Method for evaluating drop reliability of magnetic levitation protection bearing

Abstract

This application proposes a drop reliability assessment method for magnetically levitated protective bearings, relating to the field of magnetically levitated bearings. It includes: in response to a rotor drop event, acquiring rotor drop trajectory data and rotational speed information that have undergone consistency verification; inputting this data into a multi-factor coupled drop dynamics model to simulate the drop process, calculating the relative sliding velocity, calculating the normal restoring force using Hertzian contact theory, and calculating frictional heat and radial dimension increment based on the relative sliding velocity to update the real-time clearance of the protective bearing; based on the normal restoring force and the updated real-time clearance, calculating the maximum contact stress, strength safety factor, thermal safety margin index, and material wear volume, and jointly determining the survivability of the protective bearing in this round of drops and the remaining safe number of drops. This scheme can reliably acquire drop trajectory data of magnetically levitated rotors and accurately assess the survivability of the protective bearing in a single drop and the remaining safe number of drops after multiple cumulative drops.

Description

Technical Field

[0001] This application relates to the field of magnetic levitation bearings, and more specifically, to a method for assessing the drop reliability of magnetic levitation protective bearings. Background Technology

[0002] Magnetic levitation bearings utilize electromagnetic force to suspend the rotor between the stator and stator, achieving high-speed rotation without mechanical contact. They are widely used in high-end equipment such as the main helium blower in high-temperature gas-cooled reactors and large helium compressors. Protective bearings, as the last line of defense in heavy-duty magnetic levitation bearing systems, are responsible for providing mechanical support and preventing destructive collisions between the stator and rotor when the magnetically levitated rotor loses levitation.

[0003] Existing heavy-duty magnetic levitation bearing systems typically employ the following technical solutions to address magnetic levitation rotor drop accidents: monitoring the rotor's position using a single-channel displacement sensor and performing force verification on the protective bearing based on Hertzian contact theory, treating the physical clearance of the protective bearing as a fixed geometric parameter, and assessing its mechanical strength solely by calculating the maximum contact stress. However, in developing this application, the inventors discovered the following drawbacks in the above approach: firstly, some key trajectory data during the drop process is easily lost, affecting subsequent evaluation of the protective bearing; secondly, the accuracy of the above approach in assessing the protective bearing's survivability in a single drop and the remaining safe number of drops after multiple cumulative drops is insufficient, easily leading to evaluation errors.

[0004] Therefore, ensuring that the fall trajectory data of the magnetic levitation rotor is not lost, and accurately assessing the survivability of the protective bearing in a single fall and the remaining safe number of falls after multiple cumulative falls, have become urgent technical problems to be solved. Summary of the Invention

[0005] The purpose of this application is to provide a drop reliability assessment method for magnetic levitation protective bearings, which can ensure that the drop trajectory data of the magnetic levitation rotor is not lost, and to accurately assess the survivability of the protective bearing in a single drop and the remaining number of safe drops after multiple cumulative drops.

[0006] This application is implemented as follows: This application provides a drop reliability assessment method for a magnetically levitated protective bearing, comprising the following steps: In response to a rotor drop event, acquiring rotor drop trajectory data and rotational speed information for this drop. The rotor drop trajectory data is obtained by real-time acquisition from at least two sets of displacement sensors, and the position information of the magnetically levitated rotor is verified for consistency. The rotational speed information is obtained by real-time acquisition of the magnetically levitated rotor by a rotation sensor. The rotor drop trajectory data and rotational speed information are input into a preset multi-factor coupled drop dynamics model to simulate the drop process of the magnetically levitated rotor, calculate the relative sliding velocity at the contact point, calculate the normal restoring force using nonlinear Hertzian contact theory, and calculate the frictional heat and radial dimension increment based on the relative sliding velocity to update the real-time clearance of the protective bearing. Based on the normal restoring force and the updated real-time clearance, calculating the maximum contact stress of the inner ring of the protective bearing, the strength safety factor, the thermal safety margin index, and the material wear volume generated by this drop, and jointly determining the survivability of the protective bearing in this round of drops and the remaining safe drop count based on the strength safety factor, the thermal safety margin index, and the cumulative material wear volume.

[0007] Compared with the prior art, this application has at least the following advantages or beneficial effects: This application ensures the continuity and reliability of rotor drop trajectory data by employing at least two sets of displacement sensors to verify the consistency of the magnetic levitation rotor's position information during the data acquisition phase. Simultaneously, it simulates the drop process and calculates the normal restoring force using a multi-factor coupled drop dynamics model, and calculates frictional heat and radial dimension increments based on relative sliding velocity, updating the real-time clearance of the protective bearing in real time. This overcomes the shortcomings of traditional methods that treat clearance as a fixed parameter, enabling the identification of real-time clearance loss due to thermal expansion and predicting thermal seizure failures. Furthermore, based on the normal restoring force and the updated real-time clearance, it comprehensively calculates the maximum contact stress, strength safety factor, thermal safety margin index, and material wear volume, jointly determining the protective bearing's current-cycle survivability and remaining safe drop count. This overcomes the limitations of single mechanical index assessment, comprehensively evaluating the true survivability of the protective bearing from three dimensions: mechanical impact, thermal failure, and cumulative wear, allowing for high-precision evaluation of the protective bearing's survivability in a single drop and the remaining safe drop count under multiple cumulative drops. Attached Figure Description

[0008] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0009] Figure 1This is a flowchart of an embodiment of a drop reliability assessment method for a magnetically levitated protective bearing according to this application; Figure 2 This is a system framework diagram of an embodiment of this application; Figure 3 This is a flowchart of yet another embodiment of the drop reliability assessment method for a magnetically levitated protective bearing according to this application; Figure 4 This is a comparison diagram of the rotor radial displacement response during the drop process in one embodiment of this application and the traditional model; Figure 5 This is a thermo-mechanical coupling evolution diagram of the temperature of the inner ring of the protective bearing and the effective clearance in one embodiment of this application. Detailed Implementation

[0010] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. It should be understood that this application is not limited to the exemplary embodiments described herein.

[0011] In this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, without necessarily requiring or implying any such actual relationship or order between these entities or operations.

[0012] Existing heavy-duty magnetic levitation bearing systems typically employ a single-channel displacement sensor to monitor the rotor's position in response to magnetic levitation rotor drop accidents, and perform force verification on the protective bearing based on Hertzian contact theory. However, in developing this application, the inventors discovered at least two shortcomings in the aforementioned approach. These shortcomings and their causes include: First, regarding sensor configuration, when a heavy-duty magnetic levitation rotor falls and impacts the protective bearing, the enormous impact load and severe vibration can easily cause signal saturation, jumps, or even hardware damage to the single-channel displacement sensor, resulting in the loss of the magnetic levitation rotor's drop trajectory data and affecting subsequent assessments. Second, in terms of dynamic modeling, existing solutions treat the physical clearance of the protective bearing as a fixed geometric parameter, neglecting the thermal expansion effect caused by frictional heat and the cumulative wear caused by multiple drops. This leads to insufficient accuracy in assessing the protective bearing's survivability in a single drop and the remaining safe number of drops after multiple cumulative drops.

[0013] Based on the above analysis, this application proposes a drop reliability assessment method for magnetically levitated protective bearings. It collects rotor drop trajectory data through redundant verification of multiple sets of displacement sensors and dynamically updates the real-time clearance using a multi-factor coupled drop dynamics model incorporating a thermo-coupling mechanism. This solves the problems of easy data loss during drop and the inability to predict thermal seizure failures, enabling accurate assessment of the protective bearing's survivability in a single drop and the remaining safe number of drops after multiple cumulative drops.

[0014] After introducing the basic principles of this application, various non-limiting embodiments of this application will be described in detail below with reference to the accompanying drawings. Unless otherwise specified, the various embodiments and features described below can be combined with each other.

[0015] Please see Figure 1 The drop reliability assessment method for this magnetic levitation protective bearing includes the following steps: Step S101: In response to the rotor drop event, acquire the rotor drop trajectory data and rotation speed information of this drop. The rotor drop trajectory data is obtained by real-time acquisition from at least two sets of displacement sensors and after consistency verification of the position information of the magnetic levitation rotor. The rotation speed information is obtained by real-time acquisition of the magnetic levitation rotor by the rotation sensor.

[0016] During normal operation of the magnetic levitation bearing system, the position information of the magnetic levitation rotor is collected in real time by at least two sets of displacement sensors. The consistency of the position information collected by these two sets of sensors is verified, and abnormal or excessively deviated data is discarded to generate displacement data. At the same time, the rotation speed information of the magnetic levitation rotor is collected in real time by a rotation sensor.

[0017] Thus, once a rotor drop event is detected, the rotor drop trajectory data can be generated based on the previously acquired real-time displacement data, and the rotor's rotational speed information during the drop can be generated based on the previously acquired real-time rotational speed information. By employing at least two sets of displacement sensors and performing consistency verification, the data loss problem caused by single sensor failure is avoided, effectively ensuring the integrity and reliability of the rotor drop trajectory data.

[0018] Step S102: Input the rotor drop trajectory data and rotation speed information into the preset multi-factor coupled drop dynamics model to simulate the drop process of the magnetic levitation rotor, calculate the relative sliding speed at the contact point, calculate the normal restoring force using nonlinear Hertzian contact theory, and calculate the frictional heat and radial dimension increment based on the relative sliding speed to update the real-time clearance of the protective bearing in real time.

[0019] In step S102, the rotor drop trajectory data and rotational speed information obtained in step S101 are used as input parameters and fed into a pre-constructed multi-factor coupled drop dynamics model. This model first simulates the complete drop process of the magnetically levitated rotor from instability to contacting the protective bearing. During the simulation, the model calculates the relative sliding velocity at the contact point between the magnetically levitated rotor and the protective bearing. Simultaneously, the model uses nonlinear Hertzian contact theory to calculate the normal restoring force based on the contact state between the magnetically levitated rotor and the protective bearing. Further, based on the calculated relative sliding velocity and the normal restoring force, the model calculates the frictional heat generated by relative sliding during the drop process and calculates the radial dimension increment caused by frictional heat based on the thermo-mechanical coupling principle. Finally, this radial dimension increment is used to dynamically update the real-time clearance of the protective bearing, reflecting the influence of thermal expansion on the clearance. That is, by introducing a multi-factor coupled drop dynamics model that includes a thermo-mechanical coupling mechanism, step S102 can capture the radial dimension increment caused by frictional heat in real time and dynamically update the real-time clearance of the protective bearing, thus providing a more realistic clearance state for subsequent evaluation.

[0020] Step S103: Based on the normal restoring force and the updated real-time clearance, calculate the maximum contact stress, strength safety factor, thermal safety margin index, and material wear volume of the inner ring of the protective bearing. Based on the strength safety factor, thermal safety margin index, and cumulative material wear volume, jointly determine the survivability of the protective bearing in this round of drops and the remaining number of safe drops.

[0021] Understandably, step S103 first calculates the maximum contact stress borne by the inner ring of the protective bearing in this drop, based on the normal restoring force and Hertzian contact theory, and compares this stress with the material yield strength to generate a strength safety factor. Next, based on the updated real-time clearance and temperature data during the drop, a thermal safety margin index characterizing the risk of thermal failure is calculated. Then, based on the normal restoring force and relative sliding speed, the material wear volume generated by this drop is calculated using wear theory. Finally, the indices of the above three dimensions are jointly judged: on the one hand, the strength safety factor and thermal safety margin index are used to determine whether the protective bearing has the ability to survive this round of drops; on the other hand, the material wear volume generated by this drop is added to the historical cumulative wear volume, and the remaining safe drop count of the protective bearing is estimated based on the cumulative material wear volume.

[0022] In other words, this application does not verify the mechanical strength of a single drop, but conducts a comprehensive evaluation from multiple dimensions such as mechanical, thermal and wear factors. This not only allows for a more accurate assessment of the immediate survivability of a single drop, but also a more accurate prediction of the remaining lifespan after multiple cumulative drops, providing a scientific quantitative basis for the maintenance and replacement of protective bearings and the management of system reliability.

[0023] In summary, this application acquires reliable data using at least two sets of displacement sensors, then inputs this data into a dynamic model that simultaneously simulates impact and frictional heat generation. Finally, it comprehensively evaluates the survivability of the protective bearing from three dimensions: strength, thermal safety, and wear. Specifically, this application solves the problem of displacement data loss caused by the easy failure of a single sensor by employing at least two sets of displacement sensors for consistency verification; it overcomes the deficiency of traditional methods that ignore thermal expansion effects by introducing a multi-factor coupled drop dynamic model capable of calculating frictional heat and radial dimension increments; and it achieves accurate assessment of the single-cycle survivability and remaining number of cycles of the protective bearing by jointly considering the three dimensions of strength, thermal safety, and cumulative wear.

[0024] Specifically, firstly, this application employs at least two sets of displacement sensors to collect the position information of the magnetically levitated rotor in real time during the data acquisition phase, and obtains the rotor drop trajectory data after consistency verification. This design directly solves the problem in existing technologies where single-channel displacement sensors are prone to failure under drop impact, leading to the loss of critical trajectory data. Through the redundant configuration of multiple sets of sensors and the data verification mechanism, it ensures that even if one sensor fails due to severe vibration, continuous and reliable rotor drop trajectory data can still be obtained, providing a complete data foundation for subsequent evaluation.

[0025] Secondly, this application inputs the acquired rotor drop trajectory data and rotational speed information into a pre-defined multi-factor coupled drop dynamics model. This model not only simulates the drop process of the magnetically levitated rotor and calculates the normal restoring force using nonlinear Hertzian contact theory, but also calculates frictional heat and radial dimension increment based on relative sliding speed, thereby updating the real-time clearance of the protective bearing in real time. This design overcomes the shortcomings of traditional methods that treat the physical clearance of the protective bearing as a fixed geometric parameter. By introducing a thermo-mechanical coupling mechanism, this application quantifies the thermal expansion effect caused by frictional heat generation as a radial dimension increment and dynamically subtracts it from the initial clearance, so that the real-time clearance can truly reflect the trend of gradually decreasing due to temperature rise during the drop process. Based on this, this application can accurately identify thermal seizure faults caused by the complete disappearance of the real-time clearance, thereby accurately predicting the safety hazards of thermal seizure risk.

[0026] Finally, based on the normal restoring force and the updated real-time clearance, this application comprehensively calculates the maximum contact stress, strength safety factor, thermal safety margin index, and material wear volume generated by the drop on the protective bearing's inner ring. Based on these calculations, it jointly determines the protective bearing's survivability in this round of drops and the remaining safe drop count. This multi-dimensional comprehensive evaluation scheme overcomes the limitations of existing technologies that are limited to assessing only the maximum contact stress as a single mechanical indicator. By simultaneously introducing the thermal safety margin index and material wear volume, this application can comprehensively reflect the true survival status of the protective bearing under the coupled effects of multiple factors from three dimensions: mechanical impact, thermal failure risk, and cumulative wear. Specifically, the strength safety factor and thermal safety margin index are used to determine whether the drop leads to structural collapse or thermal seizure, while the cumulative material wear volume is used to quantitatively predict the remaining safe drop count after multiple drops. This provides precise numerical constraints for the material selection, structural optimization, and life-cycle reliability management of the protective bearing (including survivability in a single drop and the remaining safe drop count after multiple cumulative drops).

[0027] Based on the aforementioned scheme, in some implementations of this application, before the step of obtaining rotor drop trajectory data and rotation speed information in response to a rotor drop event, the drop reliability assessment method for the magnetic levitation protective bearing further includes: constructing a two-dimensional axis trajectory of the magnetic levitation rotor using orthogonally arranged first-direction displacement data and second-direction displacement data; calculating the instantaneous composite radial displacement of the magnetic levitation rotor in the drop plane based on the two-dimensional axis trajectory; calculating the ratio of the instantaneous composite radial displacement to the nominal clearance on one side of the protective bearing as a contact state determination coefficient; when the contact state determination coefficient is greater than or equal to a set value, determining that the magnetic levitation rotor and the protective bearing have made mechanical contact, thereby confirming that a rotor drop event has occurred.

[0028] Understandably, this implementation pre-determines whether a rotor fall event has occurred before acquiring data, constructs a shaft center trajectory using orthogonally arranged bidirectional displacement data, and calculates a contact state determination coefficient, thereby accurately identifying the start time of the fall. That is, by constructing a two-dimensional shaft center trajectory using orthogonally arranged bidirectional displacement data, the true motion state of the magnetically levitated rotor in the plane can be accurately captured. Using the ratio of instantaneous synthetic radial displacement to the nominal clearance on one side as the determination criterion provides a quantitative and objective triggering condition for the rotor fall event, ensuring that subsequent data acquisition and evaluation processes only initiate when a fall actually occurs, avoiding misjudgments or unnecessary computational resource consumption.

[0029] Based on the aforementioned scheme, in some implementations of this application, at least two sets of displacement sensors include inductive displacement sensors divided into a main measurement group and a redundant measurement group; the rotation sensor is an inductive speed sensor. The drop reliability assessment method for this magnetic levitation protective bearing also includes: in terms of hardware manufacturing, a position sensor target is manufactured using a silicon steel sheet stacking process, and an insulating layer is used to isolate adjacent silicon steel sheets to block the flow path of induced current in the axial direction of the magnetic levitation rotor, effectively reducing eddy current losses. In terms of displacement measurement, the inductive displacement sensor adopts a differential configuration, with a positive probe and a negative probe arranged in each measurement degree of freedom direction. The real-time inductance of the positive probe and the real-time inductance of the negative probe change in opposite directions with the radial displacement of the magnetic levitation rotor, thereby enabling sensitive detection of displacement. In terms of speed measurement, the detection end face of the inductive speed sensor faces the eccentric ring structure fixed on the magnetic levitation rotor, and the real-time speed of the magnetic levitation rotor is calculated by detecting the frequency of air gap changes caused by the rotation of the eccentric ring structure.

[0030] Understandably, this implementation improves the reliability and accuracy of data acquisition by dividing the displacement sensor into a primary measurement group and a redundant measurement group and employing a differential configuration, while optimizing the sensor target manufacturing process and the speed sensor structure. Specifically, the division into primary and redundant measurement groups provides hardware redundancy for displacement detection, preventing data loss due to single-point failures. The combination of positive and negative probes in the differential configuration can cancel common-mode interference, improving measurement linearity and accuracy. The silicon steel sheet lamination process effectively reduces eddy current losses and improves signal quality. The eccentric ring structure, combined with an inductive speed sensor, enables non-contact speed measurement, resulting in a simple structure and high reliability.

[0031] Based on the aforementioned scheme, in some implementations of this application, the displacement sensor includes a main measurement group displacement sensor and a redundant measurement group displacement sensor. The steps for acquiring rotor drop trajectory data include: First, calculating the absolute deviation between the displacement readings of the main measurement group displacement sensor and the displacement readings of the redundant measurement group displacement sensor. When the calculated absolute deviation is greater than the maximum permissible deviation threshold, it indicates that there is a significant inconsistency between the readings of the two groups of sensors. At this time, it is necessary to further detect whether the sensor output voltage is within the range formed by the lower limit and the upper limit of the effective voltage, and determine which group of sensors is working normally. Next, a weighted switching coefficient is generated based on the obtained detection results. The displacement readings of the main measurement group displacement sensor and the displacement readings of the redundant measurement group displacement sensor are weighted and calculated using the weighted switching coefficient to obtain the final fused displacement data. This final displacement data is then used as the rotor drop trajectory data for subsequent analysis.

[0032] Understandably, this implementation calculates the reading deviation between the main measurement group and the redundant measurement group, and dynamically generates a weighted switching coefficient by combining this with the validity detection of the sensor output voltage. This allows for intelligent fusion or switching between the two sets of data to obtain reliable final displacement data. In other words, by introducing redundant measurement groups and a dynamic weighted switching mechanism, the problem of data loss due to the easy failure of single-channel displacement sensors under drop impact can be effectively avoided. Specifically, when the main measurement group malfunctions, it can automatically identify and switch to a reliable redundant data source, or fuse the two sets of data in a weighted manner, thus ensuring the continuity and accuracy of the rotor drop trajectory data and providing a valid data foundation for subsequent drop reliability assessment.

[0033] Based on the aforementioned scheme, in some implementations of this application, the multi-factor coupled drop dynamics model is constructed through kinematic differential equations that include gravity, unbalanced excitation force, and contact reaction force. Specifically, this includes: First, establishing kinematic equations with the geometric center of the protective bearing as the origin, which describes the translational differential relationships of the magnetically levitated rotor in the horizontal and vertical directions. Next, calculating the unbalanced excitation force component originating from the mass eccentricity of the magnetically levitated rotor, and the contact reaction force component exerted by the protective bearing on the magnetically levitated rotor. It should be noted that this contact reaction force component is synthesized from the normal restoring force and the tangential friction force, where the tangential friction force is determined based on the normal restoring force and the sliding friction coefficient. Through this implementation, the kinematic differential equations completely describe the effects of various forces on the magnetically levitated rotor during the drop process.

[0034] Understandably, this implementation establishes kinematic equations with the geometric center of the protective bearing as the origin, incorporating gravity, unbalanced excitation force, and the contact reaction force (composed of normal restoring force and tangential friction force) into the differential equations of motion. This constructs a dynamic model that accurately reflects the drop process of the magnetically levitated rotor. By simultaneously considering gravity, unbalanced excitation force, and contact reaction force, it overcomes the limitation of traditional models that only focus on elastic contact forces. In particular, by decomposing the contact reaction force into normal restoring force and tangential friction force, the model can more accurately simulate the complex interaction between the magnetically levitated rotor and the protective bearing, providing a precise mechanical basis for subsequent calculations of relative sliding speed, frictional heat, and radial dimension increments.

[0035] Based on the aforementioned scheme, in some implementations of this application, the step of calculating the normal restoring force using nonlinear Hertzian contact theory includes: First, determining the Hertzian contact stiffness coefficient based on the elastic modulus of the journal material of the magnetic levitation rotor and the inner ring material of the protective bearing. Simultaneously, calculating the radial penetration depth of the magnetic levitation rotor's journal into the inner ring surface of the protective bearing. Based on this, the normal restoring force is calculated as the sum of an elastic force term and a damping force term. The elastic force term is proportional to the nonlinear exponent of the radial penetration depth, reflecting the characteristic of nonlinear growth of contact force with penetration depth; the damping force term is proportional to the nonlinear damping coefficient and the instantaneous velocity of the radial penetration depth, used to describe energy dissipation during the collision process.

[0036] Understandably, this implementation decomposes the normal restoring force into an elastic force term related to the radial penetration depth and a damping force term related to the penetration velocity, and determines the stiffness coefficient based on the material's elastic modulus, thereby more realistically simulating the contact and collision process between the magnetic levitation rotor and the protective bearing. Specifically, by introducing a damping force term, this implementation incorporates both elastic recovery and energy dissipation into the calculation of the normal restoring force, making it closer to real-world drop collision scenarios than the traditional purely elastic Hertzian contact model. Furthermore, the use of a Hertzian contact stiffness coefficient determined based on the material's elastic modulus ensures the physical accuracy of the stiffness parameters. In addition, the elastic force term uses a nonlinear exponential power, accurately reflecting the stiffness change characteristics resulting from the increase in contact area with penetration depth.

[0037] Based on the aforementioned scheme, in some implementations of this application, the step of calculating frictional heat and radial dimension increment based on relative sliding speed to update the real-time clearance of the protective bearing includes: First, calculating the instantaneous frictional heat power based on the relative sliding speed and normal restoring force. Then, calculating the radial dimension increment caused by frictional heat through thermo-mechanical coupling integral relationship (cumulatively integrating the instantaneous frictional heat power over time). Finally, subtracting the radial dimension increment from the initial clearance of the protective bearing yields the real-time clearance at the current moment. It should be noted that the radial dimension increment represents the additional radial space occupied by the magnetic levitation rotor journal and the inner ring of the protective bearing due to thermal expansion caused by frictional heat; the initial clearance minus this increment is the remaining effective clearance.

[0038] Understandably, this implementation achieves dynamic updating of the real-time clearance of the protective bearing by subtracting the radial dimension increment caused by frictional heat from the initial clearance, thus reflecting the real-time impact of thermal expansion on the clearance. In other words, this implementation establishes a quantitative link between frictional heat and clearance changes by introducing a thermo-mechanical coupling integral relationship, overcoming the shortcomings of traditional methods that ignore the thermal expansion effect. Furthermore, the real-time update of the clearance allows the evaluation model to dynamically track the clearance decay trend, providing a direct basis for subsequent determination of thermal seizure failures, thereby improving the accuracy of drop reliability assessment.

[0039] Based on the aforementioned scheme, in some implementations of this application, the calculation steps for the maximum contact stress and strength safety factor of the inner ring of the protective bearing include: First, extracting the maximum instantaneous value of the normal restoring force from the output results of the dynamic model of the drop process. Then, based on Hertzian contact theory, and combining the composite elastic modulus, effective contact length, and equivalent radius of curvature of the inner ring of the protective bearing and the journal of the magnetic levitation rotor, calculating the maximum contact stress borne by the inner ring material of the protective bearing. This maximum contact stress represents the maximum pressure experienced by the inner ring of the protective bearing during the drop impact. Finally, comparing the yield strength limit of the inner ring material of the protective bearing with the calculated maximum contact stress, i.e., dividing the yield strength limit by the maximum contact stress, to generate a strength safety factor characterizing the structural strength.

[0040] Understandably, this implementation extracts the maximum instantaneous value of the normal restoring force and calculates the maximum contact stress by combining it with material parameters. This stress is then compared with the yield strength limit to generate a strength safety factor, thereby effectively quantifying the impact resistance of the protective bearing. By extracting the maximum instantaneous value rather than the average value, the most severe impact moment during the drop can be captured, making the assessment results safer and more reliable. Furthermore, by quantitatively comparing the maximum contact stress with the yield strength limit, a clear numerical basis is provided for determining whether the protective bearing has undergone plastic deformation or structural failure, solving the problem of existing solutions that lack quantified safety boundaries in assessments based on single mechanical indicators.

[0041] Based on the aforementioned scheme, in some implementations of this application, the calculation steps for the thermal safety margin index and the material wear volume generated by the drop include: First, obtaining the instantaneous highest temperature of the contact area, calculating the difference between the instantaneous highest temperature of the contact area and the ambient temperature, and the difference between the material failure critical temperature threshold and the ambient temperature. Finally, dividing the former difference by the latter difference, thereby calculating the normalized thermal safety margin index based on the ratio of the two differences. The closer this index is to 1, the farther away from thermal failure and the larger the safety margin. When calculating the material wear volume, based on the Akard wear law, the material wear volume caused by a single drop is calculated using the Akard wear coefficient, normal restoring force, relative sliding speed, and Vickers hardness value of the inner ring material protecting the bearing. That is, by integrating the product of the normal restoring force and the relative sliding speed over time, multiplying by the Akard wear coefficient, and dividing by the Vickers hardness value, the material wear volume caused by a single drop is obtained.

[0042] Understandably, this implementation calculates a normalized thermal safety margin index by measuring the temperature rise ratio and uses mechanical parameters based on Akard's wear law to calculate the material wear volume, thereby quantitatively assessing the health status of the protective bearing from two dimensions: thermal failure risk and cumulative wear. In other words, by introducing a normalized thermal safety margin index, complex temperature data is transformed into intuitive dimensionless values ​​between 0 and 1, facilitating a unified judgment standard. Simultaneously, the wear volume calculation based on Akard's wear law provides a physical basis for quantitatively assessing the cumulative lifespan after multiple drops, solving the problem of existing solutions lacking a comprehensive quantitative analysis of thermal safety and cumulative wear.

[0043] Based on the aforementioned scheme, in some implementations of this application, the step of jointly determining the survivability of the protective bearing in this round of drops and the remaining safe drop count based on the strength safety factor, thermal safety margin index, and cumulative material wear volume includes: First, determining the survivability of this round of drops: when the strength safety factor is greater than a preset strength threshold and the thermal safety margin index is greater than a preset thermal safety critical value, the protective bearing is determined to have the survivability of this round of drops; otherwise, if any index fails to meet the condition, structural collapse or thermal seizure failure is determined. Then, determining the remaining safe drop count: obtaining the allowable maximum wear volume of the protective bearing, adding the accumulated material wear volume generated in this drop to the historical accumulated wear volume to obtain the updated accumulated wear volume, and then calculating the remaining safe drop count based on the difference between the allowable maximum wear volume and the accumulated wear volume, and the representative material wear volume of a single drop.

[0044] Understandably, this implementation determines survivability in the current cycle by comparing the strength safety factor and thermal safety margin indicators with their respective thresholds. Simultaneously, it calculates the remaining safe drop count based on the difference between the allowable maximum wear volume and the cumulative wear volume, thus achieving a joint assessment across two time dimensions: single and multiple drops. In other words, this implementation introduces logical judgments to ensure that survivability is only recognized when both strength safety and thermal safety are simultaneously met, avoiding the one-sidedness of assessing a single indicator. Furthermore, the quantitative calculation of the remaining safe drop count provides a clear time window for preventative maintenance of the bearing, thereby accurately predicting the cumulative lifespan after multiple drops.

[0045] To enable those skilled in the art to more intuitively understand this application, a specific example will be provided below. This example is an exemplary demonstration combining the overall technical paradigm of this application with some optional implementation details. It should be noted that the following demonstration is intended to aid understanding and does not constitute an exhaustive list of all embodiments of this application, nor does it imply that this application must include all the details described below in its specific implementation.

[0046] Reference Figure 2 This example demonstrates a drop reliability assessment method for magnetically levitated protective bearings, applied to a heavy-duty magnetically levitated bearing system. The heavy-duty magnetically levitated bearing system comprises a magnetically levitated rotor, a magnetically levitated bearing stator, a protective bearing, a sensor probe array, and a magnetically levitated bearing control cabinet. This system is configured for use in a high-temperature reactor main helium blower or helium compressor.

[0047] In a heavy-duty magnetic levitation bearing system, a sensor probe array is responsible for acquiring real-time position and rotational speed information of the magnetic levitation rotor relative to the magnetic levitation bearing stator. The signal output terminal of the sensor probe array is connected to the signal input interface of the magnetic levitation bearing control cabinet via a shielded cable. The magnetic levitation bearing control cabinet integrates signal modulation and demodulation circuitry, an active control algorithm unit, and a power amplifier.

[0048] To meet the data accuracy requirements of the drop reliability assessment method for the magnetically levitated protective bearing in this example, the sensor probe array includes 5 inductive speed sensors and 10 inductive displacement sensors.

[0049] The 10 inductive displacement sensors are divided into a main measurement group and a redundant measurement group according to their measurement degrees of freedom and redundancy configuration. The main measurement group includes: sensor X1 for monitoring the X-direction displacement of the upper radial bearing, sensor Y1 for monitoring the Y-direction displacement of the upper radial bearing, sensor Z1 for monitoring the axial displacement, sensor X2 for monitoring the X-direction displacement of the lower radial bearing, and sensor Y2 for monitoring the Y-direction displacement of the lower radial bearing.

[0050] The redundant measurement group includes: a redundant sensor RX1 for monitoring the X-direction displacement of the upper radial bearing, a redundant sensor RY1 for monitoring the Y-direction displacement of the upper radial bearing, a redundant sensor RZ1 for monitoring the axial displacement, a redundant sensor RX2 for monitoring the X-direction displacement of the lower radial bearing, and a redundant sensor RY2 for monitoring the Y-direction displacement of the lower radial bearing.

[0051] The five inductive speed sensors include the first-channel speed input sensor SP1, the second-channel speed input sensor SP2, and the third-channel speed input sensor SP3. The inductive speed sensors also include a redundant second-channel speed input sensor RSP2 and a redundant third-channel speed input sensor RSP3.

[0052] Both inductive displacement and inductive speed sensors utilize the inductive detection principle. The stator and rotor of the position sensor are both constructed from pressed silicon steel sheets. The rotor of the position sensor serves as the sensor target, fixed to the magnetically levitated rotor. The target of the speed sensor is designed as an eccentric ring structure.

[0053] The inductive displacement sensor employs a differential configuration. A positive probe and a negative probe are arranged in each measurement degree of freedom direction. When the magnetically levitated rotor undergoes displacement, the air gap between the positive probe and the sensor target, and the air gap between the negative probe and the sensor target, change in opposite directions.

[0054] The inductance of a single-sided probe coil of an inductive displacement sensor is defined as follows: Inductance of a single-sided probe coil With the number of turns of the probe coil Vacuum permeability Cross-sectional area of ​​iron core and total air gap They satisfy a physical relationship: ; In the formula, This indicates the inductance of a single-sided probe coil; This indicates the number of turns in the probe coil for a single-sided probe coil; Represents the vacuum permeability under vacuum conditions; This indicates the cross-sectional area of ​​the probe's core. This indicates the total air gap between the probe end face and the sensor target.

[0055] In the differential configuration, the modulation and demodulation circuit within the magnetic levitation bearing control cabinet applies high-frequency sinusoidal excitation signals to both the forward and negative probes. The inductance of the forward probe is defined as... The inductance of the negative probe is defined as The relationship between the demodulated voltage signal output by the modulation and demodulation circuit and the inductance of the positive and negative probes is as follows: ; In the formula, This represents the demodulated voltage signal after synchronous demodulation and filtering. This represents the signal amplification gain coefficient of the demodulation circuit; This indicates the amplitude of the excitation signal applied to the bridge; Indicates the inductance of the forward probe; This indicates the inductance of the negative probe.

[0056] The inductive displacement sensor eliminates even-order harmonic nonlinear terms and outputs a voltage signal proportional to the displacement of the magnetically levitated rotor.

[0057] The interface circuit within the magnetic levitation bearing control cabinet further converts the demodulated voltage signal into a standard current signal. The final current signal output to the control system is defined as... The current signal and the demodulated voltage signal follow a linear conversion relationship: ; In the formula, This indicates the current signal output to the host computer or control system. This represents the bias current value corresponding to zero displacement; This represents the conversion factor from voltage to current. This represents the demodulated voltage signal output by the demodulation circuit.

[0058] In heavy-duty magnetic levitation bearing systems, the sensitivity of inductive displacement sensors is set to 6V / mm, with a linear range greater than 3mm and a resolution less than 0.5μm. The signal transmission distance of both inductive displacement and inductive speed sensors is greater than or equal to 60 meters.

[0059] The magnetic levitation bearing control cabinet employs a redundant power supply design for all inductive displacement and speed sensors. The position and speed signal processing circuits are also redundantly designed. When any sensor in the main measurement group fails, the control cabinet can switch to the corresponding redundant sensor group for data acquisition, ensuring that even in the event of a magnetic levitation rotor falling into the protective bearing, the system can still record complete rotor trajectory data.

[0060] Reference Figure 2In this example of a drop reliability assessment method for a magnetically levitated protective bearing, the sensor probe array employs a specific high-precision layout within the mechanical structure of the heavy-duty magnetically levitated bearing system. An upper radial bearing X-direction displacement sensor X1 and an upper radial bearing Y-direction displacement sensor Y1 are positioned at the upper radial bearing location. The measurement axis of the upper radial bearing X-direction displacement sensor X1 is spatially perpendicular to the measurement axis of the upper radial bearing Y-direction displacement sensor Y1. Similarly, a lower radial bearing X-direction displacement sensor X2 and a lower radial bearing Y-direction displacement sensor Y2 are positioned at the lower radial bearing location. The measurement axis of the lower radial bearing X-direction displacement sensor X2 is spatially perpendicular to the measurement axis of the lower radial bearing Y-direction displacement sensor Y2.

[0061] Each inductive displacement sensor contains two opposing sensor probes, forming a differential measurement pair. Taking the upper radial bearing X-direction displacement sensor X1 as an example, X1 consists of a positive probe X1+ and a negative probe X1-. The positive probe X1+ and the negative probe X1- are symmetrically mounted on both sides of the magnetically levitated rotor. When the magnetically levitated rotor is at its mechanical center position, the distance between the positive probe X1+ and the sensor target is equal to the distance between the negative probe X1- and the sensor target.

[0062] The nominal air gap between the probe end face and the sensor target is defined as follows when the magnetic levitation rotor is in the mechanical center position: The radial displacement of the magnetically levitated rotor from the mechanical center along the measurement axis is defined as... When the magnetically levitated rotor undergoes radial displacement... At that time, the actual air gap at the forward probe X1+ becomes The actual air gap at the negative probe X1 becomes .

[0063] Based on the principle of inductive detection, the inductance constant is defined as... Inductance constant The real-time inductance of the forward probe X1+ is determined by the number of turns of the probe coil, the vacuum permeability, and the cross-sectional area of ​​the iron core. With nominal air gap and radial displacement Satisfies the functional relationship: ; Real-time inductance of negative probe X1 With nominal air gap and radial displacement Satisfies the functional relationship: ; The modulation and demodulation circuit inside the magnetic levitation bearing control cabinet performs differential processing on the signals from the positive probe X1+ and the negative probe X1-. This differential processing eliminates common-mode interference and linearizes the input displacement and output voltage. The linearized displacement output voltage signal is defined as... Displacement output voltage signal With radial displacement The relationship is: ; In the formula, This represents the displacement output voltage signal that is proportional to the displacement after being processed by the differential bridge and demodulation circuit. This represents the gain coefficient of a differential amplifier circuit. Indicates the amplitude of the excitation signal; Indicates radial displacement; Indicates the nominal air gap.

[0064] Axial displacement sensor Z1 and redundant axial displacement sensor RZ1 are arranged on the side of the thrust disk of the magnetic levitation rotor. The probe surface of axial displacement sensor Z1 is perpendicular to the disk surface of the thrust disk. When the magnetic levitation rotor undergoes axial movement, the air gap between the thrust disk surface and the probe of axial displacement sensor Z1 changes, thereby causing a change in inductance.

[0065] Five inductive speed sensors are arranged along the circumference of the magnetically levitated rotor. The detection end face of each inductive speed sensor faces the speed sensor target. The speed sensor target is an eccentric ring fixed to the magnetically levitated rotor. The rotation of the eccentric ring causes a periodic change in the air gap detected by the inductive speed sensors.

[0066] The magnetic levitation bearing control cabinet calculates the rotational speed of the magnetic levitation rotor by detecting the frequency of changes in the air gap. The real-time rotational speed of the magnetic levitation rotor is defined as... The pulse frequency obtained after shaping the output signal of an inductive speed sensor is defined as follows: Pulse frequency With real-time speed Satisfy physical relationship: ; In the formula, This indicates the pulse frequency output by the speed sensor signal conditioning circuit; This indicates the real-time rotational speed of the magnetic levitation rotor.

[0067] In the redundant measurement group, redundant sensors RX1, RY1, RX2, and RY2 are installed adjacent to the main measurement group sensors X1, Y1, X2, and Y2, respectively. The redundant sensors monitor the same target point as their corresponding main sensors, ensuring that the heavy-duty magnetic levitation bearing system can maintain continuous and high-precision monitoring of the magnetic levitation rotor's position and speed even when the sensor probe array is subjected to external impact or a single-point failure.

[0068] In the drop reliability assessment method of the magnetic levitation protective bearing in this example, in order to ensure the integrity and accuracy of signal acquisition under the conditions of magnetic levitation rotor drop and severe vibration, the position sensor target and the speed sensor target adopt specific anti-eddy current and mechanical structure design.

[0069] The position sensor targets include radial displacement sensor targets and axial displacement sensor targets. Both radial and axial displacement sensor targets are manufactured using a silicon steel sheet lamination process. This silicon steel sheet lamination process uses an insulating layer to isolate adjacent silicon steel sheets, thus blocking the flow path of the induced current along the axial direction of the magnetically levitated rotor.

[0070] The magnetic levitation bearing control cabinet injects a high-frequency excitation signal into the inductive displacement sensor probe. This high-frequency excitation signal generates an alternating magnetic field on the surface of the position sensor target. This alternating magnetic field induces eddy current losses within the conductive material. The position sensor target, employing a silicon steel sheet lamination process, can significantly reduce the eddy current loss power density.

[0071] Define the eddy current loss power density within the position sensor target as: Eddy current loss power density With excitation frequency Magnetic flux density amplitude Thickness of a single silicon steel sheet and material resistivity Satisfy physical relationship: ; By reducing the thickness of a single silicon steel sheet By selecting silicon steel material with high resistivity, the position sensor target component reduces thermal effects and improves the Q value and signal-to-noise ratio of the inductive displacement sensor.

[0072] The speed sensor target is designed as an eccentric ring structure. This eccentric ring structure is interference-fitted to the end of the magnetically levitated rotor. The eccentric ring structure has a geometric center and a rotational center. A predetermined eccentric distance exists between the geometric center and the rotational center.

[0073] When the magnetic levitation rotor has an angular velocity During rotation, the instantaneous air gap between the inductive speed sensor probe and the speed sensor target changes periodically over time. The instantaneous air gap of the inductive speed sensor is defined as... Instantaneous air gap With time The functional relationship is as follows: ; In the formula, Indicates in The distance from the probe end face of the inductive speed sensor to the outer surface of the speed sensor target at any given time; This indicates the average installation air gap of the eccentric ring structure. This represents the eccentricity distance between the geometric center of the eccentric ring structure and the center of rotation. This represents the real-time rotational angular velocity of the magnetically levitated rotor; Represents a time variable.

[0074] The position sensor target and speed sensor target are non-replaceable components throughout the entire lifecycle of the heavy-duty magnetic levitation bearing system. The heavy-duty magnetic levitation bearing system integrates a mechanical limit protection structure. This structure limits the maximum radial and axial displacement range of the magnetic levitation rotor under drop accident conditions.

[0075] The mechanical limiting protection structure ensures that a safe clearance is maintained between the surface of the position sensor target and the end face of the sensor probe array when the magnetic levitation rotor loses levitation and falls into the inner ring of the protective bearing. This safe clearance prevents mechanical collisions between the position sensor target, the speed sensor target, and the sensor probe, thus ensuring that the heavy-duty magnetic levitation bearing system can still obtain effective rotor position and speed data for fault analysis via the sensor probe array during and after the fall.

[0076] Reference Figure 2 The high-precision displacement and speed signal acquisition and demodulation method adopts the differential inductive detection principle. The differential inductive detection principle is based on the physical characteristic that the impedance of the inductive sensor coil changes with the air gap. A high-frequency constant-amplitude sine wave is generated by the signal generation circuit inside the magnetic levitation bearing control cabinet as the excitation signal. This high-frequency constant-amplitude sine wave is simultaneously applied to both the positive and negative probe coils of the inductive displacement sensor.

[0077] The displacement of the magnetically levitated rotor causes a differential change in the inductance of the positive and negative probe coils. This differential change causes a shift in the amplitude of the midpoint voltage of the measuring bridge. The demodulation circuit within the magnetically levitated bearing control cabinet extracts the characteristic signal reflecting the differential change in inductance using synchronous detection technology.

[0078] To physically eliminate even-order harmonic distortion and counteract common-mode interference caused by temperature drift, the demodulation circuit's signal processing logic constructs a normalized inductance difference ratio. The normalized inductance difference ratio is defined as... Normalized inductance difference ratio By substituting the geometric air gap models of the positive and negative probes into the differential calculation logic, the following results are obtained: ; The arithmetic logic unit in the magnetic levitation bearing control cabinet corresponds to the normalized inductance difference ratio. The expression is simplified algebraically. This algebraic simplification process eliminates the inductance constant. The influence of this was investigated, and a normalized inductance difference ratio was established. With real-time displacement A purely linear relationship between them: ; Based on the aforementioned linear relationship, the magnetic levitation bearing control cabinet can directly map the demodulated voltage signal into physical displacement values ​​without the need for complex nonlinear compensation. This linearization characteristic ensures that the sensor system maintains constant sensitivity throughout the large dynamic range of the magnetic levitation rotor's drop process, thus providing distortion-free motion trajectory data for multi-factor coupled drop reliability analysis.

[0079] In this example of the drop reliability assessment method for magnetically levitated protective bearings, achieving key technical indicators relies on precise matching of circuit parameters within the magnetically levitated bearing control cabinet and impedance optimization of the transmission link. The sensitivity of the inductive displacement sensor is set to 6 volts per millimeter. The resolution of the inductive displacement sensor is set to less than 0.5 micrometers. The signal transmission distance for both the inductive displacement sensor and the inductive speed sensor is set to greater than or equal to 60 meters.

[0080] To achieve a sensitivity of 6 volts per millimeter, the signal amplification link within the magnetic levitation bearing control cabinet adjusts the gain of the differentially demodulated voltage signal. The system's displacement sensitivity is defined as... Displacement sensitivity The total gain of the demodulation circuit Excitation signal amplitude and the nominal air gap of the sensor probe Joint decision: ; To achieve a resolution of less than 0.5 micrometers, the magnetic levitation bearing control cabinet integrates a low-noise preamplifier and a high-order low-pass filter in the signal processing circuit. The system's measurement resolution is limited by the circuit's inherent noise level. The system's measurement resolution is defined as... Measurement resolution The root mean square noise voltage at the system output and displacement sensitivity The signal-to-noise ratio (SNR) constraint relationship between them is satisfied: ; To achieve a signal transmission distance of 60 meters or more, the magnetic levitation bearing control cabinet's output interface employs a current loop drive method. This current loop drive method must overcome the voltage drop caused by the line resistance of the long-distance transmission cable. The voltage compliance range of the output drive circuit is defined as follows: Voltage compliance range Long-distance load driving conditions must be met: ; In the formula, This indicates the maximum driving voltage that the voltage-to-current conversion circuit can provide; This indicates the maximum operating current in the signal transmission circuit, with a value of 20 mA. This represents the input load resistance of the remote receiver; This represents the DC resistance per unit length of the transmission cable. This indicates the physical wiring distance between the sensor probe array and the monitoring system, with a value greater than or equal to 60 meters.

[0081] By selecting low-resistivity shielded twisted-pair cable as the transmission medium and increasing the power supply voltage of the voltage-to-current conversion circuit, the heavy-duty magnetic levitation bearing system ensures that the terminal reception error of the current signal is lower than the allowable threshold of the system design at a transmission distance of 60 meters, thereby ensuring that the data source on which the drop reliability analysis is based has high fidelity.

[0082] Reference Figure 3 The multi-factor coupled drop protection logic based on redundant sensing relies on the coordinated operation of hardware and software for sensor redundancy and fault switching mechanisms. The magnetic levitation bearing control cabinet is equipped with dual independent DC regulated power supply modules. These modules power the main measurement group sensors and the redundant measurement group sensors of the sensor probe array, respectively. The signal acquisition card within the magnetic levitation bearing control cabinet has independent analog-to-digital conversion channels, receiving signals from both the main measurement group displacement sensors and the redundant measurement group displacement sensors.

[0083] The digital signal processing unit inside the magnetic levitation bearing control cabinet executes a real-time data consistency verification algorithm. Within each servo control cycle, the digital signal processing unit synchronously reads the output data from the main measurement group displacement sensor and the output data from the redundant measurement group displacement sensors.

[0084] The displacement reading of the main measurement group displacement sensor is defined as follows: The displacement reading of the redundant measurement group displacement sensor is defined as... The digital signal processing unit calculates the displacement readings of the main measurement group's displacement sensors. Displacement readings from redundant measurement group displacement sensors The absolute deviation value between. The absolute deviation value is defined as... Absolute deviation value Satisfies algebraic relations: ; The magnetic levitation bearing control cabinet has a preset maximum allowable deviation threshold. When the absolute deviation value is less than or equal to the maximum allowable deviation threshold, the magnetic levitation bearing control cabinet determines that both the main measurement group displacement sensor and the redundant measurement group displacement sensor are working normally. When the absolute deviation value is greater than the maximum allowable deviation threshold, the magnetic levitation bearing control cabinet initiates fault diagnosis and signal switching logic.

[0085] The fault diagnosis and signal switching logic is based on the validity range of the signal amplitude. The lower limit of the effective voltage of the sensor output signal is defined as follows: Define the effective voltage upper limit as The magnetic levitation bearing control cabinet detects whether the output voltage of the sensor is at the lower limit of the effective voltage. With the upper limit of effective voltage Within the defined interval.

[0086] The magnetic levitation bearing control cabinet generates weighted switching coefficients based on the fault diagnosis results. The weighted switching coefficients are defined as follows: The displacement data that ultimately participates in magnetic levitation control and drop trajectory recording is defined as follows: Displacement data Weighted switching coefficient Decide: ; In the formula, This indicates the displacement data that is sent to the control algorithm or data recording unit after being arbitrated by redundant logic. This represents the weighted switching coefficients used to select the signal source. The value can only be 1 or 0; This indicates the displacement reading of the displacement sensor in the main measurement group; This indicates the real-time displacement value of the redundant measurement group displacement sensor.

[0087] In the fault diagnosis and signal switching logic, when the output voltage of the main measurement group displacement sensor is within the effective range and is not marked as faulty, the magnetic levitation bearing control cabinet sets the weighted switching coefficient to 1, and the system uses the displacement reading of the main measurement group displacement sensor. When the output voltage of the main measurement group displacement sensor exceeds the effective range or a power failure occurs, and the output voltage of the redundant measurement group displacement sensor is within the effective range, the magnetic levitation bearing control cabinet sets the weighted switching coefficient to 0, and the system seamlessly switches to the displacement reading of the redundant measurement group displacement sensor.

[0088] This fault switching mechanism ensures that even if a single sensor channel fails due to impact or vibration, the heavy-duty magnetic levitation bearing system can still obtain continuous rotor position information through redundant channels under extreme conditions such as multi-factor coupled drop of the magnetic levitation rotor, thereby maintaining the monitoring capability of protecting the bearing contact state.

[0089] Reference Figure 3 In this example of the drop reliability assessment method for magnetically levitated protective bearings, the rotor state monitoring logic under drop conditions is executed by the drop trajectory recording unit within the magnetically levitated bearing control cabinet. The drop trajectory recording unit is configured to activate a high-speed data latching mode the instant the magnetically levitated rotor experiences instability and a fall. The high-speed data latching mode synchronously records real-time position data uploaded by the main measurement group displacement sensor or redundant measurement group displacement sensors at a sampling frequency of 10 kHz to 50 kHz.

[0090] The magnetic levitation bearing control cabinet constructs a two-dimensional axis trajectory of the magnetic levitation rotor using orthogonally arranged X-direction and Y-direction displacement data. The instantaneous composite radial displacement of the magnetic levitation rotor within the drop plane is defined as... Instantaneous composite radial displacement Displacement is monitored in real time in the X direction. Real-time monitoring of displacement in the Y direction Obtained through geometric synthesis: ; The magnetic levitation bearing control cabinet will instantaneously synthesize radial displacement. The mechanical contact state between the magnetically levitated rotor and the inner ring of the protective bearing is identified by comparing the nominal clearance of the protective bearing with the clearance on one side. The nominal clearance of the protective bearing on one side is defined as... The contact state determination coefficient is defined as follows: Contact state determination coefficient The calculation logic is as follows: ; When the contact condition determination coefficient is equal to or greater than 1, the magnetic levitation bearing control cabinet determines that the magnetic levitation rotor has mechanically collided or scraped against the protective bearing. The drop trajectory recording unit then marks the current contact time point and calculates the radial impact velocity of the magnetic levitation rotor at the moment of contact.

[0091] Define the radial impact velocity of the magnetically levitated rotor as Radial impact velocity This reflects the momentum intensity when the magnetically levitated rotor impacts the protective bearing. The magnetically levitated bearing control cabinet obtains the radial impact velocity by performing differential calculations on the real-time position data. : ; In the formula, This represents the radial impact velocity of the magnetically levitated rotor as it moves radially during the fall. This indicates real-time displacement monitoring in the X direction; This indicates real-time displacement monitoring in the Y direction; This represents the sampling time variable.

[0092] To assess the cumulative damage to the protective bearing caused by a single drop, the magnetic levitation bearing control cabinet further calculates the instantaneous radial impact energy at the drop contact point. The instantaneous radial impact energy is defined as... Instantaneous radial impact energy The equivalent drop mass and radial impact velocity of the magnetically levitated rotor satisfy the following physical relationship: ; In the formula, This represents the instantaneous radial impact energy possessed by the magnetically levitated rotor at the moment of impact with the inner ring of the protective bearing; This represents the total mass of the magnetically levitated rotor; This indicates the radial impact velocity of the magnetically levitated rotor.

[0093] The magnetic levitation bearing control cabinet stores the calculated instantaneous synthetic radial displacement, contact state determination coefficient, radial impact velocity, and instantaneous radial impact energy in non-volatile memory in real time. The data stored in the non-volatile memory constitutes the original analysis sample of the drop reliability assessment method for the magnetic levitation protective bearing in this example, and is used for subsequent correction and verification of the protective bearing life degradation model.

[0094] Reference Figure 3 A multi-factor coupled drop dynamics model was used to construct the kinematic equations of the magnetically levitated rotor during the drop process. The kinematic equations take the geometric center of the protective bearing as the origin of the coordinate system. The kinematic equations describe the planar motion of the magnetically levitated rotor under the combined action of gravity, unbalanced excitation force, and contact reaction force of the protective bearing.

[0095] The mass of the magnetically levitated rotor is defined as The displacement of the magnetically levitated rotor along the horizontal X-axis is defined as... The displacement of the magnetically levitated rotor along the perpendicular Y-axis is defined as... The translational differential equations for a magnetically levitated rotor are as follows: ; In the formula, This represents the unbalanced excitation force component of the magnetically levitated rotor in the X-axis direction; This indicates the X-axis contact reaction force exerted by the protective bearing on the magnetically levitated rotor; This represents the unbalanced excitation force component of the magnetically levitated rotor in the Y-axis direction; This indicates the contact reaction force in the Y-axis direction exerted by the protective bearing on the magnetically levitated rotor; It represents the acceleration due to gravity.

[0096] The unbalanced excitation force originates from the mass eccentricity of the magnetically levitated rotor. The mass eccentricity of the magnetically levitated rotor is defined as... The rotational angular velocity of the magnetically levitated rotor is defined as... The formula for calculating the unbalanced excitation force components is: ; The contact reaction force of the protective bearing on the magnetically levitated rotor is a combination of the normal restoring force and the tangential frictional force. The normal restoring force is defined as... The coefficient of sliding friction is defined as... The projection relationship of the contact reaction force onto the coordinate axes is as follows: ; In the formula, This represents the contact reaction force in the X-axis direction; This represents the contact reaction force in the Y-axis direction.

[0097] The aforementioned kinematic equations form the basis for the dynamic behavior of the heavy-duty magnetic levitation bearing system under drop accident conditions. By numerically integrating and solving this set of differential equations, the multi-factor coupled drop dynamics model can predict the axis trajectory, collision velocity, and rebound amplitude of the magnetic levitation rotor.

[0098] Reference Figure 3 The contact-collision and thermodynamic coupling model, as the core solution submodule of the aforementioned multi-factor coupled drop dynamics model, describes the microscopic dynamic behavior and thermodynamic effects when the magnetically levitated rotor and the inner ring of the protective bearing come into mechanical contact. Together with the macroscopic kinematic equations, it constitutes the complete multi-factor coupled drop dynamics model. The contact-collision and thermodynamic coupling model uses nonlinear Hertzian contact theory to calculate the normal restoring force. The model also considers the influence of material damping characteristics on energy dissipation.

[0099] Define the normal restoring force as Normal restoring force It is a function of the depth of the magnetic levitation rotor intruding into the inner ring of the protective bearing. Normal restoring force. The calculation formula is: ; In the formula, Indicates normal restoring force; This indicates the Hertzian contact stiffness coefficient, which depends on the elastic modulus of the magnetic levitation rotor journal material and the material protecting the inner ring of the bearing. This indicates the radial penetration depth of the magnetic levitation rotor journal into the surface of the inner ring of the protective bearing; This represents the nonlinear elasticity index defined by Hertzian contact theory; This represents the nonlinear damping coefficient during the contact collision process; This represents the damping index. The value is usually 1; This indicates the instantaneous velocity at which the journal of the magnetic levitation rotor radially penetrates the inner ring of the protective bearing.

[0100] The relative sliding motion between the magnetically levitated rotor and the inner ring of the protective bearing generates frictional heat. This frictional heat causes thermal expansion of the magnetically levitated rotor journal and the inner ring of the protective bearing. The thermal expansion effect alters the effective clearance of the protective bearing.

[0101] Define the relative sliding velocity at the contact point as Relative sliding speed The speed is determined by both the rotational speed and the revolution speed of the magnetically levitated rotor: ; In the formula, This represents the angular velocity of the magnetically levitated rotor. Indicates the physical radius of the journal of the magnetically levitated rotor; This represents the eddy current velocity of the magnetically levitated rotor as it revolves around the center of the protective bearing.

[0102] The contact collision and thermo-mechanical coupling model calculates instantaneous frictional heat power based on relative sliding velocity and normal restoring force. This instantaneous frictional heat power is converted into thermal energy, causing an increase in material temperature.

[0103] Define the radial dimension increment caused by thermal expansion as Radial dimension increment Over time, this accumulates and corrects for any remaining clearance in the protective bearing. Radial dimension increment. Satisfying the thermo-coupling integral relationship: ; In the formula, Indicates the linear thermal expansion coefficient of the material in contact with the material; Indicates the journal radius of the magnetic levitation rotor; Indicates the specific heat capacity of the material in contact with the material; Indicates the equivalent mass of the contact area involved in heat absorption; The heat distribution coefficient represents the conversion of frictional heat into heat entering the material's interior; Indicates the dynamic sliding friction coefficient; Indicates instantaneous normal restoring force; Indicates instantaneous relative sliding velocity; This represents the integration variable, time.

[0104] The multi-factor coupled drop dynamics model utilizes the calculated radial dimension increment. The clearance status of the protected bearing is updated in real time. To quantify the assessment of the risk of thermal seizure, this embodiment explicitly defines the initial clearance and the real-time clearance.

[0105] Define the initial gap as Its value is equal to the nominal clearance on one side of the protective bearing. Define the real-time interval as Real-time gap This represents the remaining effective physical clearance between the inner ring of the protective bearing and the journal of the magnetically levitated rotor after accounting for material thermal expansion and deformation under the influence of thermo-mechanical coupling. Real-time clearance. Satisfying the following algebraic relations: ; Magnetic levitation bearing control cabinet monitors real-time gap The changing trend of the real-time interval. When the decay reaches zero or a negative value, a thermal lock-up fault is determined to have occurred in the system. To more intuitively reflect the safety margin, the system further calculates the real-time gap ratio. Defined as: ; The multi-factor coupled drop dynamics model includes a numerical solution module to generate simulation data. The module uses the structural parameters of the heavy-duty magnetic levitation bearing system and the initial drop state as the initial boundary conditions for the simulation. It employs a set time step to perform discretized numerical integration on the translational differential equations and the contact-collision-thermal coupling model. Within each time step, the module iteratively calculates the instantaneous displacement, relative sliding velocity, normal restoring force, and contact point temperature of the magnetic levitation rotor. After the set total simulation time span, the module aggregates the discrete calculation results from all time steps into a time series, thereby generating the simulation data. Specifically, the simulation data includes the time history data of the normal restoring force and the time history data of the contact point temperature.

[0106] Reference Figure 3The multi-factor coupled drop dynamics model uses a reliability assessment index calculation module to quantitatively analyze the simulation data output by the numerical solution module. The reliability assessment index calculation module extracts the normal restoring force time history data and contact point temperature time history data from the simulation data. Based on Hertzian contact theory, the reliability assessment index calculation module calculates the maximum contact stress of the inner ring of the protective bearing under drop impact.

[0107] The maximum contact stress is defined as Maximum contact stress This characterizes the peak pressure that the inner ring material of the protective bearing withstands during a single drop impact. Maximum contact stress. The calculation formula is: ; In the formula, This represents the maximum instantaneous value of the normal restoring force during the fall. This indicates the composite elastic modulus of the inner ring material of the protective bearing and the journal material of the magnetic levitation rotor. This indicates the effective axial contact length between the inner ring of the protective bearing and the journal of the magnetically levitated rotor. This indicates the equivalent radius of curvature at the contact point between the inner ring of the protective bearing and the journal of the magnetically levitated rotor.

[0108] The reliability assessment index calculation module compares the maximum contact stress with the yield strength of the material protecting the bearing inner ring. Based on the comparison result, the module generates a strength safety factor. The strength safety factor is defined as... Strength safety factor The calculation logic is as follows: ; In the formula, This indicates the yield strength limit of the material protecting the inner ring of the bearing; This represents the calculated maximum Hertzian contact stress.

[0109] The reliability assessment index calculation module evaluates the risk of thermal failure of the protective bearing under high-speed frictional heat generation conditions. This module calculates the thermal safety margin index. The thermal safety margin index is defined as... Thermal safety margin index This reflects the proximity between the highest temperature in the contact area and the material failure temperature. ; In the formula, This represents the normalized thermal safety margin, with a value ranging from 0 to 1. This represents the instantaneous highest temperature in the contact area calculated by the contact collision and thermo-coupling model; This indicates the ambient temperature of the magnetic levitation bearing system. This indicates the critical temperature threshold at which the material protecting the inner ring of the bearing softens or the lubricating coating fails.

[0110] The reliability assessment index calculation module estimates the wear life of the protective bearing based on Akard's law of wear. This module also calculates the material wear volume caused by a single drop. The material wear volume is defined as... Material wear volume It is directly proportional to the contact pressure and the relative sliding distance: ; In the formula, Represents the dimensionless Archad wear coefficient; Indicates instantaneous normal restoring force; Indicates instantaneous relative sliding velocity; Represents the time integral variable; This indicates the Vickers hardness value of the material protecting the inner ring of the bearing.

[0111] The multi-factor coupled drop dynamics model performs a joint judgment logic based on the strength safety factor, thermal safety margin index, and material wear volume. The specific judgment method is as follows: (1) Determination of single drop survivability: A multi-condition Boolean AND logic is adopted. The system presets a strength safety factor threshold and a thermal safety margin critical value. Since the maximum contact stress is already used as a bottom-level variable in the calculation of the strength safety factor, only the strength safety factor and the thermal safety margin index need to be compared during the determination. The protective bearing is determined to have the ability to survive this drop if and only if the calculated instantaneous strength safety factor is greater than the set threshold and the instantaneous thermal safety margin index is greater than the set critical value; if either index is lower than the threshold, the structural collapse or thermal seizure failure is determined to have occurred.

[0112] (2) Determination of cumulative lifespan after multiple drops: An accumulated dissipation model based on equivalent physical clearance is adopted. The system sets the maximum allowable wear volume of the protective bearing and accumulates the material wear volume generated by each single drop event. By subtracting the historical accumulated wear volume from the maximum allowable wear volume, dividing by the representative material wear volume of a single drop, and rounding down, the remaining safe number of drops for the protective bearing under the current operating conditions is calculated and determined.

[0113] The evaluation results stored in the database provide quantified boundary condition constraints for the structural optimization of the magnetic levitation rotor system.

[0114] Specific application examples: To more intuitively understand the application of the drop reliability assessment method for magnetic levitation protective bearings in this example, the following explanation is provided in conjunction with a specific engineering project.

[0115] Implementation object parameters: This embodiment is applied to the prototype system of the primary loop main helium blower of a 10MW high temperature gas-cooled reactor.

[0116] Magnetic levitation rotor parameters: Total mass Rated operating speed Rotor journal diameter .

[0117] Protect bearing parameters: Select back-to-back mounted angular contact ceramic ball bearings, nominal clearance on one side. The inner ring is made of high-nitrogen stainless steel, and the rolling elements are made of silicon nitride ceramic.

[0118] Sensor configuration: Configure two sets of inductive displacement sensors (10 probes in total) with primary / redundant configuration and an eccentric ring speed sensor.

[0119] Fall accident scenario simulation: The operating condition is as follows: When the main helium blower is running at full speed (4200 RPM), a sudden power failure in the power amplifier power supply module causes the active magnetic levitation force to disappear instantly. Under the action of gravity, the magnetic levitation rotor falls from the magnetic center position and impacts the inner ring of the protective bearing.

[0120] Implementation process: Step 1: Redundant signal acquisition and cleaning. At the moment of impact, the main measurement group sensor experiences a shock vibration of up to 50g, causing millisecond-level spike noise in the output signal of sensor X1. At this time, the fault diagnosis logic in the control cabinet detects the absolute deviation between X1 and the redundant sensor RX1. The threshold of 0.05mm has been exceeded. The system automatically adjusts the weighted switching coefficient. Setting it to 0 allows for seamless switching to data from the redundant sensor RX1, ensuring the continuity of the drop trajectory recording.

[0121] Step Two: Thermo-coupling calculation. As the rotor undergoes high-frequency reverse whirl within the inner ring of the protective bearing, the contact collision and thermo-coupling model begins operation. The model calculates the instantaneous relative sliding velocity within the first 0.5 seconds. The average speed is 35 m / s. Instantaneous frictional heat power is calculated based on the formula, and the temperature rise of the inner ring is obtained by integration.

[0122] Traditional methods predict that the gap will remain at 0.25mm and the rotor will stop smoothly after 2 seconds.

[0123] The method in this application predicts: the thermal expansion of the inner ring due to frictional heat generation, and the effective gap at 1.2 seconds. The gap has been reduced by 0.08 mm, and the remaining gap is insufficient to maintain normal vortexing, which is predicted to lead to the risk of thermal seizure.

[0124] Step 3: Design Revision. Based on the prediction results of the method in this application, the design team added a heat-blocking layer between the protective bearing housing and the stator, and selected a special alloy steel with a lower coefficient of thermal expansion as the inner ring material. After recalculation, the thermal safety margin index... The value was increased from 0.3 to 0.8, which met the design requirements.

[0125] The experimental verification and effect comparison are as follows: To verify the authenticity of this solution, a physical test was conducted on a 1:1 magnetic levitation bearing drop test bench.

[0126] Experimental group: using the heavy-duty magnetic levitation bearing system of this application.

[0127] Control group: a protective bearing system designed using traditional Hertzian contact theory.

[0128] Test conditions: Power off drop at 4200 RPM full speed, repeated 5 times.

[0129] The experimental results are as follows:

[0130] The results of the comparison are as follows: Experiments show that traditional design methods, when neglecting the thermo-coupling effect, underestimate the risk of thermal expansion during the drop process, leading to rapid loss of the protective bearing clearance at high temperatures and bearing seizure. This application, by introducing a thermo-coupling model and redundant sensing, not only accurately predicts clearance changes but also records the entire drop process data completely through redundant sensors, verifying the model's accuracy and increasing the system's survival probability under extreme conditions by approximately 40%.

[0131] Figure 4 The curves showing the vibration displacement of the magnetic levitation rotor in the X-axis direction as a function of time under a drop condition of 4200 RPM are presented.

[0132] Solid line (model of this application): represents the rotor trajectory calculated using the thermo-coupling model of this application. It can be seen that in the post-drop period, due to the reduction in clearance caused by frictional heat, the damping effect is enhanced, and the vibration decay rate is in better agreement with the experimental data.

[0133] Dashed line (traditional model): Represents the traditional model that only considers Hertzian contact. Its predicted vibration amplitude decays slowly and fails to predict the later rebound suppression, which deviates from the actual physical process.

[0134] Circular markers (experimental data): These represent discrete sampling points measured on the drop test bench, demonstrating the high fidelity of the model in this application.

[0135] Figure 5 It demonstrates the core physical processes of thermo-coupling phenomena.

[0136] The left-hand Y-axis (solid line) represents the change in the temperature of the inner ring of the protective bearing over time.

[0137] The right-hand Y-axis (dashed line) represents the real-time gap ratio.

[0138] As the temperature rises (solid line), the thermal expansion of the material causes the real-time clearance to decrease rapidly (dashed line). When the real-time clearance ratio falls into the high-risk zone for thermal seizure (less than 0.2) marked in gray in the figure, it indicates that the remaining clearance is insufficient to accommodate the thermal deformation and eccentric movement of the rotor, and the system is about to experience a jamming failure.

[0139] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from the spirit or essential characteristics of this application. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of this application is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this application. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for assessing the drop reliability of a magnetically levitated protective bearing, characterized in that, The method includes: In response to a rotor fall event, the rotor fall trajectory data and rotation speed information are acquired. The rotor fall trajectory data is obtained by real-time acquisition of the position information of the magnetic levitation rotor from at least two sets of displacement sensors, and the rotation speed information is obtained by real-time acquisition of the magnetic levitation rotor from the rotation sensor. The rotor drop trajectory data and the rotation speed information are input into a preset multi-factor coupled drop dynamics model to simulate the drop process of the magnetic levitation rotor, solve the relative sliding speed of the contact point, calculate the normal restoring force using nonlinear Hertzian contact theory, and calculate the frictional heat and radial dimension increment based on the relative sliding speed to update the real-time clearance of the protective bearing in real time. Based on the normal restoring force and the updated real-time clearance, the maximum contact stress, strength safety factor, thermal safety margin index, and material wear volume of the inner ring of the protective bearing are calculated. Based on the strength safety factor, the thermal safety margin index, and the cumulative material wear volume, the survivability of the protective bearing in this round of drops and the remaining number of safe drops are jointly determined.

2. The method according to claim 1, characterized in that, Before the step of acquiring rotor fall trajectory data and rotation speed information in response to a rotor fall event, the method further includes: Using orthogonally arranged displacement data in the first and second directions, a two-dimensional axis trajectory of the magnetically levitated rotor is constructed. The instantaneous composite radial displacement of the magnetically levitated rotor in the drop plane is calculated based on the two-dimensional axis trajectory. The ratio of the instantaneous synthetic radial displacement to the nominal clearance on one side of the protective bearing is calculated as the contact state determination coefficient. When the contact state determination coefficient is greater than or equal to a set value, it is determined that the magnetic levitation rotor and the protective bearing have made mechanical contact, thereby confirming that the rotor drop event has occurred.

3. The method according to claim 1, characterized in that, The at least two sets of displacement sensors include inductive displacement sensors divided into a main measurement group and a redundant measurement group; the rotation sensor is an inductive speed sensor. The method further includes: The position sensor target is manufactured using a silicon steel sheet lamination process, and an insulating layer is used to isolate adjacent silicon steel sheets to block the flow path of induced current in the axial direction of the magnetic levitation rotor. The inductive displacement sensor adopts a differential configuration, with a positive probe and a negative probe arranged in each measurement degree of freedom direction. The real-time inductance of the positive probe and the real-time inductance of the negative probe change in opposite trends with the radial displacement of the magnetic levitation rotor. The detection end face of the inductive speed sensor is directly opposite the eccentric ring structure fixed on the magnetic levitation rotor. The real-time speed of the magnetic levitation rotor is calculated by detecting the frequency of air gap change caused by the rotation of the eccentric ring structure.

4. The method according to claim 1, characterized in that, The displacement sensor includes a main measurement group displacement sensor and a redundant measurement group displacement sensor. The steps for acquiring the rotor drop trajectory data include: Calculate the absolute deviation between the displacement readings of the main measurement group displacement sensors and the displacement readings of the redundant measurement group displacement sensors; When the calculated absolute deviation value is greater than the maximum permissible deviation threshold, check whether the output voltage of the sensor is within the range formed by the lower limit of the effective voltage and the upper limit of the effective voltage. Based on the obtained detection results, a weighted switching coefficient is generated. The displacement readings of the main measurement group displacement sensor and the displacement readings of the redundant measurement group displacement sensor are weighted and calculated using the weighted switching coefficient to obtain the final displacement data. The final displacement data is then used as the rotor drop trajectory data.

5. The method according to claim 1, characterized in that, The multi-factor coupled drop dynamics model is constructed through motion differential equations that include gravity, unbalanced excitation force, and contact reaction force, specifically including: Establish kinematic equations with the geometric center of the protective bearing as the origin of the coordinate system. The kinematic equations describe the translational differential relationships of the magnetically levitated rotor in the horizontal and vertical directions. The calculations are based on the unbalanced excitation force component originating from the mass eccentricity of the magnetically levitated rotor, and the contact reaction force component applied by the protective bearing to the magnetically levitated rotor. The contact reaction force component is composed of the normal restoring force and the tangential friction force, and the tangential friction force is determined based on the normal restoring force and the sliding friction coefficient.

6. The method according to claim 5, characterized in that, The step of calculating the normal restoring force using nonlinear Hertzian contact theory includes: The Hertzian contact stiffness coefficient is determined based on the elastic modulus of the journal material of the magnetic levitation rotor and the inner ring material of the protective bearing. Calculate the radial penetration depth of the journal of the magnetic levitation rotor into the inner ring surface of the protective bearing; The normal restoring force is calculated as the sum of an elastic force term and a damping force term. The elastic force term is proportional to the nonlinear exponent of the radial penetration depth, and the damping force term is proportional to the nonlinear damping coefficient and the instantaneous velocity of the radial penetration depth.

7. The method according to claim 1, characterized in that, The step of calculating frictional heat and radial dimension increment based on the relative sliding speed to update the real-time clearance of the protective bearing includes: Calculate the instantaneous frictional heat power based on the relative sliding speed and the normal restoring force; The radial dimension increment caused by frictional heat was calculated using a thermo-coupling integral relationship. The real-time clearance is obtained by subtracting the radial dimension increment from the initial clearance of the protective bearing.

8. The method according to claim 1, characterized in that, The calculation steps for the maximum contact stress and strength safety factor of the inner ring of the protective bearing include: Extract the maximum instantaneous value of the normal restoring force during the drop process. Based on Hertzian contact theory, and combined with the composite elastic modulus, effective contact length, and equivalent radius of curvature of the inner ring of the protective bearing and the journal of the magnetic levitation rotor, calculate the maximum contact stress borne by the inner ring material of the protective bearing. The yield strength limit of the inner ring material of the protective bearing is compared with the calculated maximum contact stress to generate a strength safety factor characterizing the structural strength.

9. The method according to claim 1, characterized in that, The calculation steps for the thermal safety margin index and the material wear volume caused by this drop include: The instantaneous highest temperature of the contact area is obtained, the difference between the instantaneous highest temperature of the contact area and the ambient temperature is calculated, and the difference between the material failure critical temperature threshold and the ambient temperature is calculated. Based on the ratio of the two differences, a normalized thermal safety margin index is calculated. Based on the Achard wear law, the material wear volume caused by a single drop is calculated using the Achard wear coefficient, the normal restoring force, the relative sliding speed, and the Vickers hardness value of the inner ring material of the protective bearing.

10. The method according to claim 1, characterized in that, The step of jointly determining the survivability of the protective bearing in this round of drops and the remaining number of safe drops based on the strength safety factor, the thermal safety margin index, and the cumulative material wear volume includes: When the strength safety factor is greater than the preset strength threshold and the thermal safety margin index is greater than the preset thermal safety critical value, it is determined that the protective bearing has the ability to survive this round of drop; otherwise, it is determined that a structural collapse or thermal seizure failure has occurred. In addition, the maximum allowable wear volume of the protective bearing is obtained, the material wear volume generated by this drop is accumulated and added to the historical cumulative wear volume, and the remaining number of safe drops is calculated based on the difference between the maximum allowable wear volume and the accumulated wear volume, and the material wear volume representative of a single drop.

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