A method for identifying shafting load fluctuation amplitude based on main engine working status

Abstract

The present invention relates to the field of fluctuation amplitude identification technology, and specifically to a method for identifying the fluctuation amplitude of shaft loads in combination with the main engine operating state, comprising real-time acquisition of dynamic load signals from shaft monitoring points, main engine lubricating oil temperature signals, and main engine speed signals; calculation of a viscosity compensation coefficient based on the main engine lubricating oil temperature signal and main engine speed signal, and compensation of the dynamic load signal for viscosity effects to generate a compensated load signal. The present invention achieves effective correction of additional errors in the dynamic load signal of the shaft system caused by changes in the lubrication state by constructing a viscosity compensation model jointly driven by temperature and speed. The present invention introduces a joint modeling method of strain-load conversion coefficients and temperature compensation terms, and automatically calculates the viscosity compensation coefficient based on the main engine operating conditions. This can significantly improve the physical consistency and data accuracy of the load signal under low-temperature and low-speed conditions, and reduce the problem of load amplitude drift caused by viscosity errors.

Description

Technical Field

[0001] The present invention relates to the technical field of fluctuation amplitude identification, and in particular to a method for identifying the fluctuation amplitude of shafting loads in combination with the working state of a main engine. Background Art

[0002] In large rotating equipment or ship main propulsion systems, shaft load signals are widely used for fault warning, load analysis, and health assessment as important indicators of structural status and operating conditions. However, during cold start-up, low-speed operation, or extreme environmental conditions of the main engine, the lubricating oil temperature is low and the oil viscosity increases significantly, which can easily generate viscous additional loads on key parts such as thrust bearings and couplings. This viscous effect will be superimposed on the actual load signal, introducing non-structural fluctuation components, causing the monitoring system to misjudge, or even mask early weak abnormal characteristics, affecting the accuracy of operational reliability judgment.

[0003] In the existing technology, shaft load signals are usually directly collected for subsequent analysis, without fully considering the coupling relationship between the lubrication status and the main engine operating parameters (such as oil temperature and speed). When the lubricating oil status changes, the signal processing method without viscous error compensation is prone to problems such as zero drift and amplitude amplification, thereby affecting the accuracy of fluctuation identification and trend assessment; in addition, traditional methods are mostly based on fixed models or empirical value processing, and lack dynamic adaptability to different temperature and speed conditions. Therefore, it is urgent to construct a load signal compensation mechanism based on the main engine operating status to achieve effective identification and correction of viscous interference, and improve the accuracy and stability of the load monitoring system under complex working conditions. Summary of the Invention

[0004] Based on the above objectives, the present invention provides a method for identifying the shaft load fluctuation amplitude in combination with the main engine working status, which can integrate working condition perception, dynamic compensation and fluctuation energy ratio judgment to achieve accurate identification and abnormal distinction of the shaft load fluctuation amplitude.

[0005] A method for identifying shaft load fluctuation amplitude in combination with the main engine working state comprises the following steps:

[0006] S1: Real-time acquisition of dynamic load signals of shaft monitoring points, main engine lubricating oil temperature signals, and main engine speed signals;

[0007] S2: Calculating a viscosity compensation coefficient based on the engine lubricating oil temperature signal and the engine speed signal, performing viscosity effect compensation on the dynamic load signal, and generating a compensated load signal.

[0008] Furthermore, the S1 includes:

[0009] S11: The original strain signal is collected by the strain sensor installed at the thrust bearing of the shaft system, and the original strain signal is converted into a dynamic load signal using a dynamic load conversion algorithm;

[0010] S12: The temperature signal is collected by a PT100 temperature sensor immersed in the lubricating oil cavity of the main engine, and a third-order polynomial fitting is used to correct the nonlinear error to obtain a corrected lubricating oil temperature signal;

[0011] S13: The pulse signal is collected by the magnetoelectric speed sensor installed on the flywheel ring gear of the main engine, and the real-time speed is calculated using the period measurement method;

[0012] S14: performing time synchronization processing on the dynamic load signal, lubricating oil temperature signal and real-time rotation speed.

[0013] Furthermore, the S12 includes:

[0014] S121: By immersing the PT100 platinum resistance temperature sensor into the lubricating oil chamber of the host, the resistance value of the sensor is measured in real time to obtain the corresponding raw temperature signal data;

[0015] S122: Based on the pre-completed five-point calibration result, a third-order polynomial fitting model is used to perform nonlinear correction on the original temperature signal data, and a corrected lubricating oil temperature signal is output.

[0016] Furthermore, the S2 includes:

[0017] S21: Calculate the viscosity compensation coefficient based on the oil temperature and engine speed, combined with the temperature characteristics and shear effect of the lubricating oil, and weigh the impact of temperature and speed on the load signal;

[0018] S22: Correcting the original dynamic load signal using the calculated viscosity compensation coefficient to obtain a true load value;

[0019] S23: Determine whether to enable compensation to avoid overcorrection.

[0020] Furthermore, the S21 includes:

[0021] S211: Calculating the influence of the temperature term on the viscosity compensation based on the difference between the current lubricating oil temperature and the standard reference temperature and the characteristic that the lubricating oil viscosity changes with temperature;

[0022] S212: Based on the ratio of the real-time speed of the main engine to the rated speed, the influence of the shear thinning effect on the load is evaluated, and the weighted synthesis is performed with the temperature term to obtain the final viscosity compensation coefficient.

[0023] Furthermore, the S212 includes:

[0024] S2121: Based on the ratio between the current real-time speed of the main engine and the rated speed, the shear state of the oil film is determined, and the influence of the speed on the change of the lubrication resistance is estimated;

[0025] S2122: Perform weighted fusion of the shear thinning effect and the temperature effect on viscosity, and output a viscosity compensation coefficient that is ultimately used to correct the load signal.

[0026] Furthermore, the S23 includes:

[0027] S231: Determine whether the current lubricating oil temperature is lower than a preset temperature threshold, and whether the main engine speed is lower than a preset speed threshold;

[0028] S232: If both conditions are met, the viscous compensation operation is enabled; otherwise, the default coefficient is used and no compensation processing is performed.

[0029] Furthermore, the S231 includes:

[0030] S2311: Determine whether the currently collected lubricating oil temperature is lower than a set temperature threshold, and identify a low-temperature operating condition;

[0031] S2312: Determine whether the current speed of the host is lower than the set speed threshold and identify the sticking risk in the low-speed state.

[0032] Furthermore, the S232 includes:

[0033] S2321: If the oil temperature is lower than the temperature threshold and the speed is lower than the speed threshold, the conditions for enabling viscosity compensation are met;

[0034] S2322: Enable the sticky compensation operation when the conditions are met, otherwise use the default compensation coefficient to maintain the original signal unchanged.

[0035] Beneficial effects of the present invention:

[0036] The present invention realizes effective correction of additional errors in the dynamic load signal of the shaft system caused by changes in the lubrication state by constructing a viscosity compensation model jointly driven by temperature and speed. Compared with the traditional method of directly using the original strain signal, the present invention introduces a joint modeling method of strain-load conversion coefficient and temperature compensation term, and automatically calculates the viscosity compensation coefficient according to the main engine operating conditions. It can significantly improve the physical consistency and data accuracy of the load signal under low temperature and low speed conditions, and reduce the load amplitude drift problem caused by viscosity error.

[0037] The present invention sets dual threshold criteria of temperature and speed to dynamically determine whether to enable compensation operation, while ensuring the compensation effect and avoiding excessive correction under high temperature or stable working conditions, thereby improving the algorithm stability and engineering adaptability. The present invention greatly improves the load error correction rate in the cold start phase and effectively retains the real load change characteristics. It is suitable for the operation monitoring and signal preprocessing of various types of rotating equipment such as ships, compressors, and wind power, and has good versatility and practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 is a flow chart of a method according to an embodiment of the present invention;

[0040] Figure 2 This is a signal acquisition diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0042] It should be noted that, unless otherwise defined, the technical or scientific terms used in the present invention should have the usual meanings understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0043] like Figure 1-Figure 2 As shown, a method for identifying the shaft load fluctuation amplitude in combination with the main engine working state includes the following steps:

[0044] S1: Real-time collection of dynamic load signals of shaft system monitoring points, main engine lubricating oil temperature signals and main engine speed signals.

[0045] S1 specifically includes:

[0046] S11: High-sensitivity strain sensors are placed at the shaft thrust bearing to obtain information on the minute deformation of the bearing structure during actual operation. Since the shaft load will cause structural strain, this strain value can be used to indirectly estimate the load size. To improve the accuracy of load estimation, a temperature compensation mechanism is introduced and a dynamic load conversion model is constructed, which is expressed as:

[0047] ;

[0048] in, The dynamic load value of the shaft system indicates the instantaneous magnitude of the actual force on the shaft system and reflects the actual load-bearing condition of the shaft system during operation. It is the core object of structural health diagnosis and load fluctuation analysis. Realize the linear mapping of strain signal and load, the second Used to correct zero drift errors caused by changes in environment or lubricating oil temperature, thereby ensuring the consistency and reliability of load data under different thermal states. It is the dynamic load value, which indicates the instantaneous magnitude of the actual force on the shaft system. The strain-load conversion factor is used to convert the strain value into an equivalent load value. The value range is 0.85-1.25. It is obtained through static load test calibration and is related to the sensor type, installation position, and structural stiffness. The range covers common thrust bearing configurations. is the measured microstrain value, which is the original signal output by the strain sensor and has a value range of , set the sensor range according to the actual load conditions of the shaft system, is the temperature compensation coefficient, which is used to offset the zero drift of the strain signal caused by temperature changes. The value range is , obtained through hot box calibration experiments, negative values ​​indicate that the signal is smaller due to temperature increase, and the value is related to the thermal expansion characteristics of the material. It is the difference between the real-time oil temperature and the calibration temperature, and its value range is The calibration temperature is generally selected at 25°C. Considering the possible ambient temperature range during actual operation (such as -15°C to 65°C), the upper and lower limits are set to ±40°C.

[0049] S12: Accurately obtaining the lubricating oil temperature of the main engine is crucial for the subsequent modeling of the viscous effect. An immersed PT100 platinum resistance temperature sensor is used to obtain the sensor resistance value in real time inside the oil cavity. Considering the extreme temperature areas (especially The following) has a significant nonlinear response, so a third-order polynomial fitting model is used to correct the nonlinear error, which is expressed as:

[0050] ;

[0051] in, is the lubricating oil temperature value after correction, the value range is , covering the lubricating oil temperature range of typical marine engines in extremely cold and high-load operating environments, is the resistance value of the PT100 temperature sensor, ranging from 80 to 250, and the fitting coefficients The oil temperature is measured with high accuracy in the whole working range through the five-point calibration method. is the fitting coefficient of the cubic term of resistance, The level is obtained by five-point calibration regression, which depicts the curvature change of the strongest interval (low temperature section) of PT100 nonlinear response. is the fitting coefficient of the resistance quadratic term, and its value range is , represents the mid-order rate of change in nonlinear correction, and its value is related to the distribution of calibration points. It is the fitting coefficient of the first-order resistance term, with a value range of 2.0-2.5, close to the leading term of the linear part, and consistent with the linear slope of PT100 at normal temperature. is a constant term used for overall translation correction, and its value range is , reflects the baseline offset between the starting resistance and the actual temperature, and compensates for the overall drift error of the curve. Its value is related to the zero-point resistance of the sensor and the calibration temperature.

[0052] S13: Speed ​​is an important parameter to characterize the operating status of the main engine and has a direct impact on the frequency distribution of shaft load fluctuations. A magnetoelectric speed sensor installed on the main engine flywheel ring gear is used to record the periodic pulse signal generated by the gear rotation. In order to suppress the measurement error caused by transient disturbances, a periodic measurement method is used to record the periodic pulse signal generated by the gear rotation. Continuous pulse time period The average speed is calculated as follows:

[0053] ;

[0054] in, The real-time speed (i.e., the main engine flywheel speed per minute) is an important operating parameter that characterizes the main engine's working state. It directly affects the shafting load fluctuation frequency distribution and dynamic response accuracy. It is usually matched with the diesel main engine's workload and speed, and its value range is 50-1200. The number of teeth on the flywheel ring gear is determined by the host model and the ring gear structure. The value range is 90-180. More teeth means higher pulse resolution, which helps to improve the speed accuracy at low speed. It is preset on different host models and is not a dynamically changing parameter during operation. is continuous The total time length of a pulse signal, ranging from 0.01 to 1.2, is derived from the actual sampling period and must ensure coverage. A complete pulse cycle to avoid errors caused by incomplete pulses. The pulse counting base (the number of selected continuous pulses) indicates the number of continuous pulses used for averaging. It is an important parameter for controlling sampling stability and response speed. The commonly used values ​​are 32 or 64. In low-speed operation scenarios, in order to enhance anti-jitter capability, The value is 64. In scenarios with high speed or real-time requirements, The value is 32 to improve the response speed. It can significantly reduce the instantaneous speed error caused by periodic jitter and is suitable for slow-changing scenarios with shaft system fluctuation frequency below 0.1Hz.

[0055] S14: To ensure that data from different sensors (strain, temperature, and speed) can be collaboratively used for viscosity compensation and spectrum analysis, the three signals are time-aligned with high precision to control the sampling time error within ±1ms, thereby eliminating the interference of asynchronous sampling on the identification of load fluctuation amplitude and ensuring the consistency and timeliness of signal fusion analysis.

[0056] S2: Calculate the viscosity compensation coefficient based on the host lubricating oil temperature signal and the host speed signal, perform viscosity effect compensation on the dynamic load signal, and generate a compensated load signal.

[0057] S2 specifically includes:

[0058] S21: In order to correct the influence of lubricating oil on shaft load measurement under different temperature and speed conditions, a viscosity compensation coefficient model is introduced. The viscosity compensation coefficient model comprehensively considers the exponential effect of oil temperature on lubricating oil viscosity and the linear effect of speed on oil film shear thinning effect. The viscosity compensation coefficient is calculated by taking oil temperature and speed as input variables, and is expressed as:

[0059] ;

[0060] in, Is the viscosity compensation coefficient, which is used to correct the effect of lubricating oil on shaft load measurement at different temperatures and speeds. is the weight factor, satisfying , used to adjust the influence weights of temperature and speed terms, is the temperature term weight factor, with a value range of 0.6-0.8. The influence of temperature on lubricating oil viscosity is much greater than that of speed. Therefore, under most working conditions, the temperature term weight is greater than the speed term. In extremely cold environments, a drop in oil temperature will cause a sharp increase in viscosity. If no weighted compensation is applied, the bearing force will be seriously misjudged. is the speed item weight factor, with a value range of 0.2-0.4. At low speeds, the oil film shear effect weakens, the fluidity of the lubricating layer decreases, and the viscosity effect increases. Therefore, appropriate compensation weight should be given, but its influence is still second only to the temperature item. Viscosity-temperature coefficient, determined through lubricating oil characteristic test, is used to characterize the sensitivity of oil viscosity to temperature changes, with a value range of 0.028-0.035. The larger the value, the more sensitive the viscosity is to temperature. Reference temperature, fixed to the standard operating temperature of lubricating oil , is the real-time speed, The rated speed of the host is determined according to the host model and the value range is 500-1000;

[0061] S22: Obtaining the viscosity compensation coefficient Finally, in order to eliminate the viscosity error caused by the decrease in oil temperature or low speed, it is introduced into the original load signal for correction. The correction idea is to scale the load signal proportionally to restore its stress response performance under standard working conditions. The compensated load signal is expressed as:

[0062] ;

[0063] in, is the original dynamic load value, The compensated load value is used for subsequent fluctuation amplitude identification and abnormality judgment, which can better reflect the actual force characteristics of the bearing and facilitate fault diagnosis and trend analysis. Viscosity compensation coefficient, used to correct the effect of lubricating oil on shaft load measurement at different temperatures and speeds;

[0064] S23: To avoid the risk of miscompensation caused by unnecessary signal correction, a sticky compensation activation judgment mechanism is introduced. The sticky compensation calculation process is executed only when two conditions are met simultaneously. Specifically, the following are the conditions:

[0065] (1) The current oil temperature is lower than 0, indicating that the lubricating oil viscosity is in a high-risk range;

[0066] Here, 0 is the preset temperature threshold, which is the typical critical point at which lubricants enter the high-viscosity nonlinear change region. Most industrial lubricants experience a sharp increase in viscosity and a significant decrease in fluidity below 0°C, which can easily cause viscous drift errors in the load sensing signal. Below 0°C, the uncompensated load signal error can reach over 10%, while above 0°C, the error is significantly reduced. Therefore, selecting 0°C as the temperature trigger condition can effectively identify the risk of viscous distortion and ensure the necessity and stability of compensation.

[0067] (2) The current main engine speed is less than 30% of the rated speed, indicating insufficient shear thinning effect;

[0068] Among them, 30% of the rated speed is the preset speed threshold. When the main engine speed is lower than 30% of the rated speed, the oil film shear rate is insufficient and the lubricating oil thinning effect is significantly weakened, causing it to maintain a high viscosity state. At this time, the oil film resistance between the bearings increases, making it easier to introduce viscous pseudo-fluctuations in the load signal. Setting it to 30% of the rated speed is widely used in low-speed working condition identification. It is an engineering experience boundary point for distinguishing normal operation from potential viscous interference. It can ensure sensitivity while avoiding false triggering at high speeds.

[0069] If any of the conditions is not met, it is considered that the working condition has little influence on the viscosity error, and the default is , no compensation processing is performed, thus ensuring that the system strikes a balance between efficiency and accuracy.

[0070] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A method for identifying shaft load fluctuation amplitude in combination with the main engine working status, characterized in that: The following steps are involved: S1: Real-time acquisition of dynamic load signals of shaft monitoring points, main engine lubricating oil temperature signals, and main engine speed signals; S2: calculating a viscosity compensation coefficient based on the engine lubricating oil temperature signal and the engine speed signal, performing viscosity effect compensation on the dynamic load signal, and generating a compensated load signal; The S2 includes: S21: Calculate the viscosity compensation coefficient based on the oil temperature and engine speed, combined with the temperature characteristics and shear effect of the lubricating oil, and weigh the impact of temperature and speed on the load signal; S22: Correcting the original dynamic load signal using the calculated viscosity compensation coefficient to obtain a true load value; S23: Determine whether to enable compensation to avoid overcorrection; The S23 includes: S231: Determine whether the current lubricating oil temperature is lower than a preset temperature threshold, and whether the main engine speed is lower than a preset speed threshold; S232: If both conditions are met, the viscous compensation operation is enabled; otherwise, the default coefficient is used and no compensation processing is performed.

2. The method for identifying shaft load fluctuation amplitude in combination with the main engine working state according to claim 1, characterized in that: Said S1 comprises: S11: The original strain signal is collected by the strain sensor installed at the thrust bearing of the shaft system, and the original strain signal is converted into a dynamic load signal using a dynamic load conversion algorithm; S12: The temperature signal is collected by a PT100 temperature sensor immersed in the lubricating oil cavity of the main engine, and a third-order polynomial fitting is used to correct the nonlinear error to obtain a corrected lubricating oil temperature signal; S13: The pulse signal is collected by the magnetoelectric speed sensor installed on the flywheel ring gear of the main engine, and the real-time speed is calculated using the period measurement method; S14: performing time synchronization processing on the dynamic load signal, lubricating oil temperature signal and real-time rotation speed.

3. The method for identifying shaft load fluctuation amplitude in combination with the main engine working state according to claim 2, characterized in that: The S12 includes: S121: By immersing the PT100 platinum resistance temperature sensor into the lubricating oil chamber of the host, the resistance value of the sensor is measured in real time to obtain the corresponding raw temperature signal data; S122: Based on the pre-completed five-point calibration result, a third-order polynomial fitting model is used to perform nonlinear correction on the original temperature signal data, and a corrected lubricating oil temperature signal is output.

4. The method for identifying shaft load fluctuation amplitude in combination with the main engine working state according to claim 1, characterized in that: The S21 includes: S211: Calculating the influence of the temperature term on the viscosity compensation based on the difference between the current lubricating oil temperature and the standard reference temperature and the characteristic that the lubricating oil viscosity changes with temperature; S212: Based on the ratio of the real-time speed of the main engine to the rated speed, the influence of the shear thinning effect on the load is evaluated, and the weighted synthesis is performed with the temperature term to obtain the final viscosity compensation coefficient.

5. The method for identifying shaft load fluctuation amplitude in combination with the main engine working state according to claim 4 is characterized in that: The S212 includes: S2121: Based on the ratio between the current real-time speed of the main engine and the rated speed, the shear state of the oil film is determined, and the influence of the speed on the change of the lubrication resistance is estimated; S2122: Perform weighted fusion of the shear thinning effect and the temperature effect on viscosity, and output a viscosity compensation coefficient that is ultimately used to correct the load signal.

6. The method for identifying shaft load fluctuation amplitude in combination with the main engine working status according to claim 1 is characterized in that: The S231 includes: S2311: Determine whether the currently collected lubricating oil temperature is lower than a set temperature threshold, and identify a low-temperature operating condition; S2312: Determine whether the current speed of the host is lower than the set speed threshold and identify the sticking risk in the low-speed state.

7. The method for identifying shaft load fluctuation amplitude in combination with the main engine working state according to claim 6, characterized in that: The S232 includes: S2321: If the oil temperature is lower than the temperature threshold and the speed is lower than the speed threshold, the conditions for enabling viscosity compensation are met; S2322: Enable the sticky compensation operation when the conditions are met, otherwise use the default compensation coefficient to maintain the original signal unchanged.

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