Inductive angular position sensor

Abstract

To provide an inductive angular position sensor in which a receiver coil has circuit features that become smaller than those reasonable for high-resolution measurement designs.SOLUTION: When multiple receiver coils are used in a three-phase configuration or the like and when each of the multiple receiver coils is in a twisted loop configuration, different spatial frequencies are utilized for a rotor coil and the receiver coils. The spatial frequency of the receiver coils may be kept smaller than the rotor coil. In this condition, the fundamental frequency of the angular position sensor is shifted to the least common multiple of the spatial frequencies, making the angular resolution of the inductive angular position sensor high, while the circuit features of the receiver coils are maintained at a reasonable size.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Patent Application No. 17 / 822,604, filed August 26, 2022.

[0002] The present disclosure relates to position sensors, and more particularly, to inductive angular position sensors that can provide high angular resolution with low resolution circuitry. [Background technology]

[0003] Many applications requiring motion, such as automobiles, robotics, etc., require measurement of linear or angular position (e.g., pedal angle, arm angle, etc.). Inductive position sensors are desirable for such applications because they can provide accurate measurements while withstanding harsh environmental conditions. Increasing the resolution of these sensors may be desirable, but may be limited by the corresponding increase in manufacturing costs required for high resolution circuits. Summary of the Invention

[0004] In some aspects, the technology described herein relates to an inductive angular position sensor including an excitation coil located in a first plane, the excitation coil having a circular shape around an axis of symmetry that intersects the first plane at a center of the excitation coil; a rotor coil having a first rotational symmetry of a first order about the axis of symmetry, the rotor coil located in a second plane separated from the first plane by an air gap and configured to rotate about the axis of symmetry, the rotor coil configured to receive an excitation signal from the excitation coil through exciter-rotor inductive coupling; and a receiver coil having a second rotational symmetry of a second order about the axis of symmetry, the receiver coil located in the first plane and configured to generate a received signal based on rotor-receiver inductive coupling that varies sinusoidally as the rotor coil rotates, the first order and the second order being different.

[0005] In some aspects, the techniques described herein relate to an inductive angular position sensor, where the second order is smaller than the first order.

[0006] In some aspects, the technology described herein relates to an inductive angular position sensor, where a received signal has a fundamental frequency that is a least common multiple of a first order and a second order.

[0007] In some aspects, the technology described herein relates to an inductive angular position sensor, where the period of the fundamental frequency corresponds to a range of rotation of a rotor coil that is 360 degrees divided by the least common multiple of a first order and a second order.

[0008] In some aspects, the techniques described herein relate to an inductive angular position sensor, where a first order of a first rotational symmetry of a rotor coil is a multiple of a second order of a second rotational symmetry of a receiver coil.

[0009] In some aspects, the technology described herein relates to an inductive angular position sensor, where the receiver coil is in a twisted loop configuration.

[0010] In some aspects, the techniques described herein relate to an inductive angular position sensor, where the receiver coil is a first receiver coil, the inductive angular position sensor further including a second receiver coil in a twisted loop configuration positioned at 120 degrees about an axis of symmetry relative to the first receiver coil, and a third receiver coil in a twisted loop configuration positioned at 240 degrees about an axis of symmetry relative to the first receiver coil.

[0011] In some aspects, the technology described herein relates to an inductive angular position sensor in which a receiver coil includes traces that alternate between on a top surface of a printed circuit board and on a bottom surface of the printed circuit board in vias through the printed circuit board.

[0012] In some aspects, the technology described herein relates to an inductive angular position sensor, where the rotor coil and receiver coil are external to the interior of the excitation coil.

[0013] In some aspects, the technology described herein relates to an inductive angular position sensor, where the rotor coil is a multi-winding rotor coil including a first winding having a first lobe ratio and a second winding having a second lobe ratio.

[0014] In some aspects, the technology described herein relates to a position sensor system, the position sensor system including an inductive angular position sensor including an excitation coil located in a first plane, the excitation coil having a circular shape around an axis of symmetry that intersects the first plane at a center of the excitation coil, and a rotor coil having a first rotational symmetry of a first order about the axis of symmetry, the rotor coil located in a second plane separated from the first plane by an air gap and configured to rotate about the axis of symmetry, the rotor coil configured to receive an excitation signal from the excitation coil through exciter-rotor inductive coupling, and a rotor coil configured to generate a plurality of received signals. a plurality of receiver coils arranged in a first direction, each of the plurality of receiver coils having a second rotational symmetry of a second order smaller than the first order about an axis of symmetry, the plurality of receiver coils configured to generate a plurality of received signals; a transceiver circuit connected to the excitation coil and configured to generate an excitation signal and further configured to receive a plurality of received signals from the plurality of receiver coils, the plurality of received signals having a fundamental frequency that is a multiple of the first order and the second order; and an angle calculation module configured to calculate an angle measurement based on the plurality of received signals.

[0015] In some aspects, the techniques described herein relate to a position sensor system, wherein the fundamental frequency is a least common multiple of a first order and a second order.

[0016] In some aspects, the technology described herein relates to a position sensor system, wherein a plurality of receiver coils are each in a twisted loop configuration.

[0017] In some aspects, the techniques described herein relate to a position sensor system, where a plurality of receiver coils includes a first receiver coil, a second receiver coil, and a third receiver coil arranged in a three-phase configuration, where the first receiver coil, the second receiver coil, and the third receiver coil are arranged at an angle of 120 degrees to each other about an axis of symmetry.

[0018] In some aspects, the techniques described herein relate to a position sensor system, the position sensor system further including a processing module configured to convert a first received signal from a first receiver coil, a second received signal from a second receiver coil, and a third received signal from a third receiver coil into a pair of quadrature signals.

[0019] In some aspects, the techniques described herein relate to a position sensor system, wherein a rotor coil has a first angular period corresponding to a first rotational symmetry, a plurality of receiver coils each have a second angular period corresponding to a second rotational symmetry, and the angular measurements have a resolution smaller than the first angular period and the second angular period.

[0020] In some aspects, the technology described herein relates to a position sensor system, wherein the rotor coil is a multi-winding rotor coil including a first winding having a first lobe ratio and a second winding having a second lobe ratio.

[0021] In some aspects, the techniques described herein relate to a method for measuring an angle, the method including: generating a first magnetic field using an excitation coil located in a first plane, the excitation coil being symmetric about an axis of symmetry; rotating a rotor coil about the axis of symmetry to an angle, the rotor coil being in a second plane parallel to the first plane and separated from the first plane by an air gap, the rotor coil having a first spatial frequency; coupling the first magnetic field from the excitation coil to the rotor coil to generate a current in the rotor coil; coupling a second magnetic field generated by the current in the rotor coil to a receiver coil in the first plane, the receiver coil having a second spatial frequency; receiving a received signal from the receiver coil having an amplitude corresponding to an angle of the rotor coil; and comparing the received signal from the receiver coil to a sinusoidal signal to measure the angle, the sinusoidal signal having a fundamental frequency corresponding to a least common multiple of the first and second spatial frequencies.

[0022] In some aspects, the techniques described herein relate to a method for measuring an angle, wherein a second spatial frequency of the receiver coil is less than a first spatial frequency of the rotor coil.

[0023] In some aspects, the techniques described herein relate to a method for measuring an angle, where a sensor resolution of the angle is higher than a first resolution corresponding to a first spatial frequency or a second resolution corresponding to a second spatial frequency.

[0024] In some aspects, the techniques described herein relate to a method for measuring an angle, wherein the rotor coil is a multi-winding rotor coil including a first winding having a first lobe ratio and a second winding having a second lobe ratio.

[0025] The foregoing illustrative summary, as well as other illustrative objects and / or advantages of the present disclosure, and the manner in which they are accomplished, are further described in the following detailed description and its accompanying drawings. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 is a (prior art) schematic diagram of an inductive angular position sensor in accordance with certain embodiments. [Diagram 2] 1 illustrates an example of an angle calculation according to a possible implementation of the present disclosure. [Diagram 3] 1 is a schematic diagram of a position sensor system according to a possible implementation of the present disclosure. [Figure 4] FIG. 1 is a (prior art) schematic diagram of an inductive angular position sensor in accordance with certain embodiments. [Diagram 5] 5 is a graph of the harmonic content (i.e., harmonic distortion) of the signal produced by the inductive angular position sensor of FIG. 4 for different air gaps as the rotor coil is rotated. [Figure 6] FIG. 1 is a schematic diagram of an inductive angular position sensor according to a possible implementation of the present disclosure. [Figure 7] 7 is a graph of the harmonic content (i.e., harmonic distortion) of the signal produced by the inductive angular position sensor of FIG. 6 for different air gaps as the rotor coil is rotated. [Figure 8] 1 illustrates generally a multi-winding rotor coil for an inductive angular position sensor according to a possible implementation of the present disclosure. [Figure 9] 1 illustrates an inductive angular position sensor according to a possible implementation of the present disclosure. [Figure 10] 10 is a graph of the harmonic content (i.e., harmonic distortion) of the signal produced by the inductive angular position sensor of FIG. 9 as the rotor coil is rotated. [Figure 11] 1 is a flowchart of a method for measuring an angle according to a possible implementation of the present disclosure.

[0027] The elements of the drawings are not necessarily to scale relative to each other. Like reference numbers indicate corresponding parts throughout the several views. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] An inductive angular position sensor may include three basic coils: an exciter coil (i.e., excitation coil), a stator coil (i.e., receiver coil), and a target coil (i.e., rotor coil). The rotor coil may be physically attached to the moving part, while the excitation coil and receiver coil are at fixed locations. As the rotor coil moves, changes in inductive coupling between the rotor coil and the receiver coil can be sensed and mapped to corresponding changes in the position of the moving part. In practice, each of these basic coils may be made more complex to improve performance. These improvements may include mitigating stray inductive coupling, removing ambiguity from the angle measurements, reducing harmonic distortion, and increasing resolution.

[0029] The added complexity to improve performance can require coils that may be difficult to manufacture in a cost-effective manner. For example, trace width, trace separation, via size (e.g., diameter) may be too small for standard manufacturing techniques. This disclosure describes techniques to improve the performance of inductive position sensors while maintaining a reasonable size for standard manufacturing techniques. In particular, this disclosure describes techniques for increasing the resolution of inductive angular position sensors with reduced circuit size and complexity. This disclosure further discloses possible implementations of high resolution, low complexity inductive angular position sensors in which the rotor design reduces harmonic distortion.

[0030] FIG. 1 illustrates a basic inductive angular position sensor. The inductive angular position sensor 100 includes an excitation coil 110. The excitation coil 110 is stationary and can be coupled to an alternating current source (i.e., AC source 112). The AC source 112 is configured to generate an excitation signal at a frequency (e.g., radio frequency (RF)) that can be in the megahertz (MHz) range of the electromagnetic spectrum. The excitation coil 110 is planar and defines a first plane. Current in the excitation coil 110 can generate an excitation (magnetic field) field that transverses the first plane. The excitation coil has a circular shape that is substantially symmetric about an axis of symmetry 105 that is located at the center of the excitation coil and that transverses the plane of the excitation coil. For example, the excitation coil can be a spiral having multiple turns. The spiral can form a ring (or annulus), and other coils can be located within the ring (or annulus) as shown, or outside the ring (or annulus).

[0031] The inductive angular position sensor 100 further includes a rotor coil 120 (i.e., a target coil). The rotor coil is planar and defines a second plane separated from the first plane by an air gap 121(d). The inductive coupling between the exciter coil 110 and the rotor coil 120 (i.e., the exciter-rotor inductive coupling) is independent of the angle (θ) but is a function of the air gap 121. For example, the exciter-rotor inductive coupling decreases as the air gap 121 increases.

[0032] The rotor coil 120 may be movable in a plane and may be rotated through an angle 123 (θ) about an axis of symmetry 105 that intersects the plane of the rotor coil at the center of the rotor coil. The rotor coil 120 forms a pattern with a repeating (i.e., rotationally symmetric) angular (θ) dependence. The pattern includes a plurality of lobes, and as shown in FIG. 1, the rotor coil has four lobes regularly positioned about the axis 105. Each lobe has a period 122 that includes a positive portion (i.e., positive lobe 124) and a negative portion (i.e., negative lobe 125). The positive lobe shown in FIG. 1 is defined as the portion of the rotor coil at a first radius from the axis of symmetry 105, and the negative lobe is the portion of the rotor coil at a second radius from the axis of symmetry 105, the first radius being greater than the second radius. In other words, the rotor coil may be rotationally symmetric about the axis of symmetry 105, and the order of the rotational symmetry may correspond to the number of lobes (i.e., periods). For example, rotor coil 120 has rotational symmetry of the fourth order (ie, four-fold symmetry).

[0033] The rotor coil 120 is configured to receive an excitation signal from the excitation coil 110 through exciter-rotor inductive coupling (i.e., coupling). The coupled magnetic field from the excitation coil can induce a current flowing in the rotor coil 120, which can in turn generate a secondary magnetic field corresponding to the excitation signal.

[0034] The inductive angular position sensor 100 further includes a plurality of receiver coils configured to receive the secondary magnetic field of the rotor coil 120 through inductive coupling (i.e., coupling) between the rotor coil 120 and the receiver coil. The plurality of receiver coils are each planar and lie in approximately the same plane (i.e., a first plane) as the excitation coil 110 (e.g., ±1000 microns). Thus, the coupling (i.e., rotor-to-receiver inductive coupling) between the rotor coil 120 and the receiver coils may be a function of the air gap 121(d). For example, a larger air gap may have less coupling than a smaller air gap. The plurality of receiver coils are stationary with respect to the movement (i.e., rotation) of the rotor coil 120.

[0035] As shown in FIG. 1, the inductive angular position sensor 100 includes a first receiver coil 130 and a second receiver coil 140. As shown, the first receiver coil 130 forms a first pattern that is substantially the same as the pattern of the rotor coil 120. Similarly, the second receiver coil 140 forms a second pattern that is substantially the same as the pattern of the rotor coil 120. In other words, the first pattern of the first receiver coil 130 is substantially the same as the second pattern of the second receiver coil 140. As shown, the first receiver coil 130 and the second receiver coil 140 have a rotationally symmetric period 122, a quarter angle shift, about the axis of symmetry 105. In other words, the receiver coils can be spatially rotated with respect to each other.

[0036] As the rotor coil 120 rotates about the axis 105, the inductive coupling between the rotor coil 120 and the first receiver coil 130 changes. For example, the inductive coupling between the rotor coil 120 and the first receiver coil 130 may be greatest at an angle where the patterns (i.e., the positive and reverse lobes) are aligned. Conversely, the inductive coupling between the rotor coil 120 and the first receiver coil 130 may be least at an angle where the reverse lobe 125 of the rotor coil 120 is aligned with the positive lobe 124 of the first receiver coil 130.

[0037] The signal received by the first receiver coil 130 may generate a first receive signal that varies sinusoidally according to the rotor coil angle (θ). In the implementation shown in FIG. 1, the first receive signal may repeat four times during one complete rotation of the rotor coil 120. For example, as shown in FIG. 1, rotating the rotor through an angle range corresponding to the rotationally symmetric period 122 (i.e., 90 degrees) may correspond to one electrical period of the first receive signal. In other words, the first receive signal may have a spatial frequency (i.e., frequency) corresponding to the rotationally symmetric order (i.e., 4). Similarly, the second receiver coil 140 may generate a second receive signal that varies sinusoidally and repeats four times during one complete rotation of the rotor coil 120. The first receive signal and the second receive signal may have the same frequency but may be electrically phase shifted relative to each other due to their spatial offset.

[0038] An electrical phase shift between the first and second receive signals (e.g., electrically 90°) corresponds to an angle shift between the receiver coils (e.g., mechanically 22.5°). The first and second receive signals may be in quadrature, such that the first receive signal corresponds to the sine of the angle (i.e., SIN(θ)) and the second receive signal corresponds to the cosine of the angle (i.e., COS(θ)). Thus, the angle (θ) measurement may be calculated as the arctangent of the receive signal, as shown in the following equation: This arctangent calculation approach may be desirable because it cancels out amplitude changes common to the first and second receive signals.

number

[0039] FIG. 2 illustrates an example of an angle calculation according to a possible implementation of the present disclosure. The angle calculation includes an inverse tangent (i.e., arctangent) calculation 210 that uses a cosine signal (con(θ)) from a first coil 230 and a sine signal (sin(θ)) from a second coil 240. The inverse tangent calculation 210 can output an angle signal 220 that repeats according to the number of periods of the receiver coil. FIG. 2 includes a graph of angle signal amplitude versus angle (θ) for one revolution (i.e., 360°) of the rotor coil. Measuring the angle (θ) for measurement 250 may require first determining which angle range (i.e., which period) the measurement 250 corresponds to. As shown, the measurement corresponds to the second period, which represents a rotor coil angle of 90 degrees to 180 degrees (i.e., 90°<θ≦180°). The angle of the measurement 250 is then determined by interpolating between 90 degrees and 180 degrees based on the value of the measurement 250 and the angle signal 220. In other words, the period determination portion of the angle calculation corresponds to the most significant bit (MSB) of the measurement, and the interpolated portion of the angle calculation corresponds to the least significant bit (LSB) of the measurement.

[0040] Increasing the number of periods (i.e., the order of rotational symmetry) can make the angle measurement more accurate, but requires more complex (e.g., denser) circuitry, especially when additional features are included to improve signal performance (e.g., reduce harmonics). For example, a high-resolution inductive angular position sensor may require narrower trace widths, narrower trace spacing, and smaller vias than a low-resolution inductive angular position sensor when the diameters of the two sensors are equal. One technical problem solved by the present disclosure is to reduce the number of receiver coil periods (i.e., the number of lobes) for a given accuracy of angle measurement. This may have the technical effect of reducing the manufacturing cost of the inductive angular position sensor 100.

[0041] The angle calculation technique shown in FIG. 2 uses two receiver coils. In practice, more receiver coils may be used. For example, four receiver coils may generate differential (i.e., plus / minus) cosine and differential (i.e., plus / minus) sine signals, which may be used in the arctangent calculation technique to calculate the angle. In another possible implementation, signals from three receiver coils may be processed to obtain sine (SIN(θ)) and cosine (COS(θ)) signals, which are required for the arctangent calculation approach to calculate the angle. The three receiver coil implementation is discussed in detail below.

[0042] FIG. 3 is a schematic diagram of a position sensor system 300 including an inductive angular position sensor 301 having three receiver coils, according to a possible implementation of the present disclosure. The inductive angular position sensor 301 includes an excitation coil 310 that is driven (e.g., differentially) with an excitation signal (e.g., 4 MHz). The inductive angular position sensor 301 further includes a rotor coil 320 configured to receive the excitation signal. In other words, the excitation coil is coupled to the rotor coil to induce (i.e., generate) an AC current in the rotor coil. The inductive angular position sensor 301 further includes a first receiver coil 330, a second receiver coil 340, and a third receiver coil 350 arranged in a three-phase configuration as shown. Each receiver coil is configured to receive a modulated excitation signal from the rotor coil, the modulation being dependent on the angle between the rotor coil and each receiver coil. The position sensor system 300 further includes a transmitter / receiver circuit (i.e., a transceiver circuit 360). The transceiver circuitry 360 may include drivers to differentially drive the excitation coils 310 and may further include amplifiers configured to amplify the induced voltage signals from each coil. The position sensor system 300 may further include a processing module 370 configured to convert the received signals (i.e., three-phase signals) from the three receiver coils into quadrature signals (i.e., sin(θ), cos(θ)). In a possible implementation, the processing module is configured to perform Clarke transformation to generate sine (sin(θ)) and cosine (cos(θ)) signals from the three-phase signals. The position sensor system 300 may further include an angle calculation module 380 configured to determine an angle based on the quadrature signals, as described in connection with FIG. 2.

[0043] The receiver coil includes a parasitic inductance that may be caused by a connection between the receiver coil and the transceiver circuit 360. The first receiver coil 330 includes a first parasitic inductance 331, the second receiver coil 340 includes a second parasitic inductance 341, and the third receiver coil 350 includes a third parasitic inductance 351. The parasitic inductances may receive an excitation signal from the excitation coil through inductive coupling. The induced voltage signal (i.e., received signal) of the receiver coil may be given by the following equation:

number

[0044] In these equations, the amplitude (A) depends on the air gap 121(d) and the amplitude of the excitation signal. The offsets B1, B2, and B3 are parasitic voltages that are independent of the rotor coil position. In practice, these parasitic voltages (B1, B2, B3) can be compensated in the system by additional coils (not shown). The angle (θ) is the angle (in degrees) between the rotor coil and a particular receiver (i.e., stator) coil.

[0045] The induced voltage signal of the second receiver coil 340 has a phase shift of 120 degrees with respect to the induced voltage signal of the first receiver coil 330 due to their relative positions, and the induced voltage signal of the third receiver coil 350 has a phase shift of 240 degrees with respect to the induced voltage signal of the first receiver coil 330 due to their relative positions.

[0046] The accuracy of the angle measurements determined by the position sensor system 300 may depend on how well the induced voltage signal matches a perfect sine wave given by the above equation. In reality, the induced voltage signal is not a perfect sine wave. An imperfect sine wave may be characterized as a sum of harmonics with higher amplitude harmonic components corresponding to more distortion in the sine wave signal. Thus, reducing the amplitude of these harmonic components from the inductive angular position sensor 301 may help increase the accuracy of the angle measurements determined by the position sensor system 300.

[0047] 4 is a schematic diagram of an inductive angular position sensor according to certain embodiments. The inductive angular position sensor is symmetrical about an axis of symmetry 440 at the center of the coil and has an overall size corresponding to an outer diameter (i.e., diameter 450). The inductive angular position sensor 400 includes an excitation coil 410 located inside an annulus defined by a rotor coil 420 and a receiver coil 430 (i.e., a stator coil). However, in other possible implementations, the excitation coil may be outside the annulus. For clarity, only one receiver coil 430 is shown.

[0048] The excitation coil 410 and the receiver coil 430 may be disposed on a first printed circuit board (PCB) and the rotor coil 420 may be disposed on a second printed circuit board with an air gap between them. The air gap may be less than 1 millimeter (e.g., 100 microns (μm)). The amplitude of the harmonic distortion may be inversely proportional to the air gap, so a sensor with a smaller air gap will have more harmonic distortion than a sensor with a larger air gap.

[0049] The rotor coil 420 includes nine positive and nine inverse lobes of equal size with a period of 40 degrees (i.e., lobe ratio=50 / 50), while the receiver coil 430 includes nine positive and nine inverse lobes of equal size with a period of 40 degrees. In other words, the rotor coil and receiver coil each have rotational symmetry of order 9 (i.e., 9-fold symmetry). In this configuration, a 40 degree change in the mechanical rotation of the rotor coil 420 can generate a 360 degree change in the periodic sinusoidal signal. Thus, the fundamental frequency of the inductive angular position sensor 400 is 9, and the resolution of the inductive angular position sensor 400 is based on this 40 degree period.

[0050] The receiver coil 430 is in a twisted loop configuration, including a first loop that follows a first path 431 in a counterclockwise direction around the annulus, and a second loop that follows a second path 432 in a clockwise direction around the circumference of the annulus. The first and second loops are prevented from shorting by vias that allow the first loop to be on the top layer of the first PCB while the second loop is on the bottom layer of the first PCB, or vice versa. For example, the first loop can be on the top layer of the first PCB during the first half of each lobe period and on the bottom layer during the second half of each lobe period. Conversely, the second loop can be on the bottom layer of the first PCB during the first half of each lobe period and on the top layer during the second half of each lobe period. The transition between the top and bottom layers can be implemented using vias (e.g., plated through holes, pins, etc.) through the first PCB.

[0051] The twisted loop configuration configures the receiver coil 430 to substantially cancel the signal coupled from the excitation coil 410 such that the receiver coil receives the signal primarily (e.g., all) from the coil 420. Cancellation occurs because the twisted pair creates a series of loops around a circumference with adjacent loops of opposite (winding) direction. For example, a first loop of the twisted pair may have a counterclockwise direction 433 and a second loop of the twisted pair adjacent to the first loop may have a clockwise direction 434. In addition, the twisted loop configuration of the receiver coil 430 substantially eliminates even harmonics in the induced voltage signal.

[0052] As mentioned above, only one receiver coil is shown in FIG. 4. In practice, the inductive angular position sensor 400 may include three receiver coils (i.e., three-phase receiver coils), each located at a position (i.e., fixed position) rotated 120 degrees (i.e., ±120°) from the position of the other two receiver coils (i.e., about the axis of symmetry) on the first PCB. Furthermore, each of the three-phase receiver coils has a twisted loop configuration. The circuitry required to implement three receiver coils may become more complex as the symmetry of the coils increases. For example, the trace width, via diameter, and trace spacing become much smaller as the symmetry increases.

[0053] 5 is a graph of the harmonic content (i.e., harmonic distortion) of the signal generated by the inductive angular position sensor 400 of FIG. 4 as the rotor coil is rotated. As shown in FIG. 5, the fundamental frequency 501 of the inductive angular position sensor 400 is 9 cycles per revolution (i.e., F FUND = 9 cycles / revolution), which corresponds to the order of rotational symmetry of the rotor / stator. The amplitude of the fundamental frequency is normalized to an amplitude of 0 decibels (i.e., 0 dB). The rotation of the rotor coil also generates harmonics of the fundamental frequency. The frequency content (i.e., frequency) of the induced voltage signal may be given by the following equation:

number

[0054] In the above equation, M is the harmonic order. Due to the twisted pair configuration of the receiver coil, only odd orders are included. Higher order frequency components (i.e., M=3, 5, 7, ...) may have amplitudes that are always reduced compared to the fundamental frequency amplitude. The highest amplitude harmonic in this example has a frequency of 27, which is lower in amplitude (e.g., -12 dB lower) than the fundamental frequency (i.e., 9 cycles / revolution). Thus, the harmonic suppression 502 defined herein may be the difference between the amplitude of the fundamental frequency and the highest amplitude harmonic (e.g., 12 dB). Harmonics for various air gaps (e.g., Gap 1 = 100 μm, Gap 2 = 200 μm, Gap 3 = 300 μm, Gap 4 = 400 μm) are plotted, showing that the rate of reduction of harmonics increases as the air gap increases, but the harmonic suppression 502 is approximately the same (e.g., within 5 dB) for the highest amplitude harmonic frequency (i.e., 27).

[0055] The resolution of an inductive angular position sensor may correspond to the fundamental frequency of the combination of the rotor and receiver coils. When the order of rotational symmetry of the rotor coil is equal to the order of rotational symmetry of the receiver coil, the fundamental frequency (i.e., the lowest frequency of all harmonics) is the order of symmetry (i.e., symmetric) of the two coils. In other words, by increasing the symmetry of both coils, the resolution of the angle measurement can be increased. Meeting the increased resolution requirement with an inductive angular position sensor having an order of rotational symmetry of the rotor coil that is the same as the order of rotational symmetry of the receiver coil comes at the expense of circuit complexity, especially for three-phase receiver coils. In other words, increasing the symmetry of both coils to increase the resolution may face limitations. This disclosure describes techniques to circumvent these limitations.

[0056] The present disclosure describes an inductive angular position sensor in which the order of rotational symmetry of the rotor coil differs from the order of rotational symmetry of the receiver coil. In this case, higher harmonics shared by both coils can be effectively at the fundamental frequency of the coil combination. The shared higher harmonics provide increased resolution of the angle measurement even while the receiver symmetry is kept low. Furthermore, any reduced measurement amplitude can be compensated for with a smaller offset since harmonic suppression of the higher modes can be greater. Table 1 below illustrates harmonics for different rotor coil and receiver coil configurations. The examples shown in Table 1 can be helpful in understanding the principles of the present disclosure and are not intended to be limiting. [Table 1]

[0057] Table 1 includes three inductive angle sensors with the same overall size corresponding to the outer diameter (i.e., diameter 450). As shown in Table 1, the first inductive angular position sensor (i.e., sensor 1) has a rotor / receiver coil 9-fold symmetry. This symmetry combination corresponds to a fundamental frequency of 9 cycles per revolution (cycles / revolution) and an angular period of 40 degrees (see, e.g., FIG. 2), where the angular period corresponds to a range of revolutions of the rotor coil, which is 360 degrees ÷ symmetry. The second inductive angular position sensor (i.e., sensor 2) has a rotor / receiver coil 21-fold symmetry. This symmetry combination corresponds to a fundamental frequency of 21 cycles / revolution and an angular period of 17 degrees. In other words, increasing the symmetry of both the rotor coil and receiver coil from 9 cycles / revolution to 21 cycles / revolution can reduce the angular period from 40 degrees to 17 degrees. The first inductive angular position sensor has a seventh order mode with a frequency of 63 cycles / revolution and an angular period of 5.7 degrees, and the second inductive angular position sensor has a third order mode with a frequency of 63 cycles / revolution and an angular period of 5.7 degrees.

[0058] As shown in Table 1, the third angular position sensor (i.e., sensor 3) has a rotor coil 21-fold symmetry and a receiver coil 9-fold symmetry. With this combination of symmetry, the shared higher order mode (i.e., 63 cycles / revolution) of the first and second angular position sensors becomes the first mode excited in the third inductive angular position sensor. Thus, the third angular position sensor has an effective 63-fold symmetry, a fundamental frequency of 63 cycles / revolution corresponding to an angular period of 5.7 degrees. The resolution of the third angular position sensor is higher than the first angular position sensor without increasing the symmetry of the receiver coils. Additionally, the resolution of the third angular position sensor is higher than the second angular position sensor, which has a lower symmetry of the receiver coils.

[0059] 6 illustrates an inductive angular position sensor according to a possible implementation of the present disclosure. The inductive angular position sensor 600 is symmetrical about an axis of symmetry 640 at the center of the coil and has an overall size corresponding to an outer diameter (i.e., diameter 450). The inductive angular position sensor 600 includes an excitation coil 610 located inside an annulus defined by a rotor coil 620 and a receiver coil 630 (i.e., a stator coil). For clarity, only one receiver coil 630 is shown, but in practice multiple receiver coils may be used, each one positioned with an angular shift relative to the other receiver coils (e.g., a three-phase receiver coil).

[0060] The excitation coil 610 and the receiver coil 630 can be disposed on a first printed circuit board (PCB) and the rotor coil 620 can be disposed on a second printed circuit board with an air gap (d) between them, which can be less than 1 millimeter (e.g., 100 microns (μm)).

[0061] The rotor coil 420 includes 21 positive and 21 reverse lobes of equal size with a period of 17 degrees (i.e., lobe ratio=50 / 50), while the receiver coil 430 includes 9 positive and 9 reverse lobes of equal size with a period of 40 degrees. In other words, the rotor coil 620 has rotational symmetry of order 21, and the receiver coil has rotational symmetry of order 9 (i.e., 9-fold symmetry). In this configuration, a 5.7 degree change in mechanical rotation of the rotor coil 420 can generate a 360 degree change in the periodic sinusoidal signal. Thus, the fundamental frequency of the inductive angular position sensor 600 is 63 cycles / revolution, and the resolution of the inductive angular position sensor 600 is based on this 5.7 degree period.

[0062] The receiver coil 630 is in a twisted loop configuration, including a first loop that follows a first path in a counterclockwise direction around the annulus, and a second loop that follows a second path in a clockwise direction around the circumference of the annulus. The first and second loops are prevented from shorting by vias that allow the first loop to be on the top layer of the first PCB while the second loop is on the bottom layer of the first PCB, or vice versa. For example, the first loop can be on the top layer of the first PCB during the first half of each lobe period and on the bottom layer during the second half of each lobe period. Conversely, the second loop can be on the bottom layer of the first PCB during the first half of each lobe period and on the top layer during the second half of each lobe period. The transition between the top and bottom layers can be implemented using vias (e.g., plated through holes, pins, etc.) through the first PCB.

[0063] FIG. 7 is a graph of the harmonic content (i.e., harmonic distortion) of the signal generated by the third inductive angular position sensor of Table 1. As shown in FIG. 7, the fundamental frequency 701 of the inductive angular position sensor is at a harmonic that is the least common multiple (LCM) of the rotor frequency (i.e., 21) and the stator frequency (i.e., 9), which in this example is 63 cycles / revolution (i.e., 1(LCM)=63) and is normalized to an amplitude of 0 decibels (i.e., 0 dB). The rotation of the rotor coil also generates a harmonic of the fundamental frequency. The next higher harmonic (i.e., 3(LCM)=189) is at a frequency of 189 cycles / revolution, which is well separated from the fundamental frequency by a first harmonic frequency bandwidth (i.e., bandwidth 703) of 126 cycles / revolution. The highest amplitude harmonic in this example has a frequency of 189 cycles / revolution, which is lower than the fundamental frequency by an amount equal to the harmonic suppression 702 (e.g., 19 dB). Harmonics for various air gaps (e.g., Gap 1 = 100 μm, Gap 2 = 200 μm, Gap 3 = 300 μm, Gap 4 = 400 μm) are plotted to show that the harmonic suppression of each is spread over a wide range (e.g., within a 22 dB range). Higher order harmonics can be canceled and further suppressed using multiple rotor windings. In other words, the rotor coil of the angular position sensor can be implemented as a multiple winding rotor coil.

[0064] FIG. 8 illustrates a multi-winding rotor coil for an inductive angular position sensor according to a possible implementation of the present disclosure. The multi-winding rotor coil 800 includes a first rotor winding 810 and a second rotor winding 820. The first rotor winding 810 and the second rotor winding 820 may be adjacent traces (i.e., do not cross or overlap). For example, the first rotor winding 810 and the second rotor winding 820 may be two continuous traces on a layer (e.g., a surface) of a PCB. The first rotor winding 810 and the second rotor winding 820 may define a ring having an outer radius 831 and an inner radius 832 about an axis of symmetry 840. The first rotor winding 810 and the second rotor winding 820 may have the same frequency (i.e., order) of rotational symmetry. As shown, the first rotor winding 810 and the second rotor winding 820 have a frequency of 21 cycles per revolution, with each cycle including a positive lobe at a radius that is approximately the outer radius 831 and a reverse lobe at a radius that is approximately the inner radius 832.

[0065] A lobe ratio may be defined as a first portion (e.g., a first percentage) of a cycle that is a positive lobe to a second portion (e.g., a second percentage) of the cycle that is a reverse lobe. As shown, the first rotor winding 810 has a first lobe ratio and the second rotor winding 820 has a second lobe ratio, the first lobe ratio being different than the second lobe ratio. In the implementation shown in FIG. 8, the first rotor winding 810 has a first positive lobe portion 811 that is 60% of the cycle and a first reverse lobe portion 821 that is 40% of the cycle. Thus, the first lobe ratio is 60 / 40. The second rotor winding 820 has a second positive lobe portion 821 that is 40% of the cycle and a second reverse lobe portion 822 that is 60% of the cycle. Thus, the second lobe ratio is 40 / 60. The lobe ratio may vary in different implementations. In general, the lobe ratio of the windings may be different so that one winding can fit within another without overlapping. The multi-winding rotor coil 800 can reduce the fifth (M=5) and seventh (M=7) harmonics through cancellation of the magnetic fields coupled to / from the multi-winding rotor. For example, the fifth harmonic can be canceled by both rotors having a 40 / 60 lobe ratio, and the seventh harmonic can be canceled by shifting (i.e., rotating) one rotor coil relative to the other, so that the combined coupling of the rotor coils to the receiver coil does not include the seventh harmonic.

[0066] FIG. 9 illustrates an inductive angular position sensor according to a possible implementation of the present disclosure. The inductive angular position sensor 900 is symmetrical about an axis of symmetry 940 at the center of the coil and has an overall size corresponding to an outer diameter (i.e., diameter 950). The diameter 950 of the implementation shown in FIG. 9 is 38 millimeters. The inductive angular position sensor 900 includes an excitation coil 910 located inside an annulus defined by a receiver coil 930 (i.e., a stator coil). The excitation coil 910 defines a first plane. The excitation coil 910 and the receiver coil 930 are approximately in the same plane.

[0067] The inductive angular position sensor 900 includes a rotor coil configured to rotate (e.g., above the receiver coil 930) about an axis of symmetry 940. The rotor coil 920 is substantially planar in a second plane. The first and second planes are separated by an air gap that is 100 microns. The rotor coil 920 is implemented as a multi-winding rotor coil having a first rotor winding and a second rotor winding. The first rotor winding has a first lobe ratio that is different from the second lobe ratio of the second rotor winding. In the illustrated implementation, the first rotor winding has a first lobe ratio of 60 / 40 and the second rotor winding has a second lobe ratio of 40 / 60. The first rotor winding and the second rotor winding have the same number of positive / negative lobes (i.e., frequency, symmetry). In the illustrated implementation, the rotor symmetry is 21 (i.e., 21 positive lobes, 21 reverse lobes). The multi-winding rotor coil is configured to attenuate (eg, cancel) the 5th and 7th harmonics in the response of the inductive angular position sensor 900.

[0068] The receiver coil 930 of the inductive angular position sensor is implemented as a three-phase receiver coil including three receiver coils. Each receiver coil has the same number of positive / negative lobes (i.e., frequency, symmetry). Each of the three receiver coils includes two loops arranged as a twisted pair. In the illustrated implementation, the first loop has 9 frequencies (i.e., symmetric) and the second loop has 9 frequencies (i.e., symmetric). Thus, each of the three receiver coils has a total of 18 loops for a total of 54 loops in a full rotation about the axis of symmetry. Since each loop includes two vias, the three-phase receiver coil in the twisted loop configuration shown in FIG. 9 includes 108 vias. The three receiver coils are spatially arranged with a 120 degree rotation between the coils. The receiver coil 930 is configured to cancel even harmonics (i.e., 2nd, 4th, 6th, etc.) as a result of the twisted loop configuration. The receiver coil 930 is configured to cancel the 3rd, 9th and 15th harmonics as a result of the three-phase configuration.

[0069] FIG. 10 is a graph of the harmonic content (i.e., harmonic distortion) of the signal generated by the inductive angular position sensor of FIG. 9. As shown in FIG. 10, the fundamental frequency 1001 of the inductive angular position sensor is 63 cycles per revolution (i.e., F FUND =63), which is the least common multiple (i.e., LCM) of the rotor coil symmetry (i.e., 21) and the receiver coil symmetry (i.e., 9). In the graph, the amplitude of the fundamental frequency is normalized to 0 decibels (i.e., 0 dB), and the harmonic suppression 902 is an amount (e.g., 60 dB) that effectively eliminates the effects of higher harmonics. As shown, all harmonics are effectively eliminated due to the cancellation effect described above. For example, (i) the multiple winding rotor coil reduces the 5th and 7th harmonics to levels well below the fundamental frequency (e.g., >60 dB); (ii) the three-phase receiver coil reduces the 3rd, 9th, and 15th harmonics to levels well below the fundamental frequency (e.g., >60 dB); and (iii) the twisted loop configuration of each receiver coil eliminates even harmonics.

[0070] This combined harmonic cancellation effect helps the angle calculation to generate angle measurements with very high accuracy. For example, the angle calculation can determine the period with 6-bit accuracy for a fundamental frequency of 63. Furthermore, the angle calculation can interpolate with (at least) 10-bit accuracy when the harmonic suppression is sufficient to effectively remove higher harmonics (i.e., harmonic suppression ≧60 dB). This can correspond to an angle measurement accuracy of 16 bits or 20 arc seconds. Such accuracy in a sensor with a small size (e.g., 38 mm diameter) would not be practically possible without the techniques described herein. For example, without the techniques described herein, high angle measurement accuracy at a small size would require much more complex and expensive PCB circuitry.

[0071] FIG. 11 is a flow chart of a method for measuring an angle. The method 1100 includes a step 1110 of generating a first magnetic field using an excitation coil located on a first plane. The excitation coil is symmetric about an axis of symmetry located at the center of the excitation coil. The method 1100 further includes a step 1120 of rotating the rotor coil to an angle about (i.e., at) the axis of symmetry. The rotor coil is located in a second plane that is parallel to the first plane and separated from the first plane by an air gap. The rotor coil has a first spatial frequency (i.e., first frequency, first symmetry). The method 1100 further includes a step 1130 of coupling a first magnetic field from the excitation coil to the rotor coil to generate a current in the rotor coil. The method 1100 further includes coupling 1140 a second magnetic field generated by the current in the rotor coil to a receiver coil in the first plane, the receiver coil having a second spatial frequency (i.e., second frequency, second symmetry). The method further includes receiving 1150 a received signal from the receiver coil having an amplitude corresponding to an angle of the rotor coil. The method further includes comparing 1160 the received signal from the receiver coil to a sinusoidal signal to measure the angle. The sinusoidal signal has a fundamental frequency corresponding to the least common multiple of the first and second spatial frequencies.

[0072] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. Methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure. As used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. As used herein, the term "comprises" and variations thereof are used synonymously with the term "comprises" and variations thereof and are open, non-limiting terms. As used herein, the term "optional" or "optionally" means that the subsequently described feature, event, or circumstance may or may not occur, and that the description includes instances when the feature, event, or circumstance occurs and instances when it does not occur. Ranges may be expressed herein as from "about" one particular value and / or to "about" another particular value. When such a range is expressed, the embodiment includes from one particular value and / or to another particular value. Similarly, when values ​​are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant in relation to the other endpoint, and independently of the other endpoint.

[0073] Some implementations may be implemented using various semiconductor processing and / or packaging technologies. Some implementations may be implemented using various types of semiconductor processing technologies associated with semiconductor substrates, including, but not limited to, Silicon (Si), Gallium Arsenide (GaAs), Gallium Nitride (GaN), Silicon Carbide (SiC), and / or the like.

[0074] Although certain features of the described implementations have been illustrated as described herein, those skilled in the art will now conceive many modifications, substitutions, changes, and equivalents. It will therefore be understood that the appended claims are intended to cover all such modifications and changes as fall within the scope of the implementations. It will be understood that these are presented by way of example only, not limitation, and that various changes in form and details may be made. Any part of the apparatus and / or method described herein may be combined in any combination, except in mutually exclusive combinations. The implementations described herein may include various combinations and / or subcombinations of features, components and / or features of the different implementations described.

[0075] In the above specification, when an element is referred to as being on, connected to, electrically connected to, coupled to, or electrically coupled with another element, it will be understood that the element may be directly on, connected to, or coupled with the other element, or there may be one or more intervening elements. On the other hand, when an element is referred to as being directly on, directly connected to, or directly coupled with another element, there are no intervening elements present. Throughout the detailed description of the present invention, the terms directly on, directly connected to, or directly coupled may not be used, but elements illustrated as being directly on, directly connected to, or directly coupled may be referred to as such. The claims of this application (if included) may be amended to describe the exemplary relationships described herein or shown in the drawings.

[0076] As used herein, the singular can include the plural, unless in view of the context the specific instance clearly indicates. Spatially relative terms (e.g., throughout, above, above, below, lower, below, etc.) are intended to encompass different orientations of the device during use or operation in addition to the orientation shown in the drawings. In some implementations, the relative terms above and below can include vertically above and vertically below, respectively. In some implementations, the term adjacent can include laterally adjacent or horizontally adjacent.

Claims

1. 1. An inductive angular position sensor, comprising: an excitation coil located in a first plane, the excitation coil having a circular shape about an axis of symmetry that intersects the first plane at a center of the excitation coil; a multi-winding rotor coil having a first rotor winding and a second rotor winding and having a first rotational symmetry of a first order about said axis of symmetry, said multi-winding rotor coil lying in a second plane separated from said first plane by an air gap and configured to rotate about said axis of symmetry, said multi-winding rotor coil configured to receive an excitation signal from said excitation coil through exciter-to-rotor inductive coupling; a receiver coil having a second rotational symmetry of a second order about the axis of symmetry, the receiver coil lying in the first plane and configured to generate a received signal based on rotor-to-receiver inductive coupling that varies sinusoidally as the multi-winding rotor coil rotates, the first order and the second order being different; 1. An inductive angular position sensor comprising:

2. the first order of the first rotational symmetry of the multi-winding rotor coil is a multiple of the second order of the second rotational symmetry of the receiver coil; 2. The inductive angular position sensor of claim 1, wherein a period of the fundamental frequency of the received signal corresponds to a range of rotation of the multi-winding rotor coil that is 360 degrees divided by the least common multiple of the first order and the second order.

3. 1. A position sensor system comprising:

1. An inductive angular position sensor, comprising: an excitation coil located in a first plane, the excitation coil having a circular shape about an axis of symmetry that intersects the first plane at a center of the excitation coil; a multi-winding rotor coil having a first rotor winding and a second rotor winding and having a first rotational symmetry of a first order about said axis of symmetry, said multi-winding rotor coil lying in a second plane separated from said first plane by an air gap and configured to rotate about said axis of symmetry, said multi-winding rotor coil configured to receive an excitation signal from said excitation coil through exciter-to-rotor inductive coupling; an inductive angular position sensor comprising: a plurality of receiver coils configured to generate a plurality of receive signals, each of the plurality of receiver coils having a second rotational symmetry of a second order smaller than the first order about the axis of symmetry, the plurality of receiver coils configured to generate a plurality of receive signals; a transceiver circuit coupled to the excitation coil and configured to generate the excitation signal, and further configured to receive the plurality of received signals from the plurality of receiver coils, the plurality of received signals having fundamental frequencies that are multiples of the first order and the second order; an angle calculation module configured to calculate an angle measurement based on the plurality of received signals; A position sensor system comprising:

4. A position sensor system as described in claim 3, wherein the first rotor winding has a first lobe ratio and the second rotor winding has a second lobe ratio.

5. 1. A method for measuring an angle, comprising: generating a first magnetic field using an excitation coil located in a first plane, the excitation coil being symmetric about an axis of symmetry; rotating a multi-winding rotor coil about the axis of symmetry to the angle, the multi-winding rotor coil being in a second plane parallel to the first plane and separated from the first plane by an air gap, the multi-winding rotor coil having a first rotor winding and a second rotor winding and having a first spatial frequency; coupling the first magnetic field from the excitation coil to the multi-winding rotor coil to generate a current in the multi-winding rotor coil; coupling a second magnetic field generated by the current in the multi-winding rotor coil to a receiver coil in the first plane, the receiver coil having a second spatial frequency; receiving a receive signal from the receiver coil having an amplitude corresponding to an angle of the multi-winding rotor coil; comparing the received signal from the receiver coil with a sinusoidal signal, the sinusoidal signal having a fundamental frequency corresponding to a least common multiple of the first spatial frequency and the second spatial frequency, to measure the angle; A method comprising:

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