Stator and rotor interference monitoring method and monitoring device and motor and electric tool

Abstract

The application discloses a kind of monitoring methods of stator and rotor interference, comprising the following steps, six phases of motor are respectively labeled as 0, 1, 2, 3, 4 and 5, the current value of each phase in six phases with serial number 0, 1, 2, 3, 4 and 5 is obtained;After completing current value acquisition, first filtering is carried out, the current value of each phase obtained is stored by digital value, and every six phases is as a period, after recording a period, continue to record the next period, at least record 3 periods;The current value of six phases in the same period is compared, if the current value of six phases in the same period appears periodic change, then it represents that current appears periodic fluctuation;The current value of the same phase in different periods is compared, if the current value of the same phase in different periods appears periodic change, then it also represents that current appears periodic fluctuation.The application also discloses monitoring device and motor based on the above monitoring method.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of motor safety, in particular to a stator and rotor interference monitoring method, a monitoring device, a motor and a power tool. BACKGROUND

[0002] Three-phase motors have a wide range of applications due to their high operating efficiency, high operating stability, and fast startup, etc. For example, three-phase motors are used in many power tools. In order to ensure the stability of the motor during operation and avoid the stator and rotor of the motor from being stuck together to cause motor failure, a motor structure is disclosed in patent publication CN114421683A. In this structure, a circular arc surface is provided on the opposite surfaces of the stator and rotor to reduce the probability of interference between the stator and rotor. When the degree of interference is too large, the rotor may be stuck during operation. Although the circular arc surface can reduce the probability of the stator and rotor being stuck due to interference, for motors that need to operate in high-dust environments (including but not limited to motors on electric saws), dust will inevitably mix in the motor. The mixing of dust in the motor will cause the gap between the stator and rotor to become smaller. Therefore, for motors that need to operate in high-dust environments, regardless of the structure, the mixing of dust will cause the gap between the stator and rotor to become smaller. Therefore, for motors that need to operate in high-dust environments, in order to ensure their safe and reliable operation, their operation process must be monitored, and any slight interference must be addressed immediately. SUMMARY

[0003] The present application proposes a motor stator and rotor interference monitoring method to solve the above problems.

[0004] The technical solutions adopted by the present application are as follows:

[0005] A stator and rotor interference monitoring method includes the following steps:

[0006] S1 (current value acquisition step): Label the six phases of the motor as 0, 1, 2, 3, 4, and 5, respectively, and acquire the current value of each phase in the six phases with serial numbers 0, 1, 2, 3, 4, and 5;

[0007] S2 (storage step), store the acquired current value of each phase as a digital value, and record each six-phase as a cycle. After recording a cycle, continue to record the next cycle. At least 3 cycles are recorded;

[0008] S3 (analysis step), compare the current values of the six phases in the same cycle, if the current values of the six phases in the same cycle appear periodic change, it represents that the current appears periodic fluctuation; compare the current values of the same phase in different cycles, if the current values of the same phase in different cycles appear periodic change, it also represents that the current appears periodic fluctuation.

[0009] S4 (judgment step), if it is found that the current appears periodic fluctuation, it is judged that the interference appears between the stator and the rotor, if the current does not appear periodic fluctuation, it is judged that the interference does not appear between the stator and the rotor.

[0010] The principle of the monitoring method is as follows, because the motor is running when the rotor is running, the interference will change the speed or the resistance it receives, which will be very intuitive on the current of the motor, and the rotor is periodic, so the point of interference will appear periodically as long as the rotor is rotating, so the current change can be monitored to determine whether the interference appears between the rotor and the stator.

[0011] The monitoring method can determine whether the motor appears interference by acquiring the current values of the motor and analyzing whether the current values of the motor appear periodic change, which is more reliable. Because the motor generates current when running, the monitoring method is more reliable than the traditional vibration monitoring analysis method and thermal imaging monitoring method, and can realize full monitoring of the motor running without disassembling the motor.

[0012] In summary, the monitoring method determines whether the stator and the rotor of the motor appear interference by monitoring the change of the motor phase current, which is convenient and reliable, and the motor can be monitored as soon as it is started, and the whole monitoring process does not need to disassemble the motor.

[0013] Optionally, it also includes a filtering step, which is performed after the current value is acquired, and then the acquired current value is stored.

[0014] Because harmonic interference, power frequency fluctuation, grid voltage fluctuation and load fluctuation will cause the current to change, in order to exclude the current change caused by the above reasons, the filtering processing is performed after sampling to exclude the above interference.

[0015] Optionally, the filtering step includes signal digitization, frequency and time domain processing and algorithm implementation.

[0016] In the monitoring method, the filtering uses the software of the acquisition module for filtering processing, which includes the following three steps.

[0017] First step, signal digitization,

[0018] Firstly, the continuous analog signal is converted into discrete digital signal by ADC (analog-to-digital converter) (i.e. sampling and quantization are completed). Meanwhile, the sampling frequency (e.g. 10 kHz) in this step needs to meet the Nyquist criterion (> 2 times the highest frequency of the signal).

[0019] Secondly, frequency domain and time domain processing

[0020] Firstly, frequency domain filtering: the signal is converted into frequency domain by Fourier transform, and then inverse transformed back into time domain after filtering specific frequency components.

[0021] Then, time domain filtering: the signal is processed in time domain by difference equation or sliding window algorithm.

[0022] Thirdly, algorithm implementation: the current and historical sampling values are weighted and calculated based on difference equation or convolution operation, and the filtered signal is output.

[0023] A monitoring device suitable for the monitoring method described above, comprising a collection module, a storage module and an analysis and operation module, the collection module is used to acquire current value and perform filtering processing, the storage module is used to store current value, and the analysis and operation module is used to analyze whether the current value stored in the storage module has periodic fluctuation.

[0024] The working process of the monitoring device is as follows: firstly, the collection module collects phase current of the camera, and after the phase current is collected, filtering processing is performed first to exclude the interference factors such as harmonic interference, power frequency fluctuation, grid voltage fluctuation and load fluctuation, then the current value is stored in the storage module, the collection of current data is performed in six phases as one cycle, the storage module stores the current value in cycles, and the analysis and operation module analyzes the current value between different phases in the same cycle and the current value between different cycles of the same phase to determine whether the current has periodic change, if the current value has periodic change, it is determined that interference occurs between the stator and the rotor of the motor.

[0025] Optionally, the collection module comprises an ADC collection module.

[0026] The current is converted from analog signal to digital signal by using the ADC collection module, which facilitates subsequent filtering processing.

[0027] Optionally, the storage module comprises but is not limited to RAM, and the operation and analysis module comprises but is not limited to CPU.

[0028] A motor comprising the monitoring device described above.

[0029] An electric tool comprising the motor described above.

[0030] The present application has the beneficial effects that whether the stator and the rotor of the motor interfere with each other is determined through monitoring the change of the motor phase current, the monitoring is convenient and reliable, and the motor can be monitored as soon as it is started to operate, and the whole monitoring process does not need to disassemble the motor. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description only represent some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art based on these drawings.

[0032] Figure 1 is a schematic diagram of the connection relationship of each module of the monitoring device;

[0033] In the drawings, the reference signs are: 1, acquisition module; 2, storage module, 3, analysis and operation module. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned purposes, features and advantages of the present application more apparent and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the drawings.

[0035] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the present application, therefore the present application is not limited by the specific embodiments disclosed below.

[0036] In the description of the present application, it should be noted that the terms used herein are only for the purpose of describing the specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. For the convenience of description, the size of each part shown in the drawings is not drawn according to the actual proportional relationship. The technology, method and equipment known to those skilled in the related art can not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as part of the authorized description. In all examples shown and discussed herein, any specific value should be interpreted as merely exemplary, and not as a limitation. Therefore, other examples of exemplary embodiments can have different values. It should be noted that similar reference signs and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0037] Embodiment 1

[0038] A stator and rotor interference monitoring method, comprising the following steps.

[0039] S1 (current value acquisition step): six phases of the motor are labeled as 0, 1, 2, 3, 4 and 5 respectively, and the current value of each phase in the six phases with serial numbers 0, 1, 2, 3, 4 and 5 is acquired;

[0040] S2 (filtering step), after the current value is acquired, filtering is performed first to exclude the case that the current changes due to harmonic interference, power frequency fluctuation, grid voltage fluctuation and load fluctuation;

[0041] S3 (storage step), the acquired current value of each phase is stored by digital value, and each six phases are taken as a period, and the recording of the next period is continued after the recording of one period is completed, and at least 3 periods are recorded;

[0042] S4 (analysis step), the current values of the six phases in the same period are compared, if the current values of the six phases in the same period change periodically, it represents that the current changes periodically; the current values of the same phase in different periods are compared, if the current values of the same phase in different periods change periodically, it also represents that the current changes periodically;

[0043] S5 (judgment step), if it is found that the current changes periodically, it is judged that the interference between the stator and the rotor occurs, if the current does not change periodically, it is judged that the interference between the stator and the rotor does not occur.

[0044] In the embodiment, the software of the acquisition module is used for filtering processing, and the whole filtering process includes the following three steps.

[0045] First step, signal digitization,

[0046] Firstly, the continuous analog signal is converted into discrete digital signal (i.e. sampling + quantization is completed) through ADC (analog-to-digital converter). At the same time, the sampling frequency (such as 10 kHz) in this step needs to meet the Nyquist criterion (> 2 times the highest frequency of the signal).

[0047] Second step, frequency domain and time domain processing

[0048] Firstly, frequency domain filtering: the signal is converted to frequency domain through Fourier transform, and after filtering specific frequency components, it is inversely transformed back to time domain.

[0049] Then, time domain filtering: the signal is directly processed in time domain through difference equation or sliding window algorithm.

[0050] Third step, algorithm implementation, i.e. based on difference equation or convolution operation, the current and historical sampling values are weighted and calculated, and the filtered signal is output.

[0051] In combination with the table, the current periodic change in the embodiment is described in detail.

[0052] Table 1

[0053] 0 1 2 3 4 5 A Large Small Small Large Small Small B Large Small Small Large Small Small C Large Small Small Large Small Small D Large Small Small Large Small Small

[0054] Table 2

[0055] 0 1 2 3 4 5 A Small Small Small Large Small Small B Large Small Small Small Small Small C Small Small Small Large Small Small D Large Small Small Small Small Small

[0056] Table 3

[0057] 0 1 2 3 4 5 A Large Large Large Large Large Large B Small Small Small Small Small Small C Large Large Large Large Large Large D Small Small Small Small Small Figure 1

[0058] The above tables 1-3 are combined to make a detailed explanation of whether there is interference in the monitoring method.

[0059] The 0-5 in the horizontal direction of tables 1-3 represent six phases of the motor, and A, B, C, and D represent four cycles. The above three tables only show four cycles, but in fact, the cycles are repeated continuously, and there are more than four cycles of A, B, C, and D. The tables 1-3 do not enumerate them. In order to more clearly show the change of current value, only large or small is used to describe the current value in each phase. Large represents normal current value, and small represents less than normal current value.

[0060] First, looking at table 1, in cycles A to D, the current values of 0 and 3 phases are large, and the current values of 1, 2, 4, and 5 phases are small. This is a typical periodic change, which indicates that there is interference between the stator and the rotor of the motor.

[0061] Next, looking at table 2, in cycles A to D, the current values of 0-5 phases change in each cycle, but the change of current value in the same cycle is not periodic. However, in different cycles, the same phase appears a periodic change of current, such as 0 phase in cycles A-D, the current appears a periodic change of small and large. Similarly, 3 phase also appears a periodic change of small and large in cycles A-D. Therefore, the current value of the same phase changes periodically in different cycles in table 2, so there is also interference between the stator and the rotor of the motor.

[0062] Finally, looking at table 3, in cycles A to D, the current values of 0-5 phases do not change in the same cycle, but the current value of the same phase changes periodically in different cycles. Therefore, the motor also has interference as shown in table 3.

[0063] It should be particularly pointed out that Tables 1-3 only enumerate several current periodic change cases, and other current periodic change cases are not enumerated one by one in this embodiment. As long as the current periodic change is monitored, it means that the stator and the rotor of the motor have the interference phenomenon.

[0064] Embodiment 2

[0065] A monitoring device for monitoring whether the stator and the rotor of the motor have the interference, adopts the monitoring method as shown in Embodiment 1 to monitor.

[0066] As shown in the accompanying drawings, ​ The monitoring device includes a collection module 1, a storage module 2 and an analysis and operation module 3. The collection module is used to acquire the current value and perform filtering processing. The storage module is used to store the current value. The analysis and operation module is used to analyze whether the current value stored in the storage module has the periodic fluctuation.

[0067] The working process of the monitoring device is as follows. The collection module collects the phase current of the motor. After the phase current is collected, the filtering processing is performed first. After the interference factors such as harmonic interference, power frequency fluctuation, grid voltage fluctuation and load fluctuation are excluded, the current value is stored in the storage module. The current data is collected in six phases as one cycle. The storage module stores the current value in cycles. The analysis and operation module analyzes the current value between different phases in the same cycle and the current value between different cycles of the same phase to determine whether the current has the periodic change. If the current value has the periodic change, it is determined that the stator and the rotor of the motor have the interference.

[0068] In this embodiment, the collection module includes an ADC collection module.

[0069] The current is sampled by the ADC collection module, so that the current can be converted from an analog signal to a digital signal, which is convenient for subsequent filtering processing.

[0070] In this embodiment, the storage module includes but is not limited to RAM, and the operation analysis module includes but is not limited to CPU.

[0071] In this embodiment, the monitoring device can be a single-chip microcomputer integrated with the ADC collector, the RAM and the CPU.

[0072] Embodiment 3

[0073] A brushless three-phase motor includes a stator and a rotor, which can rotate relative to each other. The monitoring device as shown in Embodiment 2 is used to monitor whether the stator and the rotor have the interference.

[0074] Embodiment 4

[0075] An electric tool comprising the motor as shown in embodiment 3, which can be an electric drill, an electric saw or other types of tools, and the motor used in the environment with high dust can also adopt the motor as shown in embodiment 3. In the electric tool, the motor with the monitoring device in embodiment 3 is adopted, so that the running state of the motor can be monitored at any time during use, the reliability during use is ensured, and the failure caused by the interference between the stator and the rotor of the motor is reduced.

[0076] The above-mentioned embodiments only express some embodiments of the present application, which are described in more detail and in more detail, but cannot be understood as the limitation of the patent scope of the present application. It should be pointed out that for those skilled in the art, the technical solutions recorded in the above-mentioned embodiments can still be modified, or some technical features can be replaced equivalently. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for monitoring stator-rotor interference, characterized in that, Includes the following steps, Steps for obtaining current value: Label the six phases of the motor as 0, 1, 2, 3, 4 and 5 respectively, and obtain the current value of each of the six phases with the serial numbers 0, 1, 2, 3, 4 and 5 respectively; The storage step involves storing the acquired current value of each phase as a digital value, with each six phases constituting a cycle. After recording one cycle, the recording continues for the next cycle, with a minimum of three cycles recorded. The analysis steps involve comparing the current values ​​of the six phases within the same period. If the current values ​​of the six phases within the same period show periodic changes, it indicates that the current has experienced periodic fluctuations. Similarly, comparing the current values ​​of the same phase within different periods also indicates that the current has experienced periodic fluctuations. The judgment process is as follows: if periodic fluctuations in the current are found, it is determined that there is interference between the stator and the rotor; if there are no periodic fluctuations in the current, it is determined that there is no interference between the stator and the rotor.

2. The stator and rotor interference monitoring method according to claim 1, characterized in that, It also includes a filtering step, in which the current value is first filtered after acquisition, and then the acquired current value is stored.

3. The stator and rotor interference monitoring method according to claim 2, characterized in that, The filtering steps include signal digitization, frequency domain and time domain processing, and algorithm implementation.

4. A monitoring device applicable to the monitoring method as described in any one of claims 1 to 3, characterized in that, It includes a data acquisition module, a storage module, and an analysis and calculation module. The data acquisition module is used to acquire current values ​​and perform filtering processing. The storage module is used to store current values. The analysis and calculation module is used to analyze whether the current values ​​stored in the storage module have periodic fluctuations.

5. The monitoring device according to claim 4, characterized in that, The acquisition module includes an ADC acquisition module.

6. The monitoring device according to claim 4, characterized in that, The storage module includes RAM, and the analysis and processing module includes a CPU.

7. An electric motor, characterized in that, Includes the monitoring device as described in any one of claims 4 to 6.

8. A power tool, characterized in that, Including the motor as described in claim 7.

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