding element 22a of the shielding body 22 surrounds the coil arrangement 14 on all sides. The receiving coil 18 is arranged so that its surface in its coil plane extends parallel to the rectangular surface of the excitation coil 16 and faces the end face 12 of the sensor device 10 and thus faces the end face 13 of the object 11. The excitation coil 16, the receiving coil 18 and the first shielding element 22a form the "head" of the sensor device 10. Alternatively, excitation coil 16 can also be arranged toward end face 12 of sensor device 10 and thus toward end face 13 of object 11 , or excitation coil 16 can surround reception coil 18 essentially in its own coil plane, or both coils 16 , 18 can be wound on the same coil former (not shown).

[0086] like Figure 2CAs shown, the printed circuit board 24 is arranged on the side of the first shielding element 22a away from the end face 12. The connection parts 26a, 26b of the excitation coil 16 and the connection parts 28a, 28b of the receiving coil 18 are electrically connected to the printed circuit board 24. The sensor electronic device 30 is arranged on the side of the printed circuit board 24 away from the coil arrangement 14. Alternatively, this surface may only have welding points for contacting the sensor electronic device arranged on another printed circuit board. The second shielding element 22b of the shielding body 22 can optionally be configured as a copper layer on at least one layer of the printed circuit board 24. The shielding elements 22a and shielding elements 22b (if present), the excitation coil 16, the receiving coil 18 and the sensor electronic device 30 are enclosed in a housing 34. The connecting cable 36 extends to the outside through the housing 34 and can be connected to a power supply. In addition, the connecting cable 36 may include leads for one or more output signals. The end face 12 of the sensor device 10 corresponds to the end face of the housing 34 facing the object 11.

[0087] according to Figure 3A , Figure 3B The sensor device 10 of the second embodiment example shown in FIG is configured in printed circuit board technology, namely as a multilayer printed circuit board 38. The coils 16, 18a, 18b are depicted as rectangular surface areas ( Figure 3A ) or dotted line ( Figure 3B ). For the sake of clarity, the windings of the coils 16, 18a, 18b are not shown. The planar rectangular excitation coil 16 and the first planar rectangular receiving coil 18a and the second planar rectangular receiving coil 18b overlap in mutually parallel printed circuit board layers. Viewed along the axis S1, the first receiving coil 18a and the second receiving coil 18b each have windings that are directed in opposite directions. The coil sections 21a, 21b of the first receiving coil 18a and the coil sections 40a, 40b of the second receiving coil 18b overlap so that the coil sections 40a or 40b are parallel to the edge regions of the coil sections 21a or 30b. The polarization of the coil sections 21a, 40a and the polarization of the coil sections 21b, 40b are the same in each case and are indicated by "+" or "-". In other words, the receiving coils 18a, 18b have an anti-symmetric polarizable configuration. The first receiving coil 18 a and the second receiving coil 18 b are electrically connected in series and may be electrically considered as a single receiving coil in circuit engineering terms.

[0088] The first shielding element 22a of the shielding body 22 is made as a metal layer on the inner surface of the housing 34 of the sensor device 10. The metal layer completely surrounds the coil arrangement 14. The second shielding element 22b of the shielding body 22 is configured as a metallization layer between the layers of the coil arrangement 16, 18a, 18b and the layers of the sensor electronics 30. The excitation coil 16, the receiving coils 18a, 18b and the shielding elements 22a, 22b form the "head" of the sensor device 10. The end face 12 of the sensor device 10 corresponds to the end face of the housing 34 facing the object 11. The sensor electronics 30 has a first printed circuit board layer 42 and a second printed circuit board layer 44, on or in which one or more circuits and / or logic components for exciting the receiving coil 16 and for signal conditioning and signal processing of one or several signals of the excitation coil 16 and the first receiving coil 18a and the second receiving coil 18b are mounted.

[0089] FIG. 4A to FIG. 4D Show FIG. 3A to FIG. 3B Implementation of the coil arrangement 14 in . Figure 4A , Figure 4B The excitation coil 16 shown in FIG. 1 is arranged in two superimposed layers 46, 48 of a printed circuit board 38, the edges of which are shown as dashed lines. The windings 46 or 48 of the excitation coil 14 in the two layers 50 or 52 are connected together by means of via holes 54 in each case. The windings 56 and 58 of the receiving coil 18a or 18b are formed by circuit board conductors in two layers 60 or 62 of the printed circuit board 24 and are connected together by via holes 63. On the two layers 60, 62, the windings 56, 58 of the coil sections 21a or 40a and 21b or 40b are arranged opposite each other in each case, while the windings 56 of the coil sections 21a, 21b and the windings 58 of the coil sections 40a, 40b shown in the drawing plane point in the same direction on both the left and right sides on the two layers 60, 62. The connections 26a, 26b of the receiving coil 16 for connection to the sensor electronics and the connections 28a, 28b of the first receiving coil 18a and the second receiving coil 18b are in each case configured as vias, to which leads for the sensor electronics can also be soldered.

[0090] Figure 5 A top view of a coil arrangement 14 arranged within the first shielding element 22a is shown. The coil arrangement 14 may be, for example, FIG. 2A to FIG. 2C , Figure 3A , Figure 3BThe coil arrangement 14 is spaced apart from the lateral shielding element 22a such that a distance d exists between the region in which the coil arrangement 14 extends and the lateral shielding element 22a, the distance d being at least 10% of the width b of the inner opening 64 of the first shielding element 22a, measured perpendicularly to the sensitive axis A1, and forming a corresponding coil-free region 66.

[0091] Fig. 6A , Figure 6B A coil arrangement 14 for a sensor device 10 according to a fourth embodiment example is shown, which is configured similarly to Figure 3A , Figure 3B . The coils 16, 18a, 18b of the coil arrangement 14 are depicted as rectangular surface areas. For the sake of clarity, the windings of the coils 16, 18, 68 are not shown. However, a second receiving coil 68 rotated 90 degrees from the first receiving coil 18 is arranged so that the sensor device 10 has two sensitive axes S1, S2 instead of one sensitive axis S1. The half coils of the receiving coil 68 have reference symbols 69a, 69b. The receiving coil 18 can be, for example, Figure 3A , Figure 3B 18a, 18b in the sensor arrangement 10. Thus, the sensor arrangement 10 is configured to determine the longitudinal position P of the object 11 along the sensitive axis S1 and the transverse position L of the object 11 along the sensitive axis S2. Furthermore, all coils 16, 18, 68 have a square cross section. Thus, the coil-free area 66 between the first shielding element 22a and the coil arrangement 14 is arranged adjacent to the edge of the respective coil 16, 18, 68. The distance d can be selected such as Figure 5 The second shielding element (not shown) and the printed circuit board of the sensor electronics have a rectangular configuration. The first receiving coil 18a and the second receiving coil 68 are electrically connected independently of each other.

[0092] Just like in Figure 3A , Figure 3B As in , the coil arrangement 14 may also include additional receiving coils in the end region of the first receiving coil 18 and additional receiving coils in the end region of the receiving coil 68 , which in each case increase the sensitivity in the end region of the respective receiving coil 18 , 68 .

[0093] Figure 7 The sensor electronics 30 shown in FIG. 1 has an oscillating unit 70 which is electrically connected via a capacitor 71 to the FIG. 2A to FIG. 2C , Figure 3A , Figure 3B or Fig. 6A , Figure 6BThe excitation coil 16 in the sensor electronics 30 is electrically connected to the demodulator unit 72 of the sensor electronics 30. The demodulation unit 72 in the form of a demodulator is electrically connected to one or more receiving coils 18, 68 of the coil arrangement 14. Since the coils 18a and 18b are connected in series and do not have to be electrically connected separately to the electronic circuit of the demodulation unit 72, in the following, reference is made to Figures 7 to 9 , the receiving coil for the longitudinal sensitive axis S1 is designated as the receiving coil 18 .

[0094] Furthermore, an evaluation unit 74 is coupled to the oscillation unit 70 and the demodulation unit 72 .

[0095] The oscillation unit 70 is configured to determine and emit a first parameter DSS indicating the presence of an object 11 in the vicinity of the coil arrangement 14 from the electrical signal of the excitation coil 16, which is a voltage or a current, in particular in a fixed longitudinal position, at a vertical distance D between the sensor end face 12 and the object 11. The first parameter DSS also depends on the longitudinal position P and the lateral position L of the object 11 (if a lateral displacement of the object 11 is possible). The oscillation unit 70 may also be configured so that not one but several signal parameters are determined and emitted from the electrical signal of the excitation coil 16. In this case, DSS represents a first set of parameters. The oscillation unit 70 is also configured to determine and output a reference signal PHA to the demodulation unit 72, the phase of which has a predetermined relationship with the phase of the voltage or current in the excitation coil 16.

[0096] The demodulation unit 72 is configured to determine a second parameter PSS from the voltage induced in the receiving coil 18 and output it to the evaluation unit 74. In addition, the second parameter PSS depends on the distance D and the lateral position L of the object 11 (if a lateral displacement of the object 11 is possible). The demodulation unit 72 is configured to determine the parameter PSS based on the reference signal PHA. The demodulation unit 72 can also be configured so that not one but several signal parameters are determined from the induced voltage of the receiving coil 18 and output them. In this case, PSS represents the second set of parameters.

[0097] The evaluation unit 74 is configured for jointly evaluating the first parameter DSS and the second parameter PSS or the first set of parameters DSS and the second set of parameters PSS and for determining the longitudinal position P of the object 11 and optionally the vertical distance D of the object 11 .

[0098] It should be noted that in order to Fig. 6A , Figure 6BThe receiving coil 68 in the second receiving coil 18 forms a second sensitive axis S2 and in order to determine the third parameter LSS (not shown), a second demodulation unit is required, or the first demodulation unit 72 can be used for demodulating the voltages of the two receiving coils 18, 68 in time division multiplexing operation. Similar to the parameter PSS that can be determined from the induced voltage of the receiving coil 18, the third parameter LSS can be determined from the induced voltage of the third receiving coil 68, and similar to the first parameter PSS that can be processed for determining the longitudinal position P, the third parameter LSS can be processed for determining the lateral position L.

[0099] exist Figure 8 In the first embodiment example of the sensor electronics 30 shown, the oscillating unit 70 is formed as Figure 7 The oscillating circuit 80 in the oscillation unit 70 is configured to supply energy to the excitation coil 16 so that the excitation coil 16 can operate as an inductance element of the LC circuit to self-oscillate, and the capacitor 71 can operate as a capacitance element of the LC circuit to self-oscillate. The demodulator 82 of the oscillation unit 70 is formed as a circuit and is configured to supply energy to the excitation coil 16 so that the excitation coil 16 can operate as an inductance element of the LC circuit to self-oscillate. OSC The amplitude detector outputs a demodulated voltage U as the amplitude characteristic of the oscillator. D , and / or configured as a frequency detector to output an oscillator voltage U OSC The oscillation frequency f OSC As the first parameter or the first set of parameters DSS. In addition, there is a linear relationship between the demodulated voltage and the oscillator amplitude. It is also possible to use the oscillator current instead of the oscillator voltage U OSC , and replace the demodulation voltage U with another voltage that represents the amplitude of the oscillator current D In this case, the demodulator 82 is also configured as an amplitude detector. Alternatively, the demodulator 82 may be configured as a frequency detector of the oscillation frequency of the oscillator current.

[0100] The quadrature phase detector 84 of the oscillation unit 70 is formed as a circuit and is configured to output a binary signal, that is, a square wave signal I ref , Q ref , which is relative to the oscillator voltage U OSC The phase corresponds to the in-phase reference signal I ref Or the quadrature phase reference signal Q ref These two signals I ref , Q ref Together they form the reference signal PHA.

[0101] The demodulation unit 72 is configured as a phase-sensitive demodulator 86, which uses I ref , Q refOne input signal of the demodulator 86 is the voltage induced in the receiving coil 18, which is amplified by the amplifier 88. Another input signal of the phase-sensitive demodulator 86 is the output signal of the quadrature phase detector 64, i.e., I ref , Q ref One output signal of the demodulator 86 is a second parameter PSS or a second set of parameters PSS, which represents a demodulated voltage. The demodulated voltage may have two components of the amplified induced voltage, namely, an in-phase component U I and the quadrature phase component U Q .

[0102] Fig. 9 The second embodiment example of the sensor electronics 30 shown in FIG. Figure 7 is configured similar to Figure 8 However, the quadrature phase detector 84 is configured as a phase detector 85, whose output signal is the phase reference signal φ ref , which is related to the oscillator voltage U OSC The phases of have a predetermined relationship. Instead of the dual-channel phase-sensitive demodulator 86, a phase-sensitive demodulator 87 is provided which uses a phase reference signal φ ref Perform synchronous demodulation and output the amplitude U related to the phase φ As the second parameter PSS, instead of the in-phase component U I Or the quadrature phase component U Q .

[0103] In operation of the sensor device 10, an oscillating circuit 70 of the sensor device 10 is supplied with a sinusoidal current. A magnetic field is formed in the excitation coil 16, which generates eddy currents and magnetic polarization in the object 11. Due to the back action of the object 11 on the excitation coil 16, the electrical signal in the excitation coil changes. In addition, due to the back effect of the object 11, a voltage is induced in the receiving coil 18, 68. A first parameter DSS or a first group of DSS and a phase reference signal PHA are determined by means of the oscillation unit 70. The phase reference signal PHA is output to a demodulation unit 72, which uses the phase reference signal PHA to determine a second parameter PSS from the amplified induced voltage of the receiving coil 18 and optionally a third parameter LSS from the amplified induced voltage of the receiving coil 68. The signal DSS and the signals PSS, LSS are output to an evaluation unit 74.

[0104] To determine the position P and the distance D, an algorithm implemented in the evaluation unit 74 of the sensor electronics 30 is executed, with which a dimensionless proximity signal S is formed from the first parameter DSS. N . Approach signal S N It can be specifically defined as SN =a(U D0 -U D ) or S N = b(f OSC0 -f OSC ) or S N =a(U D0 -U D )+ b(f OSC0 -f OSC ). In the foregoing, a and b represent scaling factors, and U D0 and f OSC0 In each case the demodulation voltage U D and the oscillation frequency f OSC The no-object value of .

[0105] Furthermore, the dimensionless longitudinal position signal S is formed from the second parameter PSS P , which is specifically determined as S P = c*U I , S P =d*U Q , S P =c*U I +d*U Q , S P =e*U φ , where c, d and e are scaling factors. Assume that the voltage U has been subtracted at this time I , U Q or possible background signal.

[0106] Then, the reduced longitudinal position signal V P The longitudinal position signal S P With proximity signal S N V P =S P / S N The relationship of form.

[0107] In addition, the mechanical phase P M It can optionally be formed by the arctan2 function, defined as P M =arctan2(V P , B*S N ), where B is the scaling factor.

[0108] Ratio V P and mechanical phase P M It may further optionally be scaled and linearized in order to determine the longitudinal position P.

[0109] If it is known at what vertical distance D the object 11 is expected to move, the scaling factor B can be established in advance, for example at the factory. Alternatively or additionally, B can be determined by means of a learning process performed before the method, in which the object 11 moves at least through the middle of the longitudinal measuring range of the sensor device 10 and from the proximity signal S N Absolute amount of S NL , such as its maximum value, or its longitudinal position signal V P The value at the point where B is zero. NL Inversely proportional, that is, B = k / S NL , where k is another scaling factor, the result is that the arctan2 function represents a monotonic function, in particular the property that the motion of an object is as linear as possible within a certain range.

[0110] Due to the change of the oscillation parameters, the approximation signal S N , and the induced voltage of the receiving coil 18 and thus the longitudinal position signal S P Both are determined by the reverse effect of the inductance of the same object 11, reducing the longitudinal position signal V P "Relative" is independent of the distance D. By calculating the mechanical phase P M A prerequisite for determining the position is that the distance D between the object 11 and the end face 12 of the sensor device 10 does not deviate significantly from the distance at which the scaling factor B is determined.

[0111] To determine the lateral position L, the third parameter LSS can be examined and evaluated in exactly the same way instead of PSS.

[0112] In order to determine the distance, a previous calibration of the sensor device with respect to the longitudinal position P and optionally the transverse position L can be performed for different distances D.

[0113] In another evaluation method that can be implemented by the evaluation unit 74, a multivariable, non-linear function of one or more of the above-mentioned parameters DSS, PSS and LSS may be used. For example, an artificial neural network may be used, which has been previously trained to determine the position P and optionally the lateral position L and / or optionally the distance D. The training of the artificial neural network may require a previous learning process, which is performed for the type of sensor device 10 (e.g. for its size or its design) or for the environment in which the sensor device is used (e.g. at the factory) during the design phase or in the individual production of the sensor device.

[0114] FIG. 11 shows the U curves of different materials, such as structural steel, stainless steel, and aluminum, when the object 11 travels through the middle of the longitudinal measurement range. I (x-axis 90 in arbitrary units) and U QThe correlation relationship between the y-axis 92 (arbitrary units) and the curves 94a-94c is obtained by comparing the determined parameter PSS (here U I , U Q ) and different object positions, it is possible to draw conclusions about the material type. Alternatively or additionally, the material type of the object can be determined based on the typical phase of the voltage induced by the object 11 in one or more receiving coils 18, 68. If it can be assumed that the determination of the phase is not prevented by too narrow an amplitude, the typical phase can be defined as the most frequently occurring phase value (or average value) of the induced voltage within a time period. It may be necessary to take into account that the sign of the induced voltage also depends on the object position and to correct the corresponding phase shift before determining the average value ... oscillator voltage U OSC The material type of the object can be determined from the typical relationship between the amplitude change and the phase change of the proximity signal. In this regard, the typical ratio can be considered as a constant and assumed to be known in advance. Due to possible measurement inaccuracies, it is advantageous or necessary to determine the above relationship at larger values ​​of the proximity signal or longitudinal position signal or over a period of time.

[0115] FIG. 11A to FIG. 11E The various quantities in the above signal evaluation step are shown. These quantities are when the object 11 moves along Figure 1 104a-106a; solid line), D=0.50 mm (curves 98b, 100b, 102b, 104b, 106b; dashed line) and D=0.75 mm (curves 98c, 100c, 102c, 104c, 106c; dotted line) as a function of the object position P (x-axes 96a-96e in millimeters (mm)) for different vertical object distances D=0.25 mm (curves 98a, 100a, 102a, 104a, 106a; solid line), D=0.50 mm (curves 98b, 100b, 102b, 104b, 106b; dashed line) and D=0.75 mm (curves 98c, 100c, 102c, 104c, 106c; dashed line). The y-axes 108a-108e are given in arbitrary units for the corresponding quantities in each case.

[0116] Fig.11A and Fig. 11B Shows the quantity U in different cases D and S N , where in this particular case the proximity signal is formed as S N =(U D0 -U D ). D0 and U D is a digital value corresponding to voltage and can be considered as a dimensionless value. Fig. 11C The quadrature component U of the induced voltage is shown Q changes. Fig.11A , Fig. 11B and Fig. 11C In , it should be noted that the shape of the curve depends on the distance D. In contrast, Fig.11D As shown, the ratio V L Basically independent of the object position P. Ratio V L The determination of does not require a learning process, but is only possible if a learning operation is performed beforehand at each object distance D in each case. Fig.11E The mechanical phase P shown in M However, if for a housing having a longitudinal extension of 15 mm, the total length of the coil arrangement 14 is assumed to be 12.5 mm, Fig.11D Medium V M The curve is compared with the linearized measuring range of about 10 mm by determining the mechanical phase P M Determining the longitudinal position P provides a larger measuring range or a linearization range of approximately 18 mm. Fig.11E Each curve 106a-106c shown in FIG. 1 is calculated after a corresponding separate learning operation with a distance-specific B value, so the B value is calculated as B=k / S NL , where the object-specific k factors are the same.

Claims

1. An inductive sensor device (10) for determining a longitudinal position (P) of an object (11) along a sensitive axis (S1) of the sensor device (10), the object (11) being movable at a distance from an end face (12) of the sensor device (10) and being at least partially electrically conductive and / or magnetically polarizable, wherein the sensor device (10) comprises a coil arrangement (14) and sensor electronics (30), wherein the coil arrangement (14) comprises: a substantially planar excitation coil (16), by means of which an alternating magnetic field can be generated for inducing eddy currents and / or magnetic polarization in the object (11); and a first receiving coil (18; 18a-18b), which is configured substantially planar and is arranged substantially parallel to the excitation coil (16). 16) and overlapping with the excitation coil (16), wherein the excitation coil (16) and the first receiving coil (18; 18a-18b) are arranged substantially parallel to the end face (12) of the sensor device (10), wherein the sensor electronics (30) is configured to: determine at least one parameter (DSS) of the electrical signal of the excitation coil (16), the parameter (DSS) being variable due to the inductive back effect of the object (11), and at least one parameter (PSS) of the voltage induced in the first receiving coil (18; 18a-18b) due to the inductive back effect of the object (11); and determine the longitudinal position (P) based on the determined parameter (DSS) of the electrical signal of the excitation coil (16) and the determined parameter (PSS) of the induced voltage of the first receiving coil (18; 18a-18b).

2. A sensor device as claimed in claim 1, wherein the sensor electronics (30) is configured to determine a vertical distance (D) of the object (11) between the end face (11) of the sensor device (10) and the object (11) based on at least one determined parameter (DSS) of the electrical signal of the excitation coil (16) and at least one determined parameter (PSS) of the induced voltage of the first receiving coil (18; 18a-18b).

3. The sensor device of claim 1, wherein the first receiving coil (18; 18a-18b) has an anti-symmetric polarizable configuration along the sensitive axis (S1).

4. A sensor device (10) as claimed in claim 1, wherein the coil arrangement (14) has a second receiving coil (18b), which is configured essentially in a planar manner and is arranged essentially parallel to the excitation coil (16) and overlaps with the excitation coil (16), wherein the second receiving coil (18b) overlaps with the first receiving coil (18a) in its end region and is electrically connected in series with the first receiving coil (18a).

5. The sensor device (10) of claim 4, wherein the coil arrangement (14) has at least a third receiving coil (68), the third receiving coil (68) being of a substantially planar configuration and being arranged substantially parallel to and overlapping the excitation coil (16) and defining an additional sensitive axis (S2) of the sensor device (10), the additional sensitive axis (S2) being substantially perpendicular to the sensitive axis (S1) of the first receiving coil (18; 18a, 18b) or extending in the sensitive axis (S1), wherein the sensor electronics (30) is configured to determine at least one parameter (LSS) of a voltage induced in the third receiving coil (68) due to the inductive back effect of the object (11), and is configured to determine a lateral position (L) of the object (11) along the additional sensitive axis (S2) based on the determined at least one parameter (DSS) of the electrical signal of the excitation coil (16) and the determined at least one parameter (LSS) of the induced voltage of the third receiving coil (68).

6. A sensor device (10) as claimed in claim 5, wherein the coil arrangement (14) has a fourth receiving coil, which is configured essentially in a planar manner and is arranged essentially parallel to the excitation coil (16) and overlaps with the excitation coil (16), wherein the fourth receiving coil overlaps with the third receiving coil (68) in its end region and is electrically connected in series with the third receiving coil (68).

7. A sensor device (10) as claimed in claim 6, wherein the excitation coil (16), the first receiving coil (18; 18a), the second receiving coil (18b), the third receiving coil (68) and / or the fourth receiving coil are arranged on or in one or more layers (50, 52, 60, 62) of a printed circuit board (38).

8. The sensor device (10) according to claim 6, wherein the excitation coil (16), the first receiving coil (18; 18a), the second receiving coil (18b), the third receiving coil (68) and / or the fourth receiving coil are manufactured by winding technology.

9. The sensor device (10) as claimed in claim 7, wherein the windings (56, 58) of the coil sections (21a, 21b; 40a, 40b) of the receiving coil (18; 18a-18b; 68) are oriented relative to each other as viewed along their respective sensitivity axes (S1, S2).

10. The sensor device (10) as claimed in claim 8, wherein the receiving coils (18; 18a-18b; 68) have windings (20a, 20b) that are substantially centrally crossed, viewed along their respective sensitivity axes (S1, S2).

11. The sensor device (10) as claimed in claim 1, wherein the sensor device (10) further comprises a first shielding element (22a), which is electrically conductive and is arranged laterally, in particular completely, around the coil (14).

12. The sensor device (10) as claimed in claim 1, wherein the sensor device (10) further comprises a second shielding element (22b), which is electrically conductive and planar and is arranged on a side of the coil arrangement (14) facing away from the object (11).

13. A sensor device (10) as claimed in claim 11, wherein, viewed in a direction perpendicular to the sensitive axis (S1, S2), symmetrically and on either side of the coil arrangement (14), in each case a coil-free area (66) is arranged adjacent to the first shielding element (22a), the width (d) of the coil-free area (66) being at least 10% of the width (b) of the opening (64) of the first shielding element (22a).

14. The sensor device (10) as claimed in claim 1, wherein the excitation coil (16) can be driven substantially with a periodic, in particular substantially sinusoidal, current or a periodic, in particular substantially sinusoidal, voltage.

15. The sensor device (10) as claimed in claim 1, wherein the excitation coil (16) is part of an oscillating circuit (80) of the sensor electronics (30).

16. The sensor device (10) according to claim 1, wherein the excitation coil (16) is a part of a self-oscillating LC oscillating circuit (80) as an inductive element of the LC circuit.

17. The sensor device (10) according to claim 1, wherein the at least one parameter (DSS) determined from the electrical signal of the excitation coil is a frequency (f OSC ) or amplitude (U D ).

18. The sensor device (10) as claimed in claim 1, wherein the sensor electronics (30) is configured to determine a proximity signal (S) based on a change of a determinable parameter of the electrical signal of the excitation coil (16) caused by the presence of the object (11). N ), the proximity signal (S N ) indicates a change in said at least one parameter (DSS) caused by said presence of said object (11).

19. The sensor device (10) of claim 1, wherein the sensor electronics (30) is configured to determine at least one reference signal (PHA; I ref , Q ref ; φ ref ), the phase of the at least one reference signal has a predetermined ratio with the phase of the electrical signal of the excitation coil (16).

20. The sensor device (10) of claim 19, wherein the sensor electronics (30) is configured to detect the presence of a reference signal (PHA; φ ref ) determines at least one parameter (PSS, LSS) of the induced voltage from synchronous demodulation of the induced voltage.

21. The sensor device (10) according to claim 20, wherein the at least one parameter (PSS, LSS) is the amplitude (U φ ), wherein the phase of a phase-dependent phase reference signal has a predetermined ratio to the phase of the electrical signal of the excitation coil (16).

22. The sensor device (10) of claim 19, wherein the sensor electronics (30) is configured to detect the presence of a reference signal (PHA); ref , Q ref ) performs quadrature demodulation on the induced voltage to determine at least one parameter (U) of the induced voltage I , U Q ).

23. The sensor device (10) according to claim 22, wherein the at least one parameter (PSS, LSS) of the induced voltage is a phase-dependent amplitude (U I , U Q ).

24. The sensor device (10) according to claim 18, wherein the sensor electronics (30) is configured to determine a longitudinal position signal (S ) from the at least one parameter (PSS, LSS) of the induced voltage. P ), wherein the longitudinal position signal (S P ) based on at least one parameter (PSS, LSS) of the induced voltage.

25. The sensor device (10) of claim 24, wherein the sensor electronics (30) is configured to convert the reduced longitudinal position signal (V M ) is determined as the longitudinal position signal (S P ) and the proximity signal (S N ) ratio, so that according to the reduced longitudinal position signal (V M ) determines the longitudinal position (P).

26. The sensor device (10) of claim 25, wherein the sensor electronics (30) is configured to determine the reduced longitudinal position signal (V M ) determines the longitudinal position (P).

27. The sensor device (10) of claim 25, wherein the sensor electronics (30) is configured to detect the reduced longitudinal position signal (V P ) and the proximity signal (S N ) is multiplied by the scaling factor (B) determined in the previous learning process to convert the mechanical phase (P M ) is determined as arctan2 so that according to the mechanical phase (P M ) determines the longitudinal position (P).

28. The sensor device (10) of claim 27, wherein the sensor electronics (30) is configured to cause the mechanical phase (V P ) linearization.

29. The sensor device (10) as claimed in claim 26, wherein the linearization is performed with respect to the material type of the object.

30. The sensor device (10) of claim 1, wherein the sensor electronics (30) is configured to determine the type of object material of the object (11) based on a typical phase of the voltage induced by the object (11) relative to the phase of the electrical signal of the excitation coil (16), or wherein the sensor electronics (30) is configured to determine the type of object material of the object (11) based on an oscillator voltage (U) caused by the presence of the object (11). OSC ) is used to determine the type of material of the object (11) by a typical ratio of amplitude change and frequency change.

31. The sensor device (10) of claim 1, wherein the sensor electronics (30) implements a self-parameterizing evaluation algorithm.

32. A sensor device (10) as claimed in claim 1, wherein the sensor electronics (30) are configured to adaptively parameterize an evaluation algorithm, adaptively determine the type of the object material of the object (11) and / or adaptively identify changes in a measurement arrangement.

33. A sensor device (10) as claimed in claim 32, wherein the sensor electronics (30) is configured for adaptive parameterization of the evaluation algorithm, determining one or more values ​​of at least one parameter (DSS, PSS, LSS) and storing them temporarily or permanently.

34. A method for operating an inductive sensor device (10) for determining a longitudinal position (P) of an object (11) along a sensitive axis (S1) of the sensor device (10), the object (11) being movable at a distance from an end face (12) of the sensor device (10) and being at least partially electrically conductive and / or magnetically polarizable, wherein the method comprises: - generating an alternating magnetic field of an excitation coil (16) of a coil arrangement (14) of the sensor device (10) for inducing eddy currents and / or magnetic polarization in the object (11), wherein the excitation coil (16) is substantially planar, - determining, by means of the sensor electronics (30) of the sensor device (10), at least one parameter (DSS) of the electrical signal of the excitation coil (16), the parameter (DSS) being changed by the inductive back effect of the object (11); and at least one parameter (PSS) of a voltage induced in a first receiving coil (18; 18a-18b) of the coil arrangement (14) due to the inductive back effect of the object (16), wherein the first receiving coil (18; 18a-18b) is of a substantially planar configuration and is arranged substantially parallel to and overlapping the excitation coil (16), wherein the excitation coil (16) and the first receiving coil (18; 18a-18b) are arranged substantially parallel to the end face (12) of the sensor device (10), - Determining the longitudinal position (P) with the aid of the sensor electronics (30) based on the at least one parameter (DSS) of the electrical signal of the excitation coil (16) and the at least one parameter (PSS) of the induced voltage of the first receiving coil (18; 18a, 18b).

35. A program for a data processing device, the program being configured to perform the steps of the method as claimed in claim 34 when executed by the data processing device.

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