Monitoring and protecting method and system for speed reducer

Abstract

The invention discloses a monitoring and protecting method and system for a speed reducer, which can extract micro-features strongly related to stator winding faults, such as fundamental frequency and side frequency components, specific sub-harmonic components and the like, by synchronously collecting three-phase current of a driving motor and performing spectral analysis. The characteristics are very sensitive to winding turn-to-turn short circuit, insulation aging and other early faults, effective coverage of traditional vibration monitoring blind areas is achieved, and fault discovery time is greatly advanced. By calculating the health degree index of the stator winding, the electrical characteristics are quantified into a visual and continuous evaluation index. Furthermore, the electrical health index is intelligently combined with the analysis result of the vibration signal. The fusion breaks the barrier between electrical and mechanical monitoring, so that the system can comprehensively consider electrical hidden dangers and mechanical conditions like experienced engineers, and make more comprehensive and more accurate judgment on the overall health state and risk level of the speed reducer system.

Description

Technical Field

[0001] This invention relates to the technical field of speed reducer monitoring, specifically to a speed reducer monitoring and protection method and system. Background Technology

[0002] As a core component of the power transmission system, the operating status of the speed reducer directly affects the reliability, safety, and production efficiency of the entire production equipment. Traditional speed reducer monitoring and protection technologies mostly rely on vibration analysis or temperature monitoring. Vibration analysis is relatively effective for damage to mechanical components such as gears and bearings (e.g., pitting, tooth breakage), but it is extremely insensitive to electrical faults inside the drive motor, especially early insulation degradation and inter-turn short circuits in the stator windings. These types of electrical faults initially cause only weak electromagnetic changes, which are difficult to reflect in vibration signals. By the time abnormal vibration signals appear, the fault has often progressed to the middle or late stages, potentially leading to serious consequences such as motor burnout. Summary of the Invention

[0003] This application provides a monitoring and protection method and system for a speed reducer, which aims to solve the problem that existing monitoring technologies cannot detect early insulation degradation and inter-turn short circuits in the early stages of a fault in a timely manner.

[0004] To address the aforementioned technical problems, firstly, this application provides a monitoring and protection method for a speed reducer, comprising:

[0005] The three-phase current signal of the drive motor and the vibration signal of the reducer are collected synchronously.

[0006] Spectral analysis is performed on the three-phase current signal to extract characteristic current harmonic components related to stator winding faults; the characteristic current harmonic components include fundamental frequency sideband components and specific subharmonic components.

[0007] Based on the characteristic current harmonic components, the stator winding health index is calculated;

[0008] Based on the stator winding health index and the preset winding fault threshold, generate early warning or protection commands related to the stator winding insulation status.

[0009] Based on the analysis results of the vibration signal and the warning or protection command, a comprehensive protection action is performed on the reducer.

[0010] In one embodiment, the method for performing spectral analysis on the three-phase current signal to extract characteristic current harmonic components related to stator winding faults includes:

[0011] The three-phase current signals acquired synchronously are subjected to Clarke transform and Park transform to obtain the d-axis current and q-axis current in a two-phase rotating coordinate system.

[0012] Perform a fast Fourier transform on the q-axis current to obtain the q-axis current spectrum;

[0013] In the q-axis current spectrum, the amplitude of the sideband pairs centered on the power supply fundamental frequency and with the motor rotation frequency as the interval are identified and extracted as the fundamental frequency sideband components.

[0014] In the q-axis current spectrum, the amplitudes of the 5th and 7th harmonics are identified and extracted as the specific harmonic components.

[0015] In one embodiment, the method for calculating the stator winding health index based on the characteristic current harmonic components includes:

[0016] Obtain the first composite amplitude of the fundamental frequency sideband component and the second composite amplitude of the specific subharmonic component;

[0017] Calculate the first normalized deviation and the second normalized deviation of the first composite amplitude and the second composite amplitude relative to their respective health baseline values;

[0018] The sequences of the first normalized deviation and the second normalized deviation within a preset historical time window are obtained respectively, and the first deterioration trend factor and the second deterioration trend factor corresponding to the first normalized deviation and the second normalized deviation are calculated.

[0019] The stator winding health index is calculated using a multi-feature fusion health model based on the first normalized deviation, the second normalized deviation, the first deterioration trend factor, and the second deterioration trend factor.

[0020] In one embodiment, the method for generating a warning or protection command related to the stator winding insulation state based on the stator winding health index and a preset winding fault threshold is as follows:

[0021] The first winding fault threshold, the second winding fault threshold, and the third winding fault threshold are preset, and the first winding fault threshold > the second winding fault threshold > the third winding fault threshold.

[0022] The stator winding health index is compared with the winding fault threshold in real time.

[0023] If the stator winding health index drops below the first winding fault threshold for the first time, a first-level warning instruction is generated, which is used to trigger a status prompt.

[0024] If the stator winding health index remains below the first winding fault threshold for more than a first preset time or drops below the second winding fault threshold for the first time, a secondary alarm and protection command is generated. The secondary alarm and protection command is used to trigger load reduction or speed reduction operation control.

[0025] If the stator winding health index drops below the third winding fault threshold, a level three emergency stop command is generated. This level three emergency stop command is used to directly control the drive motor to stop running.

[0026] In one embodiment, a first timer is started when load reduction or speed reduction operation control is executed;

[0027] If the stator winding health index rises above the second winding fault threshold before the first timer reaches the first preset time limit, the load reduction or speed reduction command will be automatically cancelled, the system will return to normal power operation, and this event will be recorded as a recoverability warning.

[0028] If the stator winding health index is still lower than the second winding fault threshold when the first timer reaches the first preset time limit, the third-level emergency shutdown command will be automatically executed.

[0029] In one embodiment, the method for performing comprehensive protection actions on the reducer by combining the analysis results of the vibration signal with the early warning or protection command is as follows:

[0030] The analysis results of the vibration signal are obtained, and the analysis results include at least the vibration severity level;

[0031] The decision is made by fusing the action level corresponding to the warning or protection command with the vibration severity level:

[0032] If the vibration severity level indicates that the vibration is normal or slightly abnormal, the original action corresponding to the action level of the warning or protection command shall be executed.

[0033] If the vibration severity level indicates moderate vibration abnormality, the action level corresponding to the warning or protection command will be raised by one level and the corresponding protection action will be executed.

[0034] If the vibration severity level indicates a severe vibration abnormality or malfunction, then regardless of the action level corresponding to the warning or protection command, the highest level of emergency shutdown protection action will be executed.

[0035] The protection actions, from lowest to highest level, include: status indication, reduced load and speed operation, and emergency shutdown.

[0036] In one embodiment, the method for determining the severity level of vibration by acquiring the analysis results of the vibration signal is as follows:

[0037] Calculate the effective velocity value of the vibration signal within a preset frequency band;

[0038] Set a first preset threshold and a second preset threshold, wherein the first preset threshold is less than the second preset threshold;

[0039] Perform spectral analysis on the vibration signal to identify and extract the amplitude of at least one characteristic frequency associated with the failure of the gearbox bearing and / or gear;

[0040] The effective value of the velocity is compared with a first preset threshold and a second preset threshold; if the effective value of the velocity is ≥ the second preset threshold, the severity level of the vibration is determined to be severe abnormality.

[0041] If the first preset threshold ≤ effective velocity value < second preset threshold and the amplitude of the characteristic frequency exceeds a preset multiple of the baseline value of the amplitude of the characteristic frequency, then the severity level of the vibration is determined to be severe abnormal; otherwise, it is determined to be moderate abnormal.

[0042] If the effective value of velocity is less than the first preset threshold and the amplitude of the characteristic frequency exceeds the baseline value of the amplitude of the characteristic frequency, the severity level of vibration is determined to be slightly abnormal; otherwise, the vibration is determined to be normal.

[0043] Secondly, this application also provides a monitoring and protection system for a speed reducer, used to implement the aforementioned monitoring and protection method for the speed reducer, the system comprising:

[0044] The synchronous acquisition module is used to synchronously acquire the three-phase current signal of the drive motor that drives the reducer, as well as the vibration signal of the reducer.

[0045] The current analysis and feature extraction module, connected to the synchronous acquisition module, is used to perform spectrum analysis on the three-phase current signal and extract characteristic current harmonic components related to stator winding faults. The characteristic current harmonic components include fundamental frequency sideband components and specific harmonic components.

[0046] The health assessment module, connected to the current analysis and feature extraction module, is used to calculate the stator winding health index based on the characteristic current harmonic components.

[0047] The instruction generation module, connected to the health assessment module, is used to generate early warning or protection instructions related to the insulation status of the stator winding based on the stator winding health index and a preset winding fault threshold.

[0048] The vibration analysis module, connected to the synchronous acquisition module, is used to analyze the vibration signal and obtain vibration analysis results;

[0049] The integrated decision-making and execution module is connected to the instruction generation module and the vibration analysis module, respectively, and is used to combine the vibration analysis results with the early warning or protection instructions to execute integrated protection actions for the reducer.

[0050] In one embodiment, the current analysis and feature extraction module includes:

[0051] The coordinate transformation unit is used to perform Clarke transformation and Park transformation on the three-phase current signal and output the q-axis current signal in a two-phase rotating coordinate system.

[0052] A spectrum analysis unit, connected to the coordinate transformation unit, is used to perform a fast Fourier transform on the q-axis current signal to generate the q-axis current spectrum;

[0053] The feature extraction unit, connected to the spectrum analysis unit, is used to synchronously extract from the q-axis current spectrum: the amplitude of the sideband pairs centered on the power supply fundamental frequency and spaced at the motor rotation frequency as the fundamental frequency sideband components, and the amplitudes of the 5th and 7th harmonics as the specific harmonic components.

[0054] In one embodiment, the integrated decision-making and execution module includes a multi-source information fusion decision-making unit;

[0055] The multi-source information fusion decision unit is connected to the instruction generation module and the vibration analysis module. It has a built-in decision logic table or rule engine to execute the fusion decision logic of the vibration severity level and the corresponding action level of the warning or protection instruction.

[0056] The beneficial effects of the above-mentioned monitoring and protection methods and systems for speed reducers are as follows:

[0057] By synchronously acquiring the three-phase current of the drive motor and performing spectrum analysis, micro-features strongly correlated with stator winding faults, such as fundamental frequency sideband components and specific subharmonic components, can be extracted. These features are extremely sensitive to early faults such as inter-turn short circuits and insulation aging, effectively covering the "blind spots" of traditional vibration monitoring and significantly advancing fault detection time. By calculating the stator winding health index, electrical characteristics are quantified into an intuitive and continuous evaluation indicator. Furthermore, this electrical health index is intelligently combined with the analysis results of vibration signals. This integration breaks down the barriers between electrical and mechanical monitoring, enabling the system to comprehensively consider electrical hazards and mechanical conditions, making a more comprehensive and accurate judgment on the overall health status and risk level of the reducer system, much like an experienced engineer. Attached Figure Description

[0058] Figure 1 This is a schematic flowchart illustrating the monitoring and protection method for a speed reducer according to an embodiment of this application;

[0059] Figure 2 The present application provides a schematic diagram of the monitoring and protection system for a speed reducer.

[0060] Figure 3 The embodiment of this application shows a cross-sectional structural schematic diagram of the speed reducer. Detailed Implementation

[0061] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0062] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be an intermediary component present. Conversely, when a component is said to be "directly" connected to another component, there is no intermediary component.

[0063] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0064] like Figure 1 As shown, this application provides a monitoring and protection method for a speed reducer, including:

[0065] S1. Synchronously acquire the three-phase current signal of the drive motor and the vibration signal of the reducer;

[0066] The three-phase current signal is obtained from the power input terminal (usually located on the inverter output side or inside the motor junction box) of the three-phase asynchronous motor or permanent magnet synchronous motor driving the reducer. The three-phase current signal contains information such as the motor's torque, efficiency, magnetic field symmetry, and winding health. Any asymmetry in the stator winding (such as inter-turn short circuits) will introduce specific harmonic distortions into the current waveform.

[0067] The vibration signal of the speed reducer is acquired through an accelerometer installed near the input shaft bearing housing, output shaft bearing housing, or in the middle of the speed reducer housing. The vibration signal directly reflects the mechanical condition of rotating components such as gears and bearings inside the speed reducer, such as meshing impact, wear, imbalance, and misalignment. Its amplitude and frequency components are directly related to the type and severity of mechanical faults.

[0068] A data acquisition card with multi-channel synchronous sampling capability is used. The three-phase current signal converts the large current in the motor main circuit into a small voltage signal acceptable to the acquisition card through a current transformer or Hall current sensor, and is then connected to the three analog input channels of the data acquisition card (corresponding to phases A, B, and C). The vibration signal is directly connected to another analog input channel of the acquisition card through the output signal (usually a voltage signal) of the accelerometer.

[0069] Three-phase current signal acquisition and vibration signal acquisition refer to sharing the same high-precision timestamp or sampling clock to ensure that each current and vibration data point is precisely aligned on the time axis. The current harmonic variations caused by stator winding faults should be temporally correlated with specific frequency vibrations that may be induced by electromagnetic force imbalance. Only synchronous acquisition allows for verification of this correlation in subsequent spectrum or time-frequency analysis, enabling more in-depth research into fault mechanisms or interference elimination. If acquisition is asynchronous, when the system detects abnormal current and vibration, it cannot determine whether they are two manifestations of the same fault event or two independent, accidental events. Synchronized timestamps are crucial information for making correct fusion decisions.

[0070] S2. Perform spectrum analysis on the three-phase current signal to extract characteristic current harmonic components related to stator winding faults; the characteristic current harmonic components include fundamental frequency sideband components and specific subharmonic components.

[0071] The method for performing spectral analysis on the three-phase current signal to extract characteristic current harmonic components related to stator winding faults includes:

[0072] S21. Perform Clarke transform and Park transform on the synchronously acquired three-phase current signals to obtain the d-axis current and q-axis current in a two-phase rotating coordinate system.

[0073] S22. Perform a fast Fourier transform on the q-axis current to obtain the spectrum of the q-axis current;

[0074] S23. In the q-axis current spectrum, identify and extract the amplitude of the sideband pairs centered on the power supply fundamental frequency and with the motor rotation frequency as the interval as the fundamental frequency sideband component.

[0075] S24. In the q-axis current spectrum, identify and extract the amplitudes of the 5th and 7th harmonics as the specific harmonic components.

[0076] For example, we have a 4-pole motor with a power supply frequency of 50Hz and a rated speed of approximately 1450rpm (rotation frequency fr≈24.17Hz). We have synchronously acquired the instantaneous value sequence of the three-phase currents A, B, and C. The Clarke transform transforms the currents Ia, Ib, and Ic in the three-phase stationary coordinate system (a, b, c) to the two-phase stationary coordinate system (α, β). That is, Iα = Ia; Iβ = (Ia + 2 * Ib) / sqrt(3).

[0077] The Parker transformation transforms a two-phase stationary coordinate system (α, β) into a two-phase rotating coordinate system (d, q) synchronously with the rotor magnetic field. That is, [Id; Iq] = [cosθ, sinθ; -sinθ, cosθ] * [Iα; Iβ]. The real-time electrical angle θ of the rotor can be obtained through an encoder. In this example, the motor rotates at approximately 1450 rpm, and θ increases linearly with time. The d-axis current is the component aligned with the rotor's main magnetic field, primarily reflecting the excitation state. The q-axis current is the component perpendicular to the rotor's main magnetic field, directly generating electromagnetic torque. For an ideally symmetrical motor, the three-phase fundamental current Iq will be a stable DC value after this transformation. However, when an asymmetrical fault occurs in the stator winding, the reverse rotating magnetic field or pulsating magnetic field caused by the fault cannot be completely stationary in the (d, q) coordinate system; it will manifest as AC modulation of the DC signal Iq. After the transformation, we obtain two new time series: Id(t) and Iq(t).

[0078] Applying a Fast Fourier Transform to the obtained Iq(t) time series, we obtain a spectrum (frequency-amplitude graph) of the Iq signal. The horizontal axis represents frequency (Hz), and the vertical axis represents the amplitude (A) of the corresponding frequency component. Under ideal healthy conditions, the spectrum shows only a high peak at 0Hz (DC), with other frequency components exhibiting extremely low amplitudes. However, when an early asymmetrical fault occurs in the stator winding, in addition to the main peak at 0Hz, a significant, high-amplitude bulge appears at a specific frequency position on the spectrum; this is the characteristic current harmonic component we are looking for.

[0079] On the spectrum, with the power supply fundamental frequency f1 = 50Hz as the center, find positions to the left and right at a distance equal to the motor rotational frequency fr ≈ 24.17Hz. Specifically, these are two frequency points: f1 - fr ≈ 25.83Hz and f1 + fr ≈ 74.17Hz. Read the spectral amplitudes corresponding to these two frequency points; for example, the amplitudes are measured as 25.83Hz = 0.15A and 74.17Hz = 0.12A. Record these amplitudes (0.15A, 0.12A) as characteristic values ​​of the fundamental frequency sideband components. Their appearance and increase are direct evidence of the modulation of the rotating magnetic field by winding asymmetry.

[0080] Extract specific harmonic components. On the spectrum, directly locate the positions of the 5th and 7th harmonic frequencies. Specifically, the coordinates are: 5*f1 = 250Hz and 7*f1 = 350Hz. Read the spectral amplitudes corresponding to these two frequency points; for example, the amplitudes are measured as 0.08A at 250Hz and 0.10A at 350Hz. Record these amplitudes (0.08A, 0.10A) as characteristic values ​​of the specific harmonic components. Their significant increase indicates that the symmetry of the three-phase motor system has been disrupted, generating a strong negative sequence current, pointing to a more specific winding fault.

[0081] Directly searching for the sidebands f1±fr in the original three-phase current spectrum yields very weak signals that are easily overwhelmed by noise and fundamental frequency leakage. However, after Parker transformation to the q-axis, the fundamental frequency (50Hz) is converted to DC (0Hz), and the fault modulation effect is shifted and concentrated near fr (24.17Hz) and its harmonics. This separates the characteristic frequency from the DC main peak, significantly improving the signal-to-noise ratio and making extraction more accurate.

[0082] S3. Calculate the stator winding health index based on the characteristic current harmonic components;

[0083] The method for calculating the stator winding health index based on the characteristic current harmonic components includes:

[0084] S31. Obtain the first composite amplitude of the fundamental frequency sideband component and the second composite amplitude of the specific subharmonic component;

[0085] S32. Calculate the first normalized deviation and the second normalized deviation of the first comprehensive amplitude and the second comprehensive amplitude relative to their respective health benchmark values, respectively.

[0086] S33. Obtain the sequences of the first normalized deviation and the second normalized deviation within a preset historical time window, and calculate the first deterioration trend factor and the second deterioration trend factor corresponding to the first normalized deviation and the second normalized deviation.

[0087] S34. Calculate the stator winding health index using a multi-feature fusion health model based on the first normalized deviation, the second normalized deviation, the first deterioration trend factor, and the second deterioration trend factor.

[0088] In S2, we obtain the sideband amplitudes: (0.15A, 0.12A). The 5th harmonic amplitude is 0.08A, and the 7th harmonic amplitude is 0.10A. The healthy reference amplitudes established by the system in the initial learning phase are: sideband reference: (0.02A, 0.02A); 5th / 7th harmonic reference: (0.01A, 0.01A).

[0089] The first composite amplitude is usually obtained by adding the amplitudes of the two sidebands. That is, Aside = 0.15A + 0.12A = 0.27A, where 0.27A represents the total intensity of the fault characteristics caused by the modulation effect.

[0090] The second comprehensive amplitude is the sum of the amplitudes of the 5th and 7th harmonics. Aharm = 0.08A + 0.10A = 0.18A, where 0.18A represents the total intensity of the fault characteristics caused by the three-phase asymmetry.

[0091] The first normalized deviation, Dside, is calculated as follows: (Current composite amplitude - Healthy baseline amplitude) / Healthy baseline amplitude = (0.27A - 0.04A) / 0.04A = 5.75. Dside = 5.75 means the current sideband characteristic intensity is 6.75 times that of the healthy baseline (i.e., an increase of 575%). This is a significant anomaly.

[0092] The second normalized deviation, Dharm = (0.18A - 0.02A) / 0.02A = 8.0. Dharm = 8.0 means the harmonic characteristic intensity is 9 times the healthy baseline. This also indicates a severe asymmetry.

[0093] The sequences of the first and second normalized deviations within a preset historical time window are obtained respectively, and the first and second deterioration trend factors corresponding to the first and second normalized deviations are calculated. This step analyzes historical data to determine whether the fault is developing steadily, slowly, or accelerating. Let's assume we examine the values ​​of Dside and Dharm recorded hourly over the past 24 hours (time window).

[0094] For example, the Dside sequence: [1.0, 1.5, 2.0, 3.0, 4.0, 5.0, 5.75];

[0095] Dharm sequence: [2.0, 3.0, 4.5, 5.5, 6.5, 7.2, 8.0].

[0096] A linear fit is performed on the Dside sequence to obtain the slope Sside. Assume Sside = 0.8 (units / hour). That is, the sideband deviation has increased by an average of 0.8 per hour over the past 24 hours.

[0097] The first deterioration trend factor is: Tside = max(0, Sside * τ). τ is a time scale constant, typically set to 24 (hours). Tside = 0.8 * 24 = 19.2. This value is very large, indicating a rapid rate of deterioration.

[0098] Similarly, the slope Shm = 0.85 (units / hour) obtained by fitting the Dharm sequence. Therefore, the second deterioration trend factor Tharm = 0.85 * 24 = 20.4.

[0099] The stator winding health index HI is calculated as follows: HI = 100 / [1 + W1 * Dside + W2 * Dharm + W3 * Tside + W4 * Tharm]. W1: Weight of the first normalized deviation (current sideband state); W2: Weight of the second normalized deviation (current harmonic state), usually slightly higher than the sideband weight because it indicates a more specific fault; W3: Weight of the first deterioration trend factor (sideband trend), assigning higher weight to the trend; W4: Weight of the second deterioration trend factor (harmonic trend), assigning the highest weight, emphasizing the danger of accelerated deterioration. Therefore, HI = 100 / [1 + 0.1 * 5.75 + 0.15 * 8.0 + 0.3 * 19.2 + 0.4 * 20.4] = 100 / [1 + 0.575 + 1.2 + 5.76 + 8.16] = 100 / 16.695 ≈ 5.99. The calculated HI ≈ 6.0. On a scale of 0-100, 6.0 is a very low score; if the ideal health condition is 100, then 6 is far below the ideal health condition. Therefore, this stator winding is in an extremely unhealthy state. Not only are the current fault characteristics very strong, but it is also deteriorating rapidly. The system should immediately implement the highest level of protection measures.

[0100] In this way, the stator winding health index is calculated by comprehensively considering the first normalized deviation, the second normalized deviation, the first deterioration trend factor, and the second deterioration trend factor. By assigning higher weights to the first and second deterioration trend factors, the model becomes predictive. Even if the first and second normalized deviations are not particularly high at present, if the trend deteriorates rapidly, the health index will drop quickly, achieving early warning.

[0101] S4. Generate early warning or protection commands related to the insulation status of the stator winding based on the stator winding health index and the preset winding fault threshold.

[0102] The method for generating early warning or protection commands related to the stator winding insulation status based on the stator winding health index and a preset winding fault threshold is as follows:

[0103] S41. Preset the first winding fault threshold, the second winding fault threshold and the third winding fault threshold, and the first winding fault threshold > the second winding fault threshold > the third winding fault threshold;

[0104] S42. Real-time comparison of the stator winding health index with the winding fault threshold;

[0105] S43. If the stator winding health index drops below the first winding fault threshold for the first time, a first-level warning instruction is generated, and the first-level warning instruction is used to trigger a status prompt;

[0106] S44. If the stator winding health index continues to be lower than the first winding fault threshold for more than the first preset time or drops below the second winding fault threshold for the first time, a second-level alarm and protection instruction is generated, and the second-level alarm and protection instruction is used to trigger load reduction or speed reduction operation control;

[0107] S45. If the stator winding health index drops below the third winding fault threshold, a third-level emergency shutdown instruction is generated, and the third-level emergency shutdown instruction is used to directly control the drive motor to stop running.

[0108] For example, the first winding fault threshold TH1: 75. This is the "warning line". When calculating that the stator winding health index HI is lower than this line, it indicates that there are clear signs of deterioration in the stator winding and attention should be paid.

[0109] The second winding fault threshold TH2: 50. This is the "action line". When calculating that the stator winding health index HI is lower than this line, it indicates that the fault has developed to a level that may affect performance or safety, and active protection measures need to be taken.

[0110] The third winding fault threshold TH3: 30. This is the "safety red line". When calculating that the stator winding health index HI is lower than this line, it indicates that the winding is in a high-risk state and a serious fault (such as short-circuit burnout) may occur at any time, and the machine must be stopped immediately. TH1(75)>TH2(50)>TH3(30). The lower the HI value, the worse the health status.

[0111] For example, the stator winding health index HI slowly drops from 80 to 73. Compare HI(73)<TH1(75) in real time. The stator winding health index HI drops below TH1 for the first time, and a first-level warning instruction is generated. At this time, the first-level warning instruction is sent to the human-machine interface and the monitoring center to trigger a status prompt; the triggered status includes that the indicator light changes from green to yellow, and a message pops up on the display screen: "The health of the stator winding has decreased (current value: 73), it is recommended to pay attention", etc. At this time, the speed reducer continues to operate at full speed and full load.

[0112] The stator winding health index HI hovered around 73 but never recovered above 75. This state persisted for 2.5 hours or the stator winding health index HI dropped sharply from 70 to 48. Then, when HI(48) first dropped below TH2(50), a secondary alarm and protection instruction was generated. The secondary alarm and protection instruction was sent to the control system and the actuator. The control system and the actuator controlled the indicator light to flash red and an alarm sound to sound. The display screen and remote notification were upgraded to: "Stator winding fault alarm, has entered the protection operation mode!" The system automatically sent an instruction to the frequency converter or speed control device to reduce the motor load to 70% of the rated value or reduce the speed to 85% of the rated value. The purpose was to delay the fault development speed by reducing electrical and mechanical stresses and gain precious time for planned shutdown maintenance.

[0113] If the stator winding health index HI continues to deteriorate to 28 and when HI(28) < TH3(30), a tertiary emergency shutdown instruction is generated. The tertiary emergency shutdown instruction is sent with the highest priority, directly cutting off the main circuit contactor of the motor or commanding the frequency converter to immediately stop output. The control indicator light turns red and remains on, the acoustic and optical alarm continues, and the message is updated to: "Stator winding critical! Emergency shutdown has been executed!" The reduction gear and its drive motor completely stop running, preventing catastrophic consequences such as fires and severe equipment damage that may be caused by a complete short circuit of the winding. In this way, the crude "either on or off" protection mode of the traditional protection is avoided. The primary early warning realizes predictive maintenance; the secondary protection realizes proactive risk control; the tertiary shutdown realizes ultimate safety protection.

[0114] Moreover, when the stator winding health index continuously remains below the first winding fault threshold for more than the first preset time, the secondary instruction is triggered. This design effectively filters out instantaneous interference or fluctuations, preventing misoperations caused by power grid transients or load mutations, and greatly improving the reliability and credibility of the system.

[0115] In one embodiment, when performing load reduction or speed reduction operation control, a first timer is started;

[0116] If the stator winding health index rises above the second winding fault threshold before the first timer reaches the first preset time limit, the load reduction or speed reduction instruction is automatically revoked, and it resumes normal power operation, and this event is recorded as a recoverable early warning;

[0117] If the stator winding health index is still below the second winding fault threshold when the first timer reaches the first preset time limit, the tertiary emergency shutdown instruction is automatically upgraded and executed.

[0118] For example, the first preset time limit is set to 4 hours. As the stator winding health index HI value drops to 48, the system has triggered a level 2 alarm and protection command, and the motor enters a 70% load reduction operation mode. At the moment of entering the load reduction operation mode, the system starts the first timer and begins a 4-hour countdown. At the same time, the system continuously monitors the stator winding health index HI value to see if it can recover due to the reduction in operating stress. After 2.5 hours of load reduction operation, due to the reduction in load, the heating and electrical stress of the winding decrease, and the fault development stops or even slightly reverses. The monitored stator winding health index HI value gradually rises from 48 to 52. That is, HI(52)>TH2(50), and at this time the first timer (which has been running for 2.5 hours) has not reached the 4-hour time limit. The system automatically sends a command to the control system to cancel the load reduction command, so that the motor returns to 100% rated load operation. At the same time, the first timer is reset, and the alarm status is downgraded back to level 1 warning.

[0119] If the first timer has reached its 4-hour limit and the stator winding health index HI value is still below TH2(50), the system determines that the secondary protection measures are ineffective, the fault has not been controlled, and the risk of continued operation is extremely high. The system automatically upgrades to execute a tertiary emergency shutdown command, immediately cutting off the power supply to completely stop the equipment. This effectively prevents cumulative damage in the protection mode: it avoids the equipment from operating for a long time in a "sick" reduced-load state, which could lead to the fault expanding in a hidden state and ultimately causing more serious secondary damage.

[0120] S5. Based on the analysis results of the vibration signal and the warning or protection command, execute a comprehensive protection action for the reducer.

[0121] The method for performing comprehensive protection actions on the reducer by combining the analysis results of the vibration signal with the early warning or protection command is as follows:

[0122] S51. Obtain the analysis results of the vibration signal, wherein the analysis results include at least the vibration severity level;

[0123] S52. The action level corresponding to the warning or protection command is fused with the vibration severity level to make a decision:

[0124] S53. If the vibration severity level indicates that the vibration is normal or slightly abnormal, the original action corresponding to the action level of the warning or protection instruction shall be executed.

[0125] S54. If the vibration severity level indicates moderate vibration abnormality, the action level corresponding to the warning or protection command will be raised by one level and the corresponding protection action will be executed.

[0126] S55. If the vibration severity level indicates severe vibration abnormality or malfunction, then regardless of the action level corresponding to the warning or protection command, the highest level of emergency shutdown protection action shall be executed.

[0127] The protection actions, from lowest to highest level, include: status indication, reduced load and speed operation, and emergency shutdown.

[0128] In one embodiment, the method for determining the severity level of vibration by acquiring the analysis results of the vibration signal is as follows:

[0129] Calculate the effective velocity value of the vibration signal within a preset frequency band;

[0130] Set a first preset threshold and a second preset threshold, wherein the first preset threshold is less than the second preset threshold;

[0131] Perform spectral analysis on the vibration signal to identify and extract the amplitude of at least one characteristic frequency associated with the failure of the gearbox bearing and / or gear;

[0132] The effective value of the velocity is compared with a first preset threshold and a second preset threshold; if the effective value of the velocity is ≥ the second preset threshold, the severity level of the vibration is determined to be severe abnormality.

[0133] If the first preset threshold ≤ effective velocity value < second preset threshold and the amplitude of the characteristic frequency exceeds a preset multiple of the baseline value of the amplitude of the characteristic frequency, then the severity level of the vibration is determined to be severe abnormal; otherwise, it is determined to be moderate abnormal.

[0134] If the effective value of velocity is less than the first preset threshold and the amplitude of the characteristic frequency exceeds the baseline value of the amplitude of the characteristic frequency, the severity level of vibration is determined to be slightly abnormal; otherwise, the vibration is determined to be normal.

[0135] For example, the preset frequency band is set to 10Hz-1000Hz. The effective velocity value Vrms is the vibration velocity value calculated within the preset frequency band, in mm / s; the first preset threshold TF1: 4.5mm / s; the second preset threshold TF2: 7.1mm / s (usually corresponding to the C / D zone boundary of the ISO standard, alarm / action threshold); characteristic frequency: taking the failure frequency FO of the outer ring of the reducer output shaft bearing as an example, it is assumed that its calculated value is 85Hz;

[0136] Characteristic frequency amplitude baseline value A_FO_base: The amplitude of the 85Hz frequency component measured when the device is healthy, for example, 0.05mm / s; Preset multiple K: Set to 5. That is, when the current amplitude exceeds 5 times the baseline value, the characteristic is considered very significant.

[0137] Example 1. For instance, the measured data shows Vrms = 9.0 mm / s, and the amplitude A_FO at FO(85Hz) is 0.20 mm / s (4 times the baseline value). Comparing Vrms with TF2: 9.0 ≥ 7.1. Since the root mean square velocity ≥ the second preset threshold, it is determined that the vibration severity level is severely abnormal. The final risk level is: severely abnormal. Although the amplitude of the characteristic frequency has only increased by 4 times (not exceeding 5 times), the overall risk level has seriously exceeded the standard, indicating that the equipment is under great overall mechanical stress and there may be serious imbalance, looseness or impact. At this time, there is no need to wait for the characteristic frequency to fully emerge, and it is necessary to immediately handle it as the highest risk. This reflects the principle of "overall safety first".

[0138] Example 2. The measured data is Vrms = 6.0 mm / s, and A_FO = 0.30 mm / s (6 times the baseline value of 0.05). Comparing Vrms with the threshold: TF1(4.5) ≤ 6.0 < TF2(7.1), and the condition A_FO(0.30) > A_FO_base(0.05) * K(5) = 0.25 is satisfied. Then it is determined that the vibration severity level is severely abnormal. The final risk level is: severely abnormal. Although the root mean square velocity (6.0) is only on the high side, the characteristic signal of a specific bearing fault is extremely strong. This strongly indicates that there is serious local damage (such as spalling, crack) in the bearing. This combination of "clear characteristics + increased intensity" has a very high risk, so it is determined to be severely abnormal.

[0139] Example 3. The measured data shows Vrms = 5.8 mm / s, and A_FO = 0.15 mm / s (3 times the baseline value, not exceeding 5 times). Comparing Vrms with the threshold: TF1(4.5) ≤ 5.8 < TF2(7.1). However, A_FO(0.15) < 0.25 (5 times the baseline). So it is determined that the vibration severity level is moderately abnormal. The final risk level is: moderately abnormal. The overall vibration level of the equipment has increased, which is worthy of vigilance, but no clear and strong fault evidence pointing to a specific component (such as a bearing) has been found. This may be caused by comprehensive factors such as misalignment, imbalance, and slight wear of gears, or it may be in the early stage of a fault. If the system determines it to be moderately abnormal, the action level corresponding to the warning or protection instruction will be raised by one level and then the corresponding protection action will be executed.

[0140] Example 4. The measured data shows Vrms = 3.0 mm / s, and A_FO = 0.08 mm / s (1.6 times the baseline value of 0.05). Comparing Vrms with the threshold: 3.0 < TF1(4.5). And A_FO(0.08) > A_FO_base(0.05). Then it is determined that the vibration severity level is slightly abnormal. Then the final risk level is: slightly abnormal. Then the original action corresponding to the action level of the warning or protection instruction will be executed.

[0141] like Figure 2 As shown, in a second aspect, this application also provides a monitoring and protection system for a speed reducer, used to implement the aforementioned monitoring and protection method for the speed reducer, the system comprising:

[0142] Synchronous acquisition module 1 is used to synchronously acquire the three-phase current signal of the drive motor driving the reducer, as well as the vibration signal of the reducer;

[0143] The current analysis and feature extraction module 2 is connected to the synchronous acquisition module and is used to perform spectrum analysis on the three-phase current signal and extract characteristic current harmonic components related to stator winding faults. The characteristic current harmonic components include fundamental frequency sideband components and specific subharmonic components.

[0144] The health assessment module 3 is connected to the current analysis and feature extraction module and is used to calculate the stator winding health index based on the characteristic current harmonic components.

[0145] The instruction generation module 4 is connected to the health assessment module and is used to generate early warning or protection instructions related to the insulation status of the stator winding based on the stator winding health index and the preset winding fault threshold.

[0146] Vibration analysis module 5, connected to the synchronous acquisition module, is used to analyze the vibration signal and obtain vibration analysis results;

[0147] The integrated decision-making and execution module 6 is connected to the instruction generation module and the vibration analysis module, respectively, and is used to combine the vibration analysis results with the early warning or protection instructions to execute integrated protection actions for the reducer.

[0148] In one embodiment, the current analysis and feature extraction module 2 includes:

[0149] The coordinate transformation unit is used to perform Clarke transformation and Park transformation on the three-phase current signal and output the q-axis current signal in a two-phase rotating coordinate system.

[0150] A spectrum analysis unit, connected to the coordinate transformation unit, is used to perform a fast Fourier transform on the q-axis current signal to generate the q-axis current spectrum;

[0151] The feature extraction unit, connected to the spectrum analysis unit, is used to synchronously extract from the q-axis current spectrum: the amplitude of the sideband pairs centered on the power supply fundamental frequency and spaced at the motor rotation frequency as the fundamental frequency sideband components, and the amplitudes of the 5th and 7th harmonics as the specific harmonic components.

[0152] In one embodiment, the integrated decision-making and execution module includes a multi-source information fusion decision-making unit;

[0153] The multi-source information fusion decision unit is connected to the instruction generation module and the vibration analysis module. It has a built-in decision logic table or rule engine to execute the fusion decision logic of the vibration severity level and the corresponding action level of the warning or protection instruction.

[0154] like Figure 3 As shown in the third aspect, this application also provides a speed reducer, including a mounting base 100, an input shaft sleeve 200, a large gear 300, a small gear 400, a rotating sleeve 500, an output shaft sleeve 600, and an output shaft 700. The input shaft sleeve 200 is mounted on one end of the mounting base 100, and its input end is mounted on a coupling. The large gear 300 is mounted on the output end. The inner layer of the small gear 400 meshes with the large gear 300, and its outer layer meshes with the rotating sleeve 500. The output shaft sleeve 600 is mounted on one end of the rotating sleeve 500, and the rotating sleeve 500 drives the output shaft sleeve 600 to rotate. The output shaft 700 passes through the output shaft sleeve 600. There are three small gears 400, arranged in an array on the outer layer of the large gear 300.

[0155] The input end of the coupling is connected to the motor. After the motor starts, it drives the coupling to rotate. The coupling drives the large gear 300 to rotate through the input shaft sleeve 200, which in turn drives the small gear 400 to rotate. The small gear 400 drives the rotating sleeve 500, which drives the output shaft 700 to rotate through the output shaft sleeve 600. A vibration acceleration sensor is attached to the mounting base 100 to collect the vibration signal of the reducer.

[0156] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0157] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A monitoring and protection method for a speed reducer, characterized in that: include: The three-phase current signal of the drive motor and the vibration signal of the reducer are collected synchronously. Spectral analysis was performed on the three-phase current signals to extract characteristic current harmonic components related to stator winding faults; The characteristic current harmonic components include fundamental frequency sideband components and specific subharmonic components; Based on the characteristic current harmonic components, the stator winding health index is calculated; Based on the stator winding health index and the preset winding fault threshold, generate early warning or protection commands related to the stator winding insulation status. Based on the analysis results of the vibration signal and the warning or protection command, a comprehensive protection action is performed on the reducer.

2. The monitoring and protection method for the speed reducer according to claim 1, characterized in that: The method for performing spectral analysis on the three-phase current signal to extract characteristic current harmonic components related to stator winding faults includes: The three-phase current signals acquired synchronously are subjected to Clarke transform and Park transform to obtain the d-axis current and q-axis current in a two-phase rotating coordinate system. Perform a fast Fourier transform on the q-axis current to obtain the q-axis current spectrum; In the q-axis current spectrum, the amplitude of the sideband pairs centered on the power supply fundamental frequency and with the motor rotation frequency as the interval are identified and extracted as the fundamental frequency sideband components. In the q-axis current spectrum, the amplitudes of the 5th and 7th harmonics are identified and extracted as the specific harmonic components.

3. The monitoring and protection method for the speed reducer according to claim 2, characterized in that: The method for calculating the stator winding health index based on the characteristic current harmonic components includes: Obtain the first composite amplitude of the fundamental frequency sideband component and the second composite amplitude of the specific subharmonic component; Calculate the first normalized deviation and the second normalized deviation of the first composite amplitude and the second composite amplitude relative to their respective health baseline values; The sequences of the first normalized deviation and the second normalized deviation within a preset historical time window are obtained respectively, and the first deterioration trend factor and the second deterioration trend factor corresponding to the first normalized deviation and the second normalized deviation are calculated. The stator winding health index is calculated using a multi-feature fusion health model based on the first normalized deviation, the second normalized deviation, the first deterioration trend factor, and the second deterioration trend factor.

4. The monitoring and protection method for the speed reducer according to claim 3, characterized in that: The method for generating early warning or protection commands related to the stator winding insulation status based on the stator winding health index and a preset winding fault threshold is as follows: The first winding fault threshold, the second winding fault threshold, and the third winding fault threshold are preset, and the first winding fault threshold > the second winding fault threshold > the third winding fault threshold. The stator winding health index is compared with the winding fault threshold in real time. If the stator winding health index drops below the first winding fault threshold for the first time, a first-level warning instruction is generated, which is used to trigger a status prompt. If the stator winding health index remains below the first winding fault threshold for more than a first preset time or drops below the second winding fault threshold for the first time, a secondary alarm and protection command is generated. The secondary alarm and protection command is used to trigger load reduction or speed reduction operation control. If the stator winding health index drops below the third winding fault threshold, a level three emergency stop command is generated. This level three emergency stop command is used to directly control the drive motor to stop running.

5. The monitoring and protection method for the speed reducer according to claim 4, characterized in that: When load reduction or speed reduction operation control is executed, the first timer is started; If the stator winding health index rises above the second winding fault threshold before the first timer reaches the first preset time limit, the load reduction or speed reduction command will be automatically cancelled, the system will return to normal power operation, and this event will be recorded as a recoverability warning. If the stator winding health index is still lower than the second winding fault threshold when the first timer reaches the first preset time limit, the third-level emergency shutdown command will be automatically executed.

6. The monitoring and protection method for the speed reducer according to claim 5, characterized in that: The method for performing comprehensive protection actions on the reducer by combining the analysis results of the vibration signal with the early warning or protection command is as follows: The analysis results of the vibration signal are obtained, and the analysis results include at least the vibration severity level; The decision is made by fusing the action level corresponding to the warning or protection command with the vibration severity level: If the vibration severity level indicates that the vibration is normal or slightly abnormal, the original action corresponding to the action level of the warning or protection command shall be executed. If the vibration severity level indicates moderate vibration abnormality, the action level corresponding to the warning or protection command will be raised by one level and the corresponding protection action will be executed. If the vibration severity level indicates a severe vibration abnormality or malfunction, then regardless of the action level corresponding to the warning or protection command, the highest level of emergency shutdown protection action will be executed. The protection actions, from lowest to highest level, include: status indication, reduced load and speed operation, and emergency shutdown.

7. The monitoring and protection method for the speed reducer according to claim 6, characterized in that: The method for determining the severity level of vibration based on the analysis results of the acquired vibration signals is as follows: Calculate the effective velocity value of the vibration signal within a preset frequency band; Set a first preset threshold and a second preset threshold, wherein the first preset threshold is less than the second preset threshold; Perform spectral analysis on the vibration signal to identify and extract the amplitude of at least one characteristic frequency associated with the failure of the gearbox bearing and / or gear; The effective value of the speed is compared with a first preset threshold and a second preset threshold; If the effective value of the velocity is greater than or equal to the second preset threshold, the severity level of the vibration is determined to be severe abnormality. If the first preset threshold ≤ effective velocity value < second preset threshold and the amplitude of the characteristic frequency exceeds a preset multiple of the baseline value of the amplitude of the characteristic frequency, then the severity level of the vibration is determined to be severe abnormal; otherwise, it is determined to be moderate abnormal. If the effective value of velocity is less than the first preset threshold and the amplitude of the characteristic frequency exceeds the baseline value of the amplitude of the characteristic frequency, the severity level of vibration is determined to be slightly abnormal; otherwise, the vibration is determined to be normal.

8. A monitoring and protection system for a speed reducer, used to implement the monitoring and protection method for a speed reducer as described in any one of claims 1-7, characterized in that, The system includes: The synchronous acquisition module is used to synchronously acquire the three-phase current signal of the drive motor that drives the reducer, as well as the vibration signal of the reducer. The current analysis and feature extraction module, connected to the synchronous acquisition module, is used to perform spectrum analysis on the three-phase current signal and extract characteristic current harmonic components related to stator winding faults. The characteristic current harmonic components include fundamental frequency sideband components and specific harmonic components. The health assessment module, connected to the current analysis and feature extraction module, is used to calculate the stator winding health index based on the characteristic current harmonic components. The instruction generation module, connected to the health assessment module, is used to generate early warning or protection instructions related to the insulation status of the stator winding based on the stator winding health index and a preset winding fault threshold. The vibration analysis module, connected to the synchronous acquisition module, is used to analyze the vibration signal and obtain vibration analysis results; The integrated decision-making and execution module is connected to the instruction generation module and the vibration analysis module, respectively, and is used to combine the vibration analysis results with the early warning or protection instructions to execute integrated protection actions for the reducer.

9. The monitoring and protection system for the speed reducer according to claim 8, characterized in that, The current analysis and feature extraction module includes: The coordinate transformation unit is used to perform Clarke transformation and Park transformation on the three-phase current signal and output the q-axis current signal in a two-phase rotating coordinate system. A spectrum analysis unit, connected to the coordinate transformation unit, is used to perform a fast Fourier transform on the q-axis current signal to generate the q-axis current spectrum; The feature extraction unit, connected to the spectrum analysis unit, is used to synchronously extract from the q-axis current spectrum: the amplitude of the sideband pairs centered on the power supply fundamental frequency and spaced at the motor rotation frequency as the fundamental frequency sideband components, and the amplitudes of the 5th and 7th harmonics as the specific harmonic components.

10. The monitoring and protection system for the speed reducer according to claim 9, characterized in that, The integrated decision-making and execution module includes a multi-source information fusion decision-making unit; The multi-source information fusion decision unit is connected to the instruction generation module and the vibration analysis module. It has a built-in decision logic table or rule engine to execute the fusion decision logic of the vibration severity level and the corresponding action level of the warning or protection instruction.

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