Computing device and program

Abstract

A computing device (70) is applied to a rotating body sensor having: a first sensor unit that is fixed to a rotating body (10, 20); a second sensor unit that is fixed to a base unit (42); and an excitation coil (100). One of the first sensor unit and the second sensor unit is a unit to be detected (81, 82, 181, 182, 282, 283, 381, 382), and the other is a receiving coil (110, 120). The rotating body sensor includes, as receiving coils, a first receiving coil that outputs a first voltage signal, and a second receiving coil that outputs a second voltage signal having a predetermined phase relationship with the first voltage signal. The computing device comprises: a sampling unit that acquires a sampling value, which is the first voltage signal at a timing based on the second voltage signal; and a calculating unit that calculates, on the basis of the sampling value, at least one of a force acting on the rotating body, the relative displacement of the first sensor unit with respect to the second sensor unit, and the angle of rotation of the rotating body.

Description

Arithmetic device and program CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2023-164906, filed on September 27, 2023, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a computing device and a program.

[0003] As described in Patent Document 1, a bearing device is known that supports a hub fixed to a wheel so that it can rotate relative to a vehicle body. The bearing device includes an outer ring fixed to the vehicle body, an inner ring fixed to the hub, and rolling elements provided between the outer ring and the inner ring. The bearing device is provided with a strain sensor that detects strain in the outer ring. Vehicle travel control is performed based on the detected value of the strain sensor.

[0004] Patent No. 5436191

[0005] Not only strain sensors for bearing devices that support wheels, but also sensors used on rotating bodies, are concerned that noise may be included in the detected values ​​of the sensor, which may adversely affect the processing of a computing device that uses the detected values ​​of the sensor.

[0006] A primary object of the present disclosure is to provide a computing device and a program that can suppress adverse effects caused by noise contained in the detection value of a sensor.

[0007] The present disclosure relates to a computing device applicable to a sensor for a rotating body, the computing device comprising: a first sensor unit fixed to a rotating body and rotating in association with the rotation of the rotating body around a rotation center axis extending in a predetermined axial direction; a second sensor unit fixed to a base unit and provided at a position facing the first sensor unit in the axial direction; and an excitation coil to which an AC excitation voltage is supplied; wherein one of the first sensor unit and the second sensor unit is a detection object forming an annular ring shape centered on the rotation center axis, and the other of the first sensor unit and the second sensor unit is a receiving coil that outputs an AC voltage signal that changes in accordance with the relative displacement of the detection object facing the first sensor unit when the excitation voltage is supplied to the excitation coil; and the sensor for a rotating body comprises, as the receiving coils, a first receiving coil that outputs a first voltage signal, and a second receiving coil that outputs a second voltage signal having a predetermined phase relationship with the first voltage signal; and and a calculation unit that calculates at least one of the force acting on the rotating body, the relative displacement of the first sensor unit with respect to the second sensor unit, and the rotation angle of the rotating body based on the acquired sampling value.

[0008] The rotating body sensor includes a detection target, an excitation coil, and a receiving coil. The receiving coil outputs an AC voltage signal when an excitation voltage is supplied to the excitation coil. When the rotating body rotates or a force acts on the rotating body, the relative positions of the detection target and the receiving coil change, and the amplitude of the voltage signal of the receiving coil changes. In consideration of this, the computing device calculates at least one of the force acting on the rotating body, the relative displacement between the detection target and the receiving coil, and the rotation angle of the rotating body based on the voltage signal of the receiving coil.

[0009] Here, to calculate the force acting on the rotating body, the relative displacement between the detection target and the receiving coil, and the rotation angle of the rotating body, a value at a specific timing in one period of the output voltage signal of the receiving coil may be used. In this case, there is a concern that changes in the amplitude of the voltage signal of the receiving coil due to the rotation of the rotating body will become noise and adversely affect the calculation of the force, displacement, and rotation angle. In this regard, in a configuration in which the receiving coils include a first receiving coil that outputs a first voltage signal and a second receiving coil that outputs a second voltage signal having a predetermined phase relationship with the first voltage signal, it is possible to determine the sampling timing of the first voltage signal based on the second voltage signal.

[0010] Therefore, in the present disclosure, a sampled value is acquired, which is the first voltage signal at a timing based on the second voltage signal. In this case, it is possible to acquire a value at a specific timing in one cycle of the first voltage signal as the sampled value. This reduces the influence of the rotation of the rotating body on the acquired sampled value. Therefore, it is possible to improve the accuracy of calculating at least one of the force acting on the rotating body, the relative displacement between the detection target and the receiving coil, and the rotation angle of the rotating body based on the acquired sampled value.

[0011] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is a longitudinal cross-sectional view of a wheel according to a first embodiment, Fig. 2 is a plan view of a target rotor and a detection unit, Fig. 3 is a plan view of the detection unit, Fig. 4 is a diagram showing the electrical configuration of a calculation device and a detection unit, Fig. 5 is a projection view of an excitation coil and each receiving coil in a plan view of a circuit board, Fig. 6 is a diagram showing the relative positional relationship of each receiving coil, Fig. 7 is a diagram showing a state in which an inner wheel is tilted relative to an outer wheel when a lateral load is applied to the tire, and Fig. 8 is a diagram showing a state in which a lateral load is applied to the tire and a detection unit perpendicular to the tire. 10 is a diagram illustrating the principle of detecting displacement and rotation angle; FIG. 11 is a plan view of a simplified wide receiving coil; FIG. 12 is a diagram illustrating the output voltage signal of the receiving coil and the transition of the envelope of the output voltage signal; FIG. 13 is a diagram illustrating the transition of the envelope of the output voltage signal of each receiving coil; and FIG. 14 is a characteristic diagram illustrating the relationship between the amplitude value of each signal and axial displacement. 15 is a diagram showing a change in the envelope from a reference state when a lateral load is applied, FIG. 16 is a characteristics diagram showing the relationship between the amplitude of each signal and the vertical displacement, FIG. 17 is a diagram showing the relative positioning of each receiving coil and shielding part when a vertical load is applied, FIG. 18 is a diagram showing a change in the envelope from a reference state when a vertical load is applied, FIG. 19 is a diagram showing an example of a sine wave signal and a cosine wave signal, FIG. 20 is a time chart showing an example of a process for calculating the amplitude value of a first voltage signal, FIG. 21 is a flowchart showing a control processing procedure executed by a calculation device, FIG. 22 is a plan view of a target rotor and a detection unit according to a second embodiment, FIG. 23 is a flowchart showing a control processing procedure executed by a calculation device according to a third embodiment, FIG. 24 is a plan view of a target rotor according to another embodiment, FIG. 25 is a plan view of a target rotor according to another embodiment, and FIG. 26 is a plan view of a target rotor according to another embodiment.

[0012] Several embodiments will be described with reference to the drawings. In several embodiments, functionally and / or structurally corresponding and / or associated parts may be designated by the same reference numerals or reference numerals that differ in the hundredth or more digit. For corresponding and / or associated parts, reference may be made to the descriptions of other embodiments.

[0013] First Embodiment A first embodiment of a computing device according to the present disclosure will now be described with reference to the drawings. The computing device of this embodiment is applied to a wheel sensor and is configured to be able to calculate forces acting on wheels (drive wheels). The vehicle is, for example, a four-wheeled passenger vehicle having two front wheels and two rear wheels. However, the vehicle is not limited to this, and may be a vehicle other than a four-wheeled vehicle, such as a two-wheeled vehicle. Furthermore, the use of the vehicle is not limited to passenger use.

[0014] As shown in Figure 1, the wheel unit includes, as rotating bodies, a wheel 10 and an in-wheel motor 20. The wheel 10 includes a cylindrical rim portion 11 and a circular disk portion 12 provided at the outer end of the rim portion 11 in the vehicle width direction. A tire 13 is attached to the outer periphery of the rim portion 11.

[0015] The in-wheel motor 20 is housed in the inner space of the wheel 10 surrounded by the rim portion 11 and the disc portion 12, and applies rotational power to the wheel 10. The in-wheel motor 20 is an outer rotor type motor including a rotor 30 and a stator 40 arranged radially inside the rotor 30.

[0016] The rotor 30 includes a cylindrical magnet holder 31 and a magnet unit 32 provided on the inner peripheral surface of the magnet holder 31. The magnet holder 31 faces the inner peripheral surface of the rim portion 11. The magnet unit 32 is cylindrical and concentric with the central axis of rotation of the rotor 30, and includes multiple magnets fixed to the inner peripheral surface of the magnet holder 31. In other words, the in-wheel motor 20 of this embodiment is a surface permanent magnet synchronous machine (SPMSM). In the magnet unit 32, the magnets are arranged so that their polarities alternate along a circumferential direction extending circumferentially around the central axis of rotation of the rotor 30. As a result, the magnet unit 32 has multiple magnetic poles formed along the circumferential direction. The magnets are, for example, sintered neodymium magnets. The in-wheel motor 20 may also be an interior permanent magnet synchronous machine (IPMSM).

[0017] The rotor 30 is provided with a disk-shaped flat plate portion 33 that is provided at the outer end of the magnet holding portion 31 in the vehicle width direction and connects the magnet holding portion 31 to the disk portion 12. The disk portion 12 is fixed to the flat plate portion 33 with bolts. This allows the rotor 30 and the wheel 10 to rotate integrally.

[0018] The stator 40 includes a cylindrical stator winding 41 disposed at a position facing the magnet unit 32 in the radial direction, and a cylindrical stator base portion 42 provided radially inside the stator winding 41. The stator winding 41 includes a coil side portion provided at a position facing the magnet unit 32 in the radial direction, and coil end portions provided at both axial ends of the coil side portion.

[0019] The stator base portion 42 is fixed to the vehicle body via a knuckle or the like, and holds the stator winding 41, etc. The stator base portion 42 has a cylindrical portion 43 fixed to the vehicle body. The portion of the cylindrical portion 43 that is radially adjacent to the stator winding 41 is a stator core 43a.

[0020] The stator base portion 42 has a fixed portion 44 that extends radially inward from one axial end of the cylindrical portion 43. The fixed portion 44 and the bearings 50 rotatably support the rotor 30 relative to the stator base portion 42. The radially outer end of the fixed portion 44 is formed as an annular protruding portion 45 that protrudes toward the flat plate portion 33. The portion of the protruding portion 45 that faces the flat plate portion 33 is formed as a flat surface.

[0021] The bearing 50 is a rolling bearing (e.g., a radial ball bearing) and includes an outer ring 51 corresponding to a first bearing member, an inner ring 52 corresponding to a second bearing member, and a plurality of rolling elements 53 (e.g., balls) disposed between the outer ring 51 and the inner ring 52. The outer ring 51 is fixed to the fixing portion 44 with bolts. The inner ring 52 includes a cylindrical portion 52a that faces the outer ring 51 in the radial direction, and a flange portion 52b that extends radially outward from one axial end of the cylindrical portion 52a. The flange portion 52b is fixed to the flat plate portion 33 and the disk portion 12 with bolts. Note that FIG. 1 shows a state in which the inner ring 52 and the outer ring 51 are coaxial.

[0022] The vehicle is equipped with an inverter electrically connected to the stator winding 41 and a DC power supply electrically connected to the inverter. The DC power supply is provided in the vehicle body and is, for example, a rechargeable storage battery such as a lithium-ion storage battery. The upper and lower arm switches that make up the inverter are switched on and off by a control device. This causes the rotor 30 to rotate, which in turn rotates the wheels. The inverter and control device may be provided in the vehicle body or may be built into the in-wheel motor 20. The DC power supply may also be, for example, a fuel cell.

[0023] A wheel sensor is provided in the inner space of the wheel 10. The wheel sensor detects the rotation angle θ (specifically, the electrical angle or mechanical angle) of the rotor 30 of the in-wheel motor 20, the rotational speed of the wheel, the lateral load Fy acting between the ground contact surface (ground) GL and the wheel (tire 13), and the force acting between the ground contact surface GL and the wheel in a direction perpendicular to the ground contact surface GL (hereinafter referred to as the vertical load Fz). The direction in which the lateral load Fy acts is perpendicular to the direction in which the vertical load Fz acts.

[0024] As shown in FIGS. 1 and 2, the wheel sensor includes a disk-shaped target rotor 80 and a detection unit 90.

[0025] The target rotor 80 is made of a metal material (e.g., iron or aluminum). A through hole is formed in the center of the target rotor 80, and the target rotor 80 has an annular shape. The peripheral edge of the through hole of the target rotor 80 is formed as a bent portion 80a that bends toward the disk portion 12. The bent portion 80a is fitted into a through hole formed in the center of the flat plate portion 33 of the rotor 30. The target rotor 80 is fixed to the flange portion 52b of the inner ring 52 with bolts, while being spaced apart from the flat plate portion 33 of the rotor 30 and in surface contact with the flange portion 52b. This makes the target rotor 80 and the inner ring 52 coaxial. The target rotor 80, the rotor 30, and the wheel 10 rotate together.

[0026] The radially outer end of the target rotor 80 faces the protruding portion 45 of the stator base portion 42. As shown in FIG. 2 , shielding portions 81, which are metal portions, and notches 82, which penetrate the target rotor 80 in the thickness direction, are alternately formed in the circumferential direction at the radially outer end of the target rotor 80. The shielding portions 81 and the notches 82 form an annular "detection target portion." In this embodiment, the circumferential length L1 of the shielding portions 81 and the circumferential length L2 of the notches 82 are equal. In the example shown in FIG. 2 , eight pairs of shielding portions 81 and notches 82 are provided. The shielding portions 81 and the notches 82 correspond to the "first sensor portion."

[0027] The detection unit 90 is a so-called eddy current inductive sensor. As shown in FIGS. 2, 3, and 4, the detection unit 90 includes a substrate 91, a coil portion 92 provided on the substrate 91, and a circuit portion 93. FIG. 2 is a diagram showing the target rotor 80 as viewed from the outside in the vehicle width direction. FIG. 3 is a diagram showing the substrate 91 as viewed from the outside in the vehicle width direction. The substrate 91 is fixed to the flat surface of the protruding portion 45. As a result, the substrate 91 extends in a direction perpendicular to the axial direction of the outer ring 51. In this embodiment, the substrate 91 is fixed to the flat surface at the upper end of the annular protruding portion 45. The substrate 91 is a multilayer substrate. The coil portion 92 is provided at a position facing the target rotor 80 in the axial direction.

[0028] As shown in FIG. 5A, the coil unit 92 includes an excitation coil 100, a narrow receiving coil 110, and a wide receiving coil 120. Each of the coils 100, 110, and 120 is a planar coil. Each of the coils 100, 110, and 120 is formed by wiring patterns and vias formed on each layer of the substrate 91. This structure makes it easy to arrange each of the coils 100, 110, and 120 even when a large axial space cannot be secured inside the wheel 10. Each of the receiving coils 110 and 120 corresponds to a "second sensor unit."

[0029] The excitation coil 100 is a planar coil having a plurality of turns, and is formed in an arc shape extending in the circumferential direction of the outer ring 51. The receiving coils 110, 120 are provided in an area surrounded by the excitation coil 100 in a plan view of the substrate 91. The receiving coils 110, 120 have the same circumferential length.

[0030] As shown in FIG. 6 , the radial length of the wide receiver coil 120 is greater than the radial length of the narrow receiver coil 110, and the wide receiver coil 120 has a wider radial width than the narrow receiver coil 110. Specifically, in a plan view of the substrate 91, the radially outer end of the wide receiver coil 120 is located on a first concentric circle C1 centered on the central axis LCo of the outer ring 51 (see FIG. 5 ). The radially outer end of the narrow receiver coil 110 is located on a second concentric circle C2 centered on the central axis LCo. The radius of the second concentric circle C2 is smaller than the radius of the first concentric circle C1. The radially inner end of the narrow receiver coil 110 is located on a third concentric circle C3 centered on the central axis LCo. The radius of the third concentric circle C3 is smaller than the radius of the second concentric circle C2. The radially inner end of the wide receive coil 120 is located on a fourth concentric circle C4 centered on the central axis LCo. The radius of the fourth concentric circle C4 is smaller than the radius of the third concentric circle C3.

[0031] The radially outer end of the wide receiving coil 120 protrudes from the radially outer end 81 a of the shielding portion 81 in the reference state. The reference state can be set arbitrarily. The reference state is, for example, a state in which the vehicle is stopped, specifically, a state in which the vehicle is stopped on a level road surface. CP shown in FIG. 6 is a concentric circle CP that is centered on the central axis LCo of the outer ring 51 and passes through the radially outer end 81 a of the shielding portion 81 in the reference state.

[0032] Each receiving coil 110, 120 is composed of a first portion that generates a voltage of a first polarity between the first receiving end 111, 121 and the second receiving end 118, 128 of each receiving coil 110, 120 when an excitation voltage is supplied to the excitation coil 100, and a second portion that generates a voltage of a second polarity that is opposite to the first polarity.

[0033] 5(b), in the narrow receiver coil 110, in a plan view of the substrate 91, the circumferential center portion of the narrow receiver coil 110 is a first portion 110A of one turn, and both end portions of the first portion 110A of the narrow receiver coil 110 are second portions 110B of the same number of turns (one turn) as the first portion 110A. As a result, the pattern shape of the first and second portions 110A, 110B on one side of the circumferential central axis Lt of the narrow receiver coil 110 and the pattern shape of the first and second portions 110A, 110B on the other side are symmetrical with respect to the central axis Lt.

[0034] As shown in Figure 5 (c), in the wide receiving coil 120, when viewed in a plane of the substrate 91, one side of the circumferential central axis Lt of the wide receiving coil 120 is a first part 120A, and the other side is a second part 120B.

[0035] 1 and 4 , the circuit unit 93 is electrically connected to the arithmetic unit 70. More specifically, an insertion hole 46 is formed in the protruding portion 45, and the arithmetic unit 70 and the circuit unit 93 are electrically connected via a wire inserted through the insertion hole 46. The arithmetic unit 70 may be provided on the vehicle body or may be built into the in-wheel motor 20.

[0036] The circuit unit 93 is composed of an integrated circuit, and as shown in Fig. 4, includes an excitation circuit 94 and a receiving circuit 95. The excitation circuit 94 supplies a high-frequency excitation voltage to the excitation coil 100. When the excitation voltage is supplied to the excitation coil 100, a voltage having the same or equivalent frequency as the excitation voltage is induced in the narrow receiving coil 110 and the wide receiving coil 120. The receiving circuit 95 detects the voltages across both ends of each receiving coil 110, 120 as output voltage signals.

[0037] The circuit unit 93 and the arithmetic unit 70 are primarily configured, for example, with a microcomputer. The functions provided by the microcomputers in the circuit unit 93 and the arithmetic unit 70 can be provided by software stored in a physical memory device and a computer executing the software, software alone, hardware alone, or a combination thereof. For example, when the microcomputer is implemented as a hardware electronic circuit, the function can be implemented by a digital circuit including multiple logic circuits or an analog circuit. For example, the microcomputer executes a program stored in a non-transitory tangible storage medium serving as its own storage unit. The program includes, for example, programs for the processes shown in Figures 21 and 23 (described below). A method corresponding to the program is performed by executing a set of instructions constituting the program. The storage unit is, for example, a non-volatile memory. The program stored in the storage unit can be updated via a network such as the Internet, for example, via OTA (Over the Air).

[0038] When a lateral load Fy acts on the wheel as shown in Fig. 1, the inclination α of the center axis LCi of the inner ring 52 relative to the center axis LCo of the outer ring 51 increases as shown in Fig. 7. In this case, the axial distance between each of the receiving coils 110, 120 and the target rotor 80 changes, and the amplitude of the output voltage signals of each of the receiving coils 110, 120 changes. The computing device 70 calculates the axial displacement ΔY of the target rotor 80 based on the amplitude value of the output voltage signals, and calculates the lateral load Fy based on the calculated axial displacement ΔY.

[0039] On the other hand, when a vertical load Fz acts on the wheel as shown in FIG. 1 , the center axis LCi of the inner ring 52 is displaced in a direction perpendicular to the center axis LCo of the outer ring 51 as shown in FIG. 8 . As a result, the target rotor 80 fixed to the flange portion 52b is displaced relative to the receiving coils 110, 120 fixed to the protruding portion 45. The detection unit 90 is configured so that in this case, the amplitude of the output voltage signal of the wide receiving coil 110 changes. The computing device 70 calculates the displacement of the target rotor 80 in the axial direction and in the direction perpendicular to the vehicle length direction (hereinafter referred to as the vertical displacement ΔZ) based on the amplitude values ​​of the output voltage signals of the receiving coils 110, 120, and calculates the vertical load Fz based on the calculated vertical displacement ΔZ. The process of calculating the displacements ΔY, ΔZ, the lateral load Fy, and the vertical load Fz executed by the computing device 70 will be described later.

[0040] The principle by which the detection unit 90 and the arithmetic device 70 can detect the displacements ΔY, ΔZ and the rotation angle θ will be described below.

[0041] First, an outline of the detection principle of the displacements ΔY, ΔZ and the rotation angle θ will be explained using Figures 9 and 10. As shown in Figure 9, when a high-frequency excitation voltage vr(t) is supplied to the excitation coil, a high-frequency current flows in the excitation coil. The current flowing in the excitation coil generates a magnetic flux φ(t), which interlinks with the receiving coil. A voltage ve(t) proportional to the time rate of change of the interlinked magnetic flux is induced at both ends of the receiving coil.

[0042] 10 shows a state in which the shielding portion 81 of the target rotor 80 faces a part of the receiving coil in the radial direction. Eddy currents flow in the part of the shielding portion 81 facing the receiving coil due to the interlinkage magnetic flux generated by the energization of the excitation coil. The eddy currents flowing in the shielding portion 81 generate magnetic flux in a direction that weakens the magnetic flux that generates an induced voltage in the receiving coil, thereby reducing the amplitude of the induced voltage in the receiving coil. In this case, the amplitude of the output voltage signal of the receiving coil decreases as the potential difference between both ends of the receiving coil decreases. In other words, the amplitude of the output voltage signal of the receiving coil is proportional to the area of ​​the receiving coil that does not face the shielding portion 81 in the radial direction.

[0043] 9 and 10, the detection principle of the displacements ΔY, ΔZ and the rotation angle θ will be described using Fig. 11 and Fig. 12. Fig. 11 and Fig. 12 are diagrams showing the wide receiver coil 120 and the shielding portion 81 as linear in the circumferential direction. Fig. 12 is a diagram showing the relative positional relationship between the wide receiver coil 120 and the shielding portion 81 and the transition of the output voltage signal va of the wide receiver coil 120.

[0044] 11 and 12, the direction (I+) in which current flows from the second receiving end 128 to the first receiving end 121 is referred to as the positive direction, and the direction (I-) in which current flows from the first receiving end 121 to the second receiving end 128 is referred to as the negative direction. In addition, in FIGS. 11 and 12, magnetic flux from the excitation coil 100 passes from the front side to the back side of the paper.

[0045] 12 , the central half of first portion 120A and the central half of second portion 120B are covered by shielding portion 81. A voltage that attempts to cause a current to flow in a positive direction is induced in first portion 120A, and a voltage that attempts to cause a current to flow in a negative direction is induced in second portion 120B. As a result, the induced voltages generated in first portion 120A and second portion 120B cancel each other out, and the amplitude of output voltage signal va of wide receiving coil 120 becomes zero.

[0046] At time t2, of the first portion 120A and the second portion 120B, the second portion 120B is covered by the shielding portion 81. In this case, a voltage that attempts to flow a current in the positive direction is induced in the first portion 120A, and the induced voltage in the second portion 120B becomes zero. As a result, the amplitude of the output voltage signal va of the wide receiving coil 120 becomes maximum. The amplitude of the output voltage signal va of the wide receiving coil 120 increases as the target rotor 80 approaches the wide receiving coil 120.

[0047] At time t3, the end half of first portion 120A and the end half of second portion 120B are covered by shielding portion 81. A voltage that attempts to cause a current to flow in a positive direction is induced in first portion 120A, and a voltage that attempts to cause a current to flow in a negative direction is induced in second portion 120B. As a result, the induced voltages generated in first portion 120A and second portion 120B cancel each other out, and the amplitude of output voltage signal va of wide receiving coil 120 becomes zero.

[0048] At time t4, of the first portion 120A and the second portion 120B, the first portion 120A is covered by the shielding portion 81. In this case, a voltage that attempts to flow a current in the negative direction is induced in the second portion 120B, and the induced voltage in the first portion 120A becomes zero. As a result, the amplitude of the output voltage signal va of the wide receiving coil 120 becomes maximum. The amplitude of the output voltage signal va of the wide receiving coil 120 increases as the target rotor 80 approaches the wide receiving coil 120.

[0049] In this embodiment, shielding portions 81 and notches 82 are alternately formed at the radially outer end of the target rotor 80. Therefore, the amplitude of the output voltage signal va of the wide receiving coil 120 changes periodically while the rotor 30 is rotating. As shown by the dashed lines in Figures 12 and 13, the envelope Ea of the output voltage signal va of the wide receiving coil 120 has a sinusoidal shape. For example, by setting the circumferential interval between the magnetic pole positions of the magnet unit 32 and the circumferential lengths of the shielding portions 81 and the notches 82 in a correlated manner, the amplitude or envelope can be associated with the rotation angle θ.

[0050] In this embodiment, when an excitation voltage is supplied to the excitation coil 100, the phase difference between the output voltage signal va of the wide receiver coil 120 and the output voltage signal of the narrow receiver coil 110 is 90°. Therefore, as shown by the dashed line and the dashed-dotted line in Figure 13, the phase difference between the envelope Ea of the output voltage signal va of the wide receiver coil 120 and the envelope Eb of the output voltage signal of the narrow receiver coil 110 is 90°. Hereinafter, the envelope Ea of the output voltage signal va of the wide receiver coil 120 will be referred to as a "sine wave signal," and the envelope Eb of the output voltage signal of the narrow receiver coil 110 will be referred to as a "cosine wave signal."

[0051] 13, the amplitude of the sine wave signal Ea is larger than the amplitude of the cosine wave signal Eb because, as shown in FIGS. 5A and 6, the area surrounded by the wide receiver coil 120 is larger than the area surrounded by the narrow receiver coil 110 in a plan view of the substrate 91.

[0052] 14 shows the relationship between the amplitudes of the signals Ea and Eb and the axial displacement ΔY. Here, we assume that the lateral load Fy varies. Kay denotes the deviation of the amplitude of the actual sine wave signal Ear from the amplitude of the sine wave signal Eas in the reference state. Kby denotes the deviation of the amplitude of the actual cosine wave signal Ebr from the amplitude of the cosine wave signal Ebs in the reference state.

[0053] When the direction of the lateral load Fy faces outward in the vehicle width direction, the inner wheel 52 tilts relative to the outer wheel 51 so that the upper end of the target rotor 80 approaches the stator base 42 and the lower end approaches the wheel 10. In this case, the polarities of the axial displacement ΔY and the deviation amounts Kay and Kby are positive. As the axial displacement ΔY increases in the positive direction, the deviation amounts Kay and Kby increase in the positive direction. This is because, as shown in FIG. 15( a), as the target rotor 80 approaches the receiving coils 110 and 120, the amplitudes of the actual signals Ear and Ebr increase relative to the signals Eas and Ebs in the reference state.

[0054] When the direction of the lateral load Fy is directed inward in the vehicle width direction, the inner wheel 52 tilts relative to the outer wheel 51 so that the lower end of the target rotor 80 approaches the stator base 42 and the upper end approaches the wheel 10. In this case, the polarities of the axial displacement ΔY and the deviations Kay and Kby are negative. The more negative the axial displacement ΔY, the more negative the deviations Kay and Kby. This is because, as shown in FIG. 15B , the further the target rotor 80 is from the receiving coils 110 and 120, the smaller the amplitudes of the actual signals Ear and Ebr become relative to the signals Eas and Ebs in the reference state. Meanwhile, the deviations Kay and Kby in the reference state are zero.

[0055] 16 shows the relationship between the amplitudes of the signals Ea and Eb and the vertical displacement ΔZ. Here, we assume that the vertical load Fz changes. Kaz denotes the deviation of the amplitude of the actual sine wave signal Ear from the amplitude of the sine wave signal Eas in the reference state. Kbz denotes the deviation of the amplitude of the actual cosine wave signal Ebr from the amplitude of the cosine wave signal Ebs in the reference state.

[0056] Fig. 17(a) shows the relative positional relationship between the receiver coils 110, 120 and the shielding portion 81 in the reference state. Fig. 17 is a diagram showing the receiver coils 110, 120 and the shielding portion 81 shown in Figs. 2, 5, etc., with the circumferential direction shown as a straight line. In the figure, the hatched portions are the portions of the receiver coils 110, 120 that are covered by the shielding portion 81. Fig. 18(a) shows the transitions of the signals Eas and Ebs in the reference state.

[0057] When the upward vertical load Fz increases, the upper end of the target rotor 80 is displaced upward. In this case, the polarity of the vertical displacement ΔZ and the deviations Kaz and Kbz is negative in FIG. 16 . The more negative the vertical displacement ΔZ, the more negative the deviation Kaz of the amplitude value of the sine wave signal Ea. This is because, as shown in FIG. 17( b), the area of ​​the wide receiving coil 120 covered by the shielding portion 81 increases as the target rotor 80 is displaced upward. In this case, as shown in FIG. 18( b), the amplitude of the actual sine wave signal Ear becomes smaller than the sine wave signal Eas in the reference state.

[0058] When the downward vertical load Fz increases, the upper end of the target rotor 80 is displaced downward. In this case, the polarity of the vertical displacement ΔZ and the deviations Kaz and Kbz is positive in FIG. 16 . The more the vertical displacement ΔZ increases in the positive direction, the more the deviation Kaz in the amplitude value of the sine wave signal Ea increases in the positive direction. This is because, as shown in FIG. 17( c), the area of ​​the wide receiving coil 120 covered by the shielding portion 81 decreases as the target rotor 80 displaces downward. In this case, as shown in FIG. 18( c), the amplitude of the actual sine wave signal Ear increases relative to the sine wave signal Eas in the reference state.

[0059] As shown in Fig. 16, the deviation amount Kbz of the amplitude value of the cosine wave signal Eb does not change with respect to the vertical displacement ΔZ. This is because, as shown in Figs. 17(a) to 17(c), even if the target rotor 80 displaces, the area of ​​the narrow receiver coil 110 that is covered by the shielding portion 81 does not change. In this case, even if the target rotor 80 displaces in the vertical direction as shown in Figs. 18(a) to 18(c), the actual amplitude value of the cosine wave signal Ebr will be equal to the amplitude value of the cosine wave signal Ebs in the reference state.

[0060] The slope of the deviation amount Kaz of the amplitude value of the sine wave signal Ea with respect to the vertical displacement ΔZ is smaller than the slope of the deviation amount Kay of the amplitude value of the sine wave signal Ea with respect to the axial displacement ΔY. Also, the slope of the deviation amount Kbz of the amplitude value of the cosine wave signal Eb with respect to the vertical displacement ΔZ is smaller than the slope of the deviation amount Kby of the amplitude value of the cosine wave signal Eb with respect to the axial displacement ΔY. This is because, for example, the rigidity of the wheel in the up-down direction is greater than the rigidity in the vehicle width direction.

[0061] From the above, the calculation device 70 can calculate the axial displacement ΔY and the vertical displacement ΔZ based on the amplitude values ​​A and B of the input signals Ea and Eb. The calculation device 70 can also calculate the lateral load Fy based on the calculated axial displacement ΔY. The calculation device 70 can also calculate the vertical load Fz based on the calculated vertical displacement ΔZ.

[0062] The processing performed by the calculation device 70 will be described in detail below with reference to Fig. 4. In this embodiment, the calculation device 70 performs processing to calculate the rotation angle θ in addition to the lateral load Fy and the vertical load Fz.

[0063] The receiving circuit 95 includes an envelope detection circuit that detects the envelope of the output voltage signal of each receiving coil 110, 120. The receiving circuit 95 generates a sine wave signal Ea based on the detected output voltage signal of the wide receiving coil 120. The receiving circuit 95 generates a cosine wave signal Eb based on the detected output voltage signal of the narrow receiving coil 110.

[0064] The arithmetic unit 70 includes an AD converter 71 and a signal processing unit 72. The AD converter 71 receives analog sine wave signals Ea and cosine wave signals Eb from the receiving circuit 95. The AD converter 71 converts the signals Ea and Eb into digital signals. The digital signals Ea and Eb are then input to the signal processing unit 72.

[0065] The signal processing unit 72 acquires the amplitude value A of the sine wave signal Ea and the amplitude value B of the cosine wave signal Eb. The process of acquiring the amplitude values ​​A and B will be described in detail later.

[0066] The arithmetic device 70 includes a displacement amount calculation unit 73 and a force calculation unit 74. The amplitude values ​​A and B acquired by the signal processing unit 72 are input to the displacement amount calculation unit 73. The displacement amount calculation unit 73 calculates the axial displacement ΔY and the vertical displacement ΔZ based on the input amplitude values ​​A and B. For example, the displacement amount calculation unit 73 calculates the axial displacement ΔY and the vertical displacement ΔZ based on the deviation amount of the input amplitude values ​​A and B from the amplitude value in a reference state, and map information or mathematical formula information in which the deviation amount of the amplitude values ​​A and B from the amplitude value in the reference state, the axial displacement ΔY, and the vertical displacement ΔZ are correlated.

[0067] The force calculation unit 74 receives the displacements ΔY and ΔZ calculated by the displacement amount calculation unit 73. The force calculation unit 74 calculates the lateral load Fyc based on the input axial displacement ΔY. For example, the force calculation unit 74 calculates the lateral load Fyc based on the input axial displacement ΔY and map information or formula information correlating the axial displacement ΔY and the lateral load Fy. The force calculation unit 74 calculates the vertical load Fzc based on the input vertical displacement ΔZ. For example, the force calculation unit 74 calculates the vertical load Fzc based on the input vertical displacement ΔZ and map information or formula information correlating the vertical displacement ΔZ and the vertical load Fz. The calculated lateral load Fyc and vertical load Fzc are input to the control device 15 provided in the vehicle.

[0068] The arithmetic unit 70 includes a normalization unit 75 and a rotation angle calculation unit 76. The normalization unit 75 receives the signals Ea, Eb and the amplitude values ​​A, B from the signal processing unit 72. The normalization unit 75 calculates a normalized sine wave signal Ean by dividing the input sine wave signal Ea by the amplitude value A. The normalization unit 75 also calculates a normalized cosine wave signal Ebn by dividing the input cosine wave signal Eb by the amplitude value B. The normalized signals Ean, Ebn have an amplitude value of 1.

[0069] The signals Ean and Ebn normalized by the normalizer 75 are input to the rotation angle calculator 76. The rotation angle calculator 76 calculates the rotation angle θc based on the normalized signals Ean and Ebn. For example, the rotation angle calculator 76 calculates the rotation angle θc (electrical angle) by performing an arctangent operation on the ratio between the normalized sine wave signal Ean and the normalized cosine wave signal Ebn. The calculated rotation angle θc is input to the control device 15.

[0070] The rotation angle calculation unit 76 may calculate the rotation speed of the wheel based on the time differential value of the calculated rotation angle θc, and output the calculated rotation speed to the control device 15.

[0071] For example, the calculated rotation angle θc is used for inverter switching control in the control device 15. Furthermore, for example, the calculated wheel rotation speed, lateral load Fyc, and vertical load Fzc are used for vehicle running control in the control device 15.

[0072] As described above, the amplitude values ​​A and B of the signals Ea and Eb are used to calculate the lateral load Fyc, the vertical load Fzc, and the rotation angle θc. In this case, there is a concern that changes in the signals Ea and Eb due to the rotation of the rotor 30 may adversely affect the calculation of the lateral load Fyc, the vertical load Fzc, and the rotation angle θc.

[0073] Therefore, in this embodiment, in order to obtain the amplitude values ​​A and B of the signals Ea and Eb while suppressing the influence of changes in the signals Ea and Eb due to the rotation of the rotor 30, the calculation device 70 is provided with the following configuration.

[0074] 19 shows an example of the sine wave signal Ea and cosine wave signal Eb input to the signal processing unit 72. Each of the signals Ea and Eb fluctuates around a central value E0. Because the signals Ea and Eb are 90° out of phase with each other, when one of the signals Ea and Eb reaches the central value E0, the other reaches a maximum or minimum value. Specifically, when the cosine wave signal Eb reaches the central value E0, the sine wave signal Ea reaches a maximum value EaH or a minimum value EaL. Furthermore, when the sine wave signal Ea reaches the central value E0, the cosine wave signal Eb reaches a maximum value EbH or a minimum value EbL.

[0075] The amplitude A of the sine wave signal Ea is the amount of displacement from the center value E0 to the maximum value EaH or the minimum value EaL. The amplitude B of the cosine wave signal Eb is the amount of displacement from the center value E0 to the maximum value EbH or the minimum value EbL.

[0076] The signal processing unit 72 acquires amplitude values ​​A and B of the signals Ea and Eb. The signal processing unit 72 determines the timing for acquiring the amplitude value of one of the signals Ea and Eb based on the other. As shown in FIG. 19 , the amplitude estimation period Ta1 includes a timing when the sine wave signal Ea reaches a maximum value EaH. The amplitude estimation period Ta2 includes a timing when the sine wave signal Ea reaches a minimum value EaL. The signal processing unit 72 acquires the sine wave signal Ea at a timing within the amplitude estimation periods Ta1 and Ta2 as the amplitude value A of the sine wave signal Ea. The signal processing unit 72 determines whether the sine wave signal Ea is within each of the amplitude estimation periods Ta1 and Ta2 based on the cosine wave signal Eb.

[0077] Furthermore, the amplitude estimation period Tb1 includes a timing when the cosine wave signal Eb reaches a maximum value EbH. The amplitude estimation period Tb2 includes a timing when the cosine wave signal Eb reaches a minimum value EbL. The signal processing unit 72 acquires the cosine wave signal Eb at a timing within the amplitude estimation periods Tb1 and Tb2 as the amplitude value B of the cosine wave signal Eb. The signal processing unit 72 determines whether the cosine wave signal Eb is within each of the amplitude estimation periods Tb1 and Tb2 based on the sine wave signal Ea.

[0078] 20 , the processing performed by the AD converter 71 and the signal processing unit 72 will be described. The AD converter 71 receives the sine wave signal Ea and the cosine wave signal Eb from the receiving circuit 95. The AD converter 71 performs processing to set the center value E0 of each of the input voltage signals E1 and E2 to 0, and processing to obtain the absolute value of each of the voltage signals E1 and E2 with the center value E0 set to 0.

[0079] In the following, a case will be described in which one of the sine wave signal Ea and the cosine wave signal Eb is designated as the first voltage signal E1, and the other is designated as the second voltage signal E2, and the amplitude value of the first voltage signal E1 is acquired using the second voltage signal E2. In Figure 20, (a) shows the trends of the first voltage signal E1 and the peak hold value Ep of the first voltage signal E1, (b) shows the trends of the second voltage signal E2, (c) shows the trends of the trigger signal Sg, and (d) shows the trends of the amplitude value of the sampled first voltage signal E1. Note that, of the narrow receiving coil 110 and the wide receiving coil 120, the coil that detects the output voltage signal corresponding to the first voltage signal E1 corresponds to the "first receiving coil," and the coil that detects the output voltage signal corresponding to the second voltage signal E2 corresponds to the "second receiving coil."

[0080] A threshold value Eth (>0) is set for the second voltage signal E2. Based on a comparison between the threshold value Eth and the second voltage signal E2, the trigger signal Sg is set to ON or OFF. During the period in which the trigger signal Sg is set to ON, the first voltage signal E1 has a value at a timing within the amplitude estimation period T, and the peak hold value Ep is updated. During the period in which the trigger signal Sg is set to OFF, the first voltage signal E1 has a value at a timing outside the amplitude estimation period T, and updating of the peak hold value Ep is stopped.

[0081] For example, the threshold value Eth is determined based on the minimum possible value of the amplitude value of the second voltage signal E2. Specifically, the threshold value Eth is a value between 10% and 15% of the minimum possible value of the amplitude value of the second voltage signal E2, for example, 10% of the minimum possible value.

[0082] For example, when the second voltage signal E2 is a sine wave signal Ea, the minimum possible value of the amplitude of the second voltage signal E2 is the amplitude value when at least one of the amplitude deviation amount Kay shown in Fig. 14 and the amplitude deviation amount Kaz shown in Fig. 16 is maximum in the negative direction. Also, when the second voltage signal E2 is a cosine wave signal Eb, the minimum possible value of the amplitude of the second voltage signal E2 is the amplitude value when the amplitude deviation amount Kby shown in Fig. 14 is maximum in the negative direction.

[0083] When the amplitude value of the second voltage signal E2 is small, the influence of noise contained in the second voltage signal E2 is greater than when the amplitude value of the second voltage signal E2 is large. Therefore, according to this embodiment, the threshold value Eth can be set taking into consideration a situation in which the influence of noise contained in the second voltage signal E2 is greater. Therefore, the accuracy of determining whether or not to update the peak hold value Ep can be improved based on a comparison between the threshold value Eth and the second voltage signal E2.

[0084] At time t1, the signal processing unit 72 determines that the second voltage signal E2 acquired from the AD converter 71 is equal to or less than the threshold value Eth. In this case, the signal processing unit 72 resets the peak hold value Ep and sets the trigger signal Sg to ON. Here, the signal processing unit 72 sets the peak hold value Ep to the first voltage signal E1 currently acquired from the AD converter 71. When the trigger signal Sg is set to ON, the signal processing unit 72 starts updating the peak hold value Ep.

[0085] After time t1, the signal processing unit 72 acquires the first voltage signal E1 from the AD converter 71. The signal processing unit 72 performs a filtering process to remove noise contained in the acquired first voltage signal E1. For example, the filtering process is a moving average process.

[0086] The signal processing unit 72 holds the peak value of the first voltage signal E1 at a timing within the amplitude estimation period T. Specifically, when the signal processing unit 72 determines that the magnitude of the first voltage signal E1 after filtering has become greater than the currently held peak hold value Ep, the signal processing unit 72 sets the magnitude of the first voltage signal E1 after filtering as a new peak hold value Ep. When the signal processing unit 72 determines that the magnitude of the first voltage signal E1 after filtering is equal to or less than the currently held peak hold value Ep, the signal processing unit 72 maintains the current peak hold value Ep.

[0087] During the period from time t1 to time t2, the signal processing unit 72 performs the above-described processing, causing the peak hold value Ep to increase to the peak value (i.e., the amplitude value) of the first voltage signal E1 and then to be held at that peak value. As a result, the peak value of the first voltage signal E1 acquired at a timing within the amplitude estimation period T is held in the peak hold value Ep.

[0088] At time t2, the signal processing unit 72 determines that the second voltage signal E2 acquired from the AD converter 71 is higher than the threshold value Eth. In this case, the signal processing unit 72 sets the trigger signal Sg to OFF. When the signal processing unit 72 sets the trigger signal Sg to OFF, it stops updating the peak hold value Ep. In this case, the peak hold value Ep is held at the value at time t2.

[0089] The signal processing unit 72 also acquires the peak hold value Ep held at time t2 as the amplitude value of the first voltage signal E1. Note that during the period from when the updating of the peak hold value Ep starts until time t2, the peak hold value Ep may not be the peak value of the first voltage signal E1, and therefore the peak hold value Ep is not acquired as the amplitude value of the first voltage signal E1 during this period.

[0090] From time t3 onward, the signal processing unit 72 performs the same processing as that described for the period from time t1 to time t3. In FIG. 20 , the amplitude estimation period T includes the range from time t1 to time t2, as well as the range from time t3 to time t4, the range from time t5 to time t6, and the range from time t7 to time t8. At times t3, t5, and t7, the signal processing unit 72 resets the peak hold value Ep. At times t4, t6, and t8, the signal processing unit 72 acquires the peak hold values ​​Ep at times t4, t6, and t8 as the amplitude values ​​of the first voltage signal E1. This allows the value of the first voltage signal E1 at a specific timing in one cycle of the first voltage signal E1 to be acquired. The specific timing is the timing when a specific time has elapsed since the start of one cycle of the first voltage signal E1. In this embodiment, the specific timing is the timing when the first voltage signal E1 reaches its amplitude value.

[0091] 21 shows the procedure for the control executed by the arithmetic unit 70. This control is repeatedly executed at a predetermined control period. Here, the control for acquiring the amplitude values ​​A and B of the signals Ea and Eb and calculating the lateral load Fyc, vertical load Fzc, and rotation angle θc based on the acquired amplitude values ​​A and B will be described.

[0092] In step S10, the AD converter 71 acquires the sine wave signal Ea and the cosine wave signal Eb. In this embodiment, the AD converter 71 receives the signals Ea and Eb from the receiving circuit 95. The AD converter 71 performs two processes on the received signals Ea and Eb: setting a center value E0 (specifically, the time average value of each signal Ea and Eb over one period) to zero, and calculating the absolute values ​​of the signals E1 and E2 whose center value E0 has been set to zero.

[0093] In this embodiment, the signal processing unit 72 executes the processes of steps S11 to S20 in parallel for the following two patterns regarding the combination of the first voltage signal E1 and the second voltage signal E2. Pattern 1 is a case where the sine wave signal Ea is the first voltage signal E1 and the cosine wave signal Eb is the second voltage signal E2. Pattern 2 is a case where the cosine wave signal Eb is the first voltage signal E1 and the sine wave signal Ea is the second voltage signal E2.

[0094] In step S11, the signal processing unit 72 determines whether or not to start updating the peak hold value Ep based on the second voltage signal E2 acquired from the AD converter 71. This determination process can be performed, for example, by comparing the magnitude of the acquired second voltage signal E2 with the threshold value Eth.

[0095] In the process of step S11, the signal processing unit 72 may make a positive determination in the process of step S11 by continuously determining that the magnitude of the acquired second voltage signal E2 is equal to or less than the threshold value Eth in multiple consecutive control cycles, thereby making it possible to prevent erroneous determinations in the process of step S11 caused by noise contained in the second voltage signal E2.

[0096] On the other hand, if the signal processor 72 determines not to start updating the peak hold value Ep, the process proceeds to step S12. In step S12, the signal processor 72 maintains the amplitude value of the first voltage signal E1 at the value in the previous control cycle.

[0097] If the determination in step S11 is affirmative, the process proceeds to step S13, in which the signal processing unit 72 resets the peak hold value Ep.

[0098] In step S14, the signal processor 72 sets the trigger signal Sg to ON. In step S15, the signal processor 72 acquires the first voltage signal E1 during the period in which the trigger signal Sg is ON.

[0099] In step S16, the signal processing unit 72 performs a filtering process on the acquired first voltage signal E1. The process in step S16 corresponds to the "filtering unit."

[0100] In step S17, the signal processing unit 72 updates the peak hold value Ep. As a result, the peak value of the magnitude of the first voltage signal E1 is held in the peak hold value Ep. The processes in steps S13 and S17 correspond to the "peak hold unit."

[0101] In this embodiment, as described above, the signal processing unit 72 updates the peak hold value Ep based on a comparison of the magnitude of the filtered first voltage signal E1 with the currently held peak hold value Ep. This prevents the signal processing unit 72 from becoming overloaded even if the comparison of the magnitude of the acquired first voltage signal E1 with the peak hold value Ep continues in a situation where, for example, rotation of the rotor 30 has stopped and no periodic changes occur in the amplitude of the output voltage signals of the receiver coils 110 and 120. This reduces the processing load on the signal processing unit 72.

[0102] In step S18, the signal processing unit 72 determines whether or not to stop updating the peak hold value Ep based on the second voltage signal E2 acquired from the AD converter 71. This determination process can be performed, for example, by comparing the magnitude of the acquired second voltage signal E2 with the threshold value Eth.

[0103] If the determination in step S18 is negative, the processes in steps S15 to S17 are executed again. On the other hand, if the determination in step S18 is positive, the process proceeds to step S19.

[0104] In the process of step S18, the signal processing unit 72 may make a positive determination in the process of step S18 by repeatedly determining that the magnitude of the acquired second voltage signal E2 is greater than the threshold value Eth, thereby making it possible to prevent erroneous determinations in the process of step S18 caused by noise contained in the second voltage signal E2.

[0105] In step S19, the signal processing unit 72 acquires the peak hold value Ep held at the timing when the affirmative determination is made in the processing of step S18 as the amplitude value of the first voltage signal E1. Note that in this embodiment, the amplitude value of the first voltage signal E1 corresponds to the "sampling value," and the processing of step S19 corresponds to the "sampling unit."

[0106] In step S20, the signal processing unit 72 sets the trigger signal Sg to OFF. When the trigger signal Sg is set to OFF, updating of the peak hold value Ep is stopped. This makes it possible to suppress the influence of noise on the peak hold value Ep.

[0107] After the processing of steps S12 and S20, the process proceeds to step S21. In step S21, the displacement amount calculation unit 73 calculates the axial displacement ΔY and the vertical displacement ΔZ based on the calculated amplitude values ​​A and B of each of the signals Ea and Eb. The force calculation unit 74 calculates the lateral load Fyc based on the calculated axial displacement ΔY, and calculates the vertical load Fzc based on the calculated vertical displacement ΔZ. The normalization unit 75 normalizes each of the signals Ea and Eb based on the calculated amplitude values ​​A and B and the acquired signals Ea and Eb. The rotation angle calculation unit 76 calculates the rotation angle θc based on the normalized signals Ean and Ebn.

[0108] According to the present embodiment described above, the following effects can be achieved.

[0109] The sampling timing for acquiring the amplitude value of the first voltage signal E1 is determined based on the second voltage signal E2. The first voltage signal E1 at the determined sampling timing is acquired as the amplitude value of the first voltage signal E1. In this case, it is possible to acquire the amplitude value of the first voltage signal E1 while suppressing the influence of changes in the signals E1 and E2 caused by the rotation of the rotor 30. Therefore, it is possible to improve the accuracy of calculating the axial displacement ΔY, the vertical displacement ΔZ, the lateral load Fyc, the vertical load Fzc, and the rotation angle θc based on the acquired amplitude value of the first voltage signal E1.

[0110] A peak hold value Ep, which is the peak value of the first voltage signal E1 at a timing within the amplitude estimation period T, is acquired based on the second voltage signal E2, and the peak hold value Ep is reset for each cycle of the absolute value of the first voltage signal E1. This makes it possible to appropriately acquire the amplitude value of the first voltage signal E1 in a situation where the first voltage signal E1 changes each time due to the application of the lateral load Fy and the vertical load Fz. The amplitude value of the first voltage signal E1 is highly sensitive to changes in the first voltage signal E1. Therefore, the acquired amplitude value of the first voltage signal E1 can be used to improve the accuracy of calculating the axial displacement ΔY, the vertical displacement ΔZ, the lateral load Fyc, the vertical load Fzc, and the rotation angle θc.

[0111] When the magnitude of the second voltage signal E2 is determined to be equal to or less than the threshold value Eth, the peak hold value Ep is reset. When the magnitude of the second voltage signal E2 is determined to be higher than the threshold value Eth, the retained peak hold value Ep is acquired as the amplitude value of the first voltage signal E1. In this case, by setting the threshold value Eth to as small a value as possible, the sampling timing of the amplitude value of the first voltage signal E1 can be narrowed. This effectively suppresses the influence of noise on the process of acquiring the amplitude value of the first voltage signal E1. Furthermore, by setting the threshold value Eth to as small a value as possible, it is possible to reliably perform a magnitude comparison between the second voltage signal E2 and the threshold value Eth even if the amplitude value of the second voltage signal E2 decreases.

[0112] Of the sine wave signal Ea and the cosine wave signal Eb, which are out of phase with each other by 90°, one is designated as the first voltage signal E1, and the other is designated as the second voltage signal E2. As a result, the first voltage signal E1 has an amplitude value at the timing when the second voltage signal E2 has a center value E0. Therefore, a configuration suitable for setting the threshold value Eth to a small value can be realized.

[0113] When it is determined that the magnitude of the second voltage signal E2 is equal to or less than the threshold value Eth, the peak hold value Ep is reset. In this configuration, the peak hold value Ep is reset during the period from when the magnitude of the second voltage signal E2 reaches its maximum until the magnitude of the second voltage signal E2 reaches its next maximum. In this case, the peak hold value Ep is reset for each cycle of the absolute value of the first voltage signal E1. Therefore, a configuration suitable for suppressing noise from being included in the peak hold value Ep can be realized.

[0114] When it is determined that the magnitude of the second voltage signal E2 is higher than the threshold value Eth, the held peak hold value Ep is acquired as the amplitude value of the first voltage signal E1. In this configuration, the amplitude value of the first voltage signal E1 is acquired during the period from when the peak hold value Ep is reset until the magnitude of the second voltage signal E2 reaches its maximum. In this case, the amplitude value of the first voltage signal E1 used in the calculation is updated every cycle of the absolute value of the first voltage signal E1. This allows the sampling interval of the first voltage signal E1 to be shortened. As a result, a configuration suitable for acquiring the amplitude value of the first voltage signal E1 can be realized.

[0115] The first voltage signal E1 acquired at a timing within the amplitude estimation period T is filtered, and the filtered first voltage signal E1 is used to update the peak hold value Ep. This makes it possible to prevent noise contained in the acquired first voltage signal E1 from adversely affecting the peak hold value Ep. Therefore, a configuration suitable for calculating the amplitude value of the first voltage signal E1 can be realized.

[0116] Second Embodiment The second embodiment will be described below with reference to the drawings, focusing on differences from the first embodiment. In this embodiment, as shown in FIG. 22 , a detection unit 190 is added. The detection unit 190 calculates the force acting between the ground contact patch GL and the wheel in the vehicle length direction of the vehicle (hereinafter referred to as the longitudinal load Fx) instead of the vertical load Fz. The direction in which the lateral load Fy acts is perpendicular to the direction in which the longitudinal load Fx acts. The longitudinal load Fx is used by the control device to control the running of the vehicle.

[0117] In the following description, the detection unit 90 will be referred to as the "first detection unit 90," and the detection unit 190 will be referred to as the "second detection unit 190." In addition, the components of the first detection unit 90 will be referred to as the "first substrate 91," the "first coil portion 92," and the "first circuit portion 93."

[0118] The second detection unit 190 includes a second substrate 191, a second coil section 192, and a second circuit section 193. The second coil section 192 formed on the second substrate 191 is disposed across a horizontal axis HL passing through the central axis LCi of the inner ring 52 (the rotation center of the target rotor 80). Like the first coil section 92, the second coil section 192 includes an excitation coil, a narrow receiving coil, and a wide receiving coil. For example, in a plan view of the flat surface of the target rotor 80, the second substrate 191 is disposed so that the circumferential central axis Lt of each coil of the second coil section 192 coincides with the horizontal axis HL.

[0119] Each coil of the second coil section 192 is provided near the vehicle front end or the vehicle rear end of both ends in the vehicle length direction of the target rotor 80. Below, an example will be described in which each coil of the second coil section 192 is provided at the vehicle front end.

[0120] When the vehicle accelerates, the longitudinal load Fx is assumed to be positive, and when the vehicle decelerates, the longitudinal load Fx is assumed to be negative. When the longitudinal load Fx is positive, the shielding portion 81 is displaced toward the vehicle traveling direction. This state corresponds to the state in the first embodiment in which the upward vertical load Fz acting on the wheel increases. On the other hand, when the longitudinal load Fx is negative, the shielding portion 81 is displaced toward the side opposite the vehicle traveling direction. This state corresponds to the state in the first embodiment in which the downward vertical load Fz acting on the wheel increases. When the longitudinal load Fx acts on the wheel, the amplitude of the output voltage signal in each receiving coil of the second coil portion 192 changes.

[0121] The displacement amount calculation unit 73 is capable of calculating the longitudinal displacement ΔX of the target rotor 80 and the axial displacement ΔY of the target rotor 80 based on the change in amplitude of the output voltage signal in each receiving coil of the second coil unit 192. Furthermore, the force calculation unit 74 is capable of calculating the longitudinal load Fxc based on the calculated longitudinal displacement ΔX.

[0122] The second circuit unit 193 includes an excitation circuit and a receiving circuit, similar to the first circuit unit 93. The receiving circuit of the second circuit unit 193 is electrically connected to the arithmetic device 70. The second circuit unit 193 may be provided on an IC chip separate from the IC chip on which the first circuit unit 93 is provided, or may be provided on the same IC chip as the first circuit unit 93.

[0123] Similar to the receiving circuit 95 of the first circuit section 93, the receiving circuit of the second circuit section 193 generates a sine wave signal based on the output voltage signal of the wide receiving coil of the second coil section 192, and generates a cosine wave signal based on the output voltage signal of the narrow receiving coil of the second coil section 192.

[0124] The AD converter 71 receives the sine wave signal Ea and the cosine wave signal Eb from the receiving circuit 95 of the first circuit unit 93, and also receives the sine wave signal Eb from the receiving circuit of the second circuit unit 193. Hereinafter, the sine wave signal Ea and the cosine wave signal Eb input from the receiving circuit 95 of the first circuit unit 93 will be referred to as the "first sine wave signal" and the "first cosine wave signal," and the sine wave signal and the cosine wave signal input from the receiving circuit of the second circuit unit 193 will be referred to as the "second sine wave signal" and the "second cosine wave signal."

[0125] Here, an excitation voltage is supplied to the excitation circuit of each circuit unit 93, 193, and a wide receiving coil and a narrow receiving coil are provided in each circuit unit 93, 193 so that the first and second sine wave signals are signals of the same phase, the first and second cosine wave signals are signals of the same phase, and the first and second sine wave signals and the first and second cosine wave signals are signals that are 90° out of phase with each other.

[0126] For example, the signal processing unit 72 executes the processes of steps S11 to S20 in FIG. 21 in parallel for the following four patterns relating to the combination of the first voltage signal E1 and the second voltage signal E2. Pattern 1 is a case where the first sine wave signal is the first voltage signal E1 and the second cosine wave signal is the second voltage signal E2. Pattern 2 is a case where the second cosine wave signal is the first voltage signal E1 and the first sine wave signal is the second voltage signal E2. Pattern 3 is a case where the first cosine wave signal is the first voltage signal E1 and the second sine wave signal is the second voltage signal E2. Pattern 4 is a case where the second sine wave signal is the first voltage signal E1 and the first cosine wave signal is the second voltage signal E2.

[0127] In step S21, the displacement amount calculation unit 73 calculates the longitudinal displacement ΔX, the axial displacement ΔY, and the vertical displacement ΔZ based on the calculated amplitude values ​​of the first and second sine wave signals and the first and second cosine wave signals. The force calculation unit 74 calculates the longitudinal load Fxc based on the calculated longitudinal displacement ΔX, calculates the lateral load Fyc based on the calculated axial displacement ΔY, and calculates the vertical load Fzc based on the calculated vertical displacement ΔZ. The normalization unit 75 and the rotation angle calculation unit 76 calculate the rotation angle θc, as in the first embodiment. At this time, the calculated amplitude values ​​of the first and second sine wave signals and the first and second cosine wave signals are used.

[0128] In this embodiment, the wide receiving coil of the first coil section 92 that outputs the first sine wave signal and the narrow receiving coil of the second coil section 192 that outputs the second cosine wave signal are spaced apart from each other in the circumferential direction and are provided at positions facing the target rotor 80. Furthermore, the wide receiving coil of the second coil section 192 that outputs the second sine wave signal and the narrow receiving coil of the first coil section 92 that outputs the first cosine wave signal are spaced apart from each other in the circumferential direction and are provided at positions facing the target rotor 80.

[0129] In the combination of the receiving coils that output the signals E1 and E2 described above, the receiving coils that output the signals E1 and E2 are positioned farther apart in the circumferential direction than in the first embodiment. In this case, noise caused by factors such as disturbances to the flux linkage due to energization of the excitation coil is prevented from being simultaneously included in both signals E1 and E2. Therefore, the adverse effects of noise on the process of acquiring the amplitude value of the first voltage signal E1 can be reliably prevented.

[0130] Third Embodiment A third embodiment will be described below with reference to the drawings, focusing on differences from the first embodiment. In this embodiment, a process of correcting the amplitude value of the acquired first voltage signal E1 is added to the control performed by the calculation device 70.

[0131] FIG. 23 shows the control processing procedure executed by the arithmetic unit 70.

[0132] After the process of step S19, the process proceeds to step S30. In step S30, the signal processing unit 72 corrects the amplitude value of the acquired first voltage signal E1 for an error that occurs as the wheel rotates. For example, the signal processing unit 72 corrects the amplitude value of the acquired first voltage signal E1 based on an error measured in advance before shipping the vehicle. For example, in the configuration shown in FIG. 2, it is possible to measure the error in advance based on 16 amplitude values ​​that can be obtained when the wheel rotates once (i.e., rotates 360° mechanically). Note that the error may be measured while the vehicle is running after shipping the vehicle. The process of step S30 corresponds to the "correction unit."

[0133] According to this embodiment, the amplitude value of the first voltage signal E1 can be corrected in consideration of errors that occur as the wheel rotates, thereby improving the accuracy of calculation of the amplitude value of the first voltage signal E1.

[0134] Other Embodiments The above-described embodiments may be modified as follows.

[0135] The shape of the target rotor may be changed from a configuration in which the shielding portions and the notches are alternately formed in the circumferential direction.

[0136] 24 , the target rotor 180 may have recesses 181 and protrusions 182 formed alternately in the circumferential direction in a portion of the flat plate portion 33 of the in-wheel motor 20 that faces the coil portion 92 in the axial direction. The protrusions 182 and recesses 181 form a circular "detection target portion."

[0137] 25 , the target rotor 280 may be configured to include an annular ring portion 281 and a plurality of shielding portions 282. The shielding portions 282 may protrude radially inward from the ring portion 281 and be arranged side by side in the circumferential direction. A notch 283 may be formed between adjacent shielding portions 282 in the circumferential direction. The shielding portions 282 and the notch portions 283 form an annular "detection target portion."

[0138] 26 , a target rotor 380 may be configured such that shielding portions 381 and openings 382 penetrating the target rotor 380 are alternately provided in the circumferential direction. The shielding portions 381 and the openings 382 form a circular "detection target portion."

[0139] For example, in the target rotor, non-metallic portions such as synthetic resin may be provided in the notches or openings, so that metallic portions and non-metallic portions are provided alternately in the circumferential direction.

[0140] The wide receiver coil and the narrow receiver coil may have a phase relationship in which the phase difference between their output voltage signals is a value other than 90°. The wide receiver coil and the narrow receiver coil may also have a phase relationship in which their output voltage signals are in phase. The processes of steps S11 to S20 in Figures 21 and 23 can be performed on each of the signals E1 and E2 having the above-described phase relationship.

[0141] In the second embodiment, the combination of the first voltage signal E1 and the second voltage signal E2 can be changed. For example, the first sine wave signal may be the first voltage signal E1 and the second sine wave signal may be the second voltage signal E2, or the first cosine wave signal may be the first voltage signal E1 and the second cosine wave signal may be the second voltage signal E2. Even in this case, it is possible to execute the processes of steps S11 to S20 in FIGS. 21 and 23.

[0142] In the previous FIGS. 21 and 23, the process of step S16 does not need to be performed.

[0143] 21 and 23, it is not necessary to perform the process of setting the center value E0 of each signal E1, E2 to 0 and the process of calculating the absolute value of each signal E1, E2 with the center value E0 set to 0. In this case, for example, the processes of steps S11 and S18 may be performed based on a comparison of the magnitude of the second voltage signal E2 with the threshold value Eth. This makes it possible to perform the process of resetting the peak hold value Ep and the process of obtaining the amplitude value for each cycle of the first voltage signal E1.

[0144] Alternatively, for example, a threshold value higher than the central value E0 of the second voltage signal E2 and a threshold value lower than the central value E0 of the second voltage signal E2 may be set as the threshold value of the second voltage signal E2, and the processes of steps S11 and S18 may be performed. This makes it possible to perform the reset process of the peak hold value Ep and the acquisition process of the amplitude value for each cycle that is the same as one cycle of the absolute value of the first voltage signal E1.

[0145] In the first embodiment, in the process of step S16 in FIGS. 21 and 23 , the signal processing unit 72 only needs to calculate at least one of the displacements ΔY and ΔZ, the lateral load Fyc, the vertical load Fzc, and the rotation angle θc. In this case, for example, the signal processing unit 72 does not need to calculate the rotation angle θc among the displacements ΔY and ΔZ, the lateral load Fyc, the vertical load Fzc, and the rotation angle θc. Alternatively, for example, the signal processing unit 72 may calculate only one of the displacements ΔY and ΔZ and calculate the force corresponding to the calculated displacement. Alternatively, for example, the signal processing unit 72 may directly calculate the lateral load Fyc and the vertical load Fzc based on the amplitude values ​​A and B of the signals Ea and Eb without calculating the displacements ΔY and ΔZ.

[0146] In the second embodiment, similarly to the case described above, in the processing of step S16 in FIGS. 21 and 23, the signal processing unit 72 only needs to calculate at least one of the displacements ΔX, ΔY, ΔZ, the longitudinal load Fxc, the lateral load Fyc, the vertical load Fzc, and the rotation angle θc.

[0147] The processing of step S13 in the previous Figures 21 and 23 does not have to be performed for every cycle of the absolute value of the first voltage signal E1, but may be performed every M cycles of the first voltage signal E1 (M is an integer of 2 or more) or every M cycles of the absolute value of the first voltage signal E1.

[0148] The processing of step S19 in the previous Figures 21 and 23 does not have to be performed for every cycle of the absolute value of the first voltage signal E1, but may be performed every N cycles of the first voltage signal E1 (N is an integer of 2 or more) or every N cycles of the absolute value of the first voltage signal E1.

[0149] In each of the above embodiments, configurations corresponding to the shielding portion and notch may be formed on the stator base 42 side rather than on the wheel 10 side, and the detection unit may be fixed to the wheel 10 side rather than on the stator base 42 side, with the shielding portion and notch facing the detection unit. In this case, when a force acts on the wheel, each receiving coil of the detection unit fixed to the wheel 10 side is displaced relative to the shielding portion and notch formed on the stator base 42 side. In this embodiment, each receiving coil of the detection unit corresponds to a "first sensor unit," and the shielding portion and notch formed on the stator base 42 side correspond to a "second sensor unit."

[0150] The signal processing unit 72 may determine a specific timing for acquiring a value other than the amplitude value of the first voltage signal E1 based on the second voltage signal E2, and acquire the first voltage signal at the determined specific timing as a sampled value. In this case, the specific timing may occur every R / 2 cycles (R is a positive integer) or every R cycles of the first voltage signal E1.

[0151] The signal processing unit 72 does not have to determine the specific timing for acquiring the sampled value of the first voltage signal E1 based on the second voltage signal E2. For example, the signal processing unit 72 may acquire the first voltage signal E1 as a sampled value at a timing when a predetermined time has elapsed from a reference timing of the first voltage signal E1 every R / 2 cycles (R is a positive integer) or every R cycles of the first voltage signal E1. The reference timing is, for example, the timing when the first voltage signal E1 reaches its center value E0. Even in this case, it is possible to acquire the value at a specific timing in one cycle of the first voltage signal E1 as a sampled value, for example, when the rotation speed of the rotating body is stable and the cycle of the first voltage signal E1 does not change significantly.

[0152] In this regard, in each of the above embodiments in which the specific timing for obtaining the sampling value of the first voltage signal E1 is determined based on the second voltage signal E2, the specific timing is determined based on the relative relationship between the first voltage signal E1 and the second voltage signal E2, so that even in a situation in which the period of the first voltage signal E1 may change significantly, the value of the specific timing in one period of the first voltage signal E1 can be accurately obtained.

[0153] The receiving circuit 95 does not need to generate the sine wave signal Ea and the cosine wave signal Eb, which are envelopes of the output voltage signals of the receiving coils 110 and 120 .

[0154] For example, the receiving circuit 95 may output the output voltage signals of the receiving coils 110 and 120 to the AD converter 71 instead of the sine wave signal Ea and the cosine wave signal Eb. The AD converter 71 may convert the input output voltage signals of the receiving coils 110 and 120 from analog signals to digital signals. The signal processing unit 72 may perform peak hold value updating processing on the output voltage signals of the receiving coils 110 and 120 acquired from the AD converter 71. The signal processing unit 72 may determine the timing for acquiring the peak hold value held for one of the output voltage signals of the receiving coils 110 and 120 as an amplitude value based on the peak hold value held for the other output voltage signal. Even in this case, it is possible to acquire the amplitude value A of the sine wave signal Ea and the amplitude value B of the cosine wave signal Eb, and it is possible to calculate the displacements ΔY and ΔZ and the loads Fyc and Fzc based on the acquired amplitude values ​​A and B.

[0155] The motor is not limited to one housed in a wheel, but may be, for example, an on-board motor mounted on the vehicle body. In this case, the wheel sensor may be applied to the wheels (drive and driven wheels) of the vehicle equipped with the on-board motor. Furthermore, the motor is not limited to an outer rotor type, but may be an inner rotor type.

[0156] The application of the rotating body sensor is not limited to vehicle wheels, but can be applied to any machine equipped with a rotating body, such as an aircraft propeller, a ship's screw, a rotating member of an internal combustion engine (e.g., a crankshaft), or a power generation turbine, etc. Furthermore, the rotating body is not limited to being used with its axial direction in the horizontal direction, but may also be used with its axial direction in a direction other than the horizontal direction (e.g., up and down).

[0157] The control unit and the method described herein may be implemented by a special-purpose computer configured by configuring a processor and memory programmed to perform one or more functions embodied in a computer program. Alternatively, the control unit and the method described herein may be implemented by a special-purpose computer configured by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described herein may be implemented by one or more special-purpose computers configured by combining a processor and memory programmed to perform one or more functions with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory tangible storage medium.

[0158] The following describes characteristic configurations extracted from the above-described embodiments. [Configuration 1] In a computing device (70) applicable to a sensor for a rotating body, the computing device (70) includes: a first sensor unit fixed to a rotating body (10, 20) and rotating in association with the rotation of the rotating body around a rotation center axis extending in a predetermined axial direction; a second sensor unit fixed to a base unit (42) and provided at a position facing the first sensor unit in the axial direction; and an excitation coil (100) to which an AC excitation voltage is supplied; one of the first sensor unit and the second sensor unit is a detection target unit (81, 82, 181, 182, 282, 283, 381, 382) that forms an annular shape centered on the rotation center axis; and the other of the first sensor unit and the second sensor unit is a receiving coil (110, 120) that outputs an AC voltage signal that changes in response to a relative displacement between itself and the detection target unit facing itself when the excitation voltage is supplied to the excitation coil; a first receiving coil that outputs a first voltage signal, and a second receiving coil that outputs a second voltage signal having a predetermined phase relationship with the first voltage signal, a sampling unit that acquires a sampled value that is the first voltage signal at a timing based on the second voltage signal, and a calculation unit that calculates at least one of a force acting on the rotating body, a relative displacement of the first sensor unit with respect to the second sensor unit, and a rotation angle of the rotating body based on the acquired sampled value. [Configuration 2] The computing device according to Configuration 1, further comprising: a peak hold unit that holds a peak value of the first voltage signal, wherein the sampling unit acquires the peak value held by the peak hold unit as the sampled value, and the peak hold unit resets the held peak value every M periods (M is a positive integer) of an envelope of the first voltage signal or every M periods of an absolute value of the envelope, based on the second voltage signal.[Configuration 3] The arithmetic device according to Configuration 2, wherein the period of the first voltage signal is the same as the period of the second voltage signal, the first voltage signal is out of phase with the second voltage signal, and the peak hold unit resets the held peak value during a period from when the amount of displacement of the second voltage signal from the center value of fluctuation reaches a maximum until the next maximum amount of displacement of the second voltage signal from the center value of fluctuation. [Configuration 4] The arithmetic device according to Configuration 3, wherein the sampling unit acquires, as the sampled value, the peak value held by the peak hold unit during a period from when the peak value is reset by the peak hold unit to when the amount of displacement of the second voltage signal from the center value of fluctuation reaches a maximum. [Configuration 5] The arithmetic device according to Configuration 4, wherein the peak hold unit resets the held peak value when the amount of displacement of the second voltage signal from the center value of fluctuation falls below a threshold, and the sampling unit acquires, as the sampled value, the peak value held by the peak hold unit when the amount of displacement of the second voltage signal from the center value of fluctuation becomes greater than the threshold. [Configuration 6] The arithmetic device according to configuration 1, wherein the timing occurs every R / 2 periods (R is a positive integer) or every R periods of the envelope of the first voltage signal.[Configuration 7] A computing device (70) applicable to a sensor for a rotating body, comprising: a first sensor unit fixed to a rotating body (10, 20) and rotating in association with the rotation of the rotating body around a rotation center axis extending in a predetermined axial direction; a second sensor unit fixed to a base unit (42) and provided at a position facing the first sensor unit in the axial direction; and an excitation coil (100) to which an AC excitation voltage is supplied, wherein one of the first sensor unit and the second sensor unit is a detection target unit (81, 82, 181, 182, 282, 283, 381, 382) that forms an annular shape centered on the rotation center axis, and the other of the first sensor unit and the second sensor unit is a receiving coil (110, 120) that outputs an AC voltage signal that changes in response to a relative displacement between itself and the detection target unit facing itself when the excitation voltage is supplied to the excitation coil, A computing device comprising: a sampling unit that acquires sampled values, which are the voltage signal at timings that appear every R / 2 cycles (R is a positive integer) or every R cycles of an envelope of a voltage signal output from the receiving coil; and a calculation unit that calculates at least one of a force acting on the rotating body, a relative displacement of the first sensor unit with respect to the second sensor unit, and a rotation angle of the rotating body based on the acquired sampled values. [Configuration 8] The computing device according to any one of configurations 2 to 5, wherein the peak hold unit has a filter unit that performs filtering to remove noise contained in the input first voltage signal, and holds a peak value of the first voltage signal after the filtering. [Configuration 9] The computing device according to any one of configurations 1 to 8, further comprising a correction unit that corrects an error that occurs with rotation of the rotating body with respect to the calculated sampled values. [Configuration 10] The computing device according to any one of configurations 1 to 5, wherein the first receiving coil and the second receiving coil are spaced apart from each other in a circumferential direction extending circumferentially around the central axis of rotation.

[0159] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A computing device (70) for use in a sensor for a rotating body, the computing device (70) comprising: a first sensor unit fixed to a rotating body (10, 20) and rotating in association with the rotation of the rotating body about a central axis of rotation extending in a predetermined axial direction; a second sensor unit fixed to a base unit (42) and provided at a position facing the first sensor unit in the axial direction; and an excitation coil (100) to which an AC excitation voltage is supplied; wherein one of the first sensor unit and the second sensor unit is a detection target unit (81, 82, 181, 182, 282, 283, 381, 382) forming a circular ring shape centered on the central axis of rotation, and the other of the first sensor unit and the second sensor unit is a receiving coil (110, 120) that outputs an AC voltage signal that changes in response to the relative displacement of the detection target unit facing it when the excitation voltage is supplied to the excitation coil; and the sensor for a rotating body comprises, as the receiving coil:

1. An arithmetic device comprising: a first receiving coil that outputs a first voltage signal; and a second receiving coil that outputs a second voltage signal having a predetermined phase relationship with the first voltage signal; a sampling unit that acquires a sampling value that is the first voltage signal at a timing based on the second voltage signal; and a calculation unit that calculates at least one of a force acting on the rotating body, a relative displacement of the first sensor unit with respect to the second sensor unit, and a rotation angle of the rotating body based on the acquired sampling value.

2. The arithmetic device according to claim 1, further comprising a peak hold unit which holds a peak value of the first voltage signal, wherein the sampling unit acquires the peak value held by the peak hold unit as the sampling value, and wherein the peak hold unit resets the held peak value every M periods (M is a positive integer) of an envelope of the first voltage signal or every M periods of the absolute value of the envelope based on the second voltage signal.

3. The arithmetic device of claim 2, wherein the period of the first voltage signal is the same as the period of the second voltage signal, the first voltage signal is out of phase with the second voltage signal, and the peak hold unit resets the held peak value during the period from when the displacement of the second voltage signal from the center value of fluctuation becomes maximum until when the displacement of the second voltage signal from the center value of fluctuation becomes maximum again.

4. The computing device described in claim 3, wherein the sampling unit acquires as the sampling value the peak value held by the peak hold unit during the period from when the peak value is reset by the peak hold unit to when the amount of displacement from the center value of fluctuation of the second voltage signal becomes maximum.

5. The arithmetic device according to claim 4, wherein the peak hold unit resets the held peak value when the amount of displacement from the center value of fluctuation of the second voltage signal becomes equal to or less than a threshold value, and the sampling unit acquires the peak value held by the peak hold unit as the sampling value when the amount of displacement from the center value of fluctuation of the second voltage signal becomes greater than the threshold value.

6. The arithmetic device according to claim 1, wherein the timing occurs every R / 2 periods (R is a positive integer) or every R periods of the envelope of the first voltage signal.

7. A computing device (70) applied to a sensor for a rotating body, comprising: a first sensor unit fixed to a rotating body (10, 20) and rotating with the rotation of the rotating body around a central axis of rotation extending in a predetermined axial direction; a second sensor unit fixed to a base unit (42) and provided at a position facing the first sensor unit in the axial direction; and an excitation coil (100) to which an AC excitation voltage is supplied, wherein one of the first sensor unit and the second sensor unit is a detection target unit (81, 82, 181, 182, 282, 283, 381, 382) forming a circular ring shape centered on the central axis of rotation, and the other of the first sensor unit and the second sensor unit is a receiving coil (110, 120) that outputs an AC voltage signal that changes in response to the relative displacement of the detection target unit facing it when the excitation voltage is supplied to the excitation coil, A computing device comprising: a sampling unit that acquires sampling values, which are the voltage signal at timings that appear every R / 2 periods (R is a positive integer) or every R periods of an envelope of a voltage signal output from the receiving coil; and a calculation unit that calculates at least one of a force acting on the rotating body, a relative displacement of the first sensor unit with respect to the second sensor unit, and a rotation angle of the rotating body based on the acquired sampling values.

8. The arithmetic device according to any one of claims 2 to 5, wherein the peak hold unit has a filter unit that performs filtering to remove noise contained in the input first voltage signal, and holds the peak value of the first voltage signal after filtering.

9. The computing device according to any one of claims 1 to 7, further comprising a correction section that corrects an error that occurs with the rotation of the rotating body with respect to the calculated sampling value.

10. A computing device according to any one of claims 1 to 5, wherein the first receiving coil and the second receiving coil are spaced apart from each other in a circumferential direction extending circumferentially around the central axis of rotation.

11. A program applied to a sensor for a rotating body including a first sensor unit fixed to a rotating body (10, 20) and rotating with the rotation of the rotating body around a rotation center axis extending in a predetermined axial direction, a second sensor unit fixed to a base unit (42) and provided at a position facing the first sensor unit in the axial direction, and an excitation coil (100) to which an AC excitation voltage is supplied, wherein one of the first sensor unit and the second sensor unit is a detection target unit (81, 82, 181, 182, 282, 283, 381, 382) forming a circular ring shape centered on the rotation center axis, and the other of the first sensor unit and the second sensor unit is a receiving coil (110, 120) that outputs an AC voltage signal that changes in response to the relative displacement of the detection target unit facing it when the excitation voltage is supplied to the excitation coil, and the sensor for a rotating body includes, as the receiving coil: A program comprising: a first receiving coil that outputs a first voltage signal; and a second receiving coil that outputs a second voltage signal having a predetermined phase relationship with the first voltage signal, the program causing a computer (70) to execute: a sampling process that acquires a sampling value that is the first voltage signal at a timing based on the second voltage signal; and a calculation process that calculates at least one of a force acting on the rotating body, a relative displacement of the first sensor unit with respect to the second sensor unit, and a rotation angle of the rotating body based on the acquired sampling value.

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