Linear hall-based eccentricity diagnosis method and detection system for permanent magnet motor

This application is a 371 of international application of PCT application serial no. PCT/CN2021/133956, filed on Nov. 29, 2021, which claims the priority benefit of China application no. 202111049671.3, filed on Sep. 8, 2021. The entirety of each of the above mentioned patent applications is hereby incorporated by reference herein and made a part of this specification.

The present invention relates to an eccentricity detection technology of a permanent magnet motor, particularly discloses a linear Hall-based eccentricity diagnosis method and a detection system for a permanent magnet motor, and belongs to the technical field of power generation, transformation or distribution.

Rotor eccentricity is one of the most common faults in motors, and rotor eccentricity in permanent magnet synchronous motors directly leads to asymmetrical air gap lengths, thereby resulting in unbalanced magnetic pull between a stator and a rotor. The unbalanced magnetic pull will further lead to other electrical and mechanical problems, such as unbalanced current loads in different phases, noise and vibration. Continuous operation of permanent magnet synchronous motors will result in bearing wear, increased eccentricity and even bearing fracture. Therefore, it is essential to monitor and diagnose the rotor eccentricity in the practical application of permanent magnet synchronous motors.

The most direct detection method is to determine the rotor eccentricity by detecting the magnetic field distribution inside the permanent magnet motor. The invention patent with the Patent No. CN107192947A discloses a permanent magnet synchronous motor fault diagnosis method on the basis of magnetic field monitoring. When coil fault values corresponding to coils wound on all stator teeth of a permanent magnet synchronous motor form two peaks, the fault type is determined to be an eccentric fault. The invention patent with the Patent No. CN109541461A discloses a permanent magnet synchronous motor eccentric fault diagnosis method on the basis of magnetic field distribution monitoring, in which a coil is wound on each stator tooth, the harmonic distribution is further analyzed by deducing the flux linkage value from the col voltage when the rotor rotates, such that the type, degree and direction of eccentric fault can be accurately identified. In the above method of detecting eccentricity based on an additional winding, the voltage amplitude of the additional winding is proportional to the rotational speed, resulting in great changes in the amplitude of output signal at different rotational speeds, which makes data collection difficult and increases the cost of hardware.

In order to realize the decoupling of signal amplitude and rotational speed, a linear Hall sensor can be used as a magnetic density detection element. The invention patent with the Patent No. CN108614212A discloses a decoupling diagnosis method and a device for hub motor eccentricity and demagnetization fault. According to the method, 2N Hall sensors are mounted in two stator slots radially symmetrical to the center axis of a hub motor, N Hall sensors are arranged equal intervals in an axial direction in each stator slot, Hall sensors in the two radially symmetrical stator slots are on the same diameter line, and the 2N Hall sensors are connected to an upper computer through a multi-channel voltage signal acquisition box. Faults are accurately identified based on the fault characteristics values to achieve a purpose of decoupling diagnosis of eccentricity and demagnetization coupled faults. However, the method cannot achieve accurate detection in a specific static eccentric state. The invention patent with the patent number CN113094952A discloses a static eccentricity detection method for permanent magnet motors on the basis of stray magnetic fields. In the method, the use of a neural network model increases the computational burden for eccentricity detection, and errors between the neural network model and actual motor parameters make the robustness of the detection lower, thereby involving a huger computational burden. In addition, none of the above detection methods is capable of realizing the eccentricity detection of the rotor permanent magnet type motor and the stator permanent magnet type motor at the same time.

The present application aims to accurately and quickly detect and separate static and dynamic eccentricity detection quantities in permanent magnet synchronous motors by reasonably mounting linear Hall elements and designing eccentricity detection algorithms universal to permanent magnet synchronous motors of different topologies.

In order to solve the defects in the above background art, the present invention aims to provide a linear Hall-based eccentricity diagnosis method and a detection system for a permanent magnet motor, linear Hall sensors for detecting the radial flux density mounted in the stator slots of a permanent magnet synchronous is capable of processing output signals from the lineal Hall sensors to obtain the real-time static and dynamic eccentricity detection quantities of a rotor, thereby achieving the purpose of real-time non-invasive eccentricity detection for permanent magnet motors of various topologies at a low cost, and solving the technical problems that the prior technology of eccentricity detection of permanent magnet motors involves difficulty in data collection, high cost of hardware and inability to realize simultaneous detection of static and dynamic eccentricity for motors of different topologies.

In order to achieve the above objective, the present invention provides the following technical solutions:

the present invention provides a linear Hall-based eccentricity diagnosis method for a permanent magnet motor, which is implemented by a detection system consisting of three linear Hall elements mounted in stator slots at the same space interval and a digital signal processor. Magnetically sensitive surfaces of the three Hall elements are all opposite surfaces of a rotor with permanent magnets; among the three linear Hall elements, the first linear Hall element is mounted at any position in the stator slot, the second linear Hall element is spaced apart from the first linear Hall element in a circumferential direction by an electrical angle phase difference of and the third linear Hall element is spaced apart from the second linear Hall element in a circumferential direction by an electrical angle phase difference of φ s . Then, the degree of motor eccentricity is calculated based on the output voltage signals of the three linear Hall elements.

The eccentricity diagnosis method for calculating the degree of motor eccentricity is calculated based on the output voltage signals of the three linear Hall elements is as follows:

(1) The digital signal processor converts the output voltage signals of the three linear Hall elements into digital signals through an analog-to-digital converter, and the digital signals are three-phase signals.

(2) The three-phase signals are processed into a quadrature signal with harmonics.

Assuming that the signals output by the three linear Halls are H abc =[H a , H b , H c ] T , wherein H a signal comes from the second linear Hall element, H b signal comes from the first linear Hall element, and H c comes from the third linear Hall element. The preprocessing process involves a linear combination of H abc , the three-phase signal is mapped to the two-phase stationary coordinate system, and the processed quadrature signal is H αβ0 =[H α H β , H 0 ] T , wherein, H α and H β are quadrature components, and H 0 is a DC component. The model of the above linear combination is:

(3) A complex factor filter with harmonic selection capability is configured to extract negative sequence signals and sideband signals from the above quadrature signal.

The complex factor filter is composed of a first detection filter, a second detection filter and a third detection filter that are interconnected to one another. The quadrature signal H αβ0 minus the output of the three detection filters is taken as an intermediate signal. The intermediate signal is added to the output signal of the first detection filter as the input signal of the first detection filter, and the output signal of the first detection filter is a positive sequence signal; the intermediate signal is added to the output signal of the second detection filter as the input signal of the second detection filter, and the output signal of the second detection filter is a negative sequence signal; the intermediate signal is added to the output signal of the third detection filter as the input signal of the third detection filter, and the output signal of the second detection filter is a sideband signal.

The first detection filter extracts positive sequence signal having the same frequency as the rotating electrical frequency of the motor rotor from the quadrature signal, and the first detection filter can be expressed as:

The second detection filter is capable of extracting negative sequence signals having the same frequency as the rotating electrical frequency of the motor rotor from the quadrature signal, and the second detection filter can be expressed as:

The third detection filter is capable of extracting sideband signals near the positive sequence signals from the quadrature signal, and the third detection filter can be expressed as:

(4) The amplitude of the negative sequence signals is extracted by means of phase-locked loops of a first synchronous reference system as a static eccentricity indicator, and the amplitude of the negative sequence signals is extracted by means of phase-locked loops of a second synchronous reference system as a dynamic eccentricity indicator.

(5) Twice the ratio of the static eccentricity indicator to the amplitude of the positive sequence component is taken as a static eccentricity percentage; the ratio of the dynamic eccentricity indicator to the amplitude of the positive sequence component is taken as a dynamic eccentricity percentage, and the static eccentricity percentage value and the dynamic eccentricity percentage value are taken as an eccentricity diagnosis quantity.

By employing the above technical solutions, the present invention has the following beneficial effects:

(1) The present invention the radial magnetic density of permanent magnet motors with different topological structures by mounting the Hall sensors at the same space interval in the stator slots in a circumferential direction, rapidly detects the real-time eccentricity by performing linear combination, complex factor filtering, and phase-locking processing on the output data of the Hall sensors in sequence, effectively separates static eccentricity detection quantity and dynamic eccentricity detection quantity, overcomes the defect that existing eccentricity detection methods cannot accurately detect static eccentricity in a specific state, realizes highly compact and low-cost eccentricity detection of permanent magnet motors with multi-topology structures, and realizes the separation of static eccentricity and dynamic eccentricity.

(2) The eccentricity diagnosis method for a permanent magnet motor disclosed in the present invention can be implemented by adopting a non-invasive detection system consisting of low-cost Hall sensors and a digital signal processor, and solves the problems of difficulty in data and reduces the cost of hardware compared with the eccentricity diagnosis method for a permanent magnet motor by means of additional windings.

FIG. 1 is a block diagram of a linear hall-based eccentricity detection system for permanent magnet motor provided in the present invention.

FIG. 2 is a rotor permanent magnet motor in Embodiment 1.

FIG. 3 is a stator permanent magnet motor in Embodiment 2.

FIG. 4 is a block diagram of a complex factor filter in a linear Hall-based eccentricity diagnosis method and a detection system for a permanent magnet motor provided in the present invention.

FIG. 5 is a waveform diagram of three-phase signals output by three linear Hall elements and their corresponding quadrature signal, negative sequence signal, and sideband signal in Embodiment 1.

1 . first linear Hall element; 2 . second linear Hall element; 3 . third linear Hall element; 4 . motor under detection; 6 . linear combination unit; 8 . complex factor filter; 13 . digital signal processor; 14 . first addition and subtraction combination module; 15 . second addition and subtraction combination module; 16 . third addition and subtraction combination module; 17 . fourth addition and subtraction combination module; and 18 . fifth addition and subtraction combination module.

The technical solution of the present invention will be further described below in conjunction with the accompanying drawings.

Embodiment 1: Diagnosing an Eccentricity of a Rotor Permanent Magnet Motor on the Basis of Linear Hall Elements

With reference to FIG. 1 , the present invention provides a linear Hall-based eccentricity diagnosis method and a detection system for a permanent magnet motor, the detection system includes: a first linear Hall element 1 , a second linear Hall element 2 and a third linear Hall element 3 mounted in a stator slot of a motor under detection 4 , and a digital signal processor 13 for processing the output voltage of the Hall elements. As shown in FIG. 2 , the motor under detection 4 is a three-phase 18-slot and 20-pole rotor permanent magnet motor. Three linear Hall elements are mounted in the stator slots at intervals of 2 stator slot pitches, and magnetically sensitive surfaces of the Hall elements are all opposite surfaces of a rotor with permanent magnets; among the three linear Hall elements, the first linear Hall element 1 is mounted in any slot of the stator, the second linear Hall element 2 is spaced apart from the first linear Hall element 1 in a circumferential direction by an electrical angle phase difference of φ s =2 π/9, and the third linear Hall element 3 is spaced apart from the second linear Hall element 2 in a circumferential direction by an electrical angle phase difference of φ s =2 π/9.

Taking the counterclockwise direction as a forward direction, when the rotor rotates in the forward direction at a constant speed, an electrical angle phase difference of output voltage signals between the first linear Hall element 1 and the second linear Hall element 2 is φ s =2 π/9, and an electrical angle phase difference of output voltage signals between the second linear Hall element 2 and the third linear Hall element 3 is φ s =2 π/9.

The three linear Hall elements are connected to the digital signal processor 13 . The power supply voltage of the digital signal processor 13 is 3.3 V. H a signal comes from the second linear Hall element 2 , H b signal comes from the second linear Hall element 1 , H c signal comes from the second linear Hall element 3 , and the three linear Hall elements output analog voltages ranging from 0 V to 3.3 V. In the digital signal processor 13 , the output voltage signals of the three linear Hall elements are converted into three-phase original digital signals, expressed as H abc =[H a , H b , H c ] T .

The three-phase signals are made as a linear combination, shown in the following formula:

The quadrature signal obtained upon the linear combination processing is H αβ0 =[H α , H β , H 0 ] T .

A complex factor filter with harmonic selection capability is configured to extract negative sequence signals and sideband signals from the quadrature signal.

As shown in FIG. 4 , the complex factor filter is composed of a first detection filter, a second detection filter and a third detection filter that are interconnected to one another. The quadrature signal minus the output of the three detection filters is taken as an intermediate signal, which is completed by a first addition and subtraction combination module 14 , and the output of the three detection filters is summed by a fifth addition and subtraction combination module 18 and then transmitted to the first addition and subtraction combination module 14 . The intermediate signal is added to the output signal of the first detection filter as the input signal of the first detection filter, which is completed by a second addition and subtraction combination module 15 ; the intermediate signal is added to the output signal of the second detection filter as the input signal of the second detection filter, which is completed by a third addition and subtraction combination module 16 ; and the intermediate signal is added to the output signal of the third detection filter as the input signal of the third detection filter, which is completed by a fourth addition and subtraction combination module 17 .

The first detection filter extracts positive sequence signal having the same frequency as the rotating electrical frequency of the motor rotor from the quadrature signal, and the first detection filter can be expressed as:

The second detection filter extracts negative sequence signal having the same frequency as the rotating electrical frequency of the motor rotor from the quadrature signal, and the second detection filter can be expressed as:

The third detection filter extracts sideband signals near the positive sequence signal from the quadrature signal, and the third detection filter can be expressed as:

The amplitude of the negative sequence signals is extracted by means of phase-locked loops of a first synchronous reference system as a static eccentricity indicator, and the amplitude of the negative sequence signals is extracted by means of phase-locked loops of a second synchronous reference system as a dynamic eccentricity indicator.

Finally, twice the ratio of the static eccentricity indicator to the amplitude of the positive sequence component is taken as a static eccentricity percentage; the ratio of the dynamic eccentricity indicator to the amplitude of the positive sequence component is taken as a dynamic eccentricity percentage, and the percentage value is taken as an eccentricity diagnosis quantity.

The following simulation is performed in combination with specific eccentricity conditions, and the results are illustrated in FIG. 5 , which shows the three-phase signal, quadrature signal, negative sequence signal and sideband signal, respectively. The amplitude of the negative sequence signals extracted by means of the phase-locked loops of a first synchronous reference system is shown by a dotted line, and the amplitude of the negative sequence signals is extracted by means of the phase-locked loops of a second synchronous reference system is shown by a dotted line.

(1) Before 0.3 s, the motor under detection 4 is in a non-eccentric state, and the signal frequency is 600 Hz. The negative sequence component output by the complex factor filter is 0; and the sideband component is 0.

(2) Between 0.3 s and 0.7 s, the signal frequency is 600 Hz, the motor under detection 4 is in a static eccentric state, and the static eccentric distance is 0.3 times the air gap length. The amplitude of the negative sequence signals output by the complex factor filter rises and stabilizes to be a constant value; the amplitude of the sideband signals first rises and then converges to 0. Since the dynamic eccentricity is a time-varying static eccentricity, there will be malfunctions when the static eccentricity first appears, but a predicted value of the dynamic eccentricity will converge to the actual value in a short time.

(3) Between 0.7 s and 1.1 s, the signal frequency is 600 Hz, the motor under detection 4 is in a mixed eccentric state, the static eccentric distance is 0.3 times the air gap length, and the dynamic eccentric distance is 0.2 times the air gap length. The amplitude of the negative sequence signals output by the complex factor filter remains basically unchanged; the amplitude of the sideband signals rises and remains basically unchanged.

(4) Between 1.1 s and 1.5 s, the signal frequency is 600 Hz, the motor under detection 4 is in a mixed eccentric state, the static eccentric distance is 0.3 times the air gap length, and the speed changes from 600 Hz to 200 Hz. The results of eccentricity detection remain basically unchanged, and the system is suitable for different speeds.

Finally, twice the ratio of the static eccentricity indicator to the amplitude of the positive sequence component is taken as a static eccentricity percentage 30%; and the ratio of the dynamic eccentricity indicator to the amplitude of the positive sequence component is taken as a dynamic eccentricity percentage 20%.

Embodiment 2: Diagnosing an Eccentricity of a Stator Permanent Magnet Motor on the Basis of Linear Hall Elements

With reference to FIG. 1 , the present invention provides a linear Hall-based eccentricity diagnosis method and detection system for permanent magnet motor, and as shown in FIG. 4 , the motor under detection is a three-phase 12-slot and 10-pole stator permanent magnet motor. Three linear Hall elements are mounted in the stator slots at intervals of 1 stator slot pitch. Magnetically sensitive surfaces of the Hall elements are all opposite salient-pole surfaces of a rotor with permanent magnets; among the three linear Hall elements, the first linear Hall element 1 is mounted in any slot of the stator, the second linear Hall element 2 is spaced apart from the first linear Hall element 1 in the same direction by an electrical angle phase difference of φ s =2 π/3, and the third linear Hall element 3 is spaced apart from the second linear Hall element 2 in the same direction by an electrical angle phase difference of φ s =2 π/3.

Taking the counterclockwise direction as a forward direction, when the rotor rotates in the forward direction at a constant speed, an electrical angle phase difference of output voltage signal between the first linear Hall element 1 and the second linear Hall element 2 is φ s =2 π/3, and an electrical angle phase difference of output voltage signal between the second linear Hall element 2 and the third linear Hall element 3 is φ s =2 π/3.

The three linear Hall elements are connected to the digital signal processor 13 . The power supply voltage of the digital signal processor 13 is 3.3 V. H a signal comes from the second linear Hall element 2 , H b signal comes from the second linear Hall element 1 , H c signal comes from the second linear Hall element 3 , and the three linear Hall elements output analog voltages ranging from 0 V to 3.3 V. In the digital signal processor, the output voltage signals of the three linear Hall elements are converted into three-phase original digital signal, expressed as H abc =[H a , H b , H c ] T .

A progressive linear combination of the three-phase signals is as follows:

The processed quadrature signal is H αβ0 =[H α , H β , H 0 ] T .

A complex factor filter with harmonic selection capability is configured to extract negative sequence signals and sideband signals from the quadrature signal.

The complex factor filter is composed of a first detection filter, a second detection filter and a third detection filter that are interconnected to one another. The quadrature signal minus the output of the three detection filters is taken as an intermediate signal. The intermediate signal is added to the output signal of the first detection filter as the input signal of the first detection filter; the intermediate signal is added to the output signal of the second detection filter as the input signal of the second detection filter; and the intermediate signal is added to the output signal of the third detection filter as the input signal of the third detection filter.

The first detection filter extracts positive sequence signal having the same frequency as the rotating electrical frequency of the motor rotor from the quadrature signal, and the first detection filter can be expressed as:

The second detection filter is capable of extracting negative sequence signal having the same frequency as the rotating electrical frequency of the motor rotor from the quadrature signal, and the second detection filter can be expressed as:

The third detection filter is capable of extracting sideband signal near the positive sequence signal from the quadrature signal, and the third detection filter can be expressed as:

(4) The amplitude of the negative sequence signals is extracted by means of phase-locked loops of a first synchronous reference system as a static eccentricity indicator, and the amplitude of the negative sequence signals is extracted by means of phase-locked loops of a second synchronous reference system as a dynamic eccentricity indicator.

(5) Finally, twice the ratio of the static eccentricity indicator to the amplitude of the positive sequence component is taken as a static eccentricity percentage; the ratio of the dynamic eccentricity indicator to the amplitude of the positive sequence component is taken as a dynamic eccentricity percentage, and the percentage value is taken as an eccentricity diagnosis quantity.

The foregoing descriptions are merely preferred specific implementations of the present invention, and are not intended to limit the protection scope of the present invention. Any equivalent replacements or changes made by a person skilled in the art according to the technical solutions of the present invention and the inventive concepts thereof within the technical scope disclosed in the present invention shall fall within the protection scope of the present invention.