Inductive rotary encoder

Abstract

The device comprises an inductive rotary encoder including a first member and a second member that are relatively rotatable about a rotation axis, wherein the first member has at least one scale track, the second member has an excitation coil for generating a magnetic field operated by the at least one scale track, and the second member also includes a receiving coil for detecting the magnetic field, and the relative rotational position of the first member and the second member about the rotation axis can be measured through the magnetic field. The first and / or second member includes at least one magnetic field sensor for detecting a magnetic field generated by the excitation coil or another excitation coil, and the device includes means for determining information regarding the relative arrangement of the first member and the second member in a degree of freedom other than the degree of freedom about the rotation axis from the at least one magnetic field sensor.

Description

Technology Field

[0001] The present invention relates to an inductive rotary encoder. Background Technology

[0002] Inductive rotary encoders are known and generally comprise i) a rotor for mounting on a mechanical part, such as a shaft, which is rotatable about an axis relative to a static part of the machine, and ii) a stator for mounting on a static part of the machine. Generally, the stator is an active / powered component and comprises a transmitting (or “excitation”) coil and a receiving coil (and associated electronics) for generating and detecting an alternating magnetic / electromagnetic field. In this document, the terms “magnetic field” and “electromagnetic field” are used interchangeably because the magnetic field referred to is generated by an electric current and may therefore also be referred to as an electromagnetic field. Furthermore, as is understood, references in this document to a magnetic field generated by an excitation coil or a transmitting coil refer to the “alternating” magnetic field generated by it, and for brevity, this is often simply referred to as a “magnetic field.” Generally, the rotor is a passive / unpowered component and includes scale features that manipulate the electromagnetic field detected by the stator's receiving coil(s) such that the output(s) of the stator's receiving coil(s) depend on the relative rotational orientation of the stator and the rotor around the axis. Accordingly, the relative rotational position (and / or derivative of that position) of the stator and the rotor (and further, the static and rotating parts of the machine) can be measured from the output(s) of the stator's receiving coil(s). means of solving the problem

[0003] The present invention relates to improvements related to an inductive rotary encoder. In particular, the present document describes an inductive rotary encoder device, wherein the device comprises a first member and a second member that are rotatable relative to a rotation axis, the first member having at least one scale track, and the second member having an excitation coil for generating a magnetic field and a receiving coil for detecting the magnetic field—thereby which the relative rotational position of the first member and the second member with respect to the rotation axis can be measured.

[0004] Accordingly, according to a first aspect of the present invention, an inductive rotary encoder device is provided, wherein the device comprises a first member and a second member that are rotatable relative to a rotation axis, the first member having at least one scale track, and the second member having an excitation coil for generating a magnetic field and a receiving coil for detecting the magnetic field—thereby which the relative rotational position of the first member and the second member around the rotation axis can be measured—the first member and / or the second member comprising at least one magnetic field sensor for detecting the magnetic field generated by the excitation coil or another excitation coil, and the device comprises means for determining information regarding the relative arrangement of the first member and the second member in a degree of freedom other than the degree of freedom around the rotation axis from the at least one magnetic field sensor.

[0005] Using the magnetic field generated by the excitation coil may be an efficient and convenient method for determining information regarding the relative arrangement of the first and second members in degrees of freedom other than the degrees of freedom around the rotation axis. Since the rotary encoder is an inductive rotary encoder, the rotary encoder is designed to already have components for generating a magnetic field from the excitation coil. In fact, the excitation coil generating the magnetic field—from which information regarding the relative arrangement of the first and second members in degrees of freedom other than the degrees of freedom around the rotation axis is determined—may be identical to the excitation coil generating the magnetic field—which is detected by the receiving coil and through which the relative rotational position of the first and second members can be measured.

[0006] Accordingly, to rephrase, the inductive rotary encoder may include a first member and a second member that are rotatable relative to a rotation axis, wherein the first member has at least one scale track, and the second member has an excitation coil for generating a magnetic field and a receiving coil for detecting the magnetic field (generated by the excitation coil)—thereby allowing the relative rotational position of the first member and the second member around the rotation axis to be measured—and the first member and / or the second member includes at least one magnetic field sensor for detecting the magnetic field generated by the excitation coil, and the device is characterized by including means for determining information regarding the relative arrangement of the first member and the second member in a degree of freedom other than the degree of freedom around the rotation axis from the at least one magnetic field sensor.

[0007] As is understood, another term commonly used for "excitation coil" in the field of inductive encoders is "transmit coil." Therefore, the term "transmit coil" may be used herein instead of the term "excitation coil."

[0008] As explained in the background section above, the magnetic field generated by the excitation coil or another excitation coil is an alternating magnetic field. Therefore, to generate an alternating magnetic field operated by at least one scale track, alternating current can be flowed through the excitation coil at, for example, a predetermined operating frequency.

[0009] A scale track may include a series of (electrically) conductive / nonconductive scale features, for example, in the form of an array. A scale track may include scale features in a periodic arrangement. Thus, a scale track may include (electrically) conductive / nonconductive scale features in a periodic arrangement. In other words, a scale track may include a series of alternately arranged (electrically) conductive scale features and nonconductive scale features. Thus, a scale track may include (electrically) conductive / nonconductive scale features in a periodic arrangement. In other words, a scale track may include a periodic series of alternately arranged conductive scale features and nonconductive scale features. A scale track may be configured so that the manipulation effect on a magnetic field varies in a spatially periodic manner. The spatial frequency of this spatially periodic effect may depend on the period of the scale features.

[0010] As understood, the scale track / feature may be configured to manipulate the amplitude of the (alternating) magnetic field (generated by the excitation coil). Accordingly, the scale track may be configured to manipulate / modulate the amplitude of the (alternating) magnetic field depending on the relative positions of the first member and the second member around the axis of rotation. Accordingly, the scale track may be configured to manipulate the amplitude of the (alternating) magnetic field in a periodic manner in which the spatial frequency depends on the period of the scale feature.

[0011] As is understood, references to conductive and non-conductive herein relate to electrical conductivity, and for the sake of simplification, they will be referred to simply as conductive and non-conductive. As is understood, the required or desirable resistivity levels for conductive and non-conductive features may vary depending on the application. Nevertheless, in relation to a preferred embodiment of the present invention, the electrically conductive scale feature is 1x10 - 6 Having a resistivity of less than Ω·m (e.g., the resistivity of copper is approximately 1.7 x 10⁻⁶ - 8 Ω·m), the resistivity of the non-conductive characteristic part is 1x10 - 4 It is greater than Ω·m, for example, can be significantly larger than that, for example, can be much larger than 1Ω·m, for example, 1x10 3 It can be larger than Ω·m.

[0012] As is understood, the at least one scale track may be centered on the axis of the scale track (e.g., a first) and extend around it (e.g., annularly). The excitation coil may be centered on the axis of the excitation coil and extend around it (e.g., annularly). The receiving coil may be centered on the axis of the receiving coil and extend around it (e.g., annularly). The excitation coil and the receiving coil may be centered on the same (e.g., a second) axis (i.e., the axis of the excitation coil and the axis of the receiving coil may substantially coincide) and extend around it (e.g., annularly). For example, the excitation coil and the receiving coil may be formed substantially concentrically on the second member. As is understood, in an embodiment where the scale track, excitation coil and / or receiving coil extend annularly (around their respective axes), this includes extending completely annularly and substantially completely annularly (e.g., around at least 75% of the circumference of the entire annular range, more preferably around at least 90% of the circumference of the entire annular range).

[0013] The second member may include two or more excitation coils. In a preferred embodiment, the excitation coils may be centered on the same excitation coil axis and extend around it, but are not required to be so. The second member may include two or more receiving coils. In this case, the receiving coils may be centered on the same receiving coil axis and extend around it, but are not required to be so. For example, the second member may include first and second receiving coils configured to generate, respectively, first and second signals from a magnetic field that vary periodically according to the relative rotation of the first member and the second member. The device may be configured such that the periods of the first signal and the second signal are different from each other. The first and second receiving coils may be positioned on both radial sides of the excitation coil.

[0014] The above at least one scale track (e.g., its features) may be contained within a first plane. The above excitation coil(s) may be contained within a second plane. The above receiving coil(s) may be contained within a third plane. Preferably, the second plane and the third plane may be substantially parallel, and optionally substantially coplanar. When assembled together, the first plane and the second / third plane may be preferably substantially parallel (e.g., so that the angle between any of these planes is 5° or less, more preferably 3° or less, particularly preferably 2° or less, e.g. 1° or less).

[0015] As is understood, generally, and in a preferred embodiment of the present invention, the inductive rotary encoder is configured or intended to be configured such that, in use, all axes (i.e., scale track (e.g., first) axis, excitation axis and receiving axis (e.g., second axis), and (rotation) axis) are arranged to be substantially parallel to each other (at least to the extent that the first member and the second member do not physically come into contact with each other during operation). As is understood, the degree of parallelism actually required will depend on various aspects such as the dimensions of the inductive rotary encoder and the required level of accuracy. Nevertheless, generally, it will be desirable that the angle between any two of the scale track axis, excitation axis and receiving coil axis (e.g., the angle between the first axis and the second axis) be 5° or less, more preferably 3° or less, particularly preferably 2° or less, e.g. 1° or less. In addition, generally, it is desirable that the angle between i) any axis among the scale track axis, excitation axis and receiving coil axis and ii) rotation axis be 5° or less, more preferably 3° or less, particularly preferably 2° or less, for example 1° or less.

[0016] In a preferred embodiment, the inductive rotary encoder is configured or intended to be configured such that, when in use, all axes (i.e., scale track (e.g., first) axis, excitation and reception axis (e.g., second axis), and rotation axis) are substantially aligned / coaxial (e.g., aligned / coaxial) (e.g., offset from each other by less than 10% of the reception coil diameter, more preferably less than 5% of the reception coil diameter).

[0017] As understood, the device may be configured to determine the relative rotational position of the first member and the second member about an axis of rotation and / or its derivative (e.g., velocity and / or acceleration) from the output of the receiving coil. Such rotational position may be the absolute relative rotational position of the first member and the second member about an axis of rotation. Accordingly, the device may include means for determining information regarding the relative rotational position of the first member and the second member about an axis of rotation and / or its derivative from the receiving coil. The means may include one or more "processing" or "processor" devices.

[0018] The means for determining information regarding the relative arrangement of the first member and the second member in degrees of freedom other than the degrees of freedom centered on the rotation axis from at least one magnetic field sensor may include one or more "processing" or "processor" devices.

[0019] As is understood, "processing" or "processor" devices may include custom processing devices configured for a specific application (e.g., Field Programmable Gate Arrays "FPGAs"), as well as more general processing devices that can be programmed (e.g., via software) according to the requirements of the application in which they are used. Accordingly, suitable "processing" or "processor" devices may include, for example, a CPU (Central Processor Unit), an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), etc.

[0020] The means for determining information regarding the relative arrangement of the first member and the second member in degrees of freedom other than those around the axis of rotation from at least one magnetic field sensor, and / or the means for determining the rotational position and / or derivatives (e.g., velocity and / or acceleration) of the first member and the second member around the axis of rotation from the output of the receiving coil, e.g., related "processing" or "processor" device(s), may be provided as part of one or both of the first member and the second member (in this case, preferably as part of the second member). However, it is not necessary, and such means (e.g., one or more "processing" or "processor" devices) may be provided by one or more components separate from the first member and the second member. For example, the inductive rotary encoder device may include the first member and the second member and a separate interface unit comprising the means.

[0021] Accordingly, for example, the inductive encoder device may include a controller comprising such means, for example, such "processing" or "processor" device(s). The controller may be a controller of a machine on which or to which the first member and the second member are mounted. Accordingly, for example, the device may include a machine on which or to which the first member and the second member are mounted.

[0022] As is understood, the means for determining information regarding the relative arrangement of the first member and the second member in degrees of freedom other than the degrees of freedom around the axis of rotation from the at least one magnetic field sensor and / or the means for determining the rotational position and / or derivative thereof (e.g., velocity and / or acceleration) of the first member and the second member around the axis of rotation from the output of the receiving coil may be shared or distributed between the means provided on the first member and / or the second member and another device (e.g., a machine controller) separate from the first member and / or the second member.

[0023] Information regarding the relative arrangement of the first member and the second member may include information regarding the separation between the first member and the second member (particularly, for example, axial separation measured along a rotation axis). Such information may be referred to as "ride height" information.

[0024] Information regarding the relative arrangement of the first member and the second member may include information regarding the relative tilt of the first member and the second member. This tilt may be measured around an axis perpendicular to the axis of rotation. For example, in an embodiment where the first member and the second member are substantially planar members (or at least have substantially planar opposing surfaces), information regarding the relative arrangement of the first member and the second member may include a measure of how parallel the first member and the second member (or their opposing surfaces) are. As described above, the at least one scale track (e.g., its features) may be contained within a first plane, and the excitation coil and the receiving coil may be contained within a second / third plane(s). In such a case, information regarding the relative arrangement of the first member and the second member may include a measure of how parallel the first plane and the second / third plane are.

[0025] Information regarding the relative arrangement of the first member and the second member may include information regarding the relative lateral (or "radial") position of the first member and the second member (in a direction perpendicular to the axis of rotation).

[0026] For example, information regarding the relative arrangement of the first member and the second member may include information regarding the relative eccentricity of the first member and the second member.

[0027] Generally, in use, the first member will be mounted on a rotating part of the machine and the second member will be mounted on a static part of the machine (thus, the first member may be referred to as a "rotor" and the second member as a "stator"). For example, the device may include a rotatable part (e.g., a part rotatable about a rotation axis) on which the first member is mounted and a static part on which the second member is mounted. Nevertheless, as is understood, this is not necessarily required, and the members may be mounted in reverse, or both the first member and the second member may be mounted on rotatable parts. Accordingly, the device may include first and second relative rotatable parts (parts rotatable about a rotation axis) on which the first member and the second member are mounted.

[0028] Information regarding the relative arrangement of the first member and the second member in degrees of freedom other than those around the rotation axis can be used in various ways, for example, to benefit the installer of the inductive rotary encoder and / or the system into which it is integrated. For example, such information can be used during the setup / installation of the inductive rotary encoder to indicate to the installer, for example, whether the first member and the second member have a desired relative arrangement. Optionally, such information can be used during the operation of the inductive rotary encoder to, for example, monitor the relative arrangement of the first member and the second member, provide a warning if the relative arrangement does not correspond to a desired arrangement, and / or compensate / correct the scale around the rotation axis.

[0029] The device may be configured to output information regarding the relative arrangement of the first member and the second member in degrees of freedom other than the degrees of freedom around the axis of rotation in the form of a signal perceptible to a human, for example, in the form of a visual signal and / or an auditory signal. For example, the device may include a visual setup indicator indicating whether the first member and the second member have a desired relative arrangement (based on the information). Optionally, the device is configured to output the information in the form indicating a scale of the relative arrangement of the first member and the second member in one or more degrees of freedom other than the degrees of freedom around the axis of rotation. For example, the device may be configured to output the information in a form indicating at least one magnitude (and / or at least one direction) of i) the distance between the first member and the second member, ii) the relative lateral (or "radial") position of the first member and the second member (e.g., in a direction perpendicular to the axis of rotation), and iii) the relative inclination of the first member and the second member (e.g., around an axis perpendicular to the axis of rotation).

[0030] The first member and / or the second member may include the at least one magnetic field sensor—from which information regarding the relative arrangement of the first member and the second member in degrees of freedom other than the axis of rotation is determined—but it may be preferable that the at least one magnetic field sensor be provided on the second member. Accordingly, it may be preferable that the second member include the at least one magnetic field sensor. One reason for this preference is that the second member already includes a receiving coil for detecting a magnetic field—from which the relative rotational position of the first member and the second member around the axis of rotation can be measured. Accordingly, this configuration may be beneficial to improve the manufacturing efficiency and / or simplicity of the inductive rotary encoder.

[0031] Optionally, the receiving coil (for detecting a magnetic field—wherein the relative rotational position of the first member and the second member about the axis of rotation can be measured—is or includes a magnetic field sensor—from which information regarding the relative arrangement of the first member and the second member in degrees of freedom other than the degrees of freedom about the axis of rotation is determined. For example, information regarding the separation of the first member and the second member can be determined from the output of the receiving coil, for example, by analyzing the strength, e.g., amplitude, of a signal output by the receiving coil.

[0032] There may be at least one magnetic field sensor separate from the receiving coil (for detecting a magnetic field—thereby which the relative rotational position of the first member and the second member around the rotation axis can be measured—from which information regarding the relative arrangement of the first member and the second member in a degree of freedom other than the degree of freedom around the rotation axis is determined).

[0033] The at least one magnetic field sensor may include a plurality of distinct magnetic field sensing regions (e.g., a plurality of distinct magnetic field sensors) disposed at different locations on the first member and / or the second member. These different locations may be different angular positions and / or radial positions (e.g., with respect to the scale track axis, or with respect to the receiving axis and / or excitation axis). Accordingly, the at least one magnetic field sensor may include a plurality of distinct magnetic field sensing regions (e.g., a plurality of distinct magnetic field sensors) disposed at different locations on the second member.

[0034] The at least one magnetic field sensor may include a first set of magnetic field sensing areas (e.g., a first set of magnetic field sensors) positioned at a first radial position on the first member and / or the second member, and a second set of magnetic field sensing areas (e.g., a second set of magnetic field sensors) positioned at a second radial position. The device may be configured such that one of the first set and the second set of magnetic field sensing areas is primarily sensitive to the relative tilt of the first member and the second member (i.e., the output of one of the first set and the second set of magnetic field sensing areas depends primarily on the relative tilt of the first member and the second member). The device may be configured such that one of the magnetic field sensing areas of the first set and the second set is primarily sensitive to the relative lateral / radial position of the first member and the second member (in other words, the output of one of the magnetic field sensing areas of the first set and the second set depends primarily on the relative lateral / radial position of the first member and the second member). For example, the device may be configured such that the magnetic field sensing area of ​​the first set is primarily sensitive to the relative tilt of the first member and the second member (i.e., the output of one of the magnetic field sensing areas of the first set and the second set depends primarily on the relative tilt of the first member and the second member), and the magnetic field sensing area of ​​the second set is primarily sensitive to the relative lateral / radial position of the first member and the second member (i.e., the output of one of the magnetic field sensing areas of the first set and the second set depends primarily on the relative lateral / radial position of the first member and the second member).Accordingly, for example, the device may be configured such that the output of the first set of magnetic field sensing regions is used to determine the relative tilt of the first member and the second member, and the output of the second set of magnetic field sensing regions is used to determine the relative lateral / radial position of the first member and the second member. Preferably, when in use / mounted on a machine (e.g., mounted on a relative rotatable part of the machine), the first set of magnetic field sensing regions (the first set of magnetic field sensors) are axially aligned (i.e., directly opposite) with the (electrical) conductive region (e.g., scale track) of the first member, and the second set of magnetic field sensing regions (the second set of magnetic field sensors) are axially aligned (i.e., directly opposite) with the blank region (particularly the non-conductive region) of the first member. As is understood, "axially" may refer to the axis of rotation. Also, as is understood, the above axial direction may be perpendicular to the plane of the excitation coil and / or the receiving coil.

[0035] The above at least one magnetic field sensor, for example, the first and / or second set of magnetic field sensing areas (e.g., the first and / or second set of magnetic field sensors), may include four quadrant magnetic field sensing areas (e.g., four quadrant magnetic field sensors).

[0036] At least one of the first member and the second member may include a magnetic flux increaser, wherein a current flow is generated within the magnetic flux increaser by the magnetic field of the excitation coil or another excitation coil, and the magnetic flux increaser itself generates a magnetic field that acts to increase the magnetic flux of the magnetic field detected by the receiving coil in the region of the receiving coil.

[0037] Increasing the magnetic flux in the receiving coil area may help increase signal strength and / or system sensitivity, which in turn may lead to an improvement in the signal quality and / or accuracy of the measurement of the relative positions of the first member and the second member around the rotation axis.

[0038] In a preferred embodiment, the excitation coil that generates a magnetic field generating a current flow within the magnetic flux enhancer is identical to the excitation coil that generates a magnetic field operated by the scale track and detected by the receiving coil (from which the relative rotational position of the first member and the second member about the axis of rotation can be measured).

[0039] In a preferred embodiment of the present invention, the magnetic flux enhancer comprises at least one (electrical) conductor (which is hereinafter referred to as at least one "outer" conductor) located radially outward (e.g., radially outward with respect to the axis of rotation) of the scale track(s) of the first member and the receiving coil and excitation coil of the second member; and / or at least one (electrical) conductor (which is hereinafter referred to as at least one "inner" conductor) located radially inward (e.g., radially inward with respect to the axis of rotation) of the scale track(s) of the first member and the receiving coil and excitation coil of the second member. In a preferred embodiment, the electrical conductivity of the outer conductor and / or the inner conductor is such that they are 1×10⁻⁶ -6 They are designed to have a resistivity of less than Ω·m (for example, these are approximately 1.7 × 10⁻⁶ -8 It may include copper having a resistivity of Ω·m).

[0040] In a particularly preferred embodiment of the present invention, the magnetic flux enhancer comprises both an outer conductor and an inner conductor. In this embodiment, the receiving coil and the excitation coil may be positioned radially between the outer conductor and the inner conductor (i.e., radially between the outer conductor and the inner conductor) (e.g., with respect to the axis of rotation). Likewise, the scale track(s) may be positioned radially between the outer conductor and the inner conductor. Likewise, the at least one magnetic field sensor (from which the information regarding the relative arrangement of the first member and the second member in degrees of freedom other than the degrees of freedom centered on the axis of rotation is determined) (e.g., the first and second sets of magnetic field regions / sensors) may be positioned radially between the outer conductor and the inner conductor (i.e., radially between the outer conductor and the inner conductor) (e.g., with respect to the axis of rotation).

[0041] Preferably, these outer conductors and inner conductors are separate from each other. The outer conductors and inner conductors may be physically separate. The outer conductors and inner conductors may be electrically separated / insulated from each other.

[0042] The inner conductor may be substantially planar. The outer conductor may be substantially planar. In a preferred embodiment, the planes of the inner conductor and / or the outer conductor are substantially parallel. Preferably, the inner conductor and the outer conductor may be substantially coplanar. Preferably, the planes of the inner conductor and / or the outer conductor, the plane of the at least one scale track, and the planes of the excitation coil and the receiving coil are all substantially parallel to each other (e.g., so that the angle between any of these planes is 5° or less, more preferably 3° or less, particularly preferably 2° or less, e.g. 1° or less).

[0043] As is understood (and as described herein), the magnetic flux enhancer (e.g., inner conductor and / or outer conductor) does not necessarily have to be located in the same plane as the receiving coil and the excitation coil (not necessarily coplanar with the receiving coil and the excitation coil), or does not necessarily have to be located in the same plane as the scale track (not necessarily coplanar with the scale track).

[0044] Optionally, the first member comprises a flux enhancer (e.g., at least one "outer" conductor and / or at least one "inner" conductor). In this case, it may be preferable that the flux enhancer (e.g., at least one "outer" conductor and / or the at least one "inner" conductor) is substantially coplanar with the at least one scale track. For example, if the outer conductor and / or the inner conductor are closed annular loops (which will be described in more detail below), preferably i) the plane of the flux enhancer (i.e., the outer conductor or the inner conductor) and ii) the plane of the scale track(s) is 7.5% or less (more preferably 5% or less, particularly preferably 2% or less) of the diameter of the flux enhancer, i.e., the outer conductor or the inner conductor.

[0045] Optionally, the second member comprises a flux enhancer (e.g., at least one "outer" conductor and / or at least one "inner" conductor). In this case, it may be preferable that the flux enhancer (e.g., at least one "outer" conductor and / or the at least one "inner" conductor) is substantially coplanar with at least one of the excitation coil and the receiving coil. For example, if the outer conductor and / or the inner conductor are closed annular loops (this is described in more detail below), preferably i) the plane of the flux enhancer (i.e., the outer conductor or the inner conductor) and ii) the plane of the excitation coil and the receiving coil is 7.5% or less (more preferably 5% or less, particularly preferably 2% or less) of the diameter of the flux enhancer, i.e., the outer conductor or the inner conductor.

[0046] Optionally, the first and second members include a magnetic flux enhancer (e.g., at least one "outer" conductor and / or at least one "inner" conductor).

[0047] Preferably, the magnetic flux enhancer does not extend or exist directly behind or directly forward of the at least one scale track, and also does not extend or exist directly behind or directly forward of the receiving coil and the excitation coil.

[0048] For example, the magnetic flux enhancer (e.g., at least one "outer" conductor and / or the at least one "inner" conductor) may be provided on the first member and located within the plane of the first member, and the receiving coil and the excitation coil may be provided on the second member and located within the plane of the second member (the first member and the second member and their respective planes are axially offset with respect to the axis of rotation and are therefore not coplanar).

[0049] As is understood, the reference herein stating that a flux enhancer (e.g., inner conductor and / or outer conductor) is positioned "radially" (e.g., "radially outer," "radially inner," or "radially between") with respect to the scale track and / or excitation coil and / or receiving coil and / or magnetic field sensor(s) is not intended to limit the relative configuration / arrangement of these features in the axial direction (with respect to the axis of rotation), but rather to indicate only the relative configuration in the radial direction (with respect to the axis of rotation). In other words, the use of the terms "radially outer," "radially inner," or "radially between" is not intended to require that such features be in the same plane. For example, in an embodiment where the first member comprises a magnetic flux enhancer including an "outer" (e.g., closed) annular conductive loop and an "inner" (e.g., closed) annular conductive loop, and the second member is axially offset with respect to the first member, the receiving coil and the excitation coil (and any at least one magnetic field sensor) of the second member may still be positioned "radially" between the "outer" (e.g., closed) annular conductive loop and the "inner" (e.g., closed) annular conductive loop by their respective radial positions and dimensions. In practice, this is the situation illustrated in the embodiment described above in relation to the drawings (see Fig. 7 in particular).

[0050] The at least one scale track may be centered on the scale track axis and extend around it (e.g., annularly), and the at least one outer conductor and / or the at least one inner conductor may be substantially centered on the scale track axis. As described above, the excitation coil may be centered on the excitation coil axis and extend around it (e.g., annularly). Thus, the at least one outer conductor and / or the at least one inner conductor may be substantially centered on the excitation coil axis. Also, as described above, the receiving coil may be centered on the receiving coil axis (which may be the same axis as the excitation axis) and extend around it (e.g., annularly). Thus, the at least one outer conductor and / or the at least one inner conductor may be substantially centered on the excitation / receiving coil axis.

[0051] The above at least one "outer" conductor may include a closed annular (electrical) conductive loop, and may include, for example, a conductive ring having a substantially constant radius.

[0052] The "outer" conductor may include a metal loop. Copper is one suitable metal, but as is understood, other metals may also be used. The "outer" conductor may include a metal loop. An annular conductive loop (e.g., closed) of the "outer" conductor may be centered on the "outer conductor axis" and extend around it (e.g., annularly).

[0053] The above at least one "inner" conductor may include a closed annular electrically conductive loop or a conductive disk, and may include, for example, a conductive ring having a substantially constant radius.

[0054] The "inner" conductor may include a metal loop. Copper is one suitable metal, but as is understood, other metals may also be used. The "inner" conductor may include a wire-like loop. An (e.g., closed) annular conductive loop or conductive disk of the "inner" conductor may be centered on the "inner conductor axis" and extend around it.

[0055] In a preferred embodiment, when assembled, the scale track axis, the outer conductor axis, and the inner conductor axis are all substantially parallel to each other and optionally all may be substantially aligned. As is understood, the inductive rotary encoder may be configured or intended to be configured such that, when in use / assembled, the scale track axis, the outer conductor axis, the inner conductor axis, and the rotation axis are all substantially parallel to each other and optionally all may be substantially aligned / coaxial.

[0056] In a preferred embodiment of the present invention, the receiving coil comprises a differential coil. In a preferred embodiment of the present invention, the receiving coil comprises a pair of phase-shifted coils, and accordingly, the receiving coil provides at least one pair of phase-shifted signals (e.g., a SIN signal and a COS signal). In a particularly preferred embodiment of the present invention, the receiving coil comprises a pair of phase-shifted differential coils. For example, the receiving coil may comprise a SIN coil (providing a SIN signal) and a COS coil (providing a COS signal), each of which comprises a differential coil.

[0057] The first member may have at least first, second, and third scale tracks (having different (e.g., radial) positions (e.g., different radii) on the first member). Thus, for example, the radius of the first scale track may be smaller than the radius of the second scale track, and the radius of the second scale track may be smaller than the radius of the third scale track. The second member may have at least one excitation coil for generating a magnetic field. The second member may also have a first receiving coil positioned to detect a magnetic field manipulated by the first scale track, a second receiving coil positioned to detect a magnetic field manipulated by the second scale track, and a third receiving coil positioned to detect a magnetic field manipulated by the third scale track. These may be configured so that at least three distinct signal channels can be derived from the at least first, second, and third receiving coils. The signals of the at least three distinct signal channels may change periodically according to the relative rotation of the first member and the second member around the rotation axis. For each angle of the relative rotation of the first member and the second member around the rotation axis, the signal phases of the at least three distinct signal channels may be configured to have a unique combination. As is understood, the "signal phase" of the signal channel refers to the phase component of the signal channel.

[0058] The first receiving coil and the second receiving coil may be located on the same radial side of the excitation coil. For example, the first receiving coil may be radially spaced from the excitation coil by the second receiving coil. Thus, for example, the radius of the first receiving coil may be smaller than the radius of the second receiving coil, and the radius of the second receiving coil may be smaller than the radius of the excitation coil. The third receiving coil may be located on the radial side opposite to the first and second receiving coils of the excitation coil. Thus, for example, the first and second receiving coils may be located radially inside the excitation coil, and the third receiving coil may be located radially outside the excitation coil. Thus, for example, the excitation coil may be located radially between the second receiving coil and the third receiving coil. Accordingly, for example, the radius of the first receiving coil may be smaller than the radius of the second receiving coil, the radius of the second receiving coil may be smaller than the radius of the excitation coil, and the radius of the excitation coil may be smaller than the radius of the third receiving coil.

[0059] As is understood, the device may be configured to determine the relative rotational position of the first member and the second member about an axis of rotation and / or its derivative (e.g., velocity and / or acceleration) from the signals of the at least three distinct signal channels. In an embodiment in which the signal phases of the at least three distinct signal channels have a unique combination for each angle of relative rotation of the first member and the second member about the axis of rotation, the signal phases of the at least three distinct signal channels may be used to determine the absolute relative rotational position of the first member and the second member about the axis of rotation and / or its derivative. Accordingly, the device may be configured to determine the absolute relative rotational position of the first member and the second member about the axis of rotation and / or its derivative from the signals of the at least three distinct signal channels.

[0060] For example, the device may be configured to i) take the output (e.g., phase value) of the first receiving coil and then identify what output (e.g., phase value) is expected from the second receiving coil and the third receiving coil for each scale cycle of the first scale track. The device may also be configured to ii) compare the expected output with the actual output, verify whether they match, and record the result. Additionally, the device may be configured to determine if there is only one match, in which case the matched position is used or output as an absolute relative rotational position. If there is no match or if two or more matches exist, an error state may be recorded and / or output.

[0061] Accordingly, the device may include means for determining information regarding the (e.g., absolute) rotational position and / or derivative thereof of the first member and the second member about the rotation axis from the at least three separate signal channels. The means may include one or more "processing" or "processor" devices. As previously mentioned herein, such means (e.g., "processing" or "processor" devices) for determining the position and / or derivative thereof about the rotation axis may be provided on the first member and / or the second member, and / or on another device separate from the first member and the second member (e.g., an interface unit or (e.g., a machine controller)).

[0062] A configuration of at least three signal channels can provide various advantages over a single or two-signal channel system. For example, compared to a two-channel system, a three-channel system provides greater tolerance for angular error in the output of the channels (e.g., lower-period channels) without necessarily sacrificing accuracy performance. This, in turn, provides the manufacturer with an option to simplify the inductive rotary encoder and reduce its cost. For example, all other things being equal, a three-channel system according to the present invention can provide performance equal to (or even better than) a two-channel system while having smaller components (e.g., smaller receiving coil, smaller scale track feature) and / or using less / simpler / inexpensive or even no (e.g., dynamic) signal correction for one or more channels. Furthermore, greater error tolerance allows a large number of incremental periods per rotation to be used, thereby enabling a more accurate large-diameter encoder.

[0063] For example, the device may be configured such that one of the receiving coils (e.g., a "first" receiving coil) (which may be referred to as an "incremental receiver coil") has a signal of greater amplitude and / or higher quality than the output of another receiving coil (e.g., a second and / or third receiving coil) (which may be referred to as a "first Vernier receiver coil" and a "second Vernier receiver coil"). For example, this may be attributed to one or more characteristics of each scale track (e.g., its size / quality) and / or one or more characteristics of each receiving coil (e.g., its size / quality). The quality of the signal may refer, for example, to the signal-to-noise ratio.

[0064] For example, the size of the first / incremental receiving coil may be larger than the size of the second and third (first vernier and second vernier) receiving coils. "Size" may refer to radial size / amplitude (i.e., width / amplitude measured in the radial direction). For example, the radial width or "coil amplitude" of the first / incremental receiving coil may preferably be at least 25% larger than that of the second and third (first vernier and second vernier) receiving coils, more preferably at least 50% larger than that of the second and third (first vernier and second vernier) receiving coils, and particularly preferably at least 100% larger than that of the second and third (first vernier and second vernier) receiving coils (i.e., at least twice that of the second and third (first vernier and second vernier) receiving coils). "Size" may also / alternatively refer to the diameter of the receiving coil. For example, for reasons of signal amplitude and / or quality, it may be preferable that the diameter of the first / incremental receiving coil be larger than the diameter of the second and third (first vernier and second vernier) receiving coils. That is, it may be preferable that the first / incremental receiving coil be located radially outside of the second and third (first vernier and second vernier) receiving coils. Additionally, the width (width measured in the radial direction) of the first scale track (which may be referred to as the "incremental scale track") may be larger than the width of the second and / or third scale tracks (which may be referred to as the "first vernier scale track" and the "second vernier scale track").

[0065] The device may be configured such that one or more types of automatic / dynamic signal correction are applied to the output of the first / incremental receiving coil. Types of automatic / dynamic signal correction include, but are not limited to, i) automatic / dynamic gain correction (AGC), ii) automatic / dynamic offset correction (AOC), iii) automatic / dynamic balance correction (ABC), and iv) automatic / dynamic phase correction (APC). An advantage of the above configuration of at least three receiving coils is that some or all of such automatic / dynamic signal corrections may be less important (and unnecessary) for the outputs of other receiving coils (e.g., first and second vernier receiving coils). Accordingly, optionally, fewer types of automatic / dynamic signal correction may be applied to the outputs of the second and third (e.g., first and second vernier) receiving coils compared to those applied to the output of the first / incremental receiving coil. For example, at least one type of automatic / dynamic signal correction is applied to the output of the first / incremental receiving coil, and no automatic / dynamic signal correction is applied to the outputs of the second and third (e.g., first and second verniers) receiving coils.

[0066] By using separate / different excitation coils, magnetic fields can be generated that are operated by different scale tracks and detected by different receiving coils. For example, a first excitation coil may be used to generate a magnetic field operated by the first scale track and detected by the first receiving coil, a second excitation coil may be used to generate a magnetic field operated by the second scale track and detected by the second receiving coil, and a third excitation coil may be used to generate a magnetic field operated by the third scale track and detected by the third receiving coil. In a preferred embodiment, the same excitation coil(s) are used to generate a magnetic field operated by two or more scale tracks and detected by two or more receiving coils. For example, in a preferred embodiment, one excitation coil is used to generate a magnetic field operated by each of the first, second, and third scale tracks (the first receiving coil is positioned to detect the magnetic field operated by the first scale track, the second receiving coil is positioned to detect the magnetic field operated by the second scale track, and the third receiving coil is positioned to detect the magnetic field operated by the third scale track).

[0067] As described above, the scale track may include scale features in a periodic arrangement. The periods of the first, second, and third scale tracks may differ from each other. Preferably, the first, second, and third scale tracks are configured such that the only common integer factor among the period counts (i.e., "feature count" or "line count") of the first, second, and third scale tracks is 1.

[0068] The scale track with the largest number of cycles per rotation may be referred to as the "incremental scale track," and the remaining scale tracks may be referred to as "vernier scale tracks."

[0069] In a preferred embodiment, the first, second, and third scale tracks are all centered on a single (i.e., identical) scale track axis (“first axis” or “first member axis”) and extend around it (e.g., annularly). The at least one excitation coil may be centered on an excitation coil axis and extend around it (e.g., annularly). In a preferred embodiment, the first, second, and third scale tracks are all centered on a single (i.e., identical) receiving coil axis and extend around it (e.g., annularly). In a preferred embodiment, the excitation coil(s) and the first, second, and third receiving coils are all centered on a single (i.e., identical) axis (“second axis” or “second member axis”) and extend around it (e.g., annularly) (i.e., the excitation coil axis and the receiving coil axis may substantially coincide). For example, the excitation coil and the receiving coil may be formed in a substantially concentric configuration on the second member.

[0070] The excitation coil may be a single-turn coil. The receiving coil(s) may each be a single-turn coil. The excitation coil may be a unidirectional excitation coil, so that when in use, the current flowing through the excitation coil around the coil axis flows in only one direction at any given point in time. The excitation coil may be extended circularly around the coil axis with a constant single radius. The excitation coil may include a capacitor positioned so that the excitation coil operates as a resonant circuit. The capacitor may be positioned to be aligned with the annular / circular extension of the excitation coil (i.e., positioned at the same radius as the radius of the conductor wire of the excitation coil).

[0071] The above inductive encoder may be configured to pass alternating current through the excitation coil at a predetermined operating frequency to generate the (alternating) magnetic field.

[0072] According to a second aspect of the present invention, an apparatus comprising an inductive rotary encoder is provided, wherein the inductive rotary encoder comprises a first member and a second member capable of relative rotation about a rotation axis, the first member comprises at least one scale track, the second member comprises an excitation coil for generating a magnetic field operated by the at least one scale track, the second member also comprises a receiving coil for detecting the magnetic field—thereby which the relative rotational position of the first member and the second member about the rotation axis can be measured—at least one of the first member and the second member comprises a magnetic flux enhancer, wherein a current flow is generated within the magnetic flux enhancer by the magnetic field of the excitation coil or another excitation coil, and the magnetic flux enhancer itself again generates a magnetic field that acts to increase the magnetic flux of the magnetic field detected by the receiving coil in the region of the receiving coil. The features described above in relation to the first aspect of the present invention are equally applicable to the second aspect of the present invention.

[0073] According to a third aspect of the present invention, an apparatus comprising an inductive rotary encoder is provided, wherein the inductive rotary encoder comprises a first member and a second member rotatable relative to a rotation axis, the first member having at least first, second, and third scale tracks, the second member having at least one excitation coil for generating a magnetic field, the second member also having a first receiving coil arranged to detect a magnetic field manipulated by the first scale track, a second receiving coil arranged to detect a magnetic field manipulated by the second scale track, and a third receiving coil arranged to detect a magnetic field manipulated by the third scale track, and configured such that at least three distinct signal channels can be derived from the at least first, second, and third receiving coils, and the signals of the at least three distinct signal channels change periodically according to the relative rotation of the first member and the second member around the rotation axis, and for each angle of the relative rotation of the first member and the second member around the rotation axis, the at least It is characterized by being configured such that the signal phases of three separate signal channels have a unique combination. The features described above in relation to the first aspect of the present invention are equally applicable to the third aspect of the present invention.

[0074] According to a fourth aspect of the present invention, an apparatus comprising an inductive rotary encoder is provided, wherein the inductive rotary encoder comprises a first member and a second member capable of relative rotation about a rotation axis, the first member comprises at least first and second scale tracks, the second member comprises an excitation coil for generating a magnetic field operated by the at least first and second scale tracks, and the second member also comprises a first receiving coil for detecting the magnetic field operated by the first scale track and a second receiving coil for detecting the magnetic field operated by the second scale track, thereby allowing the relative rotational position of the first member and the second member about the rotation axis to be measured. The features described above in relation to the first aspect of the present invention are equally applicable to the fourth aspect of the present invention. Brief explanation of the drawing

[0075] Now, embodiments of the present invention will be described only by way of example with reference to the following drawings. FIG. 1 is a perspective view of an inductive rotary encoder according to the present invention. Figure 2 is a schematic cross-sectional view of the inductive rotary encoder of Figure 1 mounted on a machine. Figure 3 is a plan view of the rotor of the inductive rotary encoder of Figure 1. Figure 4 is a plan view of the stator of the inductive rotary encoder of Figure 1. Figure 5 is a plan view of the quadrant of the stator of Figure 4. FIG. 6 is a plan view of the quadrant of the stator and rotor, in which the substrate of the stator is transparent so that the rotor below the stator can be seen. Figure 7 shows a schematic cross-sectional view of the stator and rotor taken along the CC line of Figure 6. FIG. 8 is a plan view showing the excitation coil of the stator and the outer and inner conductive loops of the rotor separated. Figure 9 is a block diagram of a system for calculating the scale of the relative rotational position of the rotor and the stator. Figure 10 is a graph showing how the output of the arc tangent calculator for each receiving coil changes according to the relative rotation of the stator and rotor. FIGS. 11a and FIGS. 11b illustrate schematic partial cross-sectional views of the stator and rotor and are intended to explain the effect of changes in the lateral / radial position of the stator and rotor (e.g., eccentricity) on the electromagnetic field detected by the sensor of the stator. FIGS. 12a, FIGS. 12b, and FIGS. 12c illustrate schematic partial cross-sectional views of the stator and rotor and are intended to explain the effect of relative tilt on the electromagnetic field detected by the relative tilt sensor of the stator. FIG. 13 is a schematic plan view of the outer and inner quadrant sensors of the stator. FIGS. 14a and FIGS. 14b illustrate examples of Lissajous figures obtained from outer and inner quadrant sensors. FIGS. 15a and FIGS. 15b illustrate plan views of alternative stator configurations. FIGS. 16(a) and FIGS. 16(b) separately illustrate the isometric and planar views of an exemplary excitation coil. FIG. 16(c) schematically illustrates how the magnitude of the magnetic flux density component perpendicular to the scale (i.e., the component parallel to the axis (D) through which the scale extends around it), generated by the circular unidirectional excitation coil of FIG. 16(a) and FIG. 16(b), changes over a limited radial cross-section (indicated by the dashed line in FIG. 16(b)) with and without inner and outer conductor loops (dotted line) and (solid line). FIG. 16(d) shows a plan view of an exemplary excitation coil having a folded-rectangular loop. FIG. 16(e) schematically illustrates how the magnitude of the magnetic flux density component perpendicular to the scale (i.e., the component parallel to the axis (D) through which the scale extends around it), generated by the folded rectangular loop of the excitation coil in FIG. 16(d), changes over a limited radial cross-section (indicated by the dashed line in FIG. 16(d)) with and without inner and outer conductor loops (dotted line) and (solid line). Specific details for implementing the invention

[0076] Referring to FIGS. 1 and 2, an exemplary inductive rotary encoder (100) according to the present invention comprises a rotor (200) and a stator (300). As schematically illustrated in FIG. 2, in use, the rotor (200) is mounted on a mechanical part, such as a shaft (500), which is rotatable about a static part (600) of the machine about an axis (A), and the stator (300) is mounted on a static part of the machine. Similar to a known inductive rotary encoder, the stator (300) is an active power-supplied component and includes an excitation coil and a receiving coil (described in more detail below) and associated electronics for generating and detecting an alternating electromagnetic field. Also, similar to a known inductive rotary encoder, the rotor (200) is a passive / unpowered component including a scale feature. The scale feature above manipulates the electromagnetic field detected by the receiving coil of the stator (300) (and in this example, manipulates / modulates the amplitude of the alternating electromagnetic field), so that the specific output of the receiving coil of the stator depends on the relative rotational orientation of the stator (300) and the rotor (200) around the axis (A), and thus the relative rotational position (and / or derivative thereof) of the stator (300) and the rotor (200) (and thus the relative rotational position of the static part (600) and the rotating part (500) of the machine) can be measured from the electromagnetic field. As is understood, the rotor (200) and the stator (300) can be configured in opposite ways (i.e., the rotor may have active components, i.e., an excitation coil and a receiving coil, and the stator may have passive components, i.e., a scale feature). However, due to the need for electrical connections, it may be simpler and easier for the stator to be an active power-supplied component.Additionally, since the rotor may be subjected to significant forces due to its movement and changes in speed, and thus the electronics on the active component may be vulnerable to damage caused by such forces, it may be advantageous to make the rotor a passively unpowered component. As is understood, in other embodiments, both members may be rotatable, that is, both the "stator" and the "rotor" may be rotatable, in which case both the "stator" (300) and the "rotor" (200) may be referred to as "rotors," for example, "rotor 1" and "rotor 2," or "active rotor" and "passive rotor." Nevertheless, for the sake of simplicity and convenience of explanation, the described embodiment comprises a static "stator" (300) and a "rotor" (200) rotatable relative to the stator (300).

[0077] Referring to FIG. 3, a plan view of the rotor (200) is shown. In the described embodiment, the rotor (200) comprises a disc-shaped substrate (202) provided with scale features. In the described embodiment, the substrate is formed of glass fiber, has a circular shape overall, and has a hole (203) extending through the center to allow a shaft of the machine (not shown in FIG. 3) to pass through. As is understood, the rotor substrate (202) may be formed of other materials (e.g., non-conductive materials) and does not necessarily have to have a circular shape or a hole extending through it.

[0078] The scale feature of the rotor (200) is centered on the axis (B) and extends annularly around it. In the described embodiment, the scale feature is conductive (in this embodiment, it is copper and is formed by removing a copper coating on the glass fiber substrate (202) by etching / milling, but it may also be formed by other processes such as copper plating). In an alternative embodiment, the substrate (202) may include a conductive material, in which case a non-conductive feature may be formed thereon to provide the scale feature.

[0079] In the described embodiment, the rotor (200) includes a first scale track (204), a second scale track (206), and a third scale track (208). Each scale track includes a periodic series of scale features. The periods of the first scale track (204), the second scale track (206), and the third scale track (208) are different from each other, and each scale track is configured to have an integer number of periods per rotation, and is also configured such that the phase relationship between the scale features of the three scale tracks at any angle around the axis (B) is not the same as the phase relationship at any other rotation angle. As illustrated, the first scale track (204), the second scale track (206), and the third scale track (208) are arranged concentrically with respect to each other, and thus all are centered on the same axis (B).

[0080] In the described embodiment, the rotor (200) also includes an outer conductive loop (210) made of a conductive material (copper in this embodiment) and an inner conductive loop (212) made of a conductive material (again, copper in this embodiment). The outer conductive loop (210) and the inner conductive loop (212) are centered on an axis (D) and extend annularly around it. As described in more detail below, the outer conductive loop (210) and the inner conductive loop (212) help increase the magnetic flux density in the radial space between them, thereby helping to increase the signal strength and system sensitivity of the receiving coil (described below) of the stator. As most clearly illustrated in FIGS. 6 and 7, in the described embodiment, the outer conductive loop (210) is located radially outward of all three scale tracks (204, 206, 208) and also radially outward of all coils on the stator (i.e., i) the excitation coil, ii) the first, second, and third receiving coils, and iii) the quadrant coils). Additionally, as most clearly illustrated in FIGS. 6 and 7, in the described embodiment, the inner conductive loop (212) is located radially inward of all three scale tracks (204, 206, 208) and also radially inward of all coils on the stator (i.e., i) the excitation coil, ii) the first, second, and third receiving coils, and iii) the quadrant coils). Thus, in other words, the three scale tracks (204, 206, 208) and all coils on the stator (i.e., i) the excitation coil, ii) the first, second, and third receiving coils, and iii) the quadrant coil) are positioned radially between the outer conductive loop (210) and the inner conductive loop (212).

[0081] In the described embodiment, the outer conductive loop (210) and the inner conductive loop (212) are simple circular copper loops of a closed single winding. However, they are not necessarily required to be so, and the outer conductive loop (210) and the inner conductive loop (212) may take other forms. For example, the outer conductive loop (210) and the inner conductive loop (212) may have a multiple-turn helical form (e.g., a form having a constant radius but extending axially through the substrate), include a multiple-turn spiral form (e.g., a form with a continuously changing radius), and proceed in a waveform (e.g., sinusoidal) form / path around the axis. Optionally, a plurality of distinct outer conductive loops (210) may be provided, and / or a plurality of inner conductive loops (212) may be provided. Additionally, one or both of the outer conductive loop (210) and / or the inner conductive loop (212) may be omitted as needed. Furthermore, although still an optional feature, the presence of the outer conductive loop (210) has been found to be particularly beneficial to an embodiment (described in more detail below) comprising a sensor for detecting the relative tilt of the stator and / or rotor. This is because, in addition to having the effect of increasing the signal strength of the receiving coil, at least some of the sensors used for detecting tilt and / or lateral / radial position (e.g., eccentricity) are made substantially more sensitive to the relative tilt of the rotor and stator, thereby making it easier to extract relative tilt measurements from such sensors.In particular, as described in more detail below, an inductive rotary encoder device can be configured such that, due to the outer conductive loop (210), the output of the outer quadrant coil (described below) measures only the relative tilt of the rotor (200) and the stator (300) and is assumed to be related only to this.

[0082] Additionally, the presence of one or both of the outer conductive loop (210) and / or the inner conductive loop (212) may be particularly useful in an embodiment where the number of excitation coils is less than the number of scale tracks and each receiving coil (e.g., to improve / increase magnetic flux and further signal strength).

[0083] Additionally / alternatively, the presence of one or both of the outer conductive loop (210) and / or the inner conductive loop (212) is particularly useful for increasing the magnitude of the magnetic flux density component perpendicular to the scale (or simply "magnetic flux density perpendicular to the scale") in a radially distal region relative to the excitation coil, which may be desirable when it is desirable to increase the radial width of the scale track and / or the receiving coil and / or in an embodiment where the receiving coil and its corresponding scale track cannot be located immediately radially next to the excitation coil (e.g., where there is another receiving coil and its corresponding scale track radially between the excitation coil and its receiving coil and its corresponding scale track that generates an electromagnetic field configured to sense) and / or where the excitation coil is configured to exist only on one radial side of the receiving coil and its corresponding scale track, such as when the excitation coil is a "single-direction" excitation coil (described in more detail below). In fact, the above cases are the cases of embodiments of FIGS. 4 to 7, FIG. 15, and FIG. 16(a) and FIG. 16(b), in which i) a unidirectional excitation coil (330) is used, ii) the first scale track (204) and the first receiving coil (304) have a relatively large radial width, and iii) the second receiving coil (306) and the corresponding second scale track (206) are radially positioned between the third receiving coil (308) / third scale track (208) and the excitation coil (330).In this embodiment, the inner conductive loop (212) is particularly useful for increasing the magnetic flux density perpendicular to the scale in the area of ​​the third scale track (208) and the associated third receiving coil (308) that is located radially further from the excitation coil (330) compared to the first scale track / first receiving coil (204, 304) and the second scale track / second receiving coil (206, 306) (since the second scale track (206) and the second scale receiving coil (306) are located radially between the third scale track (208) and the third receiving coil (308) and the excitation coil (330). Likewise, the outer conductive loop (210) is particularly useful for increasing the magnetic flux density perpendicular to the scale in the radially distal region of the first scale track (204) and the first receiving coil (304) (which has a significantly larger radial width compared to the second scale track / second receiving coil (206, 306) and the third scale track / third receiving coil (208, 308)). This will be explained in more detail below in relation to FIGS. 16(b) and FIGS. 16(c).

[0084] As is understood, for whatever reason, increasing the magnetic flux density of the electromagnetic field in the region of the scale track increases the eddy currents generated within the conductive scale feature, which in turn provides a larger amplitude modulation effect for the alternating electromagnetic field detected by the corresponding receiving coil.

[0085] Now, referring to FIGS. 4 and 5, FIG. 4 illustrates a top view of a stator (300), and FIG. 5 illustrates a detailed view of one quadrant of the stator (300). The stator (300) comprises a disc-shaped substrate (302) on which an excitation coil and a receiving coil are provided, together with the associated electronic device provided on the substrate (302) on the opposite side of the illustrated side. (In FIG. 5, shading of the stator substrate is omitted so that other features of the stator can be seen better.) In the described embodiment, the stator substrate (302) is made of glass fiber, has a circular shape overall, and has a hole (203) extending through the center to allow the shaft (500) of the machine to pass through. According to another embodiment of the present invention, the stator substrate (302) may be made of another non-conductive material (e.g., ceramic), does not necessarily have to have a circular shape, nor does it necessarily have to have a hole extending through the substrate.

[0086] The stator (300) comprises a first scale receiving coil (304), a second scale receiving coil (306), and a third scale receiving coil (308), which are arranged concentrically and each is centered on an axis (D) and extends substantially in a complete annular shape around it. As illustrated, the width measured in the radial direction of the first scale receiving coil (304) (e.g., "radial width" R) w )) is larger than the width of the second scale receiving coil (306) and the third scale receiving coil (308). In the illustrated embodiment, the radial width (R) of the first scale receiving coil (304) w) is approximately twice the radial width of the second scale receiving coil (306) and the third scale receiving coil (308). As is understood, this is not necessarily required, for example, that they all have the same width, or for example, that the width of the second receiving coil and / or the third receiving coil may be greater than the width of the first receiving coil. As is understood, since the receiving coil extends along a waveform (e.g., sinusoidal) path around the axis (D), another appropriate term for the radial width of the receiving coil is "coil amplitude".

[0087] In the described embodiment, each of the first scale receiving coil (304), the second scale receiving coil (306), and the third scale receiving coil (308) actually comprises a differential copper coil extending in a first sinusoidal waveform and a differential copper coil extending in a second sinusoidal waveform. The first and second differential coils are superimposed and phase-shifted by 90° relative to each other. Thus, the first differential coil may be referred to as the SIN coil, and the second differential coil may be referred to as the COS coil. Accordingly, each of the first scale receiving coil (304), the second scale receiving coil (306), and the third scale receiving coil (308) actually outputs a pair of signals in a quadrature relationship (i.e., signals phase-shifted by 90°), and thus the pair of signals may be represented, for example, as a SIN signal and a COS signal. As is understood, other configurations, such as a three-phase system comprising three sets of coils phase-shifted by 60°, are also possible. In other embodiments, each track / channel may include only a single coil, but such a system may have lower accuracy.

[0088] As illustrated in FIGS. 4 and 5, the first scale receiving coil (304), the second scale receiving coil (306), and the third scale receiving coil (308) are sinusoidal in that they extend around the axis (D) along a substantially sinusoidal path. In fact, in the described embodiment, the SIN coil and COS coil of the first scale receiving coil (304), the second scale receiving coil (306), and the third scale receiving coil (308) are each actually differential coils and have clockwise and counterclockwise windings in each period to cancel out residual magnetic fields. The coil shape is sinusoidal for harmonic suppression. Of course, the coil shape / path does not necessarily have to be sinusoidal. For example, the coil may have a different periodic shape / path to capture modulation from the scale. Also, it does not necessarily have to be a differential coil. In the described embodiment, the periods of the sinusoidal waveforms of the first scale receiving coil (304), the second scale receiving coil (306), and the third scale receiving coil (308) are different from each other (and in the described example, the periods of the sinusoidal waveforms of the first scale receiving coil (304), the second scale receiving coil (306), and the third scale receiving coil (308) are configured to match the period of the corresponding scale track). As is understood, this is not strictly necessary, but doing so may be advantageous in terms of processing and signal quality.

[0089] In the described embodiment, each of the first scale receiving coil (304), the second scale receiving coil (306), and the third scale receiving coil (308) comprises a single winding (or "single loop") coil. In another embodiment, one or more receiving coils may comprise multiple windings (or "multiple loops") coils.

[0090] As described in more detail below, when in use / assembled, the inductive encoder device is arranged such that i) the first scale receiving coil (304) and the first scale track (204) are positioned directly in front of each other (i.e., "directly facing") (in other words, the first scale receiving coil (304) is positioned axially aligned with the first scale track (204) and directly above it in the orientation shown in FIG. 7), ii) the second scale receiving coil (306) and the second scale track (206) are positioned directly in front of each other (i.e., "directly facing") (in other words, the second scale receiving coil (306) is positioned axially aligned with the second scale track (206) and directly above it in the orientation shown in FIG. 7), and iii) the third scale receiving coil (308) and the third scale track (208) are positioned directly in front of each other (i.e., "directly facing") (in other words, the third scale receiving The coil (308) is configured to be aligned axially with respect to the third scale track (208) and placed directly above it in the orientation shown in FIG. 7.

[0091] The stator (300) also includes an excitation coil (330) (which may also be referred to as a "transmitting coil") centered on the axis (D) and extending annularly around it. In the described embodiment, the excitation coil (330) is positioned radially between the first scale receiving coil (304) and the second scale receiving coil (306) and includes a single winding (or "single loop") coil.

[0092] In the described embodiment, the excitation coil (330) is a “single-direction” excitation coil in that it comprises a conductor wire extending along a circular path in a single direction around the axis (D), so that at any given point in time, current flows in only one direction around the axis (D) (e.g., clockwise or counterclockwise). In the specific embodiment described, the conductor has a substantially constant radius and thus follows a substantially circular path. A suitable exemplary excitation coil (330) having a conductor extending along a circular path in a single direction around the axis (D) is shown separately in FIG. 16(a) and FIG. 16(b).

[0093] In the described embodiment, the single-wind / loop excitation coil comprises two single-wind (copper) wires (330a, 330b) extending circularly / annularly around an axis (D), which are arranged in parallel on adjacent layers of the substrate (302) with the same radius “r” (thus being spaced apart from each other along a direction parallel to the axis (D) as shown in FIG. 16(a)). Each end of these is connected to a pair of terminals (+ / -). Thus, configured in this way, the two wires (330a, 330b) extend around the axis (D) and form a single-direction, single-winding circularly / annular excitation coil that is concentric with the first scale receiving coil (304), the second scale receiving coil (306), and the third scale receiving coil (308). The advantage of using two wires configured as described is that the resistance is reduced compared to an equivalent excitation coil having only one wire (of the same dimensions), which increases the quality (Q factor) of the excitation coil. As is understood, in an equivalent embodiment, a similar reduction in the resistance of the excitation coil can be achieved with a single wire by using a thicker wire and / or using a wire made of a material with lower intrinsic resistance.

[0094] As is understood, in other embodiments, the excitation coil (330) may comprise multiple windings or "loops," in which case the excitation coil (e.g., the wire) may be wound two or more times around the axis (D) and take on a helical shape having, for example, substantially constant radius. However, to achieve the desired magnetic field by minimizing the inductance of the excitation coil and relatively reducing the required driving voltage, it may be preferable for the excitation coil to be a single winding or "loop" excitation coil (in that it is wound around / extends around / turns around) only once rather than wound around the axis (D) multiple times (e.g., overlapping). However, as is understood, for a given desired magnetic field generated by the excitation coil, reducing the number of windings of the excitation coil implies that the level of current / ampere required through the excitation coil must be increased. This can be achieved by providing a power / drive circuit that directly provides the required level of current / ampere passing through the excitation coil (330), but the current (ampere) requirement of the power / drive circuit can be reduced by configuring the excitation coil to operate as a "resonant circuit" (also known as an "LC circuit," "tank circuit," or "tuned circuit"), for example, by allowing the excitation coil to store energy vibrating at the same frequency as the vibrating power / drive circuit. In this case, the power / drive circuit only needs to supply enough current to overcome the losses occurring in the excitation coil (330). An effective method of configuring the excitation coil (330) to operate as a resonant circuit is to configure a suitable capacitor (331) in the excitation coil (330), for example, as schematically illustrated in FIG. 16(a) and FIG. 16(b) (in this case, the capacitor may be referred to as a "resonant capacitor").In the described embodiment, the operating / driving frequency of the excitation coil of the alternating magnetic field / stator is about 3 MHz, and thus the capacitor is selected accordingly based on the inductance of the wire extending in the circle of the excitation coil.

[0095] In the specific embodiment described, due to space constraints, the ("resonant") capacitor (331) is provided on a layer of the stator substrate (302) different from the layer where the conductors (330a, 330b) of the excitation coil (330) are located (thus, in FIG. 16(a), it is shown as being at a different location from the conductors (330a, 330b) along a direction parallel to the axis (D). However, in the described embodiment, the capacitor (331) is advantageously physically positioned to be located on substantially the same radius as the conductors (330a, 330b). This may be advantageous because the capacitor (331) contributes to the electromagnetic field generated by the excitation coil (330), and therefore, placing the capacitor (331) on substantially the same radius as the conductors (330a, 330b) of the excitation coil helps to reduce distortion of the electromagnetic field generated by the excitation coil (330) in the region of the capacitor (331).

[0096] As is understood, the use of a resonant capacitor is not limited to the single-winding, single-direction embodiment described and illustrated in relation to FIG. 16(a) and FIG. 16(b), and may be useful in other excitation coil configurations. For example, the resonant capacitor may be used in an embodiment in which the coil comprises multiple windings, and may also be used in an embodiment in which the excitation coil extends and / or is wound in both clockwise and counterclockwise directions around an axis (as described below in relation to FIG. 16(d)).

[0097] In the described embodiment, there is only one excitation coil (330) shared among the three receiving coils (i.e., one excitation coil (330) is used to generate the electromagnetic field for the three receiving coils). As is understood, other excitation coil configurations are also possible. For example, two or more excitation coils may be provided, in which case ideally they would all be in a resonant state. As another example, the / each excitation coil may include a multi-winding (or "multi-loop") coil. As yet another example, the / each excitation coil may include a "folded rectangular loop."

[0098] During use / operation, the power / drive circuit causes alternating current to flow through the excitation coil (330), thereby generating an alternating electromagnetic field. Since the excitation coil (330) of the embodiment of FIG. 16(a) has a configuration that extends around the axis (D) in only one direction (i.e., a configuration that does not fold back on itself, such as in the case of a “folded rectangular loop”), at any given point in time, the current flows in only one direction around the axis (D). For example, as schematically illustrated by the arrows on the wires (330a, 330b) in FIG. 16(a), at a first point in time, the current flows through the wires (330a, 330b) in only a clockwise direction around the axis (D). As is understood, at another point in time when the current flows through the wires (330a, 330b) in the opposite direction due to the alternating current, the direction of the arrows points in the opposite direction.

[0099] The profile of the magnitude of the magnetic flux density component passing perpendicularly (i.e. parallel to the axis (D)) through the scale, generated by a unidirectional excitation coil (330) (schematically illustrated in FIG. 16(c)), contrasts with the profile of the magnitude of the magnetic flux density component passing perpendicularly (i.e. parallel to the axis (D)) through the scale, generated directly by an excitation coil (430) (schematically illustrated in FIG. 16(d)) composed of a folded rectangular loop, in which current flows in both clockwise and counterclockwise directions around the axis (D) at any given point in time (indicated by arrows on wire (430a)). As schematically illustrated by the solid line in FIG. 16(e), in this configuration, the magnetic flux density component passing perpendicularly (i.e. parallel to the axis (D)) through the scale is significantly larger and more uniform on the inside of the folded rectangular loop compared to the outside. In this configuration, as schematically illustrated in FIG. 16(d) and FIG. 16(e), the first scale receiving coil (304) may be located inside the folded rectangular loop, and the second scale receiving coil (306) and the third scale receiving coil (308) may be located on both radial sides of the folded rectangular loop. As is understood, in this case, the radial positions of the first scale track (204), the second scale track (206), and the third scale track (208) on the rotor must be changed / rearranged accordingly. As schematically illustrated in FIG. 16(d), the folded rectangular loop excitation coil (430) may optionally include a resonant capacitor (431), and if desired, as schematically illustrated in FIG. 16(d), the resonant capacitor may be positioned radially aligned with the excitation coil's conductor (430a) (this is to minimize disturbance to the magnetic field generated by this, but this is less important in the folded rectangular loop design because the magnetic field is not uniform in the folded / back-turns region).

[0100] As described above, the outer / inner conductive loop increases the magnetic flux density (magnitude of the component) passing perpendicularly into the scale, which is schematically illustrated in FIG. 16(c) and FIG. 16(e) through solid and dashed lines that schematically illustrate the magnetic flux density perpendicular to the scale for equivalent systems with and without the outer / inner conductive loop. That is, in FIG. 16(c) and FIG. 16(e), the solid line schematically represents a representative profile of the magnetic flux density passing perpendicularly into the scale in a system without the outer and inner conductive loops (210, 212), and the dashed line schematically represents a representative profile of the magnetic flux density perpendicular to the scale in a system that is identical in all respects except that it has the outer and inner conductive loops (210, 212). As is understood, increasing the magnetic flux density passing vertically into the scale feature increases the eddy currents generated therein, which in turn provides a larger amplitude modulation effect on the electromagnetic field detected by the receiving coil.

[0101] Regardless of the specific configuration of the excitation coil (330) and regardless of the presence of an outer and / or inner conductive loop, the first scale receiving coil (304), the second scale receiving coil (306), and the third scale receiving coil (308) are arranged to detect the electromagnetic field generated by the excitation coil (330) and provide an output in response. As is understood, and as described in more detail below, the electromagnetic field generated by the excitation coil (330) is affected by the presence of scale features of the first scale track (204), the second scale track (206), and the third scale track (208) on the rotor (200) (i.e., the electromagnetic field is changed) (in this embodiment, this is due to eddy currents generated within the scale features, said eddy currents having an amplitude modulation effect on the alternating electromagnetic field generated by the excitation coil (330)), and this phenomenon is used to determine the relative rotational position of the rotor (200) and the stator (300) about the axis (B / D).

[0102] In the specific embodiment described, the stator (300) also includes a first outer quadrant coil (310), a second outer quadrant coil (312), a third outer quadrant coil (314), and a fourth outer quadrant coil (316), and a first inner quadrant coil (320), a second inner quadrant coil (322), a third inner quadrant coil (324), and a fourth inner quadrant coil (326). The angle occupied by each quadrant is substantially 90°. As is understood, the length of each quadrant coil may be shorter so that the angle it occupies is less than 90°, but it may be desirable to maximize the angle occupied by each quadrant coil (within the range of the quadrant) to maximize signal strength and prevent blind spots. As described in more detail below in relation to FIGS. 13 and 14, the inner and outer quadrant coils can be used to detect the relative tilt and / or lateral / radial position (e.g., eccentricity) of the rotor (200) and the stator (300). As shown in FIGS. 6 and 7, at assembly / use, the outer quadrant coil (only the fourth outer quadrant coil (316) is shown in FIGS. 6 and 7) is positioned axially aligned with the blank region of the rotor substrate (202) (e.g., directly above in the orientation shown in FIG. 7), and the inner quadrant coil (only the fourth inner quadrant coil (326) is shown in FIGS. 5, 6 and 7) is positioned axially aligned with the third scale track (208) / directly above (in the orientation shown in FIG. 7).

[0103] As also illustrated in FIGS. 6 and 7, the radial width of the third scale track (208) is selected such that both the third scale receiving coil (308) and the inner quadrant coil (only the fourth inner quadrant coil (326) is shown in FIGS. 6 and 7) are positioned axially aligned with respect to the third scale track (208) (e.g., directly above in the orientation shown in FIG. 7).

[0104] Now, with reference to FIG. 8, the effect of the outer conductive loop (210) and the inner conductive loop (212) on the electromagnetic field generated by the excitation coil (330) is explained. In summary, the outer conductive loop (210) and the inner conductive loop (212) have the effect of "folding back" the electromagnetic field generated by the excitation coil (330) into the region where the receiving coils are located, thereby increasing the magnetic flux density in the radial space between them and helping to increase the magnetic field strength between the two coils.

[0105] According to the above description, the excitation coil (330) is located on the stator (not shown in FIG. 8), and alternating current flows within it, thereby generating an electromagnetic field around it. An arrow on the excitation coil (330) indicates the direction of the current flowing through the excitation coil (330) at a specific point in time (indicated clockwise in FIG. 8). According to the right-hand rule of electromagnetism, the excitation coil (330) is on the inner side of the loop A magnetic field is generated with polarity (inward direction of the figure) on the outside of the loop and polarity (outward direction of the figure). For convenience of explanation, only the polarity for a single half-cycle of the alternating / alternating electromagnetic field is shown in FIG. 8.

[0106] Additionally, according to the above description, an outer conductive loop (210) and an inner conductive loop (212) are provided on the rotor and are located radially outward and radially inward, respectively, of the scale tracks of the rotor (this is also not shown in FIG. 8). Both the outer conductive loop (210) and the inner conductive loop (212) pass through their loops They experience a net magnetic flux of polarity. According to Lenz's Law, they all induce a current flow opposing the magnetic field that generated it (i.e., at a specific point in time illustrated in FIG. 8, it is counterclockwise, as indicated by the arrows on the outer conductive loop (210) and the inner conductive loop (212). As a result, both the outer conductive loop (210) and the inner conductive loop (212) have ● polarity on the inner side of the loop, and on the outer side of the loop It generates polarity. Thus, within the shaded area (800, 802) of FIG. 8, the magnetic flux from the outer conductive loop (210) and the inner conductive loop (212) opposes the magnetic flux from the excitation coil (330) and reduces the magnetic flux density, whereas, in contrast, within the unshaded area (804) of FIG. 8 (the area where the scale tracks of the rotor and the scale receiving coils of the stator are located), the magnetic flux from the outer conductive loop (210) and the inner conductive loop (212) is in phase with the excitation coil (330) and acts to increase the magnetic flux density in that area.

[0107] Now, the operation of the inductive rotary encoder device (100) will be described. As described above, alternating current flows through the excitation coil (330), thereby generating an alternating electromagnetic field around it, and the first scale receiving coil (304), the second scale receiving coil (306), and the third scale receiving coil (308) are arranged to detect the alternating electromagnetic field and provide an output in response. The alternating electromagnetic field is affected (e.g., changed) by the presence of scale features on the first scale track (204), the second scale track (206), and the third scale track (208) on the rotor (200).

[0108] The effect (amplitude modulation effect in the described embodiment) of the first scale track (204), second scale track (206), and third scale track (208) on the rotor (200) on the alternating electromagnetic field detected by the respective first scale receiving coil (304), second scale receiving coil (306), and third scale receiving coil (308) varies according to the relative rotation of the rotor (200) and the stator (300) about the axis (B / D). In particular, this (amplitude modulation) effect on the alternating electromagnetic field varies in a cyclic manner, and its spatial frequency depends on the period of the scale feature. Additionally, the effect of the first scale track (204), the second scale track (206), and the third scale track (208) on the rotor (200) on the alternating electromagnetic field detected by the respective first scale receiving coil (304), the second scale receiving coil (306), and the third scale receiving coil (308) is different because their scale periods are different from each other.

[0109] Accordingly, the scale features of the first scale track (204), the second scale track (206), and the third scale track (208) on the rotor (200) impart cyclic fluctuations to the alternating electromagnetic field (e.g., in its amplitude) at different spatial frequencies, and accordingly, the spatial frequency of the cyclic fluctuation of the electromagnetic field caused by the first scale track and detected by the first scale receiving coil (304), the spatial frequency of the cyclic fluctuation of the electromagnetic field caused by the second scale track and detected by the second scale receiving coil (306), and the spatial frequency of the cyclic fluctuation of the electromagnetic field caused by the third scale track and detected by the third scale receiving coil (308) are all different from each other. Accordingly, the cyclic fluctuation of the signal generated from the first scale receiving coil (304), the second scale receiving coil (306), and the third scale receiving coil (308) has different spatial periods / space frequencies. The significance of this is explained in the following paragraph with reference to Figures 9 and 10.

[0110] As previously described in relation to FIGS. 4 and 5, each of the first scale receiving coil (304), the second scale receiving coil (306), and the third scale receiving coil (308) actually comprises superimposed differential coils, which have sinusoidal waveforms and are phase-shifted by 90° relative to each other. Accordingly, each of the first scale receiving coil (304), the second scale receiving coil (306), and the third scale receiving coil (308) actually outputs a pair of orthogonal signals (i.e., signals phase-shifted by 90°), and thus the pair of signals can be represented, for example, as a SIN signal and a COS signal. This is schematically illustrated in FIG. 9, where the first coil of the pair of coils is given the suffix "s" and the other coil of the pair is given the suffix "c". Thus, FIG. 9 shows that the first scale receiving coil (304) is a (differential) SIN coil (304 s ) and (differential) COS coil (304 c ) including, and the second scale receiving coil (306) is the SIN coil (306 s ) and COS coil (306 c ...including ) and the third scale receiving coil (308) is the SIN coil (308 s ) and COS coil (308 c It schematically illustrates the inclusion of ).

[0111] As described above, in the specific embodiment described, the first scale track (204), the second scale track (206), and the third scale track (208) on the rotor (200) impart cyclic variations (at different spatial frequencies) to the amplitude of the alternating electromagnetic field. Thus, the (differential) SIN coil (304 s , 306 s , 308 s ) and COS coil (304 c , 306 c , 308 c ) detects amplitude-modulated alternating electromagnetic signals. Accordingly, according to this specific embodiment of the present invention, the signals can be demodulated to obtain a demodulated (baseband) signal. Accordingly, in this embodiment, the stator has a SIN coil (304 s , 306 s , 308 s ) and COS coil (304 c , 306 c , 308 c It includes demodulators associated with each of ), said demodulators demodulate the signal detected by them. Thus, in FIG. 9, the SIN and COS coils (304 s , 304 c, 306 s , 306 c , 308 s , 308 c The SIN signal and COS signal output by each of ) are actually demodulated (baseband) signals.

[0112] As described, the output from each of the pair of SIN coils and COS coils corresponds to the corresponding arctangent calculator (i.e., the first arctangent calculator (304) A / Tan ), 2nd Arctangent Calculator (306 A / Tan ) and the third arctangent calculator (308 A / Tan )) provided, and the arctangent calculator calculates an angle from the pair of SIN and COS signals (e.g., in this embodiment, from the pair of demodulated / baseband SIN and COS signals). FIG. 10 shows a first arctangent calculator (304 A / Tan ), 2nd Arctangent Calculator (306 A / Tan ) and the third arctangent calculator (308 A / Tan It illustrates how the angle calculated by each of ) changes according to the relative rotation of the stator and rotor around the axis (B / D).

[0113] As described above in relation to FIG. 3, the periods of the first scale track (204), the second scale track (206), and the third scale track (208) are different from each other. In particular, the first scale track (204), the second scale track (206), and the third scale track (208), and the first scale receiving coil (304), the second scale receiving coil (306), and the third scale receiving coil (308) are configured so that the signal phases of at least three individual signal channels have a unique combination for each rotation angle of the rotor and stator around the axis (B / D). This allows the absolute rotation position to be determined from the output of three arc tangent calculators.

[0114] As is understood, each scale track, the associated scale receiving coil, and the electronic device (e.g., an arctangent calculator) form a "signal channel." In this embodiment, the first scale track (204), the first scale receiving coil (304), and the first arctangent calculator (304 A / Tan ) forms a first signal channel; a second scale track (206), a second scale receiving coil (306) and a second arc tangent calculator (306 A / Tan ) forms a second signal channel; a third scale track (208), a third scale receiving coil (308) and a third arc tangent calculator (308 A / Tan ) forms a third signal channel.

[0115] In this embodiment, the first scale track (204) has the largest integer number of cycles per rotation and may be referred to as the "incremental track" (and thus the associated channel may be referred to as the "incremental channel"). The signal channels of the second scale track (206) and the third scale track (208) have fewer cycles per rotation compared to the first scale track (204). The second and third scale tracks (208) (and thus the associated signal channels) may be referred to as the (first and second) "vernier tracks" (and thus the associated second and third signal channels may be referred to as the "vernier channels"). In the described embodiment, the first scale track (204), the second scale track (206), and the third scale track (208) are configured such that the only common integer factor of the number of cycles of all scale tracks is 1. As is understood, other terms used for "number of periods" in the field of inductive encoders include "number of features" and "number of lines."

[0116] Compared to a 2-channel system, a 3-channel system offers significantly greater degrees of freedom in selecting the number of periods for each channel and provides greater error tolerance in channel phase calculation. This error tolerance allows a large number of incremental periods per revolution to be used, thus enabling large-diameter encoders.

[0117] The relatively large error tolerance for phase detection allows small signal amplitudes to be used for vernier channels with lower signal-to-noise ratios. In fact, it has been found that in a 3-channel system, filtering and automatic / dynamic signal correction on the vernier channels may be applied only restrictively or not at all, thereby simplifying the design of the inductive rotary encoder system and reducing costs. Accordingly, as illustrated in FIG. 9, in the described embodiment, only the SIN signal and COS signal from the first scale receiving coil (304) correspond to the arctangent calculator (304 A / Tan Before being transmitted to the ), it passes through an automatic / dynamic signal corrector (305), and the automatic / dynamic signal corrector (305) performs automatic / dynamic gain correction (AGC), automatic / dynamic offset correction (AOC), automatic / dynamic balance correction (ABC), and automatic / dynamic phase correction (APC) on the output of the first scale receiving coil (304) in this embodiment.

[0118] Referring again to FIG. 9, the signals from each of the three channels (i.e., the first arctangent calculator (304) A / Tan ), 2nd Arctangent Calculator (306 A / Tan ) and the third arctangent calculator (308 A / TanEach output of the respective channel is passed to a position calculator (900), which calculates the absolute position of the stator and rotor around the axis of rotation from the signals. For example, this can be performed via a function or a look-up table based on the values ​​of each channel / outputs of the three arctangent calculators. However, in the described embodiment, the absolute position is calculated by a loop that iterates through all possible incremental cycles in turn and compares the actual vernier phase for each cycle with the expected vernier phase for that cycle. When the loop is completed, only one detected position should exist. Using an iterative loop to determine the position is particularly preferable to using other techniques, such as the technique using a look-up table. For example, an iterative loop can be more efficient, particularly in terms of memory, and can also have higher versatility (e.g., when the process is used across inductive rotary encoders of different sizes).

[0119] For example, the position calculator (900) is the first arctangent calculator (304 A / Tan After taking the value output by ), for each scale period of the first scale track / incremental channel (each of the 64 scale periods in the described embodiment), the second arctangent calculator (306 A / Tan ) and the third arctangent calculator (308 A / Tan It can be configured to identify what value is expected from ). Then, the position calculator (900) uses the expected values ​​from the second arctangent calculator (306 A / Tan ) and the third arctangent calculator (308 A / TanThe actual values ​​output by ) are compared, and it is checked whether they match. Whether they match is recorded. As described above, this is repeated for each scale cycle of the first scale track / incremental channel (each of the 64 scale cycles in the described embodiment). Only one match must exist, and in such case, the matched location is provided to the output unit (902). If there is no match or if two or more matches exist, an error status is reported to the output unit (902). The output unit (902) may be any suitable unit for outputting / communicating location information / error status via a wired or wireless connection to an external device, such as a location controller, for example.

[0120] As is understood, the arctangent calculator (304 A / Tan , 306 A / Tan , 308 A / Tan The ) and position calculator (900) may include any suitable processing unit, including but not limited to a custom processing unit configured for a specific application (e.g., a field programmable gate array ("FPGA")) as well as a more general-purpose processing unit that can be programmed (e.g., via software) according to the requirements of the application being used. Accordingly, suitable processing units include, for example, a microprocessor, CPU, FPGA, ASIC, etc.

[0121] As described above, in the described embodiment, the stator (300) comprises a first outer quadrant coil (310), a second outer quadrant coil (312), a third outer quadrant coil (314), and a fourth outer quadrant coil (316), and a first inner quadrant coil (320), a second inner quadrant coil (322), a third inner quadrant coil (324), and a fourth inner quadrant coil (326). These sensors may be used to detect the relative lateral / radial position (e.g., eccentricity) and / or relative tilt of the rotor (200) and the stator (300), or to provide a measure thereof.

[0122] As is understood, if the above axis (B)—around which the scale tracks of the rotor extend and are centered—does not coincide with the above axis (D)—around which the receiving coil of the stator extends and is centered—relative eccentricity may be said to exist between the rotor (200) and the stator (300). During operation / use, such eccentricity may exist, for example, because the rotor (200) is not positioned concentrically with the axis of rotation of the machine shaft, and / or because the stator (300) is not positioned concentrically with the axis of rotation of the machine shaft, and / or because the scale tracks and / or receiving coil are not actually centered on their assumed axes (B / D). Accordingly, the eccentricity of the rotor (200) and the stator (300) is related to the lateral / radial position of the rotor (200) and the stator (300) (i.e., related to their relative position in a degree of freedom / direction / plane perpendicular to the axis of rotation (and thus also perpendicular to the axis (B) and the axis (D))).

[0123] Relative tilt is a measure of how parallel the rotor (200) and the stator (300) are to each other. During operation / use, this relative tilt may occur, for example, because the rotor (200) is mounted on the machine such that its axis (B) (where the scale track extends and centers on that axis) is not parallel to the rotation axis (A) of the machine shaft, and / or because the stator (300) is mounted on the machine such that its axis (D) (where the scale receiving coil of the stator extends and centers on that axis) is not parallel to the rotation axis (A) of the machine shaft.

[0124] As is understood, since the scale receiving coils (304, 306, 308) are full ring sensors (i.e., substantially fully extended around the axis), the effect of having only eccentricity of the rotor (200) and / or stator (300) (i.e., having no relative tilt between the rotor (200) and the stator (300)) is offset and thus does not cause an error, and likewise, the effect of having only relative tilt between the rotor (200) and the stator (300) (i.e., having no eccentricity) is offset and thus does not cause an error.

[0125] However, it was found that when both i) eccentricity of the rotor (200) and / or the stator (300); and ii) relative tilt of the rotor (200) and the stator (300) are present, a system error is introduced into the rotational position measurement once per rotation. In particular, the error can be expressed functionally as follows: Error = (Stator Eccentricity × Rotor Tilt) + (Stator Tilt × Rotor Eccentricity) (where "×" represents the vector cross product). Thus, for example, when the stator is tilted but the rotor is not eccentric, no error occurs.

[0126] The above error of once per rotation can be calculated for a given relative tilt value and eccentricity value. In fact, it has been found that the above error of once per rotation follows the following equation.

[0127]

[0128] ζ is the relative tilt vector, ε is the relative eccentricity vector, and "x" represents the vector cross product.

[0129] Accordingly, by measuring the relative tilt and relative lateral / radial position (e.g., eccentricity) of the stator and rotor, it becomes possible to compensate for or eliminate errors during installation. To this end, as described above, the stator (300) includes two sets of quadrant coils. In particular, the stator (300) includes a first set of quadrant coils comprising a first outer quadrant coil (310), a second outer quadrant coil (312), a third outer quadrant coil (314), and a fourth outer quadrant coil (316); and a second set of quadrant coils comprising a first inner quadrant coil (320), a second inner quadrant coil (322), a third inner quadrant coil (324), and a fourth inner quadrant coil (326).

[0130] An example of how the outer quadrant coil and the inner quadrant coil can be used to detect the relative tilt and / or relative lateral / radial position (e.g., eccentricity) of the rotor (200) and the stator (300) is now explained with reference to FIGS. 11 through 14.

[0131] In relation to the detection of the relative lateral / radial position (e.g., eccentricity) of the rotor (200) and the stator (300), it should be noted that in this embodiment, the first inner quadrant coil (320), the second inner quadrant coil (322), the third inner quadrant coil (324), and the fourth inner quadrant coil (326) are arranged axially in line / directly above the scale feature (e.g., see FIG. 6 and FIG. 7). In particular, the first inner quadrant coil (320), the second inner quadrant coil (322), the third inner quadrant coil (324), and the fourth inner quadrant coil (326) are arranged axially in line / directly above the third scale track (208). Additionally, in this embodiment, the length of each of the first inner quadrant coil (320), the second inner quadrant coil (322), the third inner quadrant coil (324), and the fourth inner quadrant coil (326) corresponds to an integer number of periods of the third scale track. As a result, the axial separation between the stator (300) and the rotor (200) does not substantially affect the strength of the magnetic field detected by the first inner quadrant coil (320), the second inner quadrant coil (322), the third inner quadrant coil (324), and the fourth inner quadrant coil (326), and thus these coils are substantially unaffected / insensitive to any relative tilt of the stator (300) and the rotor (200). This is due to eddy currents generated within the scale feature that are opposite to the transmitting magnetic field. The opposing magnetic field generated by the eddy current is forced downward through the gap between the scale features, and thus the net magnetic field detected by the first inner quadrant coil (320), the second inner quadrant coil (322), the third inner quadrant coil (324), and the fourth inner quadrant coil (326) remains the same within the expected range of axial separation between the stator and the rotor during normal installation and operation conditions.

[0132] However, as schematically illustrated in FIGS. 11a and 11b, the first inner quadrant coil (320), the second inner quadrant coil (322), the third inner quadrant coil (324), and the fourth inner quadrant coil (326) are sensitive to the relative lateral position of the rotor (200) and the stator (300) (Meanwhile, for convenience of explanation, FIGS. 11a and 11b only show the excitation coil (330) and inner quadrant coils (320, 322, 324, 326) of the stator (300), and only the third scale track of the rotor (200)). For example, as illustrated in FIG. 11a, which illustrates a state in which there is no relative eccentricity "ε" between the rotor (200) and the stator (300), the net magnetic flux exposed to the opposing inner quadrant coils (illustrated as a "magnetic field envelope") is the same. In contrast, as illustrated in FIG. 11b, which illustrates a state in which there is a relative eccentricity "ε" between the rotor (200) and the stator (300), the net magnetic flux exposed to the opposing inner quadrant coils is different. Thus, the difference in output between the opposing inner quadrant coils can be used to obtain a reliable measure of the relative lateral / radial position (e.g., eccentricity) of the stator (300) and the rotor (200).

[0133] Regarding the detection of relative tilt between the rotor (200) and the stator (300), it should be noted that in this embodiment, the first outer quadrant coil (310), the second outer quadrant coil (312), the third outer quadrant coil (314), and the fourth outer quadrant coil (316) are positioned axially in line / directly above the empty area of ​​the rotor (200) (see, for example, FIG. 6 and FIG. 7). Due to this configuration, within the degree of eccentricity typically expected for the rotor (200) and the stator (300) during normal installation and operation, the first outer quadrant coil (310), the second outer quadrant coil (312), the third outer quadrant coil (314), and the fourth outer quadrant coil (316) have been found to be substantially insensitive to any relative eccentricity between the rotor (200) and the stator (300). This is schematically illustrated in FIGS. 12a and 12b, where it can be seen that there is almost no change in the state of the magnetic flux exposed to the outer quadrant coil when there is a change in the degree of eccentricity of the rotor (200) and the stator (300). In contrast, as illustrated in FIGS. 12a and 12c, there is a significant change in the state of the magnetic flux exposed to the outer quadrant coil when there is a change in the relative tilt of the rotor (200) and the stator (300). In fact, for the outer quadrant coil that is closer to the rotor due to the relative tilt, not only does the magnetic flux density (expressed as the number of magnetic flux lines) increase, but the angle of incidence of the magnetic flux passing through the outer quadrant coil decreases, and thus a greater inductive effect occurs in the quadrant coil(s) closer to the rotor (200). Therefore, the difference in output between the opposing outer quadrant coils can be used to obtain a reliable measure of the relative tilt of the stator (300) and the rotor (200).

[0134] Meanwhile, for convenience of explanation, only the excitation coil (330) and outer quadrant coils (310, 312, 314, 316) of the stator (300) are shown in FIG. 12a, FIG. 12b, and FIG. 12c, and only the outer conductive loop (210) of the rotor (200) is shown.

[0135] With the above-mentioned phenomenon in relation to FIGS. 11 and 12 in mind, now refer to FIG. 13, which schematically illustrates the outer quadrant coil, inner quadrant coil, and excitation coil (330) of the stator (300). For convenience of reference, the first outer quadrant coil (310), the second outer quadrant coil (312), the third outer quadrant coil (314), and the fourth outer quadrant coil (316) are labeled A, D, C, and B, respectively, and the first inner quadrant coil (320), the second inner quadrant coil (322), the third inner quadrant coil (324), and the fourth inner quadrant coil (326) are labeled E, K, J, and F, respectively.

[0136] By subtracting the outputs of the quadrant coils located on opposite sides, a quadrature output can be obtained from each set. For example, the following signals can be obtained from the outer quadrant coil and the inner quadrant coil.

[0137]

[0138]

[0139]

[0140]

[0141] As illustrated in FIG. 14a, plotting x1 against y1 generates a Lissajous that indicates the relative tilt of the rotor (200) and the stator (300). The center of the Lissajous in FIG. 14a is due to the tilt of the stator (300) (the effect is static), and the radius of the Lissajous in FIG. 14a is due to the tilt of the rotor (200). At a specific point in time, the position of the Lissajous (x1, y1 value) represents the tilt error vector.

[0142] As illustrated in FIG. 14b, plotting x2 against y2 generates a Lissajous that indicates the relative eccentricity of the rotor (200) and the stator (300). The center of the Lissajous in FIG. 14b is due to the eccentricity of the stator (300) (the effect is static), and the radius of the Lissajous in FIG. 14b is due to the eccentricity of the rotor (200). At a specific point in time, the position of the Lissajous (x2, y2 values) represents the eccentricity error vector.

[0143] Accordingly, the x1, y1, x2, and y2 values ​​can be used to determine the current state of relative tilt and lateral / radial position (e.g., eccentricity), and can be used to correct the position calculated by the position calculator (900). For example, as illustrated in FIG. 9, an inductive rotary encoder device may include a tilt / lateral position (e.g., eccentricity) calculator (901), said calculator (901) transmits the x1, y1, x2, and y2 values ​​to the position calculator (900), and the position calculator (900) can use them to correct the position provided to the output unit (902). Additionally, as illustrated in FIG. 9, the x1, y1, x2, and y2 values ​​may instead / additionally transmit to the output unit (902) and output to an external device. For example, the external device can use the x1, y1, x2, and y2 values ​​to correct the received position. Additionally / alternatively, instead of being used to correct position values, the x1, y1, x2, and y2 values ​​may be used to trigger a warning / error condition or to provide an indication of the relative tilt and / or lateral / radial position (e.g., eccentricity) of the stator and rotor. For example, the indication may be a visual display, thereby allowing the installer to verify that the stator and rotor are properly configured. Optionally, if the x1, y1, x2, and y2 values ​​indicate relative tilt / lateral position (e.g., eccentricity) exceeding a predetermined threshold, an error signal may be generated. Optionally, this error signal may be used to control a machine equipped with an inductive rotary encoder in a predetermined manner (e.g., causing the machine to stop upon receiving this error signal).

[0144] As is evident from the description above, in the specific embodiment described, the outer quadrant coil is primarily sensitive to and used to determine the relative tilt of the rotor (200) and the stator (300), whereas the inner quadrant coil is primarily sensitive to and used to determine the relative lateral / radial position (e.g., eccentricity) of the rotor (200) and the stator (300). As is understood, this is not necessarily required, for example, the outer quadrant coil may be configured to be primarily sensitive to and used to determine the relative lateral / radial position (e.g., eccentricity) of the rotor (200) and the stator (300), while the outer quadrant coil may be configured to be primarily sensitive to and used to determine the relative lateral / radial position (e.g., eccentricity) of the rotor (200) and the stator (300). Additionally, in another embodiment, one or both of the outer quadrant coil and the inner quadrant coil may be sensitive to both the relative tilt and lateral / radial position (e.g., eccentricity) of the rotor (200) and the stator (300). Although it is still possible to extract measurements of the relative tilt and lateral / radial position (e.g., eccentricity) from these quadrant coils, this requires more complex electronics and / or processing, and therefore it may be desirable to have one of the inner quadrant coil and the outer quadrant coil primarily sensitive to the relative tilt of the rotor and the stator, and the other primarily sensitive to the relative lateral / radial position (e.g., eccentricity) of the rotor and the stator. In another embodiment, only one set of quadrant coils is provided. In this case, the set of quadrant coils may be configured to be primarily sensitive to and used to determine the relative lateral / radial position (e.g., eccentricity) of the rotor (200) and the stator (300), or may be configured to be primarily sensitive to and used to determine the relative tilt of the rotor (200) and the stator (300).In an optional embodiment, the set of quadrant coils may be configured to be sensitive to both relative tilt and lateral / radial position (e.g., eccentricity). Although it may not be possible to extract measurements of the relative tilt and lateral / radial position (e.g., eccentricity) of the stator and rotor from only the set of quadrant coils sensitive to both relative tilt and lateral / radial position (e.g., eccentricity), the output of such a set of quadrant coils may still be useful for determining the presence of relative tilt and / or lateral / radial position (e.g., eccentricity). For example, the output may be used to indicate / determine whether the rotor and stator are relative tilted and / or eccentrically positioned during installation / setup and / or operation, which may serve as a warning that the rotor and stator are not properly set up / configured (e.g., may function as a go / no-go signal).

[0145] In the above-described embodiment, the magnetic field detected by the quadrant coil is generated by the same excitation coil that generates the magnetic field detected by the receiving coils (304, 306, 308) of the stator. However, this is not necessarily the case. For example, FIG. 15a and FIG. 15b illustrate an alternative embodiment in which the stator includes a first excitation coil (330′) and a second excitation coil (330″) that are radially spaced apart from each other. In these embodiments, the first excitation coil (330′) is operated by the scale track (204, 206, 208) of the rotor and generates the magnetic field detected by the receiving coils (304, 306, 308) of the stator. The second excitation coil (330″) generates a magnetic field that is detected by the quadrant coils (310, 312, 314, 316, 320, 322, 324, 326) and determines the relative tilt and / or lateral / radial position (e.g., eccentricity) of the rotor (200) and the stator (300). As is understood, in this embodiment, the stator (200) includes one or more conductive features configured to manipulate the magnetic field generated by the second excitation coil (330″) in the region of the quadrant coils, so that the output of the quadrant coils varies according to the relative tilt and / or lateral position (e.g., eccentricity) of the stator (300) and the rotor (200).

[0146] In the above-described embodiments, the quadrant coil was described in relation to detecting / determining the relative tilt and / or lateral / radial position (eccentricity) of the stator and / or rotor. As is understood, the output of the quadrant coil may also be used to detect / determine the surface flatness and / or non-circularity of the rotor. Also understood, in other embodiments, in addition to or alternative to the above function, the device may be configured to determine a measure of the axial separation between the stator member and the rotor member (or at least a signal indicating such separation) through, for example, i) any one or more quadrant coils; and ii) the signal strength / amplitude of any one or more receiving coils.

[0147] As is understood, the aforementioned specific radial positions of the scale tracks (204, 206, 208) and the corresponding excitation coil (330) and scale receiving coil (304, 306, 308) are not mandatory and may be arranged to have different radial positions / combinations. For example, the rotor (200) may be configured such that the first scale track (204) is radially positioned between the second scale track (206) and the third scale track (208) (thus, the stator (300) may be configured such that the corresponding first scale receiving coil (304) is radially positioned between the second scale receiving coil (306) and the third scale receiving coil (308)).

[0148] In the above-described embodiment, a plurality of scale tracks and a plurality of receiving coils are provided. However, as is understood, this is not strictly necessary, and, for example, only a single scale track and a corresponding single receiving coil may be provided.

Claims

Claim 1 An inductive rotary encoder device comprising a first member and a second member that are relatively rotatable about a rotation axis, wherein the first member comprises at least one scale track, the second member comprises an excitation coil for generating a magnetic field operated by the at least one scale track, and the second member also comprises a receiving coil for detecting the magnetic field, and wherein the relative rotational position of the first member and the second member about the rotation axis can be measured through the magnetic field, wherein the first and / or second member comprises at least one magnetic field sensor for detecting a magnetic field generated by the excitation coil or another excitation coil, and wherein the device comprises means for determining information regarding the relative arrangement of the first member and the second member in a degree of freedom other than the degree of freedom about the rotation axis from the at least one magnetic field sensor. Claim 2 An inductive rotary encoder device according to claim 1, wherein the at least one magnetic field sensor comprises a plurality of individual magnetic field sensing regions disposed at different locations on the first and / or second member. Claim 3 An inductive rotary encoder device according to paragraph 2, wherein the at least one magnetic field sensor comprises a first set of magnetic field sensing areas disposed at a first radial position on a first and / or second member and a second set of magnetic field sensing areas disposed at a second radial position. Claim 4 An inductive rotary encoder device according to any one of claims 1 to 3, wherein the at least one magnetic field sensor is provided on a second member. Claim 5 An inductive rotary encoder device according to paragraphs 3 and 4, wherein, when in use, the magnetic field sensing area of ​​the first set is aligned axially with the conductive area of ​​the first member, and the magnetic field sensing area of ​​the second set is aligned axially with the non-conductive area of ​​the first member. Claim 6 An inductive rotary encoder device according to any one of claims 1 to 5, wherein the at least one magnetic field sensor, for example, the first and / or second set of magnetic field sensing areas, comprises four quadrant magnetic field sensing areas. Claim 7 An inductive rotary encoder device according to any one of claims 1 to 6, wherein the information regarding the relative arrangement of the first member and the second member includes information regarding the relative tilt of the first member and the second member. Claim 8 An inductive rotary encoder device according to any one of claims 1 to 7, wherein the information regarding the relative arrangement of the first member and the second member includes information regarding the relative radial position of the first member and the second member. Claim 9 An inductive rotary encoder device according to any one of claims 1 to 8, wherein at least one of the first member and the second member comprises a magnetic flux enhancer, wherein a current flow is generated within the magnetic flux enhancer by the magnetic field of the excitation coil or another excitation coil, and the magnetic flux enhancer itself generates a magnetic field that acts to increase the magnetic flux of the magnetic field detected by the receiving coil in the region of the receiving coil. Claim 10 In claim 9, the excitation coil generating the magnetic field that generates current flow within the magnetic flux enhancer is the same as the excitation coil generating the magnetic field that is operated by the at least one scale track and detected by the receiving coil. Claim 11 An inductive rotary encoder device according to claim 9 or 10, wherein the magnetic flux enhancer comprises at least one conductor located radially outside the scale track of the first member and the receiving coil and excitation coil of the second member, - said at least one conductor is hereinafter referred to as at least one "outer" conductor -; and / or at least one conductor located radially inside the scale feature of the first member and the receiving coil and excitation coil of the second member, - said at least one conductor is hereinafter referred to as at least one "inner" conductor. Claim 12 An inductive rotary encoder device according to any one of claims 1 to 11, wherein the at least one scale track is centered on the scale track axis and extends annularly around it, the excitation coil is centered on the excitation coil axis and extends annularly around it, and the receiving coil is centered on the receiving coil axis and extends annularly around it, and the device is configured such that the scale track axis, the excitation coil axis, and the receiving coil axis are substantially parallel to each other and optionally coincide with each other. Claim 13 An inductive rotary encoder device according to any one of claims 1 to 12, wherein the excitation coil is a single-winding coil and / or the receiving coil is a single-winding coil. Claim 14 An inductive rotary encoder device according to any one of claims 1 to 13, configured to pass alternating current through the excitation coil at a predetermined operating frequency to generate the magnetic field. Claim 15 An inductive rotary encoder device according to any one of claims 1 to 14, wherein the at least one scale track is configured to manipulate the amplitude of the magnetic field according to the relative position of the first member and the second member around the rotation axis.

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