Strain-based permanent magnet synchronous motor vibration and temperature rise monitoring method and system

Abstract

The invention belongs to the technical field of motor monitoring, and provides a strain-based permanent magnet synchronous motor vibration and temperature rise monitoring method and a strain-based permanent magnet synchronous motor vibration and temperature rise monitoring system. And respectively establishing quantitative relation models of the strain direct-current component and the temperature rise as well as the frequency doubling component and the vibration, thereby realizing synchronous monitoring of the vibration and the temperature rise. The complexity problem that traditional vibration and temperature rise monitoring needs multi-sensor cooperation is solved, and the hardware cost is remarkably reduced. Through frequency domain feature decoupling, coupling interference of temperature rise on vibration signals is avoided, and monitoring reliability is improved. Compared with an optical fiber strain sensor, the method avoids a complex decoupling process and related instruments, and is economical and practical.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor monitoring, and particularly relates to a method and system for monitoring the vibration and temperature rise of a permanent magnet synchronous motor based on strain. Background Art

[0002] Due to its high efficiency, high power density and good dynamic performance, permanent magnet synchronous motors are widely used in industrial drives, electric vehicles, wind power generation and other fields. However, during operation, motors inevitably generate vibration and temperature rise, which not only affect the performance and lifespan of the motors, but may also lead to serious faults and shutdowns. Therefore, real-time monitoring of motor vibration and temperature rise is particularly important.

[0003] Traditional vibration monitoring methods usually rely on acceleration sensors or vibration sensors, which need to be installed on the motor housing or bearings. The installation is complex and may affect the normal operation of the motor. In addition, traditional temperature rise monitoring methods mostly use thermocouples or infrared temperature measurement technologies, which also have problems such as complex installation and slow response speed.

[0004] In recent years, strain-based monitoring methods have gradually received attention. As a highly sensitive and reliable sensor, a strain gauge can be directly pasted on the motor stator or winding to monitor the mechanical strain of the motor in real time. It has been found that in the strain signal of the motor stator or winding, the second harmonic component is closely related to the vibration magnitude, while the DC component is closely related to the temperature rise magnitude.

[0005] Based on the above background, the present invention proposes a method and system for monitoring the vibration and temperature rise of a permanent magnet synchronous motor based on strain. This method can simultaneously complete the monitoring of vibration and temperature rise using a single strain gauge, and has the advantages of simple installation, fast response speed, high reliability, etc., providing a new technical means for the health monitoring and fault diagnosis of motors. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a method and system for monitoring the vibration and temperature rise of a permanent magnet synchronous motor based on strain to solve the problems in the prior art. The technical solutions adopted by the present invention are as follows: A method for monitoring the vibration and temperature rise of a permanent magnet synchronous motor based on strain includes the following steps: Step 100: Install a strain gauge and calibrate the initial state of the sensor; Step 200: Connect the strain gauge to a signal collector, collect the original strain signal and perform analog-to-digital conversion; Step 300: Perform a fast Fourier transform in a computer to extract the amplitudes of the DC component and the second harmonic component; Step 400: Calculate the actual vibration value and temperature rise value according to the calibration model, compare with the preset threshold, and alarm if the safety limit is exceeded.

[0007] Further, step 100 includes: installing a strain gauge on the stator core, housing or winding of the permanent magnet synchronous motor, and connecting the strain gauge to a signal collector; recording the initial DC component of the strain gauge corresponding to the ambient temperature when the motor is in a stationary state; performing off-line calibration on the permanent magnet synchronous motor through a vibration table and a temperature control box, and establishing a mathematical model of double-frequency amplitude-vibration acceleration and a mathematical model of DC component-temperature rise.

[0008] Further, step 200 includes: collecting the original strain signal, amplifying and filtering it through a signal conditioning circuit, outputting a 0-5V analog signal and performing analog-to-digital conversion.

[0009] Further, step 300 includes: inputting the data of the signal collector into a computer for fast Fourier transform, extracting the DC component and the amplitude of the double-frequency component of the signal, reflecting the temperature rise through the DC component, and reflecting the vibration through the amplitude of the double-frequency component; Further, step 400 includes: after the calculation, calculating the actual vibration value and temperature rise value according to the calibration model, and comparing them with the preset threshold values. If the vibration value exceeds the set threshold or the temperature rise value exceeds the safety limit, triggering an alarm signal and recording the fault data.

[0010] Further, reflecting the vibration through the amplitude of the double-frequency component includes the following methods: The electromagnetic force expression of the end winding of the permanent magnet synchronous motor is: ; Where: Bl is the magnetic flux density at the end of the motor, i is the stator winding current, L is the length of the straight section of the winding, l is the axial length of the end winding, αl is the angle between the magnetic flux density at a certain point of the end winding and the normal, βl is the angle between the normal at a certain point of the end winding and the rotor axis, v is the speed of the straight section winding cutting the magnetic induction line, and Z is the impedance of the winding; The relationship between the winding electromagnetic force and the vibration is: ; Where: [M] is the mass matrix, [D] is the radial damping matrix, [K] is the radial stiffness matrix. y(t) is the displacement of the unit mass point, y'(t) is the velocity, and y"(t) is the acceleration.

[0011] Simplify the winding model to a cantilever beam. Let the distance between the winding surface and the neutral axis of the winding be y, and the distance between the cross-section and the end of the winding be x. The cross-section of the winding under the electromagnetic force is subjected to a bending moment, and the stress distributed on the winding surface is: ; Where: M is the bending moment of the cross-section, y is the distance from the insulation layer to the neutral axis, and Iz is the moment of inertia of the cross-section.

[0012] It is considered that the winding undergoes elastic strain under the action of electromagnetic force, and the strain expression is: ; Where: E is the elastic modulus; the vibration and strain of the winding under electromagnetic force are both consistent with the electromagnetic force frequency, and the amplitude of the second harmonic component of the strain can reflect the vibration.

[0013] Furthermore, the temperature rise is reflected by the DC component, including the following methods: The expression of the stator loss of a permanent magnet synchronous motor is: ; Where: PFe and PCu are the stator iron loss and winding copper loss respectively; ph, pc and pe are the hysteresis loss, eddy current loss and additional loss respectively; kh, kc and ke are the hysteresis loss coefficient, eddy current loss coefficient and additional loss coefficient respectively; f is the electromagnetic field frequency; m is the number of phases of the motor; I is the phase current; Rl is the winding resistance; L is the length of the straight section of the winding; Rs is the inner diameter of the stator core; nr is the rotor speed; Bm is the peak value of the air-gap magnetic flux density.

[0014] For a permanent magnet synchronous motor with an air-cooling method, the boundary conditions in the three-dimensional temperature field model and the solution domain are as follows: ; Where: S1 and S2 are the adiabatic and heat dissipation boundaries of the motor respectively; T and T0 are the motor temperature and ambient temperature respectively; kx, ky and kz are the radial, circumferential and axial thermal conductivities respectively; k is the thermal conductivity in the normal direction; q and ρ are the heat source density and material density respectively; c is the specific heat capacity; α is the surface heat dissipation coefficient.

[0015] When the temperature of the winding rises, it will undergo thermal expansion and cause thermal strain, and the expression is: ; Where: β is the thermal expansion coefficient of the material, and ΔT is the temperature change.

[0016] As shown in the above formula, the thermal strain of the winding is directly related to the temperature change. Since the temperature change is a DC quantity, the DC component of the strain can reflect the temperature rise.

[0017] A vibration and temperature rise monitoring system for a permanent magnet synchronous motor based on strain includes: a permanent magnet synchronous motor, a strain gauge, a signal acquisition instrument and a computer; the strain gauge is installed on the stator core, housing or winding of the permanent magnet synchronous motor; the strain gauge is connected to the signal acquisition instrument for collecting the original strain signal and performing analog-to-digital conversion; the signal acquisition instrument is connected to the computer for extracting the DC component and the amplitude of the second harmonic component.

[0018] The present invention has the following beneficial effects: The present invention only requires one strain gauge to simultaneously obtain vibration and temperature rise information, simplifies installation and reduces costs; the present invention first proposes a direct correlation model between the second harmonic component of the strain signal and the vibration amplitude, and between the DC component and the temperature rise; the present invention solves the complexity problem of multi-sensor collaboration required for traditional vibration and temperature rise monitoring, significantly reducing the hardware cost; the present invention decouples the frequency domain characteristics, avoiding the coupling interference of the temperature rise on the vibration signal and improving the monitoring reliability; compared with fiber optic strain sensors, this method avoids complex decoupling processes and related instruments, and is economical and practical. Description of the Drawings

[0019] Figure 1 is the overall structure diagram of the present invention; Figure 2 is the flowchart of the method of the present invention.

[0020] Figure 3 is the vibration test verification comparison diagram, with the horizontal axis being the second harmonic amplitude of the vibration acceleration and the vertical axis being the second harmonic amplitude of the strain; Figure 4 is the temperature test verification comparison diagram, with the horizontal axis being the temperature amplitude and the vertical axis being the DC component amplitude of the strain; In the figure: 1, permanent magnet synchronous motor; 2, strain gauge; 3, signal acquisition instrument; 4, computer. Detailed Embodiments

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with Figures 1 - 4 in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. If not specifically specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0022] The present invention mainly analyzes the spectral characteristics of the strain signal of the motor stator or winding, extracts its DC component (low frequency band) and second harmonic component (high frequency band related to the motor fundamental frequency), and respectively establishes a quantitative relationship model between the strain DC component and the temperature rise, and between the second harmonic component and the vibration, so as to realize the synchronous monitoring of vibration and temperature rise. It mainly includes strain signal acquisition: pasting the strain gauge on the tooth part or the winding end of the motor stator, and collecting the strain signal during operation in real time; signal processing and separation: filtering and spectral analysis of the original strain signal to separate the DC component and the second harmonic component. Vibration and temperature rise calculation: converting the second harmonic amplitude into the vibration amplitude and the DC component into the temperature rise value through a pre-calibrated mathematical model. Status warning: triggering the warning or shutdown protection mechanism according to the thresholds of vibration and temperature rise.

[0023] The system part of the present invention is: a vibration and temperature rise monitoring system for a permanent magnet synchronous motor based on strain, including: a permanent magnet synchronous motor 1, a strain gauge 2, a signal collector 3, and a computer 4; the strain gauge 2 is installed on the stator core, the housing or the winding of the permanent magnet synchronous motor 1; the strain gauge 2 is connected to the signal collector 3 for collecting the original strain signal and performing analog-to-digital conversion; the signal collector 3 is connected to the computer 4 for extracting the amplitudes of the DC component and the second harmonic component.

[0024] The present invention mainly relates to a method for monitoring the vibration and temperature rise of a permanent magnet synchronous motor based on strain, including the following steps: Step 100, install the strain gauge 2 and calibrate the initial state of the sensor; Step 200, connect the strain gauge 2 to the signal collector 3, collect the original strain signal and perform analog-to-digital conversion; Step 300, perform a fast Fourier transform in the computer 4 to extract the amplitudes of the DC component and the second harmonic component; Step 400, calculate the actual vibration value and temperature rise value according to the calibration model, compare with the preset threshold, and if it exceeds the safety limit, give an alarm.

[0025] Further, step 100 includes: installing the resistive strain gauge 2 on the stator core, the housing or the winding of the permanent magnet synchronous motor 1. Taking the case where the strain gauge is pasted on the end of the winding as an example, the other end of the strain gauge is connected to the signal collector 3; in the stationary state of the motor, record the initial DC component of the strain gauge corresponding to the ambient temperature; perform off-line calibration on the permanent magnet synchronous motor 1 through a vibration table and a temperature control box to establish a mathematical model of the second harmonic amplitude - vibration acceleration and the DC component - temperature rise.

[0026] Further, step 200 includes: in the signal collector 3, there is a signal conditioning circuit (for converting the resistance change of the strain gauge into a voltage signal and suppressing high-frequency noise) and an analog-to-digital conversion module (digitizing the signal at a sampling frequency not lower than 1 kHz); collect the original strain signal, after being amplified and filtered by the signal conditioning circuit, output a 0 - 5V analog signal and perform analog-to-digital conversion.

[0027] Further, step 300 includes: inputting the data of the signal collector 3 into the computer 4 for a fast Fourier transform, extracting the amplitudes of the DC component and the second harmonic component of the signal, and reflecting the temperature rise through the DC component and reflecting the vibration through the amplitude of the second harmonic component; Further, step 400 includes: after the calculation, calculate the actual vibration value and temperature rise value according to the calibration model, and compare with the preset threshold. If the vibration value exceeds the set threshold or the temperature rise value exceeds the safety limit, trigger an alarm signal and record the fault data.

[0028] For the calibration model of the present invention, it is a mathematical model used to convert the second-harmonic component (representing vibration) and the DC component (representing temperature rise) in the strain signal into actual physical quantities (vibration acceleration and temperature value), and it needs to be experimentally determined. For example, for a specific motor, vibration sensors, temperature sensors, and strain gauges need to be installed on the winding first, and the motor is run to different vibration amplitudes or temperatures. Then, the vibration second-harmonic and the corresponding strain second-harmonic are plotted as curves, and the temperature and the DC component of the strain are plotted as curves. Then, the vibration sensor and the temperature sensor are removed. When the motor is actually used, only the strain condition of this motor needs to be tested, and the corresponding vibration and temperature conditions can be found through the curves. These two curves (vibration second-harmonic - strain second-harmonic, temperature rise - strain DC) are the calibration model.

[0029] The calculation formula for the air-gap magnetic density of the motor on which the present invention relies is: ; In the formula: Λ 0 is the air-gap permeance, μ 0 is the vacuum permeability, g 0 is the average air-gap length, F μ and F υ are respectively the amplitudes of the μ th harmonic magnetic motive force of the rotor and the υ th harmonic magnetic motive force of the stator, and are respectively the initial phase angles of the μ th harmonic of the rotor and the υ th harmonic of the stator, p is the number of pole pairs of the motor, ω is the electrical angular velocity. The formula for the air-gap magnetic density B is based on the basic theory of the motor magnetic field, combining permeance and magnetic motive force. It covers odd harmonics of the rotor and specific harmonics of the stator, and more completely reflects the composition of the magnetic density. By summing up item by item, the contribution of each harmonic is refined, and the calculation accuracy of the magnetic density is improved. Accurate magnetic density analysis helps optimize the motor magnetic circuit and predict losses, thereby improving efficiency, reducing vibration and noise, and enhancing the comprehensive performance of the motor.

[0030] For the method of reflecting vibration by the amplitude of the second-harmonic component proposed by the present invention, it includes the following methods: The electromagnetic force expression of the end winding of the permanent magnet synchronous motor 1 is: ; In the formula: B l is the end flux density of the motor, i is the stator winding current, L is the length of the straight section of the winding,l is the axial length of the end winding, α l is the angle between the magnetic flux density at a certain point of the end winding and the normal line at that point, β l is the angle between the normal line at a certain point of the end winding and the rotor axis, v is the speed at which the straight section winding cuts the magnetic induction line, Z is the impedance of the winding. This formula is used to calculate the electromagnetic force of the end winding of the permanent magnet synchronous motor 1. By comprehensively Bl , i , αl , βl and v etc., the force on the end winding is accurately quantified. The expanded harmonic interaction terms (such as Fμ 1 Fμ 2, FμFν etc.) reveal that the electromagnetic force is generated by the coupling of different harmonic magnetomotive forces of the rotor and stator.

[0031] The relationship between the electromagnetic force of the winding and vibration is: ; In the formula: M is the mass matrix, D is the radial damping matrix, K is the radial stiffness matrix. y ( t ) is the displacement of the unit mass point, y' ( t ) is the velocity, y" ( t ) is the acceleration. This formula is based on the theory of mechanical vibration and is a second-order linear non-homogeneous differential equation with constant coefficients, establishing the mathematical relationship between electromagnetic force and mechanical vibration, facilitating the prediction of vibration response, and providing a theoretical basis for optimizing the motor structure and reducing vibration.

[0032] The winding model is simplified to a cantilever beam. Let the distance between the winding surface and the neutral axis of the winding be y, and the distance between the cross-section and the end of the winding be x. The cross-section of the winding under the electromagnetic force is subjected to a bending moment, and the stress distributed on the winding surface is: ; In the formula: M is the bending moment of the cross-section, y is the distance from the insulation layer to the neutral axis, I z is the moment of inertia of the cross-section. This formula calculates the bending stress on the winding surface, evaluates the mechanical stress of components such as the insulation layer, and ensures the structural safety of the winding under the action of electromagnetic force; through stress analysis, it prevents the insulation layer from being damaged due to excessive stress, improving the mechanical reliability of the winding and the operation stability of the motor.

[0033] It is considered that the winding undergoes elastic strain under the action of electromagnetic force, and the strain expression is: ; In the formula: E Elastic modulus; It can be seen from the above formula that both the winding vibration and strain under electromagnetic force are consistent with the electromagnetic force frequency, and the amplitude of the second harmonic component of the strain can reflect the vibration. The electromagnetic force and vibration response of the end winding are in a corresponding relationship of the same frequency. This formula analyzes the elastic strain of the winding under the action of electromagnetic force, combines the vibration frequency, and judges the winding deformation degree and vibration characteristics.

[0034] Since there is no frequency fluctuation in the temperature difference ΔT, the present invention proposes to reflect the temperature rise through the DC component, including the following methods: The stator winding temperature rise is mainly related to the stator core loss and winding copper loss. The stator loss expression of the permanent magnet synchronous motor 1 is: ; In the formula: P Fe and P Cu are the stator iron loss and winding copper loss respectively; p h , p c and p e are the hysteresis loss, eddy current loss and additional loss respectively; k h , k c and k e are the hysteresis loss coefficient, eddy current loss coefficient and additional loss coefficient respectively; f is the electromagnetic field frequency; m is the number of phases of the motor; I is the phase current; R l is the winding resistance; L is the length of the straight section of the winding; R s is the inner diameter of the stator core; n r is the rotor speed; B m is the peak value of the air-gap magnetic density. This formula is used to calculate the total stator loss of the permanent magnet synchronous motor. By calculating the iron loss and copper loss separately, different loss sources are quantified, providing heat source data for thermal analysis.

[0035] For the permanent magnet synchronous motor 1 with air cooling, the boundary conditions in the three-dimensional temperature field model and the solution domain are as follows: ; In the formula: S 1 and S 2 are the adiabatic and heat dissipation boundary surfaces of the motor respectively; T and T 0 are the motor temperature and the ambient temperature respectively; k x , k y and k z are the radial, circumferential and axial thermal conductivities respectively; k is the thermal conductivity in the normal direction; q and ρ are the heat source density and the material density respectively; c is the specific heat capacity; α is the surface heat dissipation coefficient. This formula establishes a motor temperature field model, combines the adiabatic and heat dissipation boundaries, and solves the internal temperature distribution of the motor.

[0036] The calculation formula for the heat dissipation coefficient of each part of the permanent magnet synchronous motor 1 is: ; In the formula: v 1 and v r are the air velocity on the shell surface and the rotor linear velocity respectively; p 1 is the air thermal conductivity; w s is the average air gap velocity; N uet is the Nusselt number of the stator winding end; d et is the equivalent diameter of the end winding.

[0037] For the strain analysis of the present invention: The winding model is simplified to a cantilever beam. Let the distance between the winding surface and the neutral axis of the winding be y , and the distance between the cross-section and the end of the winding be x . The cross-section of the winding under the electromagnetic force can be regarded as being subjected to a bending moment, and the stress distributed on the winding surface is: ; In the formula: M is the bending moment of the cross-section, y is the distance from the insulation layer to the neutral axis, I z is the moment of inertia of the cross-section.

[0038] It is considered that the winding undergoes elastic strain under the action of electromagnetic force, and the strain expression is: ; In the formula: E Elastic modulus.

[0039] When the temperature of the winding rises, it will undergo thermal expansion and cause thermal strain. The expression is: ; In the formula: β is the thermal expansion coefficient of the material, Δ T is the temperature change.

[0040] The strain of the end winding under the combined action of electromagnetic force and temperature rise is calculated as: ; It can be seen from the above formula that the strain of the winding under the action of electromagnetic force has two parts: a DC component and an even multiple frequency. Among them, the even multiple frequency is consistent with the vibration frequency under the action of electromagnetic force; the strain of the winding under the action of temperature rise is a DC component, and the higher the temperature, the greater the thermal strain. Therefore, the even multiple frequency strain of the end winding can reflect the magnitude of vibration, and the DC component strain can reflect the magnitude of temperature rise.

[0041] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations, variations, modifications, and substitutions made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A strain-based permanent magnet synchronous motor vibration and temperature rise monitoring method, characterized in that: The following steps are involved: Step 100, installing the strain gauge (2) and calibrating the initial state of the sensor; Step 200, the strain gauge (2) is connected to the signal acquisition device (3), the original strain signal is collected and analog-to-digital conversion is performed; Step 300, performing a fast Fourier transform in the computer (4) to extract the amplitude of the DC component and the double frequency component; Step 400, calculate the actual vibration value and temperature rise value according to the calibration model, compare them with the preset threshold value, and alarm if they exceed the safety limit.

2. The strain-based permanent magnet synchronous motor vibration and temperature rise monitoring method according to claim 1, characterized in that: Step 100 comprises: installing a strain gauge (2) on the stator core, housing or winding of a permanent magnet synchronous motor (1), and connecting the strain gauge (2) to a signal acquisition instrument (3); recording an initial DC component of the strain gauge (2) corresponding to the ambient temperature when the motor is stationary; and performing offline calibration on the permanent magnet synchronous motor (1) using a vibration table and a temperature control box, and establishing a mathematical model of double frequency amplitude-vibration acceleration and a mathematical model of DC component-temperature rise.

3. The strain-based permanent magnet synchronous motor vibration and temperature rise monitoring method according to claim 1, characterized in that: Step 200 includes: collecting the original strain signal, amplifying and filtering it through a signal conditioning circuit, outputting a 0-5V analog signal and performing analog-to-digital conversion.

4. The strain-based permanent magnet synchronous motor vibration and temperature rise monitoring method according to claim 1, characterized in that: Step 300 includes: inputting data from the signal acquisition instrument (3) into a computer (4) for fast Fourier transform, extracting the DC component and the amplitude of the double frequency component of the signal, reflecting the temperature rise through the DC component, and reflecting the vibration through the amplitude of the double frequency component.

5. The strain-based permanent magnet synchronous motor vibration and temperature rise monitoring method according to claim 1, characterized in that: Step 400 includes: after the calculation is completed, the actual vibration value and temperature rise value are calculated according to the calibration model, and compared with the preset threshold value. If the vibration value exceeds the set threshold value or the temperature rise value exceeds the safety limit, an alarm signal is triggered and fault data is recorded.

6. The strain-based permanent magnet synchronous motor vibration and temperature rise monitoring method according to claim 4, characterized in that: Vibration is reflected by the amplitude of the double frequency component, including the following methods: The electromagnetic force expression of the end winding of the permanent magnet synchronous motor (1) is: ； Where: B l is the magnetic flux density at the motor end, i is the stator winding current, L is the length of the winding straight line segment, l is the axial length of the end winding, α l is the angle between the magnetic flux density at a certain point of the end winding and the normal line, β l is the angle between the normal line at a certain point of the end winding and the rotor axis, v is the speed at which the straight segment winding cuts the magnetic flux lines, Z is the impedance of the winding; The relationship between the winding electromagnetic force and vibration is: ； Where: M ] is the mass matrix, [ D ] is the radial damping matrix, [ K ] is the radial stiffness matrix, y ( t ) is the displacement of a unit mass point, y '( t ) is the speed, y "( t ) is the acceleration; The winding model is simplified as a cantilever beam, and the distance between the winding surface and the winding neutral axis is y , the distance between the cross section and the end of the winding is x , the winding cross section under electromagnetic force is subjected to bending moment, and the stress distributed on the winding surface is: ； Where: M is the bending moment of the cross section, y is the distance from the insulation layer to the neutral axis, I z is the section moment of inertia; It is assumed that the winding undergoes elastic strain under the action of electromagnetic force, and the strain expression is: ； Where: E Elastic modulus; the vibration and strain of the winding under electromagnetic force are consistent with the frequency of the electromagnetic force, and the amplitude of the double frequency component of the strain can reflect the vibration.

7. The strain-based permanent magnet synchronous motor vibration and temperature rise monitoring method according to claim 4, characterized in that: The DC component is used to reflect the temperature rise, including the following methods: The stator loss expression of permanent magnet synchronous motor (1) is: ； Where: P Fe and P Cu They are stator iron loss and winding copper loss respectively; p h , p c and p e They are hysteresis loss, eddy current loss and additional loss respectively; k h , k c and k e They are hysteresis loss coefficient, eddy current loss coefficient and additional loss coefficient respectively; f is the electromagnetic field frequency; m is the number of motor phases; I is the phase current; R l is the winding resistance; L is the length of the winding straight line segment; R s is the inner diameter of the stator core; n r is the rotor speed; B m is the peak value of air gap magnetic density; For the air-cooled permanent magnet synchronous motor (1), the three-dimensional temperature field model and boundary conditions in the solution domain are as follows: ； Where: S 1 and S 2 are the insulation and heat dissipation boundary surfaces of the motor respectively; T and T 0 are motor temperature and ambient temperature respectively; k x , k y and k z are radial, circumferential and axial thermal conductivity respectively; k is the thermal conductivity in the normal direction; q and ρ are heat source density and material density respectively; c is the specific heat capacity; α is the surface heat dissipation coefficient; When the temperature of the winding increases, thermal expansion will occur, causing thermal strain, which can be expressed as: ； Where: β is the thermal expansion coefficient of the material, Δ T is the temperature change; As shown in the above formula, the thermal strain of the winding is directly related to the temperature change. Since the temperature change is a DC quantity, the DC component of the strain can reflect the temperature rise.

8. A strain-based permanent magnet synchronous motor vibration and temperature rise monitoring system, adopting the strain-based permanent magnet synchronous motor vibration and temperature rise monitoring method according to any one of claims 1 to 7, characterized in that: include: A permanent magnet synchronous motor (1), a strain gauge (2), a signal acquisition instrument (3) and a computer (4); the strain gauge (2) is installed on the stator core, housing or winding of the permanent magnet synchronous motor (1); the strain gauge (2) is connected to the signal acquisition instrument (3) for acquiring the original strain signal and performing analog-to-digital conversion; the signal acquisition instrument (3) is connected to the computer (4) for extracting the amplitude of the DC component and the double frequency component.

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