Motor failure detection device and motor failure detection method

Abstract

One aspect of the present disclosure is a failure detection device for a motor. The failure detection device for a motor comprises an axial displacement detection unit and a failure detection unit. On the basis of signals from a plurality of magnetic sensors that are provided along the circumference of a sensor unit that detects magnetism from a magnet that rotates with the rotary shaft of the motor, the axial displacement detection unit detects an axial displacement that is the displacement between the rotary shaft and the center of a circle that passes through the plurality of magnetic sensors, and the failure detection unit detects failure of the motor on the basis of the detected axial displacement.

Description

[Technical Field]

[0001] This disclosure relates to a motor fault detection device and a motor fault detection method. [Background technology]

[0002] Conventionally, brushless DC motors have been equipped with sensors that detect the angle of the rotating shaft, which is necessary for driving. For example, a motor is used that has a sensor section in which a flat plate magnet attached to the rotating shaft and multiple magnetic sensors, such as Hall elements, are arranged opposite it to detect changes in the magnetic field due to the switching of the magnet's north and south poles. These multiple magnetic sensors in the sensor section are arranged at equal intervals on the circumference surrounding the rotating shaft and each outputs a signal corresponding to the change in the magnetic field. Based on these signals, the rotation speed and other parameters can be calculated.

[0003] If there is a misalignment between the centers of these multiple magnetic sensors and the center of the rotation axis, errors will occur in detecting rotational speed and other parameters, making it difficult to drive the motor. Therefore, a device has been proposed to detect axial misalignment, which is the misalignment between the centers of the multiple magnetic sensors and the center of the rotation axis (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6438176 [Overview of the project] [Problems that the invention aims to solve]

[0005] In the conventional technology described above, a first group of Hall elements and a second group of Hall elements, each consisting of three Hall elements, are arranged in the sensor unit, and axial misalignment is detected based on the signals from the first group of Hall elements and the second group of Hall elements. As a result, the configuration of the sensor unit becomes complex, making it difficult to detect axial misalignment.

[0006] The present disclosure provides a technique for simplifying the detection of shaft misalignment in a brushless DC motor.

Means for Solving the Problems

[0007] A motor failure detection device according to an aspect of the present disclosure includes a shaft misalignment detection unit that detects a misalignment between the center of a circle passing through a plurality of magnetic sensors and the rotation axis based on signals from the plurality of magnetic sensors included in a sensor unit that detects magnetism from a magnet that rotates together with the rotation axis of the motor and is arranged along the circumference, and a failure detection unit that detects a failure of the motor based on the detected shaft misalignment.

Effects of the Invention

[0008] According to the present disclosure, it is possible to easily detect the misalignment between the center of a plurality of sensors that detect the angle of the rotation axis and the rotation axis.

Brief Description of the Drawings

[0009] [Figure 1] FIG. 1 is a diagram showing a configuration example of a motor module according to an embodiment. [Figure 2A] FIG. 2A is a diagram showing a configuration example of a motor according to an embodiment. [Figure 2B] FIG. 2B is a diagram showing a configuration example of a motor according to an embodiment. [Figure 3A] FIG. 3A is a diagram showing a configuration example of a sensor unit according to an embodiment. [Figure 3B] FIG. 3B is a diagram showing a configuration example of a sensor unit according to an embodiment. [Figure 4] FIG. 4 is a diagram showing a configuration example of a failure detection device according to an embodiment. [Figure 5] FIG. 5 is a diagram showing an example of signals of a magnetic sensor according to an embodiment. [Figure 6A] FIG. 6A is a diagram showing an example of the arrangement of magnetic sensors and the sector interval according to an embodiment. [Figure 6B]FIG. 6B is a diagram showing an example of the arrangement of magnetic sensors and the sector intervals according to an embodiment. [Figure 7] FIG. 7 is a diagram showing an example of the sector intervals according to an embodiment. [Figure 8A] FIG. 8A is a diagram showing an example of detecting an axial deviation according to the first embodiment. [Figure 8B] FIG. 8B is a diagram showing another example of detecting an axial deviation according to the first embodiment. [Figure 9] FIG. 9 is a diagram showing an example of a failure detection method according to an embodiment. [Figure 10A] FIG. 10A is a diagram showing an example of the sector intervals according to the second embodiment. [Figure 10B] FIG. 10B is a diagram showing an example of the sector intervals according to the second embodiment.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present disclosure will be described in detail based on the drawings. The description will be carried out in the following order. In each of the following embodiments, the same parts are denoted by the same reference numerals, and redundant descriptions are omitted. 1. Motor module 2. First embodiment 3. Second embodiment

[0011] (1. Motor module) FIG. 1 is a diagram showing a configuration example of a motor module according to an embodiment. As shown in the figure, the motor module 1 according to the embodiment includes a motor 2, an inverter circuit 3, and a control circuit 4.

[0012] The motor 2 is a three-phase brushless DC motor. This motor 2 includes a stator 23, a rotor 22, and magnetic sensors 31 to 33.

[0013] The rotor 22 is fixed to the rotating shaft 21 and rotates. Permanent magnets are arranged on this rotor 22. The rotor 22 in the figure represents the case of four poles.

[0014] The stator 23 is positioned around the rotor 22 and generates a magnetic field to rotate the rotor 22. Three field coils 24 are arranged on the stator 23 at equal intervals in the circumferential direction.

[0015] The magnetic sensors 31 to 33 detect the rotation angle (electrical angle) of the rotating shaft 21. These magnetic sensors 31 to 33 detect the rotation angle of the rotating shaft 21 by detecting changes in the magnetic field of the rotor 22, etc. For example, magnetic sensors using Hall elements can be applied to the magnetic sensors 31, etc. The magnetic sensors 31, etc. can be arranged according to the number of phases of the motor 2.

[0016] The inverter circuit 3 is the circuit that drives the motor 2. This inverter circuit 3 converts a DC voltage to an AC voltage and outputs the converted AC voltage to the motor 2. The inverter circuit 3 can be configured as a three-phase (U-phase, V-phase, and W-phase) bridge circuit. The inverter circuit 3 shown in the figure represents an example in which an IGBT (Insulated Gate Bipolar Transistor) is used as the switching element.

[0017] The control circuit 4 controls the rotation of the motor 2. This control circuit 4 controls the rotation of the motor 2 by controlling the on / off state of the switch elements that make up the inverter circuit 3. The control circuit 4 outputs a drive signal for the switch elements that make up the inverter circuit 3. In addition, the control circuit 4 detects the rotation angle of the rotation shaft 21 based on signals from the magnetic sensor 31, etc., and generates the drive signal for the switch elements mentioned above.

[0018] [Motor Configuration] Figures 2A and 2B show examples of the configuration of a motor according to the embodiment. These figures represent an example of the configuration of motor 2 and show an example of the arrangement of the magnetic sensor 31, etc. Note that the stator 23 is omitted in these figures. The sensor section 30 in these figures is made up of a substrate on which the magnetic sensor 31, etc., are arranged.

[0019] Figure 2A shows an example in which the sensor unit 30 is arranged inside the housing 20. The magnetic sensor 31 and other components of the sensor unit 30 in this figure detect changes in the magnetic field of the rotor 22.

[0020] Figure 2B shows an example where the sensor unit 30 is located outside the housing 20. The motor 2 in this figure includes a sensor magnet 40. This sensor magnet 40 can be made up of a magnet fixed to the end of the rotating shaft 21. The sensor magnet 40 rotates together with the rotating shaft 21. The sensor unit 30 in this figure is located in close proximity to the sensor magnet 40. The magnetic sensor 31 and the like in this figure detect changes in the magnetic field of the sensor magnet 40.

[0021] [Configuration of the sensor unit] Figure 3A shows an example configuration of the sensor unit according to the embodiment. The same figure shows an example configuration of the sensor unit 30. The rotor 22 and the rotating shaft 21 are schematically shown in the same figure. The rotor 22 in the figure is assumed to be a two-pole rotor. The dashed line on the rotor 22 in the figure represents the boundary of the magnetic poles. For convenience, the explanation will be given assuming a two-pole rotor 22. Note that the motor fault detection device according to this disclosure is also applicable to a multi-pole rotor 22.

[0022] The sensor unit 30 in the figure includes magnetic sensors 31, 32, and 33. The magnetic sensors 31 to 33 are arranged equidistant from the center 202 of the rotation axis 21 and along the circumference (dotted line in the figure) surrounding the center 202 of the rotation axis 21. The magnetic sensors 31 to 33 can also be arranged at equal intervals. The white circles in the figure represent the centers 201 of the magnetic sensors 31 to 33. This center 201 corresponds to the center of the circle passing through the magnetic sensors 31 to 33. In a normal motor 2, the centers 201 of the magnetic sensors 31, etc., coincide with the center 202 of the rotation axis 21.

[0023] In contrast, if the center 201 of the magnetic sensor 31, etc., does not coincide with the center 202 of the rotation axis 21, errors will occur in the detection of the rotation angle by the magnetic sensor 31, etc. This will cause problems in the driving of the motor 2. Specifically, this may result in fluctuations in the rotation speed of the motor 2, a decrease in efficiency, and failure due to the occurrence of instantaneous overcurrents. The case where the center 201 of the magnetic sensor 31, etc., does not coincide with the center 202 of the rotation axis 21 will be explained using Figure 3B.

[0024] Figure 3B shows an example of the configuration of the sensor unit according to the embodiment. This figure shows an example where the center 201 of the magnetic sensor 31 etc. does not coincide with the center 202 of the rotation axis 21. As shown in the figure, a misalignment occurs between the center 201 of the magnetic sensor 31 etc. and the center 202 (black circle) of the rotation axis 21. This misalignment between the center 201 of the magnetic sensor 31 etc. and the center 202 of the rotation axis 21 is called axial misalignment. The motor fault detection device of this disclosure detects this axial misalignment and detects a fault in the motor 2.

[0025] [Configuration of fault detection device] Figure 4 is a diagram showing an example configuration of a fault detection device according to an embodiment. The same figure is a block diagram showing an example configuration of the fault detection device 100. The fault detection device 100 comprises a misalignment detection unit 110, a fault detection unit 120, and a communication unit 130. The figure also further shows a sensor unit 30 on which magnetic sensors 31 to 33 are arranged.

[0026] The shaft misalignment detection unit 110 detects shaft misalignment based on signals from magnetic sensors 31 to 33. This shaft misalignment detection unit 110 outputs the detected shaft misalignment to the fault detection unit 120. Details of shaft misalignment detection will be described later.

[0027] The fault detection unit 120 detects a fault in the motor 2 based on the misalignment detected by the misalignment detection unit 110. The fault detection unit 120 outputs the detection result to the communication unit 130. Details of fault detection will be described later.

[0028] The communication unit 130 transmits the detection result of the motor 2 malfunction to an external device. The communication unit 130 can transmit whether or not the motor 2 is malfunctioning.

[0029] [Magnetic sensor signal] Figure 5 shows an example of a signal from a magnetic sensor according to an embodiment. The figure shows an example of a signal from a magnetic sensor. Magnetic sensors 31, etc., output a binarized signal according to the magnetic field. The part of this signal with a value of 1 represents the north pole, and the part with a value of 0 represents the south pole. "Magnetic sensor 31", "Magnetic sensor 32", and "Magnetic sensor 33" in the figure represent the waveforms of the signals from magnetic sensors 31, 32, and 33, respectively. Based on the timing of the transitions of these signals, the rotation angle of the rotation axis 21 can be divided into 60° electrical angles. These divided sections are called sectors. "Sector" in the figure represents a number that identifies the sector. Also, "Rotation angle" in the figure represents the rotation angle of the rotation axis 21 in electrical angles. θ0 to θ5 of this rotation angle represent the angles that separate the sectors.

[0030] [Sector spacing] Figures 6A and 6B show examples of the arrangement and sector spacing of a magnetic sensor according to the embodiment. Figure 6A shows an example where the center 201 of the magnetic sensor 31 and the center 202 of the rotation axis 21 coincide. In this case, the sector spacing is an electrical angle of 60°. The sector spacing when the center 201 of the magnetic sensor 31 and the center 202 of the rotation axis 21 coincide is called the reference sector spacing.

[0031] Figure 6B shows an example where the center 201 of the magnetic sensor 31 and the center 202 of the rotation axis 21 do not coincide, illustrating the case where axial misalignment occurs. As shown in the figure, axial misalignment causes variations in sector spacing.

[0032] Figure 7 shows an example of sector spacing according to the embodiment. Sector spacing L i θ i -θ i-1It is calculated by. The upper diagram in the figure shows the sector intervals when the center 201 of the magnetic sensor 31 etc. and the center 202 of the rotation axis 21 coincide. Each sector interval is an electrical angle of 60°. The lower diagram in the figure shows an example of the sector intervals when an axial deviation occurs. This sector interval L i ’ and the reference sector interval can be detected by detecting the difference.

[0033] [Detection of axial deviation] FIG. 8A is a diagram showing an example of detecting axial deviation according to the first embodiment. This figure shows the sector interval L i ’ and the difference ΔL i from the reference sector interval which is an electrical angle of 60°. It is a graph representing. The vertical axis represents ΔL i , and the horizontal axis represents the sector number. Also, this figure calculates ΔL i based on the sector intervals in the lower diagram of FIG. 7. The axial deviation detection unit 110 calculates the difference ΔL i in this figure based on the signals of the magnetic sensors 31 to 33, and detects this difference as an axial deviation. When this axial deviation is large, problems become prominent. Therefore, by comparing the axial deviation with a predetermined threshold value, it can be determined that the motor 2 in which the sensor unit 30 is arranged is faulty. The dashed line in this figure represents the threshold value. The failure detection unit 120 can detect a failure of the motor 2 when the axial deviation output from the axial deviation detection unit 110 exceeds a predetermined threshold value.

[0034] Note that the failure detection unit 120 can also detect a failure based on the number of differences ΔL i that exceed the threshold value.

[0035] FIG. 8B is a diagram showing another example of detecting axial deviation according to the first embodiment. This figure is a graph representing the integrated value Δθ i of the difference ΔL i . The vertical axis represents the integrated value Δθ i , and the horizontal axis represents the sector number. Also, this figure calculates the integrated value Δθ i based on the difference ΔL i in FIG. 8A. This integrated value Δθ iThis indicates the angular deviation from the original θi. The axial deviation detection unit 110 calculates the integrated value Δθ in the figure based on the signals from the magnetic sensors 31 to 33. i The system calculates the value and detects this accumulated value as the axis misalignment. In this case, the fault detection unit 120 determines that the motor 2 on which the sensor unit 30 is located is faulty by comparing the accumulated value with a predetermined threshold. The dashed line in the figure represents the threshold.

[0036] [Fault detection method] Figure 9 is a diagram showing an example of a fault detection method according to an embodiment. The same figure is a flowchart showing an example of the processing procedure for fault detection in the fault detection device 100. First, the fault detection device 100 is connected to magnetic sensors 31 to 33 and sensor signals are acquired (step S101). Next, the shaft misalignment detection unit 110 detects shaft misalignment based on the signals from magnetic sensors 31 to 33 (step S102). This is the difference ΔL i or the cumulative value Δθ i This can be done by calculating the difference ΔL. Next, the fault detection unit 120 detects a fault in the motor 2 based on the shaft misalignment (step S103). i or the cumulative value Δθ i This can be done based on a predetermined threshold. By following the above procedure, a failure in motor 2 can be detected. Note that failure detection can be performed during the manufacturing process of motor 2. Furthermore, failure detection can also be performed during the inspection process of motor 2 after it has been used.

[0037] Thus, the fault detection device 100 of this disclosure can detect axial misalignment based on signals from magnetic sensors 31 to 33, and can detect a fault in the motor 2 based on the detected axial misalignment. This makes it easy to detect a fault in the motor 2.

[0038] (2. Second Embodiment) In the first embodiment described above, the misalignment was detected based on the difference in sector spacing. In contrast, the second embodiment of this disclosure differs from the first embodiment in that the amount of misalignment is calculated directly from the sector spacing.

[0039] [Sector spacing] Figures 10A and 10B show examples of sector spacing according to the second embodiment. Figure 10A shows the sector spacing when the center 201 of the magnetic sensor 31 etc. and the center 202 of the rotation axis 21 coincide. Figure 10B shows the sector spacing when axial misalignment occurs. The distance between the sensor 31 etc. and the center 201 is represented by r. The coordinates of the magnetic sensors 31 to 33 are also shown in the figure. In this figure, the position of the magnetic sensor 31 is assumed to be the reference position.

[0040] As shown in Figure 10A, the x and y coordinates of the magnetic sensor 31 can be expressed as follows. x=r y=0 Furthermore, the x and y coordinates of the magnetic sensor 32 can be expressed as follows. x = rcos(2π / 3) y = rsin(2π / 3) Furthermore, the x and y coordinates of the magnetic sensor 33 can be expressed as follows. x = rcos(4π / 3) y = rsin(4π / 3)

[0041] On the other hand, in Figure 10B, which shows the situation when an axis misalignment occurs, if the coordinates of the center 202 of the rotation axis 21 are represented as (0, 0), then the center 201 of the misaligned magnetic sensor 31, etc., can be represented as (tx, ty). In that case, the x and y coordinates of the magnetic sensor 31 can be represented as follows. x = r + tx y=ty Furthermore, the x and y coordinates of the magnetic sensor 32 can be expressed as follows. x = rcos(2π / 3) + tx y = rsin(2π / 3) + ty Furthermore, the x and y coordinates of the magnetic sensor 33 can be expressed as follows. x = rcos(4π / 3) + tx y = rsin(4π / 3) + ty

[0042] Based on Figure 10B, the mechanical angular angles of magnetic sensors 31, 32, and 33 from the center 201 are denoted as θa, θb, and θc, respectively. In this case, angle θa corresponds to θ0' and θ3', angle θb corresponds to θ2' and θ5', and angle θc corresponds to θ1' and θ4'. Their relationships can be expressed, for example, as follows. θa=θ0' θb = θ2' θc = θ4' Alternatively, the average of the relevant angle detection values ​​may be taken as follows. θa = (θ0' + (θ3' - π)) / 2 θb = (θ2' + (θ5' - π)) / 2 θc = ((θ1' + π) + θ4') / 2 By rearranging the equation based on Figure 10B using the mechanical angular angles θa, θb, and θc of the magnetic sensor 31, the following equation can be obtained. tx=r×(1 / 2-((√3) / (tan(θc-θa)-tan(θb-θa)))) ···(1) ty=-r×((√3) / 2)×(tan(θc-θa)+tan(θb-θa)) / (tan(θc-θa)-tan(θb-θa)) ···(2)

[0043] Furthermore, the mechanical angular angles θa, θb, and θc of the magnetic sensor 31, etc., can be expressed using the mechanical angular angle errors Δθa, Δθb, and Δθc as shown in the following equation. θa = Δθa θb = 2π / 3 + Δθb θc = 4π / 3 + Δθc Here, the errors in the machine angle Δθa, Δθb, and Δθc can be considered sufficiently small. By expanding the tangent and utilizing relationships such as tanΔθ≈Δθ and ΔθbΔθc≈0, we can obtain the following approximate equations for equations (1) and (2). tx=r×(1 / 2-((√3) / 2)×(1+(√3)×(Δθb-Δθc)) / ((√3)+Δθb-Δθc) ···(3) ty=-r×(√3)×(Δθb+Δθc-2Δθa) / ((√3)+Δθb-Δθc) ···(4) The units are given in radians.

[0044] The axial misalignment detection unit 110 of the second embodiment can calculate the axial misalignment based on any of the above-described equations (1) and (2), and equations (3) and (4). For example, the amount of axial misalignment can be calculated based on the following equation. √((tx) 2 +(ty) 2 ) When the calculated amount of axial misalignment exceeds the threshold set as the allowable amount of axial misalignment, it can be detected as axial misalignment.

[0045] So far, we have shown the case where the rotor 22 rotates counterclockwise, but the same considerations can be applied when the rotor 22 rotates clockwise. In this case, since the rotor 22 rotates clockwise, the sector spacing can be determined in the order of θ0, θ5, θ4, θ3, θ2, and θ1.

[0046] So far we have shown the case where motor 2 is a 2-pole motor, but the same approach can be applied when motor 2 is a multi-pole motor. If the number of pole pairs is N, the sector division is from θ0 to θ 6N―1 It exists up to this point. The machine angles θa, θb, and θc can be expressed, for example, using one detection angle as follows: θa = θ0' / N θb = 2π / 3 + (θ2' - 2π / 3) / N θc = 4π / 3 + (θ4' - 4π / 3) / N Alternatively, the average of one rotation of the electrical angle can be taken as follows. θa = (θ0' + (θ3' - π)) / (2N) θb=2π / 3+((θ2'-2π / 3)+(θ5'-5π / 3)) / (2N) θc=4π / 3+((θ1'-π / 3)+(θ4'-4π / 3)) / (2N) Alternatively, the average of the machine angle over one rotation may be taken as follows. θa=(θ0'+(θ3'-π)+(θ6'-2π)+···+(θ 6N-3 -(2N-1)π)) / (2N 2 ) θb=2π / 3+((θ2'-2π / 3)+(θ5'-5π / 3)+...+(θ 6N-1 -(6N-1)π / 3)) / (2N 2 ) θc=4π / 3+((θ1'-π / 3)+(θ4'-4π / 3)+...+(θ 6N-2 -(6N-2)π / 3)) / (2N 2 )

[0047] The configuration of the fault detection device 100 other than that described herein is the same as that of the fault detection device 100 in the first embodiment, so a description will be omitted.

[0048] Thus, the fault detection device 100 of the second embodiment of this disclosure can directly calculate and detect the amount of misalignment from the sector spacing. By detecting a fault in the motor 2 based on the detected misalignment, the fault in the motor 2 can be easily detected.

[0049] Although the embodiments of this disclosure have been described above, the technical scope of this disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the gist of this disclosure. Furthermore, components from different embodiments and modifications may be combined as appropriate.

[0050] The series of processes performed by each device described herein may be implemented using software, hardware, or a combination of software and hardware. The programs constituting the software are pre-stored in a storage medium (non-transitory media) provided inside or outside each device. Then, each program is loaded into RAM when the computer is running and executed by a processor such as a CPU.

[0051] Furthermore, the processes described herein using flowcharts and sequence diagrams do not necessarily have to be executed in the order shown. Some processing steps may be executed in parallel. Additional processing steps may be adopted, and some processing steps may be omitted.

[0052] (effect) The motor fault detection device 100 comprises a misalignment detection unit 110 and a fault detection unit 120. The misalignment detection unit 110 detects magnetism from a magnet that rotates with the rotation axis of the motor 2 and detects misalignment, which is the displacement between the center of a circle passing through the multiple magnetic sensors and the rotation axis, based on signals from a sensor unit 30 that includes a plurality of magnetic sensors 31 to 33 arranged along the circumference. The fault detection unit 120 detects a fault in the motor 2 based on the detected misalignment. This makes it possible to detect misalignment from signals from the magnetic sensors 31 to 33, thus facilitating the detection of misalignment.

[0053] Furthermore, the effects described herein are merely illustrative and not limiting, and other effects may also occur.

Claims

1. A misalignment detection unit detects axial misalignment, which is the difference between the center of a circle passing through the multiple magnetic sensors and the rotation axis, based on signals from a sensor unit that includes a magnet that rotates with the motor's rotation axis and a plurality of magnetic sensors arranged along the circumference. A fault detection unit that detects a motor failure based on the detected axial misalignment. Equipped with, The shaft misalignment detection unit is a motor fault detection device that detects the difference between a plurality of sector intervals based on the signals of the plurality of magnetic sensors and a reference sector interval calculated based on the number of the plurality of magnetic sensors as the shaft misalignment.

2. The motor fault detection device according to claim 1, wherein the fault detection unit detects the fault based on the threshold value of the difference.

3. The motor fault detection device according to claim 2, wherein the fault detection unit detects the fault based on the number of differences that exceed the threshold.

4. The motor fault detection device according to claim 1, wherein the shaft misalignment detection unit detects the accumulated value of the differences for each of the plurality of sector intervals as the shaft misalignment.

5. The motor fault detection device according to claim 4, wherein the fault detection unit detects the fault based on the threshold value of the accumulated value.

6. The sensor unit has three magnetic sensors arranged at equal intervals. The axial misalignment detection unit detects the axial misalignment based on the angle corresponding to the interval at which the signal of the magnetic sensor transitions in response to the magnetism of the rotating magnet, and the distance from the center of the circle passing through the plurality of magnetic sensors to the magnetic sensor. A motor fault detection device according to claim 1.

7. The motor fault detection device according to claim 6, wherein the shaft misalignment detection unit detects the shaft misalignment based on the following formula, when the x and y coordinates of the shaft misalignment are tx and ty, respectively. tx=r×(1 / 2-((√3) / (tan(θc-θa)-tan(θb-θa)))) ty=-r×((√3) / 2)×(tan(θc-θa)+tan(θb-θa)) / (tan(θc-θa)-tan(θb-θa)) However, r is the distance between the center of the circle passing through the plurality of magnetic sensors and the magnetic sensor. θa, θb, and θc are the mechanical angles of the three magnetic sensors.

8. The motor fault detection device according to claim 6, wherein the shaft misalignment detection unit detects the shaft misalignment based on the following formula, when the x and y coordinates of the shaft misalignment are tx and ty, respectively. tx=r×(1 / 2-((√3) / 2)×(1+(√3)×(Δθb-Δθc)) / ((√3)+Δθb-Δθc) ty=-r×(√3)×(Δθb+Δθc-2Δθa) / ((√3)+Δθb-Δθc) However, r is the distance between the center of the circle passing through the plurality of magnetic sensors and the magnetic sensor. Δθa, Δθb, and Δθc are the errors in the mechanical angular angles of each of the three magnetic sensors.

9. The motor fault detection device according to claim 7 or 8, wherein the fault detection unit detects the fault based on the threshold value of the shaft misalignment.

10. The motor fault detection device according to claim 1, further comprising a communication unit for transmitting the fault detection result of the motor fault detected by the fault detection unit to an external device.

11. The system detects magnetic fields from a magnet that rotates with the motor's rotation axis, and also detects axial misalignment, which is the displacement between the center of the circle passing through the multiple magnetic sensors and the rotation axis, based on the signals from the multiple magnetic sensors in the sensor unit, which includes multiple magnetic sensors arranged along the circumference. Based on the detected misalignment, a motor failure is detected. Includes, A motor fault detection method in which the axial misalignment is detected based on the difference between a plurality of sector intervals based on the signals of the plurality of magnetic sensors and a reference sector interval calculated based on the number of the plurality of magnetic sensors.

12. The sensor unit has three magnetic sensors arranged at equal intervals. The axial misalignment is detected based on the angle corresponding to the interval at which the signal of the magnetic sensor transitions in response to the magnetism of the rotating magnet, and the distance from the center of the circle passing through the plurality of magnetic sensors to the magnetic sensor. The motor failure detection method according to claim 11.

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