Position detection device, position detection method, automated guided vehicle, and sewing machine

Abstract

One aspect of this position detection device comprises: a first sensor group including N (N is a multiple of 3) first magnetic sensors that face a magnet rotating synchronously with the rotation axis of a motor and that are positioned at prescribed intervals along the rotation direction of the magnet; a second sensor group including N second magnetic sensors arranged at positions opposite to the N first magnetic sensors across the rotation axis in the radial direction of the magnet; and a signal processing device for processing output signals outputted from each of the N first magnetic sensors and the N second magnetic sensors. The signal processing device executes an averaging process for generating N averaging signals by averaging output signals of the first magnetic sensors and output signals of the second magnetic sensors arranged at positions opposite to the first magnetic sensors across the rotation axis, and an estimating process for estimating the rotation position of a motor on the basis of the N averaging signals.

Description

Technical Field

[0001] The present invention relates to a position detection device, a position detection method, an automated guided vehicle, and a sewing device.

Background Art

[0002] Conventionally, as a motor capable of accurately controlling the rotational position, a configuration including an absolute angle position sensor such as an optical encoder or a resolver is known. However, the absolute angle position sensor is large and expensive. Therefore, Patent Document 1 discloses a method of estimating the rotational position of a motor using three inexpensive and small magnetic sensors without using an absolute angle position sensor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the position estimation method described in Patent Document 1, when a specific case occurs, the estimation accuracy of the rotational position may decrease. The specific cases are a case where the rotor shaft rotates in a state where the central axis of the rotor shaft is eccentric with respect to the central axis of the position detection magnet, and a case where the rotor shaft rotates in a state where the position detection magnet is inclined with respect to a plane orthogonal to the rotor shaft. In these cases, due to the periodic change in the gap between the position detection magnet and the three magnetic sensors, the amplitude values of the output signals of the three magnetic sensors fluctuate periodically over one cycle of the mechanical angle.

Means for Solving the Problems

[0005] One aspect of the position detection device of the present invention is a position detection device for detecting the rotational position of a motor, comprising: a first sensor group including N (N is a multiple of 3) first magnetic sensors that face a magnet rotating in synchronization with the rotational axis of the motor and are arranged at predetermined intervals along the rotational direction of the magnet; a second sensor group including N second magnetic sensors arranged on opposite sides of the rotational axis in the radial direction of the magnet to each of the N first magnetic sensors; and a signal processing device that processes the output signals output from each of the N first magnetic sensors and the N second magnetic sensors. The signal processing device performs an averaging process to generate N averaged signals by averaging the output signals of the first magnetic sensors and the output signals of the second magnetic sensors arranged on the opposite side of the rotational axis to the first magnetic sensors; and an estimation process to estimate the rotational position of the motor based on the N averaged signals.

[0006] One aspect of the position detection method of the present invention is a position detection method for detecting the rotational position of a motor, comprising: a first step of acquiring output signals from N (N is a multiple of 3) first magnetic sensors from a first sensor group including N first magnetic sensors that are opposite to a magnet that rotates in synchronization with the rotational axis of the motor and are arranged at predetermined intervals along the rotational direction of the magnet; a second step of acquiring output signals from N second magnetic sensors from a second sensor group including N second magnetic sensors that are arranged on opposite sides of the rotational axis in the radial direction of the magnet to each of the N first magnetic sensors; a third step of generating N averaged signals by averaging the output signals of the first magnetic sensors and the output signals of the second magnetic sensors arranged on the opposite side of the rotational axis to the first magnetic sensors; and a fourth step of estimating the rotational position of the motor based on the N averaged signals.

[0007] One embodiment of the automated guided vehicle of the present invention comprises a motor and a position detection device of the above embodiment for detecting the rotational position of the motor.

[0008] One embodiment of the sewing apparatus of the present invention comprises a motor and a position detection device of the above embodiment for detecting the rotational position of the motor. [Effects of the Invention]

[0009] According to the above aspects of the present invention, a position detection device, a position detection method, an automated guided vehicle, and a sewing machine are provided that can suppress a decrease in the accuracy of detecting the rotational position of a motor. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic block diagram showing the configuration of a position detection device in one embodiment of the present invention. [Figure 2] Figure 2 is a flowchart showing the learning process performed by the processing unit in this embodiment. [Figure 3] Figure 3 is an explanatory diagram of the training data obtained by the training process in this embodiment. [Figure 4] Figure 4 is a magnified view of the three averaged signals contained within one pole-pair region. [Figure 5] Figure 5 is a flowchart showing the position estimation process performed by the processing unit in this embodiment. [Figure 6] Figure 6 schematically shows the first case in which the rotor shaft rotates with its central axis eccentric to the central axis of the sensor magnet. [Figure 7] Figure 7 schematically shows the second case in which the rotor shaft rotates with the sensor magnet tilted relative to a plane perpendicular to the rotor shaft. [Figure 8] Figure 8 shows the waveforms of the first Hall signals output from the three first magnetic sensors and the waveforms of the second Hall signals output from the three second magnetic sensors in the first and second cases. [Figure 9] Figure 9 shows the waveforms of three averaged signals calculated based on the first Hall signals output from the three first magnetic sensors and the second Hall signals output from the three second magnetic sensors. [Figure 10] Figure 10 shows the external appearance of an automated guided vehicle, which is an example of an application of the present invention. [Figure 11] Figure 11 shows the external appearance of a sewing machine, which is an example of an application of the present invention. [Modes for carrying out the invention]

[0011] One embodiment of the present invention will be described in detail below with reference to the drawings. Figure 1 is a schematic block diagram showing the configuration of a position detection device 1 in one embodiment of the present invention. As shown in Figure 1, the position detection device 1 is a device that detects the rotational position (rotation angle) of the motor 100. In this embodiment, the motor 100 is, for example, an inner rotor type three-phase brushless DC motor. The motor 100 has a rotor shaft 110 and a sensor magnet 120. The rotor shaft 110 is the axis of rotation of the motor 100. The rotational position of the motor 100 means the rotational position of the rotor shaft 110.

[0012] The sensor magnet 120 is a disc-shaped magnet attached to the rotor shaft 110. The sensor magnet 120 rotates in synchronization with the rotor shaft 110. The sensor magnet 120 has P (where P is an integer of 2 or more) magnetic pole pairs. In this embodiment, as an example, the sensor magnet 120 has four magnetic pole pairs. A magnetic pole pair refers to a pair of north poles and south poles. That is, in this embodiment, the sensor magnet 120 has four pairs of north poles and south poles, for a total of eight magnetic poles.

[0013] The position detection device 1 comprises a first sensor group 10, a second sensor group 20, and a signal processing device 30. The first sensor group 10 includes N (where N is a multiple of 3) first magnetic sensors. In this embodiment, the first sensor group 10 includes three first magnetic sensors 11, 12, and 13. The second sensor group 20 includes N second magnetic sensors. In this embodiment, the second sensor group 20 includes three second magnetic sensors 21, 22, and 23.

[0014] Although not shown in FIG. 1, a circuit board is attached to the motor 100, and the first sensor group 10, the second sensor group 20, and the signal processing device 30 are arranged on the circuit board. The sensor magnet 120 is arranged at a position that does not interfere with the circuit board. The sensor magnet 120 may be arranged inside the housing of the motor 100 or outside the housing.

[0015] The first magnetic sensors 11, 12, and 13 are arranged on the circuit board opposite to the sensor magnet 120 and at a predetermined interval along the rotation direction of the sensor magnet 120. In the present embodiment, the first magnetic sensors 11, 12, and 13 are arranged at intervals of 30° along the rotation direction of the sensor magnet 120. For example, the first magnetic sensors 11, 12, and 13 are each a Hall element or a linear Hall IC. The first magnetic sensors 11, 12, and 13 each output an analog signal that varies according to the magnetic field strength.

[0016] One electrical angle cycle of each analog signal output from the first magnetic sensors 11, 12, and 13 corresponds to 1 / P of one mechanical angle cycle. In the present embodiment, since the number of pole pairs P of the sensor magnet 120 is "4", one electrical angle cycle of each analog signal corresponds to 1 / 4 of one mechanical angle cycle, that is, 90° in mechanical angle. Also, the analog signals output from the first magnetic sensors 11, 12, and 13 have a phase difference of 120° in electrical angle from each other.

[0017] Hereinafter, the analog signals output from the first magnetic sensors 11, 12, and are referred to as first Hall signals. The first magnetic sensor 11 outputs the first Hall signal HAu to the signal processing device 30. The first magnetic sensor 12 outputs the first Hall signal HAv to the signal processing device 30. The first magnetic sensor 13 outputs the first Hall signal HAw to the signal processing device 30.

[0018] The second magnetic sensors 21, 22, and 23 are positioned on the circuit board on opposite sides of the rotor shaft 110 in the radial direction of the sensor magnet 120 to each of the three first magnetic sensors 11, 12, and 13. The second magnetic sensor 21 is positioned on the opposite side of the rotor shaft 110 in the radial direction of the sensor magnet 120 to the first magnetic sensor 11. The second magnetic sensor 22 is positioned on the opposite side of the rotor shaft 110 in the radial direction of the sensor magnet 120 to the first magnetic sensor 12. The second magnetic sensor 23 is positioned on the opposite side of the rotor shaft 110 in the radial direction of the sensor magnet 120 to the first magnetic sensor 13.

[0019] The second magnetic sensors 21, 22, and 23 are arranged on the circuit board opposite the sensor magnet 120 and at predetermined intervals along the rotational direction of the sensor magnet 120. In this embodiment, the second magnetic sensors 21, 22, and 23 are arranged at 30° intervals along the rotational direction of the sensor magnet 120. For example, the second magnetic sensors 21, 22, and 23 are each Hall elements or linear Hall ICs. The second magnetic sensors 21, 22, and 23 each output an analog signal that varies according to the magnetic field strength.

[0020] Similar to the first magnetic sensors 11, 12, and 13, the electrical angle of one period of each analog signal output from the second magnetic sensors 21, 22, and 23 corresponds to a mechanical angle of 90°. Furthermore, the analog signals output from the second magnetic sensors 21, 22, and 23 have a phase difference of 120° in electrical angle from each other.

[0021] Hereinafter, the analog signals output from the second magnetic sensors 21, 22, and 23 will be referred to as the second Hall signals. The second magnetic sensor 21 outputs the second Hall signal HBu to the signal processing device 30. The second magnetic sensor 22 outputs the second Hall signal HBv to the signal processing device 30. The second magnetic sensor 23 outputs the second Hall signal HBw to the signal processing device 30.

[0022] There is a 180° mechanical angle phase difference between the first Hall signal HAu output from the first magnetic sensor 11 and the second Hall signal HBu output from the second magnetic sensor 21. There is a 180° mechanical angle phase difference between the first Hall signal HAv output from the first magnetic sensor 12 and the second Hall signal HBv output from the second magnetic sensor 22. There is a 180° mechanical angle phase difference between the first Hall signal HAw output from the first magnetic sensor 13 and the second Hall signal HBw output from the second magnetic sensor 23.

[0023] The signal processing device 30 is a device that processes the output signals from the three first magnetic sensors and the three second magnetic sensors, respectively. Based on the first Hall signals HAu, HAv, and HAw and the second Hall signals HBu, HBv, and HBw, the signal processing device 30 estimates the rotational position of the motor 100, i.e., the rotational position of the rotor shaft 110. The signal processing device 30 comprises a processing unit 31 and a storage unit 32.

[0024] The processing unit 31 is a microprocessor, such as an MCU (Microcontroller Unit). The first Hall signals HAu, HAv, and HAw, and the second Hall signals HBu, HBv, and HBw are input to the processing unit 31. The processing unit 31 is connected to the storage unit 32 via a data bus (not shown) for data communication.

[0025] The first Hall signal and the second Hall signal are converted into digital signals via an A / D converter within the processing unit 31. For the sake of clarity, the digital signals output from the A / D converter will also be referred to as the first Hall signal and the second Hall signal. Furthermore, in the following explanation, the first Hall signal and the second Hall signal input to the processing unit 31 may be collectively referred to as the "input sensor signal."

[0026] The processing unit 31 performs at least the following two processes according to the program stored in the storage unit 32. The processing unit 31 performs a learning process to acquire learning data necessary for estimating the rotational position of the rotor shaft 110 based on the input sensor signal. The processing unit 31 performs a position estimation process to estimate the rotational position of the rotor shaft 110 based on the input sensor signal and the learning data.

[0027] The memory unit 32 includes a non-volatile memory that stores programs, various setting values, and learning data necessary for the processing unit 31 to execute various processes, and a volatile memory used as a temporary storage location for data when the processing unit 31 executes various processes. The non-volatile memory is, for example, EEPROM (Electrically Erasable Programmable Read-Only Memory) or flash memory. The volatile memory is, for example, RAM (Random Access Memory).

[0028] Next, the learning process performed by the processing unit 31 will be described. Figure 2 is a flowchart showing the learning process performed by the processing unit 31 in this embodiment. The processing unit 31 performs the process shown in Figure 2 at least when the power to the position detection device 1 is turned on for the first time.

[0029] As shown in Figure 2, when the processing unit 31 starts the learning process, it first rotates the motor 100 to rotate the sensor magnet 120 together with the rotor shaft 110 (step S1). The processing unit 31 may also rotate the rotor shaft 110 by controlling the energization of the motor 100 via a motor control device (not shown). Alternatively, the rotor shaft 110 may be connected to a rotating machine (not shown), and the rotor shaft 110 may be rotated by that machine.

[0030] Then, the processing unit 31 acquires the first Hall signals HAu, HAv, and HAw output from the three first magnetic sensors 11, 12, and 13 as the sensor magnet 120 rotates (step S2).

[0031] In parallel with step S2 described above, the processing unit 31 acquires the second Hall signals HBu, HBv, and HBw output from the three second magnetic sensors 21, 22, and 23 as the sensor magnet 120 rotates (step S3).

[0032] Then, the processing unit 31 generates three averaged signals by averaging the output signal of the first magnetic sensor and the output signal of the second magnetic sensor, which is located on the opposite side of the rotor shaft 110 from the first magnetic sensor (step S4).

[0033] Specifically, the processing unit 31 generates an averaged signal Hu by averaging the first Hall signal HAu output from the first magnetic sensor 11 and the second Hall signal HBu output from the second magnetic sensor 21. The processing unit 31 generates an averaged signal Hv by averaging the first Hall signal HAv output from the first magnetic sensor 12 and the second Hall signal HBv output from the second magnetic sensor 22. The processing unit 31 generates an averaged signal Hw by averaging the first Hall signal HAw output from the first magnetic sensor 13 and the second Hall signal HBw output from the second magnetic sensor 23.

[0034] Figure 6 schematically shows the first case in which the rotor shaft 110 rotates with the central axis 111 of the rotor shaft 110 being eccentric with a displacement DL relative to the central axis 121 of the sensor magnet 120. Figure 7 schematically shows the second case in which the rotor shaft 110 rotates with the sensor magnet 120 tilted with an angle θ with respect to a plane 112 perpendicular to the rotor shaft 110.

[0035] Figure 8 shows the waveforms of the first Hall signals HAu, HAv, and HAw output from the first magnetic sensors 11, 12, and 13, and the waveforms of the second Hall signals HBu, HBv, and HBw output from the second magnetic sensors 21, 22, and 23 in the first and second cases. Figure 9 shows the waveforms of the three averaged signals Hu, Hv, and Hw calculated based on the first Hall signals HAu, HAv, and HAw and the second Hall signals HBu, HBv, and HBw.

[0036] In the first and second cases, as the rotor shaft 110 rotates, the air gap between the sensor magnet 120 and the first magnetic sensors 11, 12, and 13 changes periodically. As a result, as shown in the upper waveform of Figure 8, the amplitude values ​​of the first Hall signals HAu, HAv, and HAw fluctuate periodically over one mechanical angle period. As shown in Figure 8, one electrical angle period of each of the first Hall signals HAu, HAv, and HAw corresponds to a mechanical angle of 90°. Furthermore, the first Hall signals HAu, HAv, and HAw have a phase difference of 120° electrical angle (30° mechanical angle) from each other.

[0037] Although the second magnetic sensors 21, 22, and 23 are omitted in Figures 6 and 7, in both the first and second cases, as the rotor shaft 110 rotates, the air gap between the sensor magnet 120 and the second magnetic sensors 21, 22, and 23 also changes periodically. As a result, as shown in the lower waveform of Figure 8, the amplitude values ​​of the second Hall signals HBu, HBv, and HBw also fluctuate periodically over one mechanical angle period. Note that, as shown in Figure 8, one electrical angle period of each of the second Hall signals HBu, HBv, and HBw corresponds to a mechanical angle of 90°. Furthermore, the second Hall signals HBu, HBv, and HBw have a phase difference of 120° electrical angle (30° mechanical angle) from each other.

[0038] As shown in Figure 8, there is a phase difference of 180° in mechanical angle between the first Hall signal HAu and the second Hall signal HBu. There is a phase difference of 180° in mechanical angle between the first Hall signal HAv and the second Hall signal HBv. There is a phase difference of 180° in mechanical angle between the first Hall signal HAw and the second Hall signal HBw. This means that there is a 180° mechanical angle phase difference between the amplitude fluctuation period of the first Hall signal HAu and the amplitude fluctuation period of the second Hall signal HBu. Similarly, there is a 180° mechanical angle phase difference between the amplitude fluctuation period of the first Hall signal HAv and the amplitude fluctuation period of the second Hall signal HBv. Furthermore, there is a 180° mechanical angle phase difference between the amplitude fluctuation period of the first Hall signal HAw and the amplitude fluctuation period of the second Hall signal HBw.

[0039] In this way, by averaging a pair of first and second Hall signals whose amplitude values ​​fluctuate with a phase difference of 180° in the mechanical angle, averaged signals Hu, Hv, and Hw with constant amplitude values ​​over one mechanical angle period can be obtained, as shown in Figure 9. In this embodiment, when the sensor magnet 120 has an even number of magnetic pole pairs, the second Hall signal HBu exhibits amplitude fluctuations in which the positive and negative polarities match with respect to the amplitude fluctuations occurring in the first Hall signal HAu, with a phase difference of 180° in the mechanical angle. The same applies to the relationship between the first Hall signal HAv and the second Hall signal HBv, and the relationship between the first Hall signal HAw and the second Hall signal HBw.

[0040] As described above, if the sensor magnet 120 has an even number of magnetic pole pairs, in step S4, the processing unit 31 adds the output signal of the first magnetic sensor and the output signal of the second magnetic sensor, which is positioned on the opposite side of the rotor shaft 110 from the first magnetic sensor, and divides the sum by 2 to generate an averaged signal with a constant amplitude over one mechanical angle period.

[0041] Specifically, the processing unit 31 adds the first Hall signal HAu and the second Hall signal HBu, and divides the sum by 2 to generate an averaged signal Hu with a constant amplitude over one cycle of the mechanical angle. The processing unit 31 adds the first Hall signal HAv and the second Hall signal HBv, and divides the sum by 2 to generate an averaged signal Hv with a constant amplitude over one cycle of the mechanical angle. The processing unit 31 adds the first Hall signal HAw and the second Hall signal HBw, and divides the sum by 2 to generate an averaged signal Hw with a constant amplitude over one cycle of the mechanical angle.

[0042] Next, as shown in Figure 2, the processing unit 31 divides one period of the mechanical angle into four pole pair regions, each associated with a pole pair number representing the pole pair position of the four magnetic pole pairs, based on the three averaged signals Hu, Hv, and Hw obtained in step S4. Each of the four pole pair regions is further divided into multiple sections, and each of the multiple sections is associated with a segment number representing the rotational position of the rotor shaft 110 (step S5).

[0043] In this embodiment, in order to estimate the rotational position of the rotor shaft 110, pole pair numbers representing the pole pair positions are assigned to the four magnetic pole pairs of the sensor magnet 120. For example, as shown in Figure 1, the four magnetic pole pairs of the sensor magnet 120 are assigned pole pair numbers in the order of "0", "1", "2", and "3" in a clockwise direction.

[0044] As shown in Figure 3, the processing unit 31 divides one mechanical angle period into four pole-pair regions based on the averaged signals Hu, Hv, and Hw obtained during one mechanical angle period. In Figure 3, the period from time t1 to time t5 corresponds to one mechanical angle period. In Figure 3, "No. C" indicates the pole-pair number. The processing unit 31 divides the period from time t1 to time t2 within one mechanical angle cycle into a pole pair region associated with pole pair number "0". The processing unit 31 divides the period from time t2 to time t3 within one mechanical angle cycle into a pole pair region associated with pole pair number "1". The processing unit 31 divides the period from time t3 to time t4 within one mechanical angle cycle as a pole pair region associated with pole pair number "2". The processing unit 31 divides the period from time t4 to time t5 within one mechanical angle cycle into a pole pair region associated with pole pair number "3".

[0045] As shown in Figure 3, the processing unit 31 divides each of the four pole-pair regions into 12 sections based on the three averaged signals Hu, Hv, and Hw obtained in one cycle of the mechanical angle, and associates a segment number representing the rotational position of the rotor shaft 110 with each of the 12 sections. In Figure 3, "No. A" indicates the section number assigned to the section, and "No. B" indicates the segment number.

[0046] As shown in Figure 3, each of the 12 sections contained within the four pole-pair regions is assigned section numbers from "0" to "11". On the other hand, a number that is continuous throughout the entire period of one mechanical angle cycle is associated with each section as a segment number. Specifically, as shown in Figure 3, in the pole-pair region associated with pole-pair number "0", segment numbers "0" to "11" are associated with section numbers "0" to "11". In the pole-pair region associated with pole-pair number "1", segment numbers "12" to "23" are associated with section numbers "0" to "11". In the pole-pair region associated with pole-pair number "2", segment numbers "24" to "35" are associated with section numbers "0" to "11". In the pole-pair region associated with pole-pair number "3", segment numbers "36" to "47" are associated with section numbers "0" to "11".

[0047] Figure 4 is a magnified view of the averaged signals Hu, Hv, and Hw contained within one pole-pair region. The method for dividing the pole-pair region into 12 sections will be explained below with reference to Figure 4. In Figure 4, the reference value for amplitude is "0". In Figure 4, a positive digital amplitude value represents, for example, the digital value of the magnetic field strength of the north pole. A negative digital amplitude value represents, for example, the digital value of the magnetic field strength of the south pole.

[0048] The processing unit 31 extracts zero-crossing points, which are the points where the three averaged signals Hu, Hv, and Hw contained in each of the four pole-pair regions intersect with the reference value "0". As shown in Figure 4, the processing unit 31 extracts points P1, P3, P5, P7, P9, P11, and P13 as zero-crossing points.

[0049] The processing unit 31 then extracts the intersection points, which are the points where the three averaged signals Hu, Hv, and Hw contained in each of the four pole-pair regions intersect with each other. As shown in Figure 4, the processing unit 31 extracts points P2, P4, P6, P8, P10, and P12 as intersection points. The processing unit 31 then determines the intervals between adjacent zero-crossing points and intersection points as sections.

[0050] As shown in Figure 4, the processing unit 31 determines that the section between the zero-crossing point P1 and the intersection point P2 is the section to which section number "0" is assigned. The processing unit 31 determines that the section between intersection point P2 and zero-crossing point P3 is the section to which section number "1" is assigned. The processing unit 31 determines that the section between the zero-crossing point P3 and the intersection point P4 is the section to which section number "2" is assigned. The processing unit 31 determines that the section between intersection point P4 and zero-crossing point P5 is the section to which section number "3" is assigned. The processing unit 31 determines that the section between the zero-crossing point P5 and the intersection point P6 is the section to which section number "4" is assigned. The processing unit 31 determines that the section between intersection point P6 and zero-crossing point P7 is the section to which section number "5" is assigned.

[0051] The processing unit 31 determines that the section between the zero-crossing point P7 and the intersection point P8 is the section to which section number "6" is assigned. The processing unit 31 determines that the section between intersection point P8 and zero-crossing point P9 is the section to which section number "7" is assigned. The processing unit 31 determines that the section between the zero-crossing point P9 and the intersection point P10 is the section to which section number "8" is assigned. The processing unit 31 determines that the section between intersection point P10 and zero-crossing point P11 is the section to which section number "9" is assigned. The processing unit 31 determines that the section between the zero-crossing point P11 and the intersection point P12 is the section to which section number "10" is assigned. The processing unit 31 determines that the section between intersection point P12 and zero-crossing point P13 is the section to which section number "11" is assigned.

[0052] Furthermore, the processing unit 31 extracts feature data for each section, such as the relative magnitudes of the detected averaged signals Hu, Hv, and Hw, and the signs of each detected value, and associates the extracted feature data with the section number of each section.

[0053] As a result of step S5 being performed as described above, one cycle of the machine angle is divided into four pole-pair regions associated with pole-pair numbers, as shown in Figure 3. Each of the four pole-pair regions is divided into 12 sections, and a segment number is associated with each section number. In the following explanation, for example, the section assigned section number "0" will be referred to as "section 0," and the section assigned section number "11" will be referred to as "section 11."

[0054] Finally, the processing unit 31 acquires data showing the correspondence between feature data associated with section numbers, segment numbers representing rotational positions associated with section numbers, and pole pair numbers representing pole pair positions as learning data, and stores the acquired learning data in the storage unit 32 (step S6).

[0055] Next, the position estimation process performed by the processing unit 31 will be described. Figure 5 is a flowchart showing the position estimation process performed by the processing unit 31. After performing the learning process described above, the processing unit 31 performs the position estimation process shown in Figure 5 when the power to the position detection device 1 is turned on again. The processing unit 31 also repeatedly performs the position estimation process shown in Figure 5 at a predetermined interval.

[0056] As shown in Figure 5, when the processing unit 31 starts the position estimation process, it first obtains three first Hall signals HAu, HAv, and HAw from the first sensor group 10, which includes three first magnetic sensors 11, 12, and 13 (step S11). This step S11 corresponds to the first step in the position detection method of claim 6.

[0057] In parallel with step S11, the processing unit 31 acquires three second Hall signals HBu, HBv, and HBw from the second sensor group 20, which includes three second magnetic sensors 21, 22, and 23 (step S12). This step S12 corresponds to the second step in the position detection method of claim 6.

[0058] Then, the processing unit 31 performs an averaging process to generate three averaged signals by averaging the output signal of the first magnetic sensor and the output signal of the second magnetic sensor, which is positioned on the opposite side of the rotor shaft 110 from the first magnetic sensor (step S13). This step S13 corresponds to the third step in the position detection method of claim 6.

[0059] Similar to the learning process described above, if the sensor magnet 120 has an even number of magnetic pole pairs, in step S13, the processing unit 31 adds the output signal of the first magnetic sensor and the output signal of the second magnetic sensor, which is positioned on the opposite side of the rotor shaft 110 from the first magnetic sensor, and divides the sum by 2 to generate an averaged signal with a constant amplitude over one mechanical angle period.

[0060] Specifically, the processing unit 31 adds the first Hall signal HAu and the second Hall signal HBu, and divides the sum by 2 to generate an averaged signal Hu with a constant amplitude over one cycle of the mechanical angle. The processing unit 31 adds the first Hall signal HAv and the second Hall signal HBv, and divides the sum by 2 to generate an averaged signal Hv with a constant amplitude over one cycle of the mechanical angle. The processing unit 31 adds the first Hall signal HAw and the second Hall signal HBw, and divides the sum by 2 to generate an averaged signal Hw with a constant amplitude over one cycle of the mechanical angle.

[0061] Then, the processing unit 31 performs an estimation process to estimate the rotational position of the motor 100 based on the three averaged signals Hu, Hv, and Hw obtained in step S13 (steps S14 and S15). These steps S14 and S15 correspond to the fourth step in the position detection method of claim 6.

[0062] Specifically, the processing unit 31 identifies the current section from among the 12 sections based on the three averaged signals Hu, Hv, and Hw (step S14). For example, in Figure 4, it is assumed that the points PHu located on the waveform of the averaged signal Hu, PHv located on the waveform of the averaged signal Hv, and PHw located on the waveform of the averaged signal Hw are the detected values ​​(digital values) of each averaged signal Hu, Hv, and Hw obtained during the execution of this position estimation process. The processing unit 31 extracts feature data such as the magnitude relationship of the detected values ​​of points PHu, PHv, and PHw, and the sign of each detected value. By comparing the extracted feature data with the learning data stored in the storage unit 32, the processing unit 31 identifies the section number associated with the feature data that matches the extracted feature data as the current section. In the example in Figure 4, section 9 is identified as the current section.

[0063] Then, the processing unit 31 determines the current segment number as the rotation position of the motor 100 based on the identified current section (section number) and the learning data stored in the memory unit 32 (step S15). For example, let's assume that section 9 is identified as the current section, as described above. Let's also assume that the pole pair number at the time of execution of this position estimation process is "2". In this case, as shown in Figure 3, the processing unit 31 determines segment number "33" as the rotation position of the motor 100.

[0064] As explained above, in the first case, when the rotor shaft 110 rotates with its central axis 111 eccentric with respect to the central axis 121 of the sensor magnet 120, and in the second case, when the rotor shaft 110 rotates with the sensor magnet 120 tilted with respect to a plane 112 perpendicular to the rotor shaft 110, the amplitude values ​​of the first Hall signals HAu, HAv, and HAw fluctuate periodically over one mechanical angle period due to the periodic change in the air gap between the sensor magnet 120 and the first magnetic sensors 11, 12, and 13.

[0065] Therefore, if the rotational position of the motor 100 is detected using only the three first magnetic sensors 11, 12, and 13, as in conventional technology, when either the first or second case described above occurs, the feature data extracted from the first Hall signals HAu, HAv, and HAw cannot be correlated with the feature data included in the training data during the execution of the position estimation process, which may lead to the incorrect section number being identified as the current section. As a result, the wrong segment number is determined as the rotational position of the motor 100, and the accuracy of rotational position detection decreases.

[0066] In the position detection device 1 of this embodiment, three second magnetic sensors are positioned on opposite sides of the rotor shaft 110 in the radial direction of the sensor magnet 120 for each of the three first magnetic sensors. In this case, the second Hall signal output from the second magnetic sensor exhibits amplitude fluctuations with a phase difference of 180° in mechanical angle relative to the amplitude fluctuations occurring in the first Hall signal output from the paired first magnetic sensor. Therefore, in the position detection device 1 of this embodiment, three averaged signals are obtained in which the amplitude value remains constant over one mechanical angle period by averaging the pair of first and second Hall signals whose amplitude values ​​fluctuate with a phase difference of 180° in mechanical angle.

[0067] As a result, even if either the first or second case described above occurs, the feature data extracted from the averaged signals Hu, Hv, and Hw during the position estimation process can be correlated with the feature data included in the training data, allowing the accurate section number to be identified as the current section. Consequently, the accurate segment number can be determined as the rotational position of the motor 100, thereby suppressing a decrease in the accuracy of rotational position detection.

[0068] Furthermore, in this embodiment, the sensor magnet 120 has an even number of magnetic pole pairs. In this case, the second Hall signal output from the second magnetic sensor has amplitude fluctuations in which the positive and negative polarities match with a phase difference of 180° in mechanical angle relative to the amplitude fluctuations occurring in the first Hall signal output from the paired first magnetic sensor. Therefore, in the position detection device 1 of this embodiment, the output signal of the first magnetic sensor and the output signal of the second magnetic sensor, which is positioned on the opposite side of the rotor shaft 110 from the first magnetic sensor, are added together, and the sum is divided by 2 to obtain an averaged signal in which the amplitude value is constant over one mechanical angle period.

[0069] Furthermore, in this embodiment, the sensor magnet 120 is a disc-shaped magnet attached to the rotor shaft 110 of the motor 100. According to this embodiment, when using the sensor magnet 120 as a magnet for position detection, even if one of the following occurs, the rotor shaft 110 rotates with the central axis 111 of the rotor shaft 110 being eccentric with respect to the central axis 121 of the sensor magnet 120, or the rotor shaft 110 rotates with the sensor magnet 120 tilted with respect to a plane 112 perpendicular to the rotor shaft 110, a decrease in the accuracy of detecting the rotational position can be suppressed.

[0070] (modified version) The present invention is not limited to the embodiments described above, and the configurations described herein can be combined as appropriate, within the bounds of non-inconsistency. For example, in the above embodiment, the case in which the sensor magnet 120 has an even number of magnetic pole pairs was illustrated. However, if the sensor magnet 120 has an odd number of magnetic pole pairs, the second Hall signal output from the second magnetic sensor will have an amplitude fluctuation in which the polarity is reversed with a phase difference of 180° in mechanical angle relative to the amplitude fluctuation occurring in the first Hall signal output from the paired first magnetic sensor. Therefore, if the sensor magnet 120 has an odd number of pole pairs, the processing unit 31 may, in step S13, subtract the output signal of the second magnetic sensor, which is located on the opposite side of the rotor shaft 110 from the output signal of the first magnetic sensor, and generate an averaged signal by dividing the subtraction result by 2. This makes it possible to obtain an averaged signal with a constant amplitude value over one mechanical angle period, even if the sensor magnet 120 has an odd number of pole pairs.

[0071] In the above embodiment, an example was given in which a sensor magnet 120 is used as a magnet for position detection, that is, a magnet that rotates in synchronization with the rotor shaft 110 of the motor 100. However, a rotor magnet attached to the rotor of the motor 100 may also be used as a magnet for position detection. A rotor magnet is also a magnet that rotates in synchronization with the rotor shaft 110 and has multiple magnetic pole pairs. As a result, when using a rotor magnet as a magnet for position detection, even if either the rotor shaft 110 rotates with its central axis 111 eccentric with respect to the central axis of the rotor magnet, or the rotor shaft 110 rotates with the rotor magnet tilted with respect to a plane 112 perpendicular to the rotor shaft 110, a decrease in the accuracy of detecting the rotational position can be suppressed.

[0072] In the above embodiment, an example was given in which the first sensor group 10 includes three first magnetic sensors 11, 12, and 13, and the second sensor group 20 includes three second magnetic sensors 21, 22, and 23. However, the number of first and second magnetic sensors is not limited to three, but can be N (where N is a multiple of 3). Also, in the above embodiment, an example was given in which one set of the first sensor group and the second sensor group is provided, but multiple sets of the first sensor group and the second sensor group may be provided.

[0073] In the above embodiment, an example was given in which the sensor magnet 120 has four pole pairs, but the number of pole pairs of the sensor magnet 120 is not limited to four. Similarly, when a rotor magnet is used as a magnet for position detection, the number of pole pairs of the rotor magnet is not limited to four.

[0074] [Examples of application] Figure 10 is a schematic diagram showing the external appearance of an automated guided vehicle 200, which is an example of the application of the present invention. Figure 11 is a schematic diagram showing the external appearance of a sewing machine 300, which is an example of the application of the present invention. The automated guided vehicle 200 and the sewing machine 300 each include a motor and a position detection device for detecting the rotational position of the motor. The motor 100 described in the above embodiment can be used as the motor. The position detection device 1 of the above embodiment can be used as the position detection device. Furthermore, the applications of the present invention are not limited to the automated guided vehicle 200 and the sewing machine 300, but can be broadly applied to motor-driven devices such as robots. [Explanation of Symbols]

[0075] 1...Position detection device, 10...First sensor group, 11, 12, 13...First magnetic sensor, 20...Second sensor group, 21, 22, 23...Second magnetic sensor, 30...Signal processing device, 31...Processing unit, 32...Storage unit, 100...Motor, 110...Rotor shaft, 120...Sensor magnet (magnet), 200...Automated guided vehicle, 300...Sewing machine

Claims

1. A position detection device for detecting the rotational position of a motor, A first sensor group including N (N is a multiple of 3) first magnetic sensors that are opposite to a magnet that rotates in synchronization with the rotation axis of the motor and are arranged at predetermined intervals along the direction of rotation of the magnet, A second sensor group includes, for each of the N first magnetic sensors, N second magnetic sensors arranged on opposite sides of the rotation axis in the radial direction of the magnet, A signal processing device that processes the output signals output from each of the N first magnetic sensors and the N second magnetic sensors, Equipped with, The signal processing device is An averaging process is performed for each of the N first magnetic sensors to generate N averaged signals by averaging the output signal of one of the N first magnetic sensors and the output signal of one of the N second magnetic sensors that is positioned on the opposite side of the rotation axis from the first first magnetic sensor, thereby generating N averaged signals. An estimation process for estimating the rotational position of the motor based on the N averaged signals, Execute Position detection device.

2. The aforementioned magnet has an even number of magnetic pole pairs, The signal processing device generates the N averaged signals by performing the following process for each of the N first magnetic sensors: adding the output signal of one of the N first magnetic sensors and the output signal of one of the N second magnetic sensors located on the opposite side of the rotation axis from the first magnetic sensor, and then dividing the sum by 2. The position detection device according to claim 1.

3. The aforementioned magnet has an odd number of magnetic pole pairs, The signal processing device generates the N averaged signals by performing the following process for each of the N first magnetic sensors: subtracting the output signal of one of the N first magnetic sensors, which is located on the opposite side of the rotation axis from the first first magnetic sensor, from the output signal of one of the N first magnetic sensors, and then dividing the subtraction result by 2. The position detection device according to claim 1.

4. The magnet is a disc-shaped magnet attached to the rotating shaft of the motor. A position detection device according to any one of claims 1 to 3.

5. The magnet is a rotor magnet attached to the rotor of the motor. A position detection device according to any one of claims 1 to 3.

6. A position detection method for detecting the rotational position of a motor, A first step of acquiring output signals from a group of first sensors, which includes N (N is a multiple of 3) first magnetic sensors that are positioned opposite a magnet that rotates in synchronization with the rotation axis of the motor and are arranged at predetermined intervals along the direction of rotation of the magnet, The second step is to acquire the output signals of the N second magnetic sensors from a second sensor group that includes N second magnetic sensors positioned on opposite sides of the rotation axis in the radial direction of the magnet for each of the N first magnetic sensors, A third step involves generating N averaged signals by performing a process for each of the N first magnetic sensors to average the output signal of one of the N first magnetic sensors and the output signal of one of the N second magnetic sensors that is positioned on the opposite side of the rotation axis from the first magnetic sensor, thereby generating N averaged signals. A fourth step involves estimating the rotational position of the motor based on the N averaged signals, Having, Location detection method.

7. The aforementioned magnet has an even number of magnetic pole pairs, In the above third step, The output signal of one of the N first magnetic sensors and the output signal of one of the N second magnetic sensors, which is positioned on the opposite side of the rotation axis from the first first magnetic sensor, are added together, and the sum is divided by 2. This process is performed for each of the N first magnetic sensors to generate the N averaged signals. The position detection method according to claim 6.

8. The aforementioned magnet has an odd number of magnetic pole pairs, In the above third step, The process of subtracting the output signal of one of the N first magnetic sensors, which is located on the opposite side of the rotation axis from the first first magnetic sensor, from the output signal of one of the N first magnetic sensors, and then dividing the result of the subtraction by 2, is performed for each of the N first magnetic sensors to generate the N averaged signals. The position detection method according to claim 6.

9. The magnet is a disc-shaped magnet attached to the rotating shaft of the motor. A position detection method according to any one of claims 6 to 8.

10. The magnet is a rotor magnet attached to the rotor of the motor. A position detection method according to any one of claims 6 to 8.

11. Motor and, A position detection device according to any one of claims 1 to 5 for detecting the rotational position of the motor, An automated guided vehicle equipped with the following features.

12. Motor and, A position detection device according to any one of claims 1 to 5 for detecting the rotational position of the motor, A sewing machine equipped with the following features.

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