A method and apparatus for measuring the speed of an electric motor

Abstract

The application discloses a motor speed measurement method and device, the method comprises the following steps: at least two groups of magnetic field sensing components; the magnetic field sensing component comprises at least one Hall element group; the Hall element group comprises a first Hall element installed in a forward direction and a second Hall element installed in a reverse direction; the first Hall element is used for outputting a first measurement waveform; the second Hall element is used for outputting a second measurement waveform; a differential amplification module is arranged in one-to-one correspondence with the magnetic field sensing component; the differential amplification module is used for outputting a first differential amplification signal according to the first measurement waveform and the second measurement waveform; a shaping module is used for shaping the first differential amplification signal into a pulse square wave signal; a control module is electrically connected with the shaping module and is used for acquiring the rotating speed and rotating direction of the motor according to at least two pulse square wave signals. The technical scheme provided by the application can provide a simpler and more accurate speed measurement mode.

Description

Technical Field

[0001] This invention relates to the field of motor measurement technology, and in particular to a method and apparatus for measuring motor speed. Background Technology

[0002] Electric motors are used in various industries and have experienced rapid development. However, some industrial equipment requires stable speeds, as stable speeds improve product consistency. Therefore, motor manufacturers need to collect motor speed data during testing, and electric motors in new energy vehicles and other equipment also require speed testing to prevent overspeeding.

[0003] Traditional methods for testing motor speed involve measuring the rotational speed from the motor rotor. Specifically, this can be done using reflective strips, an encoder mounted on the motor shaft, or a tachometer directly contacting the motor shaft. These methods are relatively cumbersome and require additional manual labor during factory testing, thus impacting production efficiency. Summary of the Invention

[0004] This invention provides a method and apparatus for measuring motor speed, offering a simpler and more accurate way to measure speed.

[0005] In a first aspect, embodiments of the present invention provide a motor speed measuring device, comprising:

[0006] At least two sets of magnetic field sensing components; each magnetic field sensing component includes at least one set of Hall elements; each set of Hall elements includes a first Hall element mounted in the forward direction and a second Hall element mounted in the reverse direction; the first Hall element is used to output a first measurement waveform; the second Hall element is used to output a second measurement waveform.

[0007] A differential amplifier module is provided, corresponding to each of the magnetic field sensing components; the differential amplifier module is used to output a first differential amplified signal based on the first measurement waveform and the second measurement waveform;

[0008] The shaping module is used to shape the first differential amplified signal into a pulse square wave signal;

[0009] The control module, electrically connected to the shaping module, is used to obtain the motor speed and direction of rotation based on at least two pulse square wave signals.

[0010] Secondly, embodiments of the present invention also provide a motor speed measurement method, applicable to the motor speed measurement device provided in any embodiment of the present invention, comprising:

[0011] A first measurement waveform and a second measurement waveform are acquired by acquiring the output of multiple Hall element groups through at least two sets of magnetic field sensing components; the magnetic field sensing components include at least one Hall element group; the Hall element group includes a first Hall element mounted in a forward orientation and a second Hall element mounted in a reverse orientation; the first Hall element is used to output the first measurement waveform; the second Hall element is used to output the second measurement waveform.

[0012] Based on the first measurement waveform and the second measurement waveform, at least two first differential amplification signals are obtained;

[0013] The first differential amplified signal is shaped into a pulse square wave signal;

[0014] The motor speed and direction of rotation are obtained from at least two of the pulse square wave signals.

[0015] In this invention, a non-contact method using Hall effect sensors is employed to measure the motor's speed and direction of rotation. Specifically, at least two sets of magnetic field sensing components are installed in the motor speed measuring device. Each set includes at least one group of Hall effect sensors, comprising a first Hall effect sensor and a second Hall effect sensor mounted facing forward. A differential amplification module is used to differentially amplify the test waveforms output by the Hall effect sensors in each set of magnetic field sensing components. This cancels out external magnetic field interference when acquiring the motor's weak magnetic field, improving the accuracy of motor speed measurement. Furthermore, the motor's speed and direction of rotation can be simultaneously obtained from the test waveforms output by both sets of magnetic field sensing components. This embodiment, by measuring the motor's external magnetic field, provides a convenient and efficient way to measure the motor's speed. The high sensitivity of the Hall effect sensors further enhances the measurement accuracy. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a motor speed measuring device provided in an embodiment of the present invention;

[0017] Figure 2 This is a schematic diagram of another motor speed measuring device provided in an embodiment of the present invention;

[0018] Figure 3 A schematic diagram of the measurement waveform of a Hall element provided in an embodiment of the present invention;

[0019] Figure 4 A differential magnified schematic diagram of the measurement waveforms of the first Hall element and the second Hall element provided in an embodiment of the present invention;

[0020] Figure 5 This is a schematic diagram of another motor speed measuring device provided in an embodiment of the present invention;

[0021] Figure 6This is a waveform diagram of a pulse square wave signal provided in an embodiment of the present invention;

[0022] Figure 7 A schematic diagram of the structure of an electric motor provided in an embodiment of the present invention;

[0023] Figure 8 This is a flowchart illustrating a motor speed measurement method provided in an embodiment of the present invention. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0025] This invention provides a motor speed measuring device, such as... Figure 1 As shown, Figure 1 This is a schematic diagram of a motor speed measuring device provided in an embodiment of the present invention. The motor speed measuring device includes:

[0026] At least two sets of magnetic field sensing components 11; the magnetic field sensing component 11 includes at least one Hall element group 111; the Hall element group 111 includes a first Hall element 112 mounted in the forward direction and a second Hall element 113 mounted in the reverse direction; the first Hall element 112 is used to output a first measurement waveform; the second Hall element 113 is used to output a second measurement waveform.

[0027] The differential amplifier module 12 is configured to correspond one-to-one with the magnetic field sensing component 11; the differential amplifier module 12 is used to output a first differential amplified signal based on the first measurement waveform and the second measurement waveform.

[0028] Shaping module 13 is used to shape the first differential amplified signal into a pulse square wave signal;

[0029] The control module 14, which is electrically connected to the shaping module 13, is used to obtain the motor speed and direction based on at least two pulse square wave signals.

[0030] In this embodiment of the invention, a non-contact method using Hall elements to measure the motor's speed and direction of rotation is employed. Specifically, at least two sets of magnetic field sensing components are installed in the motor speed measuring device. Each set of magnetic field sensing components includes at least one group of Hall elements, comprising a first Hall element and a second Hall element mounted in the forward direction. A differential amplification module is used to differentially amplify the test waveforms output by the Hall elements of each set of magnetic field sensing components. This cancels out external magnetic field interference when acquiring the weak magnetic field of the motor, improving the accuracy of motor speed measurement. Furthermore, the motor's speed and direction of rotation can be simultaneously acquired using the test waveforms output by both sets of magnetic field sensing components. This embodiment, by measuring the motor's external magnetic field, provides a convenient and efficient way to measure the motor's speed. The high sensitivity of the Hall elements further enhances the measurement accuracy.

[0031] The above is the core idea of ​​this invention. The technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0032] like Figure 1 As shown, traditional motor speed measurement methods directly measure the rotational speed from the motor rotor. Some traditional methods involve installing an encoder on the rotor, while others use a tachometer to directly contact the motor shaft. Both require manual operation, increasing labor costs during factory testing. The motor speed measurement method provided in this embodiment uses a high-sensitivity Hall element to measure the motor's rotational speed and direction of rotation without contact with the rotor. This achieves efficient testing of motor speed and direction of rotation, effectively saving labor costs. Furthermore, the non-contact measurement method does not burden the original system's structure or electronic environment. In addition, high-sensitivity Hall elements (such as the HAL4901 Hall element) are characterized by high sensitivity and low noise output, making them suitable for measuring weak magnetic fields. They can accurately capture the weak magnetic fields leaked outward from the motor, improving the accuracy of speed measurement. Specifically, the Hall element measures the magnetic field leaked outward from the motor to achieve efficient testing of motor speed and direction of rotation. Because the magnetic field leaked outward from the motor is very weak and easily interfered with by external magnetic fields, pairs of high-sensitivity Hall elements are used in a differential mode to cancel out external magnetic field interference.

[0033] In this embodiment, the motor speed measuring device includes at least two sets of magnetic field sensing components 11. Optionally, two or more magnetic field sensing components 11 can be provided. Figure 1Taking two magnetic field sensing components 11 as an example, the number of magnetic field sensing components 11 can also be four or eight, etc. This embodiment does not impose a special limitation on the number of magnetic field sensing components 11. When the motor speed measuring device includes two magnetic field sensing components 11, the direction of motor rotation can be determined by the measurement waveforms output by the two magnetic field sensing components 11. The magnetic field sensing component 11 includes at least one Hall element group 111. For example, each magnetic field sensing component 11 can be provided with one Hall element group 111. Each Hall element group 111 includes a first Hall element 112 installed in the forward direction and a second Hall element 113 installed in the reverse direction. The magnetic pole direction (motor magnetic field) of the first Hall element 112 installed in the forward direction is consistent with the current direction, and outputs a positive motor signal; the magnetic pole direction (motor magnetic field) of the second Hall element 113 installed in the reverse direction is opposite to the current direction, and outputs a negative motor signal. In this embodiment, the first Hall element 112 outputs a first measurement waveform, and the second Hall element 113 outputs a second measurement waveform.

[0034] Differential amplification modules 12 are configured one-to-one to amplify the first and second measurement waveforms at least one stage to cancel out external magnetic field interference, ultimately forming the first differential amplified signal. Shaping module 13 shapes the first differential amplified signal into a more distinct pulse square wave signal and inputs it to control module 14. This allows control module 14 to obtain the motor's speed and direction of rotation based on multiple pulse square wave signals. The structure of the motor speed measuring device in this embodiment is relatively simple; using a Hall element for contactless motor measurement allows for safe and reliable measurement of motor speed and rotation direction. Optionally, the Hall element in this embodiment can be a HAL4901, which features high sensitivity and low noise output, suitable for measuring weak magnetic fields, and capable of measuring weak magnetic fields leaked from the motor, thus improving the accuracy of speed measurement.

[0035] Figure 2 This is a schematic diagram of another motor speed measuring device provided in an embodiment of the present invention. Optionally, the differential amplifier module 12 may include: a first-stage operational amplifier 121 and a second-stage operational amplifier 122; the first-stage operational amplifier 121 is configured to correspond one-to-one with the Hall element group 111; the first-stage operational amplifier 121 is used to receive a first measurement waveform and a second measurement waveform and output a second differential amplified signal; the second-stage operational amplifier 122 is used to receive two second differential amplified signals and output a first differential amplified signal.

[0036] The number of first-stage operational amplifiers 121 is the same as the number of Hall element groups. The first-stage operational amplifiers 121 are used to differentially amplify the first and second measurement waveforms output from the same Hall element group to generate a second differential amplified signal, which cancels out external interference magnetic fields. Figure 3This is a schematic diagram of the measurement waveform of a Hall element provided in an embodiment of the present invention. Figure 4 This is a differential magnified schematic diagram of the measurement waveforms of the first Hall element and the second Hall element provided in an embodiment of the present invention. (Reference) Figure 3 and Figure 4 The measurement waveform of a single Hall element exhibits significant glitches, while the second differential amplified signal, output differentially from the measurement waveforms of paired Hall elements, no longer shows significant glitches. This indicates that differentially outputting the measurement waveforms of the paired first Hall element 112 and second Hall element 113 in Hall element group 111 effectively filters out external interference signals. Figure 2 As shown, each magnetic field sensing component includes two groups of Hall elements, thus each component includes two front-mounted and two rear-mounted Hall elements, for a total of four. Two sets of first-stage operational amplifiers 121 generate two second differential amplified signals to further cancel out external interference magnetic fields. The second differential amplified signals output from the two first-stage operational amplifiers 121 are further differentially amplified to form a first differential amplified signal, thereby further canceling out external interference magnetic fields. Optionally, the differential amplification module 12 in this embodiment can be an LM324 operational amplifier circuit, which can perform two-stage differential amplification on the four Hall elements, effectively preventing external magnetic fields from interfering with the magnetic field measurement of the motor.

[0037] Optionally, the shaping module 13 in this embodiment can also be implemented using an LM324 operational amplifier circuit. For example... Figure 5 As shown, Figure 5 This is a schematic diagram of another motor speed measuring device provided in an embodiment of the present invention. The motor speed measuring device can be equipped with three LM324 operational amplifier circuits. Two of these LM324 operational amplifier circuits can differentially amplify four Hall effect sensors to form a first differential amplified signal. The last LM324 operational amplifier circuit shapes the two first differential amplified signals into a pulse square wave signal, such as... Figure 6 As shown, Figure 6This is a waveform diagram of a pulse square wave signal provided in an embodiment of the present invention. The pulse square wave signal facilitates subsequent control module 14 in measuring the motor speed based on its frequency. Control module 14 can be an STC8G1K17A microcontroller or an instrument capable of measuring frequency. Control module 14 can perform frequency measurement to calculate the speed and direction of rotation, and upload the speed and direction signals to a host computer or an instrument requiring speed display via two serial lines. Optionally, control module 14 can specifically be used to: obtain the motor speed based on the frequency of the pulse square wave signal; and obtain the motor direction based on the order of the pulse start edges between two pulse square wave signals. For example, if the two pulse square wave signals are a first pulse square wave signal and a second pulse square wave signal, and the pulse start edge of the first pulse square wave signal is earlier than the pulse start edge of the second pulse square wave signal, then the motor is rotating forward; if the pulse start edge of the first pulse square wave signal is later than the pulse start edge of the second pulse square wave signal, then the motor is rotating in reverse.

[0038] Optionally, the magnetic field sensing component may include at least: a first magnetic field sensing component and a second magnetic field sensing component; the first magnetic field sensing component is disposed at a first disposed position; the second magnetic field sensing component is disposed at a second disposed position; the time at which the first disposed position receives the motor magnetic field is different from the time at which the second disposed position receives the motor magnetic field. Because the first magnetic field sensing component and the second magnetic field sensing component receive the motor magnetic field at different times, the resulting first pulse square wave signal and the second pulse square wave signal have a phase difference. In this embodiment, the rotation direction of the motor can be determined based on the order of the pulse start edges of the first pulse square wave signal and the second pulse square wave signal.

[0039] Optionally, the output terminals of the first Hall element 112 and the second Hall element 113 in the Hall element group 111 can be electrically connected through a filter capacitor C1. The filter capacitor C1 is used to filter out the high-frequency carrier waves of the measurement waveforms of the first Hall element 112 and the second Hall element 113, further improving the accuracy of motor speed measurement.

[0040] Figure 7This is a schematic diagram of a motor structure provided in an embodiment of the present invention. Optionally, the motor speed measuring device 21 can be attached to the motor housing; it only needs to be placed close to or attached to the motor housing. It can be applied to factory testing of motors or in places where motor speed needs to be tested, offering advantages of low cost, simplicity, and reliability. Optionally, the motor speed measuring device can also be installed on the motor end cover or motor base; this embodiment does not specifically limit the specific installation position of the motor speed measuring device. This embodiment uses a non-contact rotor speed measurement method, requiring only the motor speed measuring device 21 containing a Hall element to be attached to the motor housing, allowing it to receive the magnetic field generated by the motor rotation. Compared to methods such as rotating an encoder on the motor shaft or directly contacting the motor shaft with a tachometer, this embodiment effectively reduces the labor costs during factory testing of motors. This invention uses a high-sensitivity Hall element non-contact motor rotor method to measure the motor's speed and rotation direction, and measures the magnetic field leaked outward from the motor, thereby achieving efficient testing of motor speed and rotation direction without burdening the original system structure and electronic environment, and improving the accuracy of speed measurement.

[0041] Based on the same concept, this invention also provides a motor speed measurement method, applicable to any embodiment of this invention. Figure 8 This is a flowchart illustrating a motor speed measurement method provided in an embodiment of the present invention, as shown below. Figure 8 As shown, the method in this embodiment includes the following steps:

[0042] Step S101: Obtain the first and second measurement waveforms output by multiple Hall element groups through at least two sets of magnetic field sensing components.

[0043] The magnetic field sensing component includes at least one Hall element group; the Hall element group includes a first Hall element mounted in the forward direction and a second Hall element mounted in the reverse direction; the first Hall element is used to output a first measurement waveform; the second Hall element is used to output a second measurement waveform.

[0044] Step S102: Obtain at least two first differential amplified signals based on the first measurement waveform and the second measurement waveform.

[0045] Step S103: Shape the first differential amplified signal into a pulse square wave signal.

[0046] Step S104: Obtain the motor speed and direction of rotation based on at least two pulse square wave signals.

[0047] In this embodiment of the invention, a non-contact method using Hall elements to measure the motor's speed and direction of rotation is employed. Specifically, at least two sets of magnetic field sensing components are installed in the motor speed measuring device. Each set of magnetic field sensing components includes at least one group of Hall elements, comprising a first Hall element and a second Hall element mounted in the forward direction. A differential amplification module is used to differentially amplify the test waveforms output by the Hall elements of each set of magnetic field sensing components. This cancels out external magnetic field interference when acquiring the weak magnetic field of the motor, improving the accuracy of motor speed measurement. Furthermore, the motor's speed and direction of rotation can be simultaneously acquired using the test waveforms output by both sets of magnetic field sensing components. This embodiment, by measuring the motor's external magnetic field, provides a convenient and efficient way to measure the motor's speed. The high sensitivity of the Hall elements further enhances the measurement accuracy.

[0048] Based on the above embodiments, obtaining at least two first differential amplified signals according to the first and second measurement waveforms may include: obtaining a second differential amplified signal based on the first and second measurement waveforms output from the same Hall element group; and outputting a first differential amplified signal based on the two second differential amplified signals. This embodiment performs multi-stage differential amplification on multiple pairs of first and second measurement waveforms, further reducing the interference of external magnetic fields on the motor magnetic field measurement and improving the accuracy of motor speed and direction measurement.

[0049] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A motor speed measuring device, characterized in that, include: At least two sets of magnetic field sensing components; each magnetic field sensing component includes at least one set of Hall elements; each set of Hall elements includes a first Hall element mounted in the forward direction and a second Hall element mounted in the reverse direction; the first Hall element is used to output a first measurement waveform; The second Hall element is used to output a second measurement waveform; A differential amplifier module is provided, corresponding to each of the magnetic field sensing components; the differential amplifier module is used to output a first differential amplified signal based on the first measurement waveform and the second measurement waveform; The shaping module is used to shape the first differential amplified signal into a pulse square wave signal; The control module, electrically connected to the shaping module, is used to obtain the motor speed and direction of rotation based on at least two pulse square wave signals; The magnetic field sensing component includes two groups of Hall elements; The differential amplifier module includes: a first-stage operational amplifier and a second-stage operational amplifier; The first-stage operational amplifier is configured to correspond one-to-one with the Hall element group; the first-stage operational amplifier is used to receive the first measurement waveform and the second measurement waveform and output a second differential amplified signal; The second-stage operational amplifier is used to receive the two second differential amplified signals and output the first differential amplified signal.

2. The motor speed measuring device according to claim 1, characterized in that, The control module is specifically used for: The rotational speed of the motor is obtained based on the frequency of the pulse square wave signal; The direction of the motor is obtained based on the order in which the pulse start edges appear between the two pulse square wave signals.

3. The motor speed measuring device according to claim 1, characterized in that, The motor speed measuring device is attached to the motor housing.

4. The motor speed measuring device according to claim 1, characterized in that, The motor speed measuring device is installed on the motor end cover or motor base.

5. The motor speed measuring device according to claim 1, characterized in that, The magnetic field sensing component includes at least: a first magnetic field sensing component and a second magnetic field sensing component; The first magnetic field sensing component is disposed at a first setting position; the second magnetic field sensing component is disposed at a second setting position; The time at which the first setting position receives the motor's magnetic field is different from the time at which the second setting position receives the motor's magnetic field.

6. The motor speed measuring device according to claim 1, characterized in that, The output terminal of the first Hall element in the Hall element group is electrically connected to the output terminal of the second Hall element through a filter capacitor.

7. A method for measuring the speed of a motor, characterized in that, The motor speed measuring device according to any one of claims 1-6 comprises: At least two sets of magnetic field sensing components are used to acquire a first measurement waveform and a second measurement waveform output by multiple Hall element groups; the magnetic field sensing components include at least one Hall element group; the Hall element group includes a first Hall element mounted in the forward direction and a second Hall element mounted in the reverse direction; the first Hall element is used to output the first measurement waveform; the second Hall element is used to output the second measurement waveform. Based on the first measurement waveform and the second measurement waveform, at least two first differential amplification signals are obtained; The first differential amplified signal is shaped into a pulse square wave signal; The motor speed and direction of rotation are obtained from at least two of the pulse square wave signals.

8. The motor speed measurement method according to claim 7, characterized in that, Based on the first measurement waveform and the second measurement waveform, at least two first differential amplified signals are obtained, including: The second differential amplified signal is obtained based on the first measurement waveform and the second measurement waveform output by the same Hall element group; The first differential amplified signal is output based on the two second differential amplified signals.

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