A coal mine conveyor permanent magnet eddy current coupler thermal demagnetization protection method

Abstract

This invention discloses a method for thermal demagnetization protection of permanent magnet eddy current couplers in coal mine conveyors, belonging to the field of intelligent operation and maintenance of coal mine conveyors. The method includes determining the estimated torque transmitted by the coupler, and determining the equivalent slip loss heat input by combining the input and output rotational speeds of the coupler; based on the equivalent slip loss heat input, considering the equivalent heat dissipation coefficient of the roadway, the measured temperature of the coupler, and the ambient temperature of the roadway, predicting the current coupler temperature; calculating the environmentally corrected temperature prediction residual to identify abnormal heating; when abnormal heating exists, constructing multiple types of risk evidence and calculating a thermal demagnetization risk index to determine the thermal demagnetization risk level and execute corresponding protection actions. This invention can identify the risks of high slip, abnormal heating, and torque transmission characteristic attenuation of permanent magnet eddy current couplers before the temperature reaches a dangerous threshold, thereby improving the safety and reliability of permanent magnet drive systems in long-distance coal mine conveyors.

Description

Technical Field

[0001] This invention relates to the field of intelligent operation and maintenance and safety protection technology for coal mine conveyors, and more specifically to a method for thermal demagnetization protection of permanent magnet eddy current couplers for coal mine conveyors. Background Technology

[0002] In the drive system of belt conveyors in coal mines, permanent magnet eddy current couplers are used because of their advantages such as soft start, overload buffering and impact isolation. During operation, a certain speed difference is maintained between the input side and the output side, which causes the conductor component to cut the permanent magnet magnetic field and generate induced eddy currents, thereby forming a transmitted torque.

[0003] However, coal mine conveyors typically have characteristics such as long conveying distances, high drive power, frequent heavy-load starts, and significant fluctuations in coal flow load. When the conveyor starts under heavy load, the coal feed rate suddenly increases, or the operating resistance increases, the speed difference between the input and output sides of the permanent magnet eddy current coupler increases, leading to increased slip loss and heat generation within the coupler. If the high slip and high temperature conditions persist, the magnetization capacity of the permanent magnet components may decrease, and in severe cases, irreversible thermal demagnetization may occur, thereby affecting the torque transmission capability and operational safety of the conveyor drive system.

[0004] Currently, to address the issues of temperature rise and permanent magnet demagnetization protection in permanent magnet couplers, existing methods primarily focus on loss calculation and temperature analysis. For example, the patent "A Method for Calculating Eddy Current Loss Power of a Mining Permanent Magnet Coupler" calculates the eddy current loss power of the mining permanent magnet coupler by establishing an equivalent magnetic circuit model and combining it with the energy conservation relationship, providing a basis for coupler temperature rise control, overload protection, and life assessment. Another example is the patent "A Method for Calculating the Full-Field Temperature of a Mining Magnetic Coupler," which obtains the local temperature of the copper conductor layer by arranging temperature probes and calculates the full-field temperature of the mining magnetic coupler by combining temperature fitting and thermodynamic boundary conditions, improving the accuracy and engineering applicability of coupler temperature analysis.

[0005] The aforementioned methods play a positive role in analyzing eddy current losses and temperature distribution in mining permanent magnet couplers. However, they are mainly used for loss or temperature calculations and do not fully consider the combined changes in load, slip, and roadway heat dissipation environment during the operation of long-distance coal mine conveyors. The ambient temperature, ventilation conditions, and dust adhesion in coal mine roadways affect the coupler's heat dissipation capacity, while heavy-load startup and sudden changes in coal flow cause synchronous changes in transmitted torque, slip, and temperature. Therefore, relying solely on loss calculations, temperature field calculations, fixed temperature thresholds, or a single slip threshold is insufficient to distinguish between normal heavy-load temperature rises, temperature rises due to deteriorated heat dissipation conditions, and abnormal heating caused by torque transmission characteristic attenuation. Furthermore, it is not conducive to identifying the risk of thermal demagnetization before the coupler temperature reaches a dangerous threshold.

[0006] Therefore, how to improve the thermal demagnetization risk identification and protection capabilities of permanent magnet eddy current couplers for coal mine conveyors under heavy load start-up, sudden changes in coal flow, and changes in roadway environment is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of the above shortcomings, the present invention proposes a thermal demagnetization protection method for permanent magnet eddy current couplers in coal mine conveyors, so as to overcome the above problems or at least partially solve the above problems.

[0008] To achieve the above objectives, the present invention adopts the following technical solution;

[0009] A method for thermal demagnetization protection of a permanent magnet eddy current coupler in a coal mine conveyor, comprising the following steps: The estimated value of the torque transmitted by the coupler is determined based on the torque-related parameters of the drive motor of the coal mine conveyor, and the equivalent slip loss heat input is determined by combining the speeds of the input and output sides of the coupler. Based on the equivalent slip loss heat input, the coupler temperature at the current moment is predicted by considering the equivalent heat dissipation coefficient of the roadway, the measured temperature of the coupler, and the ambient temperature of the roadway. The environmental correction temperature prediction residual is calculated based on the predicted coupler temperature and the measured coupler temperature, and abnormal heating is identified. When abnormal heating occurs, multiple types of risk evidence are constructed based on the equivalent slip loss heat input, the environmental correction temperature prediction residual, the coupler slip, the coupler temperature rise rate and torque transmission characteristic attenuation, and thermal demagnetization risk index is calculated. The thermal demagnetization risk level is determined based on the aforementioned risk evidence and the aforementioned thermal demagnetization risk index, and corresponding protective actions are executed.

[0010] Furthermore, the torque-related parameters of the drive motor of the coal mine conveyor include at least one of the following: electromagnetic torque estimate, torque current component, shaft end torque measurement, and motor operating current.

[0011] Furthermore, the equivalent slip loss heat input is determined by combining the rotational speeds on the input and output sides of the coupler, including: After converting the rotational speeds of the input and output sides of the coupler into angular velocities, the slip angular velocity is calculated. Multiplying the slip angular velocity by the estimated torque transmitted by the coupler yields the equivalent slip loss heat input.

[0012] Furthermore, based on the equivalent slip loss heat input, and considering the equivalent heat dissipation coefficient of the roadway, the measured temperature of the coupler, and the ambient temperature of the roadway, the current coupler temperature is predicted using the following formula:

[0013] In the formula, Predict the temperature of the coupler at the current moment. At the current sampling time, for The measured temperature of the coupler at any given time. The sampling period is The equivalent thermal capacity of the coupler, For equivalent slip loss heat input, The equivalent heat dissipation coefficient of the tunnel. This is the equivalent heat dissipation area of ​​the coupler. The ambient temperature of the tunnel.

[0014] Furthermore, the equivalent heat dissipation coefficient of the tunnel is determined through the following steps: Dust state quantity is estimated based on the dust concentration in the tunnel; and a dust correction factor is calculated based on the dust state quantity. Calculate the ventilation correction factor based on the tunnel ventilation velocity; The reference heat dissipation coefficient is corrected by using the dust correction factor and the ventilation correction factor within a preset heat dissipation coefficient range to obtain the equivalent heat dissipation coefficient of the roadway.

[0015] Furthermore, identifying abnormal fever includes: When the measured temperature of the coupler is consistently higher than the predicted temperature, or when the deviation continues to increase over multiple consecutive sampling periods, it is determined to be abnormal heating.

[0016] Furthermore, multiple types of risk evidence are constructed based on the equivalent slip loss heat input, the environmentally corrected temperature prediction residual, the coupler slip, the coupler temperature rise rate, and the torque transmission characteristic attenuation, including: The equivalent slip loss heat input, the environmental corrected temperature prediction residual, the coupler slip, the coupler temperature rise rate and the torque transmission characteristic attenuation are respectively smoothed and saturated normalized. The maximum value between the coupler slip normalization value and the equivalent slip loss heat input normalization value is defined as the operational strength evidence; The weighted fusion value of the normalized residual value of the environmentally corrected temperature prediction and the normalized value of the coupler temperature rise rate is defined as evidence of temperature anomalies. The normalized value of the torque transmission characteristic attenuation is defined as evidence of transmission characteristic anomaly.

[0017] Furthermore, the torque transmission characteristic attenuation is obtained through the following steps; Determine the current operating condition category and obtain the corresponding healthy reference torque; The torque transmission characteristic deviation is calculated based on the healthy reference torque and the estimated torque transmitted by the coupler. The torque transmission characteristic deviation is nonnegated and limited to obtain the torque transmission characteristic attenuation.

[0018] Furthermore, the torque transmission characteristic attenuation is only valid when the coupler is in a positive drive state and the coupler slip and the healthy reference torque respectively meet the validity judgment conditions. When invalid, it is not used as an indicator to determine the thermal demagnetization risk level. The validity criteria include that the coupler slip is within the pre-calibrated torque transmission characteristic analysis range, and that the healthy reference torque parameter is not lower than the pre-set lower limit threshold.

[0019] Further, based on the risk evidence and the thermal demagnetization risk index, the thermal demagnetization risk level is determined, and corresponding protective actions are executed; including: When at least one type of risk evidence is abnormal or the thermal demagnetization risk indicator reaches the first threshold, it is judged as a level one risk and early warning protection is implemented. When at least two types of risk evidence are abnormal and the thermal demagnetization risk index reaches the second threshold, it is judged as a level 2 risk and thermal load limiting protection is implemented. When at least two types of risk evidence are abnormal and the thermal demagnetization risk index reaches the third threshold, it is judged as a level three risk, and load reduction, speed reduction and cooling enhancement protection are implemented. When at least two types of risk evidence are abnormal and the thermal demagnetization risk index reaches the fourth threshold, it is judged as a level four risk, and the shutdown and lockout restart protection are executed. The first threshold, the second threshold, the third threshold, and the fourth threshold increase sequentially.

[0020] This invention provides a method for thermal demagnetization protection of permanent magnet eddy current couplers in coal mine conveyors. By acquiring the coupler's input-side rotational speed, output-side rotational speed, transmitted torque-related parameters, coupler temperature, conveyor belt speed, and roadway environmental parameters, the method calculates the coupler slip and equivalent slip loss heat input. It also predicts the coupler temperature based on roadway ventilation and dust conditions, obtaining the environmentally corrected temperature prediction residual. Furthermore, it calculates the torque transmission characteristic attenuation based on a healthy torque-slip reference model, and constructs three types of risk evidence: operational intensity, temperature anomaly, and transmission characteristic anomaly. This determines the thermal demagnetization risk level and implements graded protection, including early warning, load limiting, speed reduction, cooling, shutdown, and start-up interlocking. This improves the ability to identify and protect against thermal demagnetization risks in permanent magnet eddy current couplers under complex operating conditions.

[0021] Compared with fixed temperature threshold or single slip threshold protection methods, this application can comprehensively consider load changes and roadway heat dissipation environment, reduce false alarms caused by heavy load start-up, environmental changes and instantaneous measurement fluctuations, and identify the risk of thermal demagnetization before the coupler temperature reaches the dangerous protection threshold, thereby improving the safety and reliability of the coal mine conveyor drive system. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0023] Figure 1 This is a flowchart illustrating a method for thermal demagnetization protection of a permanent magnet eddy current coupler used in a coal mine conveyor, as provided in an embodiment of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] This invention discloses a method for thermal demagnetization protection of a permanent magnet eddy current coupler in a coal mine conveyor. The permanent magnet eddy current coupler includes an input-side rotor and an output-side rotor, one rotor having a permanent magnet component and the other rotor having a conductor component. When there is a speed difference between the input-side rotor and the output-side rotor, the conductor component generates induced eddy currents, and transmits torque through the interaction between the induced eddy currents and the permanent magnet magnetic field.

[0026] This embodiment obtains the coupler's input-side rotational speed, output-side rotational speed, transmission torque-related parameters, coupler temperature, conveyor belt speed, and roadway environmental parameters. It calculates the coupler slip and equivalent slip loss heat input, and obtains the environmental correction temperature prediction residual by combining roadway ventilation and dust conditions. It also calculates the torque transmission characteristic attenuation based on the healthy torque-slip reference model. Furthermore, it constructs three types of risk evidence: operating intensity, temperature anomaly, and transmission characteristic anomaly. Based on the thermal demagnetization risk level, it executes protective actions such as early warning, load limiting, speed reduction, cooling, shutdown, and start-up interlocking.

[0027] In one embodiment, the thermal demagnetization protection method includes the following specific steps: The estimated value of the torque transmitted by the coupler is determined based on the torque-related parameters of the drive motor of the coal mine conveyor, and the equivalent slip loss heat input is determined by combining the speeds of the input and output sides of the coupler. Based on the equivalent slip loss heat input, the coupler temperature at the current moment is predicted by considering the equivalent heat dissipation coefficient of the roadway, the measured temperature of the coupler, and the ambient temperature of the roadway. The environmental correction temperature prediction residual is calculated based on the predicted coupler temperature and the measured coupler temperature, and abnormal heating is identified. When abnormal heating occurs, multiple types of risk evidence are constructed based on the equivalent slip loss heat input, the environmental correction temperature prediction residual, the coupler slip, the coupler temperature rise rate and torque transmission characteristic attenuation, and thermal demagnetization risk index is calculated. The thermal demagnetization risk level is determined based on the aforementioned risk evidence and the aforementioned thermal demagnetization risk index, and corresponding protective actions are executed.

[0028] The above process will be described in detail below through specific embodiments.

[0029] Reference Figure 1 , Figure 1 This is a flowchart illustrating the thermal demagnetization protection method for the permanent magnet eddy current coupler of a coal mine conveyor in this embodiment, which includes, in sequence: Step 1: Obtain running status parameters; In some alternative implementations, this embodiment first obtains the input rotational speed of the permanent magnet eddy current coupler of the coal mine conveyor. Coupler output speed Coupler temperature Conveyor belt speed Ambient temperature in the tunnel tunnel ventilation speed and the concentration of dust in the alley and the torque-related parameters of the drive motor; among which, This represents the current sampling time.

[0030] When a transmission mechanism is provided between the drive motor and the input side of the coupler, the speed of the drive motor is converted into the speed of the input side of the coupler according to the transmission ratio.

[0031] Step 2: Determine the coupler-transmitted torque and equivalent slip loss heat input; In this embodiment, the estimated torque transmitted by the permanent magnet eddy current coupler is determined based on the torque-related parameters of the coal mine conveyor drive motor. The torque-related parameters of the drive motor of a coal mine conveyor include at least one of the following: electromagnetic torque estimate, torque current component, shaft end torque measurement, and motor operating current.

[0032] For example, when the drive motor controller is able to output an electromagnetic torque estimate At that time, the estimated value of the torque transmitted by the coupler is determined based on the transmission relationship between the drive motor and the input side of the permanent magnet eddy current coupler:

[0033] In the formula, To transmit torque estimates to the coupler, This is an estimated value for the electromagnetic torque. k At the current sampling time, This refers to the transmission ratio from the output shaft of the drive motor to the input side of the coupler. This represents the transmission efficiency of the corresponding transmission mechanism. When the drive motor is directly connected to the input side of the coupler, take... When the mechanical losses of the directly connected parts are ignored, take .

[0034] When the drive motor controller can output torque current components At that time, the estimated value of the torque transmitted by the coupler is determined according to the following formula:

[0035] In the formula, To transmit torque estimates to the coupler, For torque current components, This is the calibrated torque coefficient.

[0036] When the electromagnetic torque estimate and torque current component are unavailable, the torque transmitted by the coupler is estimated based on the operating current of the drive motor.

[0037] In the formula, To transmit torque estimates to the coupler, This is the motor operating current. This corresponds to the no-load current under operating conditions. The torque estimation coefficients are obtained through calibration tests of the drive motor and coupler transmission system.

[0038] The current estimation method is used when the drive motor is in a forward drive state and the motor current is within a preset calibration range.

[0039] When the shaft end torque measurement value can be obtained At that time, the estimated value of the torque transmitted by the coupler is determined based on the transmission relationship between the torque measurement position and the input side of the permanent magnet eddy current coupler:

[0040] In the formula, The torque estimate is transmitted to the coupler at the current sampling time. This is the measured value of the shaft end torque. The transmission ratio from the shaft end torque measurement position to the coupler input side. This represents the transmission efficiency from the shaft-end torque measurement position to the coupler input side. When the torque sensor is located at the coupler input shaft end, the value is... , .

[0041] Furthermore, the equivalent slip loss heat input is calculated through the following steps: Convert the input and output rotational speeds of the coupler into angular velocities;

[0042]

[0043] In the formula, The input speed of the coupler. The speed at the output side of the coupler. and These are the angular velocities on the input and output sides of the coupler, respectively. This represents the current sampling time.

[0044] Calculate the slip angular velocity between the input and output sides of the coupler;

[0045] In the formula, ω is the slip angular velocity.

[0046] Calculate the equivalent slip loss heat input based on the estimated torque transmitted by the coupler and the slip angular velocity;

[0047] In the formula, To transmit torque estimates to the coupler, At the current sampling time, For slip angular velocity, It represents the equivalent slip loss heat input in kW, used to characterize the equivalent heating intensity of the permanent magnet eddy current coupler caused by the relative rotation between the input and output sides, and is used for subsequent temperature prediction.

[0048] Step 3: Determine the corrected heat dissipation parameters for the tunnel environment and predict the coupler temperature; In some implementation schemes, modified heat dissipation parameters for the tunnel environment are determined, including: The dust state quantity at the current sampling time is determined based on the dust concentration in the tunnel or the dust coverage parameters on the coupler surface. When using tunnel dust concentration to estimate the dust state quantity, the calculation formula is:

[0049] In the formula, Dust state quantity, This means limiting the calculation result to between 0 and 1. The dust concentration in the alleyway. At the current sampling time, The dust accumulation coefficient, The sampling period.

[0050] According to dust state quantity Calculate the dust correction factor:

[0051] in, Dust correction factor, Let be the dust impact coefficient, and satisfy . .

[0052] Furthermore, a ventilation correction factor is calculated based on the ventilation velocity in the tunnel;

[0053] In the formula, For ventilation correction factor, This is the ventilation correction factor. For the ventilation speed of the tunnel, The reference ventilation speed is used.

[0054] Subsequently, the baseline heat dissipation coefficient was corrected using dust correction factors and ventilation correction factors within a preset heat dissipation coefficient range to obtain the equivalent heat dissipation coefficient of the roadway; the formula is expressed as:

[0055] In the formula, The equivalent heat dissipation coefficient of the tunnel. and These are the lower and upper limits of the equivalent heat dissipation coefficient, respectively. The equivalent heat dissipation coefficient without boundary constraints. ,in, The baseline heat dissipation coefficient is defined under conditions where there is no obvious forced ventilation and the heat dissipation surface is free of dust coverage. Dust correction factor, This is a ventilation correction factor.

[0056] In some implementation schemes, the coupler temperature at the current moment is predicted based on the equivalent slip loss heat input, taking into account the equivalent heat dissipation coefficient of the roadway, the measured temperature of the coupler, and the ambient temperature of the roadway, using the following formula:

[0057] In the formula, Predict the temperature of the coupler at the current moment. At the current sampling time, for The measured temperature of the coupler at any given time. The sampling period is The equivalent thermal capacity of the coupler, For equivalent slip loss heat input, The equivalent heat dissipation coefficient of the tunnel. This is the equivalent heat dissipation area of ​​the coupler. The ambient temperature of the tunnel.

[0058] Step 4: Calculate the environmentally corrected temperature prediction residual; In one optional implementation, the environmentally corrected temperature prediction residual is the difference between the measured temperature and the predicted temperature of the coupler at the current sampling time, i.e.

[0059] In the formula, To correct the residuals of temperature prediction for environmental conditions, The measured temperature of the coupler. Predicting temperature for the coupler, This represents the current sampling time.

[0060] Simultaneously, when the measured temperature of the coupler consistently exceeds the predicted temperature, or when the deviation continuously increases over multiple consecutive sampling periods, it is determined to be abnormal heating. In this embodiment, when A value greater than zero indicates that the measured temperature of the coupler is higher than the predicted temperature under the current slip loss heat input and roadway heat dissipation conditions; that is, when If the value remains large or increases over multiple consecutive sampling periods, it indicates that the coupler may be experiencing abnormal heating beyond the normal load and environmental factors considered in the model.

[0061] Step 5: Determine the demagnetization risk level and implement graded demagnetization protection; When abnormal heating occurs, this embodiment first constructs multiple types of risk evidence based on the equivalent slip loss heat input, the environmental correction temperature prediction residual, the coupler slip, the coupler temperature rise rate and torque transmission characteristic attenuation, and calculates the thermal demagnetization risk index.

[0062] In some implementation schemes, the coupler slip is calculated using the following formula:

[0063] In the formula, Indicates the coupler slip. Indicates the current sampling time. and These represent the input and output rotational speeds of the permanent magnet eddy current coupler, respectively. To prevent extremely small positive numbers with a denominator of zero.

[0064] In some implementation schemes, the formula for calculating the coupler temperature rise rate is:

[0065] In the formula, Indicates the coupler temperature rise rate. Indicates the coupler in The actual measured temperature at any given time. Indicates the coupler in The actual measured temperature at any given time. Indicates the sampling period.

[0066] In some implementations, the torque transmission characteristic attenuation is obtained through the following steps: 1) Determine the current operating condition category and obtain the corresponding healthy reference torque; for example, first determine the current operating condition category based on the conveyor operating stage, coupler input speed, conveyor belt speed, ambient temperature, and air gap condition, and divide the coupler slip range into multiple slip intervals. For operating data belonging to the same operating condition category and located in the same slip interval under healthy conditions, determine the corresponding healthy reference torque based on the coupler transmitted torque estimate according to the following healthy torque-slip reference model:

[0067] In the formula, For operating condition category G and the first j slip zone The corresponding healthy reference torque, This indicates taking the median; The health status sample number; A set of confirmed health status samples; For the first Estimated coupler transmission torque values ​​corresponding to each healthy state sample; For the first The operating condition category to which each health status sample belongs; For the first Coupler slip corresponding to each health status sample; Let j be the j-th slip interval.

[0068] After establishing the above healthy torque-slip reference model, based on the current operating condition category... and current coupler slip The current healthy reference torque can be obtained by looking up a table or interpolating between adjacent slip intervals.

[0069] In the formula, For healthy reference torque, For the healthy torque-slip reference model, for Time-based operating condition categories, for Coupler slip at any given moment.

[0070] 2) Calculate the torque transmission characteristic deviation based on the healthy reference torque and the estimated torque transmitted by the coupler;

[0071] In the formula, For healthy reference torque, To transmit torque estimates to the coupler, To prevent positive numbers with a denominator of zero.

[0072] 3) The torque transmission characteristic deviation is nonnegated and limited to obtain the torque transmission characteristic attenuation.

[0073]

[0074] In the formula, This represents the attenuation of torque transmission characteristics, used to characterize the degree of decrease in the current transmitted torque relative to the healthy reference torque under the same operating conditions and slip. This indicates a deviation in torque transmission characteristics.

[0075] Preferably, in this embodiment, the attenuation amount is updated only when the coupler is in a positive drive state and the coupler slip and healthy reference torque respectively meet the following conditions; otherwise, it is marked as invalid and the index is not used to improve the thermal demagnetization risk level.

[0076]

[0077] in, for k Coupler slip at time, for The healthy reference torque at any time and These are the lower and upper limits of slip for torque transmission characteristic analysis. This is the lower limit of the healthy reference torque.

[0078] In this embodiment, multiple types of risk evidence are constructed based on the equivalent slip loss heat input, the environmentally corrected temperature prediction residual, the coupler slip, the coupler temperature rise rate, and the torque transmission characteristic attenuation, including: First, the equivalent slip loss heat input, the environmental corrected temperature prediction residual, the coupler slip, the coupler temperature rise rate, and the torque transmission characteristic attenuation are respectively smoothed and saturated normalized; for example, the smoothing formula is:

[0079] In the formula, The term "smoothing input" refers to the equivalent slip loss heat input and the environmental correction temperature prediction residual, as described in this embodiment. For smoothing coefficients, The values ​​are zero when the temperature prediction residual and the rate of temperature rise are less than zero.

[0080] The saturation normalization formula is:

[0081] In the formula, This represents the result of smoothing the input items. and Parameters x The normal upper limit and dangerous reference value under the current operating phase, and satisfying the following conditions. , This indicates the current operating stage of the conveyor, which is determined based on the conveyor belt speed, the input speed of the coupler, and the conveyor control commands. It includes the start-up stage, steady-state operation stage, and deceleration stage.

[0082] Then, the maximum value between the coupler slip normalized value and the equivalent slip loss heat input normalized value is defined as the operational strength evidence; the formula is expressed as:

[0083] In the formula, This indicates evidence of operational strength. This represents the normalized slip value of the coupler. This represents the normalized value of the equivalent slip loss heat input; The weighted fusion value of the normalized residual value of the environmentally corrected temperature prediction and the normalized value of the coupler temperature rise rate is defined as the evidence of temperature anomalies; the formula is expressed as:

[0084] In the formula, This indicates evidence of abnormal temperature. This represents the normalized value of the environmentally corrected temperature prediction residual. This represents the normalized value of the coupler's temperature rise rate. and These are the weighted weights, and , , ; The normalized value of the torque transmission characteristic attenuation is defined as evidence of transmission characteristic anomaly; expressed as:

[0085] In the formula, This indicates evidence of abnormal transmission characteristics. This represents the normalized value of the torque transmission characteristic attenuation.

[0086] Furthermore, thermal demagnetization risk indicators were calculated based on three types of risk evidence:

[0087] In the formula, And all weighting coefficients are not less than zero.

[0088] In a preferred embodiment, based on the risk evidence and the thermal demagnetization risk index Determine the risk level of thermal demagnetization and execute corresponding protective actions; including: Set the escalation thresholds for the thermal demagnetization risk index from level one to level four. , , and ,satisfy:

[0089] when When there is no persistent evidence of abnormality, the conveyor continues to operate normally; When at least one type of risk evidence is abnormal or thermal demagnetization risk indicators achieve When the situation is deemed a Level 1 risk, the abnormal state is recorded and an early warning is issued, while the conveyor maintains its current operating status. When at least two types of risk evidence are abnormal, and the thermal demagnetization risk indicator achieve If the risk level is determined to be Level 2, the increase in coupler heat load should be limited. During the startup phase: limit startup acceleration and reduce coal feed rate; during steady-state operation: reduce coal feed rate and limit drive torque; during deceleration: maintain deceleration and stop increasing coal feed rate. When at least two types of risk evidence are abnormal, and the thermal demagnetization risk indicator achieve If the risk level is assessed as Level 3, load reduction, speed reduction, and cooling protection measures will be implemented, and coupler cooling will be activated or enhanced. During the startup phase: acceleration will be stopped and coal feeding will be reduced or suspended; during steady-state operation: conveyor belt speed and coal feed will be reduced; during deceleration: deceleration and load reduction will continue. When at least two types of risk evidence are abnormal, and the thermal demagnetization risk indicator achieve If the risk level is determined to be level four, coal feeding is stopped, the drive torque and conveyor belt speed are reduced according to the safe shutdown sequence of the conveyor, shutdown protection is executed and the machine is locked before restarting.

[0090] It should be noted that unusual risk evidence can be identified in the following ways: Each type of risk evidence is compared with its corresponding anomaly confirmation threshold to identify outliers. The number of anomalies for each type of risk evidence is counted over the most recent n sampling periods. When the number of anomalies reaches a preset threshold for the corresponding risk evidence category, the current risk evidence is deemed to be persistently abnormal. The anomaly confirmation thresholds and persistence requirements for each parameter are determined based on test data under conditions of healthy coupler operation, heavy-load startup, changes in heat dissipation environment, and abnormal transmission characteristics.

[0091] In this embodiment, after the protection action is executed, if the thermal demagnetization risk index does not decrease or the number of continuous abnormal evidence increases, the risk level is increased; if the thermal demagnetization risk index is lower than the downgrade threshold corresponding to the current level, and the number of continuous abnormal evidence decreases and maintains a preset number of sampling cycles, the risk level is reduced, and the conveyor belt speed, drive torque and coal feed are gradually restored.

[0092] This application sets downgrade thresholds for risk levels one through three. After a level four risk is locked, the start-up lockout can only be released when the coupler temperature, slip, and thermal demagnetization risk indicators are lower than the corresponding downgrade reset threshold, the key sensors and cooling devices are working normally, and the fault has been manually confirmed to be resolved.

[0093] When the coupler temperature, slip, or equivalent slip loss heat input reaches the direct shutdown threshold, the shutdown protection is directly executed and the restart is locked, regardless of the thermal demagnetization risk level determination result.

[0094] This invention constructs three types of risk evidence—operational intensity, temperature anomaly, and transmission characteristic anomaly—by utilizing coupler slip, equivalent slip loss heat input, environmentally corrected temperature prediction residual, and torque transmission characteristic attenuation. It then combines these with continuous assessment to determine the risk level of thermal demagnetization. This method comprehensively considers load changes, roadway ventilation, and dust conditions, reducing false alarms caused by heavy-load starts, environmental changes, and instantaneous measurement fluctuations. Furthermore, it implements early warning, load limiting, speed reduction, cooling, and shutdown protection before the coupler temperature reaches a dangerous threshold, thereby improving the safety and reliability of permanent magnet eddy current drive systems in coal mine conveyors.

[0095] The following description provides further examples of specific applications.

[0096] This embodiment uses a belt conveyor in the main inclined shaft of a coal mine as an example. The conveying distance is 1800m, the rated belt speed is 3.15m / s, the rated power of the drive motor is 200kW, and the rated speed is 1480r / min. The conveyor drive system uses a permanent magnet eddy current coupler to achieve non-contact flexible transmission between the drive motor and the drive drum. The permanent magnet eddy current coupler includes an input-side rotor and an output-side rotor. The input-side rotor is directly connected to the drive motor, and the output-side rotor is driven by the conveyor drive drum.

[0097] Before being put into operation, the thermal model parameters are calibrated using the operating data of the permanent magnet eddy current coupler under healthy conditions. A healthy torque-slip reference model is established under different operating conditions and slip ranges, and the normal upper limit, dangerous reference value, abnormal confirmation threshold, and risk level shift threshold for each risk parameter are determined. The parameters and reference model are stored in the protection controller.

[0098] Controller diagnostic sampling period The equivalent heat capacity of the coupler is taken as The equivalent heat dissipation area is taken as The reference heat dissipation coefficient is taken as The ventilation correction factor is taken as Dust correction factor is taken The baseline ventilation velocity is taken as... The lower and upper limits of the equivalent heat dissipation coefficient are respectively taken as and .

[0099] When performing demagnetization protection, perform the following steps: 1. Condition Measurement At a certain sampling moment, the controller acquires the rotational speed on the input side of the coupler. Coupler output speed Motor current No-load current The measured temperature at the last sampling moment of the coupler was The current measured temperature is The ambient temperature in the tunnel is The ventilation speed of the tunnel is The dust correction factor is The conveyor belt speed is .

[0100] 2. Determine the torque transmitted by the coupler and the equivalent slip loss heat input; In this embodiment, the drive controller cannot directly output the estimated electromagnetic torque and torque current components. Therefore, a calibrated motor operating current is used to estimate the torque transmitted by the coupler. The torque estimation coefficient is obtained through calibration tests of the motor current and shaft-end torque under healthy drive system conditions. The motor operating current is The no-load current is ,but:

[0101] Then, the angular velocity, slip angular velocity, and equivalent slip loss heat input are calculated sequentially, and finally obtained... ; 3. Calculate the environmentally corrected heat dissipation coefficient and predict the coupler temperature; In this embodiment, the ventilation correction factor is used. Dust impact coefficient Reference thermal coefficient The upper and lower limits of the preset heat dissipation coefficient range are respectively , , Based on the above data, after substituting it into the corresponding calculation formula, the predicted temperature of the coupler at the current sampling time is 82.4℃.

[0102] 4. Calculate the environmentally corrected temperature prediction residuals. ; The results indicate that the measured temperature of the coupler is 1.9℃ higher than the model-predicted temperature. Under the same slip, load, and roadway environment conditions, the actual temperature rise of the coupler is greater than the predicted temperature rise, indicating an abnormal temperature rise trend.

[0103] 5. Determine the demagnetization risk level and implement graded demagnetization protection; First, take Calculate the coupler slip.

[0104] Therefore, the current slip of the permanent magnet coupler is about 8.1%, which is higher than the slip level under normal steady-state operation, indicating that the coupler is in a state of significant slip operation.

[0105] The rate of temperature rise is:

[0106] In this embodiment, the conveyor is in a steady-state operation phase, the input speed of the coupler is 1480 r / min, the conveyor belt speed is 3.05 m / s, the ambient temperature in the tunnel is 34℃, the coupler uses a fixed air gap, and the current operating state is divided into working condition categories. According to the current working condition category and coupler slip Query the pre-established healthy torque-slip reference model to obtain The value is 1900 N·m; further calculations are performed on the torque transmission characteristic deviation and the torque transmission characteristic attenuation, ultimately yielding... .

[0107] Furthermore, in this embodiment, the coupler slip, equivalent slip loss heat input, environmentally corrected temperature prediction residual, temperature rise rate, and torque transmission characteristic attenuation are smoothed and saturated normalized. The smoothing process involves filtering coefficients... The smoothed values ​​stored in the protection controller at the previous sampling time are as follows: , , , , The normalization boundaries used in the normalization process are shown in Table 1. Table 1

[0108] After obtaining the calculation results, risk evidence is constructed respectively: Evidence of operational strength is ; Evidence of abnormal temperature is , ; Evidence of abnormal transmission characteristics is .

[0109] The obtained thermal demagnetization risk index is ,in .

[0110] To determine whether risk evidence remains abnormal, this embodiment sets the following abnormality thresholds for each type of evidence:

[0111] For all three types of risk evidence, the statistical window is the most recent 5 sampling periods. If the number of times the abnormal threshold is reached is no less than 4, the risk evidence of that type is considered persistently abnormal. Based on the judgment results of the most recent 5 sampling periods recorded by the protection controller, the number of abnormalities for operational intensity, temperature anomalies, and transmission characteristic anomalies are as follows:

[0112] Therefore, it can be seen that all three types of risk evidence currently constitute persistent anomalies, satisfying the condition of cross-confirmation by at least two types of risk evidence.

[0113] Based on test data from healthy operation, heavy-load start-up, changes in heat dissipation environment, and abnormal torque transmission characteristics, this embodiment sets four risk thresholds: 0.30, 0.45, 0.60, and 0.75. The corresponding downgrade thresholds are 0.25, 0.40, and 0.55.

[0114] Due to the current thermal demagnetization risk indicators Furthermore, there are three types of persistent abnormal evidence, therefore the protection controller determines the current state as a level three risk of thermal demagnetization.

[0115] At this point, the controller first records the risk status and issues an alarm, reduces the setpoint of the conveyor belt speed to 2.70 m / s, sends a load reduction command to the coal feeding control system to reduce the coal feed rate by 15%, limits the drive torque from continuing to increase, and starts or enhances the cooling device of the permanent magnet eddy current coupler.

[0116] After the protection action is executed, the controller continues to calculate the thermal demagnetization risk index and the number of pieces of evidence of persistent abnormality. When the thermal demagnetization risk index drops below the level three downgrade threshold, the following condition is met: Furthermore, if the number of consistently abnormal evidence decreases and remains stable for three consecutive sampling cycles, the risk level is reduced to Level II. Subsequently, based on the decline in risk indicators, the conveyor belt speed, drive torque, and coal feed rate are gradually restored.

[0117] If the thermal demagnetization risk index does not decrease after the protection action is executed, or if the number of continuous abnormal evidence increases, the risk level will be increased according to the preset upgrade rules. When the thermal demagnetization risk index reaches the fourth-level upgrade threshold, the controller will stop coal feeding, reduce the drive torque and conveyor belt speed according to the safe shutdown sequence of the conveyor, execute the shutdown protection, and lock out the restart.

[0118] After the Level 4 risk interlock is applied, the start interlock can only be lifted when the coupler temperature, slip, and thermal demagnetization risk indicators are all below the corresponding reset threshold, the cooling device and key sensors are working normally, and the fault has been manually confirmed to be resolved.

[0119] In this embodiment, the measured temperature, slip, and equivalent slip loss heat input of the coupler have not reached the direct shutdown threshold, therefore, three-level protection is implemented. If any of these parameters reaches the direct shutdown threshold, the shutdown protection is executed directly without waiting for the risk indicator judgment result, and restart is blocked.

[0120] Through the above-mentioned graded protection, load reduction, speed reduction and cooling measures can be taken in advance based on the comprehensive results of operating intensity, abnormal temperature and abnormal torque transmission characteristics before the coupler temperature reaches the dangerous protection threshold, thereby reducing the risk of thermal demagnetization caused by continuous high slip and abnormal heating.

[0121] Any content or technical means not mentioned in the embodiments of this invention can be obtained by referring to the prior art. This disclosure does not limit the scope of the invention and therefore will not be elaborated further.

[0122] The embodiments of the present invention have been described in detail above, and the principles and implementation methods of the present invention have been explained. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of the present invention. Those skilled in the art should understand that the embodiments of the present invention can be provided as methods, computer software program products, or electronic devices, etc. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0123] It should be noted that the word "comprising" does not exclude the presence of components or steps not listed in the claims. The words "a" or "an" preceding a component do not exclude the presence of a plurality of such components. This invention can be implemented by means of hardware comprising several different components and by means of a suitably programmed computer.

[0124] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0125] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for thermal demagnetization protection of a permanent magnet eddy current coupler in a coal mine conveyor, characterized in that the steps include... include: The estimated value of the torque transmitted by the coupler is determined based on the torque-related parameters of the drive motor of the coal mine conveyor, and the equivalent slip loss heat input is determined by combining the speeds of the input and output sides of the coupler. Based on the equivalent slip loss heat input, the coupler temperature at the current moment is predicted by considering the equivalent heat dissipation coefficient of the roadway, the measured temperature of the coupler, and the ambient temperature of the roadway. The environmental correction temperature prediction residual is calculated based on the predicted coupler temperature and the measured coupler temperature, and abnormal heating is identified. When abnormal heating occurs, multiple types of risk evidence are constructed based on the equivalent slip loss heat input, the environmental correction temperature prediction residual, the coupler slip, the coupler temperature rise rate and torque transmission characteristic attenuation, and thermal demagnetization risk index is calculated. The thermal demagnetization risk level is determined based on the aforementioned risk evidence and the aforementioned thermal demagnetization risk index, and corresponding protective actions are executed.

2. The thermal demagnetization protection method for permanent magnet eddy current couplers in coal mine conveyors as described in claim 1, characterized in that, The torque-related parameters of the drive motor of the coal mine conveyor include at least one of the following: electromagnetic torque estimate, torque current component, shaft end torque measurement, and motor operating current.

3. The thermal demagnetization protection method for permanent magnet eddy current couplers in coal mine conveyors as described in claim 1, characterized in that, The equivalent slip loss heat input is determined by combining the rotational speeds on the input and output sides of the coupler, including: After converting the rotational speeds of the input and output sides of the coupler into angular velocities, the slip angular velocity is calculated. Multiplying the slip angular velocity by the estimated torque transmitted by the coupler yields the equivalent slip loss heat input.

4. The thermal demagnetization protection method for permanent magnet eddy current couplers in coal mine conveyors as described in claim 1, characterized in that, Based on the equivalent slip loss heat input, considering the equivalent heat dissipation coefficient of the roadway, the measured temperature of the coupler, and the ambient temperature of the roadway, the current coupler temperature is predicted using the following formula: In the formula, Predict the temperature of the coupler at the current moment. At the current sampling time, for The measured temperature of the coupler at any given time. The sampling period is The equivalent thermal capacity of the coupler, For equivalent slip loss heat input, The equivalent heat dissipation coefficient of the tunnel. This is the equivalent heat dissipation area of ​​the coupler. The ambient temperature of the tunnel.

5. The thermal demagnetization protection method for permanent magnet eddy current couplers in coal mine conveyors as described in claim 1 or 4, characterized in that, The equivalent heat dissipation coefficient of the tunnel is determined through the following steps: Dust state quantity is estimated based on the dust concentration in the tunnel; and a dust correction factor is calculated based on the dust state quantity. Calculate the ventilation correction factor based on the tunnel ventilation velocity; The reference heat dissipation coefficient is corrected by using the dust correction factor and the ventilation correction factor within a preset heat dissipation coefficient range to obtain the equivalent heat dissipation coefficient of the roadway.

6. The thermal demagnetization protection method for permanent magnet eddy current couplers in coal mine conveyors as described in claim 1, characterized in that, Identifying abnormal fever includes: When the measured temperature of the coupler is consistently higher than the predicted temperature, or when the deviation continues to increase over multiple consecutive sampling periods, it is determined to be abnormal heating.

7. The thermal demagnetization protection method for permanent magnet eddy current couplers in coal mine conveyors as described in claim 1, characterized in that, Multiple types of risk evidence are constructed based on the equivalent slip loss heat input, the environmentally corrected temperature prediction residual, the coupler slip, the coupler temperature rise rate, and the torque transmission characteristic attenuation, including: The equivalent slip loss heat input, the environmental corrected temperature prediction residual, the coupler slip, the coupler temperature rise rate and the torque transmission characteristic attenuation are respectively smoothed and saturated normalized. The maximum value between the coupler slip normalization value and the equivalent slip loss heat input normalization value is defined as the operational strength evidence; The weighted fusion value of the normalized residual value of the environmentally corrected temperature prediction and the normalized value of the coupler temperature rise rate is defined as evidence of temperature anomalies. The normalized value of the torque transmission characteristic attenuation is defined as evidence of transmission characteristic anomaly.

8. The thermal demagnetization protection method for permanent magnet eddy current couplers in coal mine conveyors as described in claim 1 or 7, characterized in that, The torque transmission characteristic attenuation is obtained through the following steps; Determine the current operating condition category and obtain the corresponding healthy reference torque; The torque transmission characteristic deviation is calculated based on the healthy reference torque and the estimated torque transmitted by the coupler. The torque transmission characteristic deviation is nonnegated and limited to obtain the torque transmission characteristic attenuation.

9. The thermal demagnetization protection method for permanent magnet eddy current couplers in coal mine conveyors as described in claim 8, characterized in that, The torque transmission characteristic attenuation is only valid when the coupler is in a positive drive state and the coupler slip and the healthy reference torque respectively meet the validity judgment conditions. When invalid, it is not used as an indicator to determine the thermal demagnetization risk level. The validity criteria include that the coupler slip is within the pre-calibrated torque transmission characteristic analysis range, and that the healthy reference torque parameter is not lower than the pre-set lower limit threshold.

10. The thermal demagnetization protection method for permanent magnet eddy current couplers in coal mine conveyors as described in claim 1, characterized in that, The thermal demagnetization risk level is determined based on the aforementioned risk evidence and the aforementioned thermal demagnetization risk index, and corresponding protective actions are executed; including: When at least one type of risk evidence is abnormal or the thermal demagnetization risk indicator reaches the first threshold, it is judged as a level one risk and early warning protection is implemented. When at least two types of risk evidence are abnormal and the thermal demagnetization risk index reaches the second threshold, it is judged as a level 2 risk and thermal load limiting protection is implemented. When at least two types of risk evidence are abnormal and the thermal demagnetization risk index reaches the third threshold, it is judged as a level three risk, and load reduction, speed reduction and cooling enhancement protection are implemented. When at least two types of risk evidence are abnormal and the thermal demagnetization risk index reaches the fourth threshold, it is judged as a level four risk, and the shutdown and lockout restart protection are executed. The first threshold, the second threshold, the third threshold, and the fourth threshold increase sequentially.

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