Error elimination method and system for torsional vibration signals of low-speed diesel engine
By obtaining the torsional vibration damping effect and its own characteristics of the torsional vibration damper, hardware elimination and signal extraction analysis methods are used to solve the problem of torsional vibration signal measurement error of low-speed diesel engines, achieving high-precision torsional vibration monitoring and diagnosis, and enhancing the safety and reliability of the diesel engine.
Patent Information
- Application Number
- CN202411463987.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-21
- Publication Date
- 2025-03-04
AI Technical Summary
The prior art is difficult to accurately measure and eliminate errors in the torsional vibration signals of low-speed diesel engines, resulting in inaccuracy in torsional vibration monitoring and diagnosis.
By obtaining the torsional vibration damping effect and its own characteristics of the torsional vibration damper, hardware elimination and signal extraction analysis methods are used to improve the accuracy of torsional vibration signal acquisition, and comprehensive monitoring and diagnosis are carried out in combination with the torsional vibration damper's vibration damper's vibration damper's vibration damper's vibration damper's vibration damper's vibration damper's vibration damper's vibration damper's vibration damper's vibration damper's vibration damper's vibration damper's vibration damper's vibration damper's vibration damper's vibration damper's vibration damper is used for comprehensive monitoring and diagnosis.
It improves the accuracy of torsional vibration signal acquisition, reduces errors, and realizes accurate monitoring and diagnosis of torsional vibration of low-speed diesel engines, enhancing the safety and reliability of diesel engine shaft system operation.
Smart Images
Figure CN119555376A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of torsional vibration signal error elimination, and in particular relates to a method and system for eliminating errors in torsional vibration signals of a low-speed diesel engine. Background Art
[0002] As the "power heart" of the entire ship, the reliability of the diesel engine is directly related to the navigation performance and safety of the ship. The crankshaft torsional vibration generated by the ship's diesel engine will, on the one hand, cause additional stress on the crankshaft and its related moving parts, whose value often exceeds the working stress by several times, and have an adverse effect on the accessory shaft system. On the other hand, it will cause torsional vibration of the ship's propulsion shaft system, thereby stimulating the longitudinal vibration of the shaft system and affecting the safety of the ship's power unit. With the continuous increase in the power of ship diesel engines, malignant failures such as crankshaft fractures caused by severe torsional vibration occur from time to time, and torsional vibration has become one of the important causes of failure of ship diesel engine power systems.
[0003] Torsional vibration measurement is one of the important inspection items for ship diesel engine inspection. It can not only determine whether the torsional vibration characteristics of new models meet the specified standards during trial production and improvement, whether the resonance frequency is appropriate, whether the amplitude, torque and torsional stress exceed the allowable value, but also check whether there are defects in each process and each component during processing and assembly. In order to make a correct evaluation of the torsional vibration of the shaft system and avoid the occurrence of torsional vibration damage accidents of the diesel engine shaft system, not only detailed torsional vibration calculations should be carried out in the design stage, but also torsional vibration tests of ship diesel engines are required. Theoretical analysis and calculation results must be tested by actual tests. If the two are inconsistent, the theoretical calculation conclusions must be corrected by actual measured results. This has been clearly stipulated in the ship regulations of various countries: "The review of torsional vibration characteristics includes theoretical calculations and actual measured results. If the two are different, the actual measured results shall prevail." Torsional vibration dampers are important components for controlling the torsional vibration of diesel engine crankshafts and ensuring the safe operation of shaft systems. Marine low-speed diesel engines usually use leaf spring torsional vibration dampers due to their high power, heavy load, low speed and small range. They can not only adjust the natural frequency of the shaft system, but also reduce the torsional vibration stress and amplitude, narrow the speed restricted area, and ensure the safe and reliable operation of the ship under various working conditions. The monitoring and diagnosis module of the torsional vibration damper of the low-speed diesel engine protects the damper itself on the one hand, and monitors the torsional vibration of the shaft system in real time on the other hand, to protect the safety of the crankshaft and shaft system accessories. Summary of the invention
[0004] The embodiment of the present invention provides a method and system for eliminating errors in torsional vibration signals of a low-speed diesel engine, which can improve the accuracy of torsional vibration signal acquisition by obtaining the torsional vibration reduction effect of a torsional vibration damper and the characteristics of the torsional vibration damper itself, using methods such as hardware elimination and signal extraction and analysis, and performing comprehensive monitoring and diagnosis in combination with the torsional vibration reduction effect of the torsional vibration damper and the characteristics of the torsional vibration damper itself.
[0005] In one embodiment of the present invention, a method for eliminating errors in torsional vibration signals of a low-speed diesel engine is provided, the method comprising: S101, when the sensor support of the torsional vibration sensor of the low-speed diesel engine vibrates, the torsional vibration sensor deviates from its original installation position, and its relative position with the speed measuring gear changes, the support vibration signal of the torsional vibration sensor and the torsional vibration signal are amplitude modulated on the pulse train and the rectangular wave frequency modulated; S102, calculating the outer envelope of the original signal of the torsional vibration sensor of the low-speed diesel engine, and obtaining its analytical signal z(t) by Hilbert transforming the original signal x(t) of the torsional vibration sensor: z(t)=x(t)+j
[0006] in, is the Hilbert transform of x(t); Then, the model of the analytical signal , which is the envelope of the analytical signal; S103, performing low-pass filtering on the envelope of the analytical signal of the torsional vibration sensor based on a low-pass filter, and calculating a vibration trend item T(t) of a sensor support of the torsional vibration sensor; S104, using the original signal x(t) of the torsional vibration sensor, removing the support vibration trend term T(t) that envelops the torsional vibration sensor, and obtaining the angular velocity signal of the torsional vibration sensor ,Right now .
[0007] Furthermore, the method comprises: Two magnetoelectric speed sensors are installed on the outer ring of the torsional vibration damper at 180 degrees relative to each other, and the two magnetoelectric speed sensors at 180 degrees relative to each other have opposite frequency modulation responses to the bending vibration of the low-speed diesel engine, thereby eliminating the influence of the bending vibration of the low-speed diesel engine; A photoelectric encoder is arranged on the inner ring of the torsional vibration damper, and the synthesized signals of the dual speed sensors of the inner ring and outer ring of the torsional vibration damper are fused and corrected to improve the torsional vibration signal acquisition accuracy of the low-speed diesel engine.
[0008] Further, the method includes: using a period averaging method; For a working cycle of a low-speed diesel engine, take the data of M cycles and average them to get the instantaneous speed after the whole cycle average. ,
[0009] in, , N is the number of teeth on the gear.
[0010] Further, the method includes: using a tooth averaging method; The original signal collected by the magnetoelectric sensor is in positive and negative half cycles, corresponding to the reduction and increase of magnetic resistance, that is, the magnetoelectric signal corresponding to the tooth top and tooth root of the gear; The calculation cycle is the time it takes for the diesel engine crankshaft to rotate one index. Calculation based on uniform gear indexing will produce periodic errors. The error can be reduced by gear averaging, that is,
[0011] , N is the number of teeth interval calculated by average tooth number. When m is taken, the calculated number of teeth interval should not be a divisor of the total number of teeth as much as possible.
[0012] Furthermore, the method comprises: Among the various harmonic amplitudes of the torsional vibration of a low-speed diesel engine, the amplitude and phase characteristics of the 0.5 harmonic torsional vibration are most sensitive to the working state of each cylinder, and the quantitative analysis is accurate, which is suitable for monitoring and diagnosis of each cylinder of the diesel engine. The 0.5 harmonic torsional amplitude value in the normal state is taken as the characteristic threshold. If it is greater than the characteristic threshold, the operation of each cylinder of the diesel engine will increase unevenly, and the possibility of failure will increase. The oil temperature and oil pressure information of the torsional vibration damper is obtained in real time through the oil temperature and oil pressure sensors. Combined with the torsional vibration monitoring signal, multi-source data fusion technology is used to diagnose the state of the torsional vibration damper in real time.
[0013] Furthermore, the method comprises: If the low-speed diesel engine has no torsional vibration, the instantaneous speed of its shaft system is equal to its average speed, the shaft rotates at a constant speed, the angles rotated by the shaft in equal time are equal, and the time required for each gear to rotate is equal, that is, the period of the pulse signal is equal; When the low-speed diesel engine shaft system undergoes torsional vibration, when the two motion vectors of rotational motion and torsional vibration are in the same direction, the instantaneous angular velocity increases, and the pulse period formed by the gear teeth passing through the sensor measuring point position decreases; conversely, the instantaneous angular velocity component decreases, and the pulse period formed by the gear teeth passing through the sensor measuring point position increases.
[0014] Furthermore, the method comprises: Perform equally spaced polynomial interpolation on the data between two points on the left and right of the zero-crossing moment, or perform equally spaced polynomial interpolation on the entire original data.
[0015] Furthermore, the method comprises: According to the original data, the moment when the rising edge crosses zero is taken, and the position where the signal "-" and "+" change is determined. K data acquisition points are taken before and after this position, and the interpolation function is constructed with 2k points. Interpolation processing is performed at equal intervals between ti and ti+1. The zero-crossing moment is searched for the interpolated data, that is, the two points where "-" and "+" change, and the two-point interpolation method is used to obtain the precise zero-crossing moment.
[0016] In another embodiment of the present invention, a system for eliminating the error of a torsional vibration signal of a low-speed diesel engine is provided, based on a method for eliminating the error of a torsional vibration signal of a low-speed diesel engine as described in any one of the above items, comprising: a frequency modulation processing module, a first processing module, a second processing module and an output module; The frequency modulation processing module is used for the amplitude modulation of the pulse train and the frequency modulation of the rectangular wave of the support vibration signal and the torsional vibration signal of the torsional vibration sensor of the low-speed diesel engine when the sensor support of the torsional vibration sensor vibrates, the torsional vibration sensor deviates from its original installation position, and the relative position between the torsional vibration sensor and the speed measuring gear changes; The first processing module is used to calculate the outer envelope of the original signal of the torsional vibration sensor of the low-speed diesel engine, and obtain its analytical signal z(t) by Hilbert transforming the original signal x(t) of the torsional vibration sensor: z(t)=x(t)+j
[0017] in, is the Hilbert transform of x(t); Then, the model of the analytical signal , which is the envelope of the analytical signal; The second processing module performs low-pass filtering on the envelope of the analytical signal of the torsional vibration sensor based on a low-pass filter to calculate the vibration trend item T(t) of the sensor support of the torsional vibration sensor; The output module uses the original signal x(t) of the torsional vibration sensor to envelop the support vibration trend term T(t) of the torsional vibration sensor to obtain the angular velocity signal of the torsional vibration sensor. ,Right now .
[0018] The beneficial effects brought by the present invention are as follows: It can be seen from the above scheme that the embodiment of the present invention provides a method and system for eliminating the error of the torsional vibration signal of a low-speed diesel engine. When the sensor support of the torsional vibration sensor vibrates, the torsional vibration sensor deviates from its original installation position, and the support vibration signal and the amplitude modulation of the pulse string and the frequency modulation of the rectangular wave by the torsional vibration signal are determined; the outer envelope of the original signal of the torsional vibration sensor is calculated, and the original signal is transformed to obtain an analytical signal; the envelope of the analytical signal of the torsional vibration sensor is low-pass filtered based on a low-pass filter, and the vibration trend term of the sensor support is calculated. The original signal of the torsional vibration sensor is used to remove the enveloped support vibration trend term to obtain the angular velocity signal of the torsional vibration sensor. The technical scheme of the present invention improves the torsional vibration signal acquisition accuracy by obtaining the torsional vibration damping effect of the torsional vibration damper and the characteristics of the torsional vibration damper itself, and adopts methods such as hardware elimination and signal extraction analysis, and performs comprehensive monitoring and diagnosis in combination with the vibration damping effect of the torsional vibration damper and the characteristics of the torsional vibration damper itself. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 A flow chart showing a method for eliminating errors in torsional vibration signals of a low-speed diesel engine according to an embodiment of the present invention; Figure 2 A diagram showing the position correspondence between a torsional vibration sensor support and a gear in a method for eliminating errors in torsional vibration signals of a low-speed diesel engine according to an embodiment of the present invention; Figure 3 A schematic diagram showing the torsional vibration monitoring principle of a method for eliminating errors in torsional vibration signals of a low-speed diesel engine according to an embodiment of the present invention; Figure 4 A schematic diagram of torsional vibration signal analysis and extraction showing a method for eliminating errors in torsional vibration signals of a low-speed diesel engine according to an embodiment of the present invention. DETAILED DESCRIPTION
[0020] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0021] In order to improve the accuracy of torsional vibration signal acquisition of low-speed machines and eliminate errors, this solution is improved from two aspects: hardware and data processing. In terms of hardware, a three-sensor mode is used to perform signal fusion correction to eliminate errors caused by bending moments. In terms of data processing, the vibration interference of the sensor mounting base is eliminated by calculating the envelope of the original signal; the sampling rate is doubled under the same conditions through the half-pulse period calculation method to improve the acquisition accuracy; the processing accuracy of the zero-crossing moment is improved through the polynomial linear interpolation method; the double averaging method is used to achieve a balance between efficiency and accuracy without significantly increasing the amount of calculation.
[0022] like Figure 1 and Figure 2 As shown, Figure 1 A flow chart showing a method for eliminating errors in a torsional vibration signal of a low-speed diesel engine according to an embodiment of the present invention is shown. Figure 2 A diagram showing the position correspondence between a torsional vibration sensor support and a gear in a method for eliminating errors in a torsional vibration signal of a low-speed diesel engine according to an embodiment of the present invention.
[0023] Figure 1 A method for eliminating errors in torsional vibration signals of a low-speed diesel engine is provided, the method comprising: S101. When the sensor support of the torsional vibration sensor of the low-speed diesel engine vibrates, the torsional vibration sensor deviates from its original installation position, and its relative position with the speed measuring gear changes. The support vibration signal of the torsional vibration sensor and the torsional vibration signal are amplitude modulated on the pulse string and frequency modulated on the rectangular wave.
[0024] In the embodiment of the present invention, in order to obtain an accurate torsional vibration signal, it is crucial to ensure the accuracy of the continuous time-series pulse train. In the process of using a sensor to obtain a pulse train from a speed measuring gear, the vibration of the sensor mounting seat is very likely to cause angular displacement of the shaft system, which is reflected in the monitoring signal as disturbance to the amplitude of the original signal output by the sensor and the frequency of the rectangular wave signal.
[0025] Figure 2 In the example, when the sensor support vibrates, the sensor will leave the original installation position, and its relative position with the speed gear will also change. As shown in the figure below, the change in the distance between the sensor and the speed gear can be approximately regarded as the projection of the sensor displacement AA' on the y-axis. This change will affect the amplitude of the sensor output signal, and the x-axis component of the above displacement will affect the frequency of the signal. Therefore, the vibration of the sensor support will definitely affect the accuracy of the output signal and thus have an adverse effect on the measurement of torsional vibration.
[0026] By modulating the pulse train amplitude and the rectangular wave frequency of the sensor support vibration signal and the torsional vibration signal, the signal form shown in the figure below is obtained. From the original waveform of the sensor, it can be seen that the vibration of the sensor support only modulates the original signal, and the original frequency of the carrier signal does not change. However, since the comparison threshold voltage remains unchanged, the frequency of the square wave pulse formed after conditioning is modulated, and direct torsional vibration measurement will measure a pseudo torsional vibration signal.
[0027] S102, calculating the outer envelope of the original signal of the torsional vibration sensor of the low-speed diesel engine, and obtaining its analytical signal z(t) by Hilbert transforming the original signal x(t) of the torsional vibration sensor: z(t)=x(t)+j
[0028] in, is the Hilbert transform of x(t); Then, the model of the analytical signal , which is the envelope of the analytical signal; S103, performing low-pass filtering on the envelope of the analytical signal of the torsional vibration sensor based on a low-pass filter, and calculating a vibration trend item T(t) of a sensor support of the torsional vibration sensor; S104, using the original signal x(t) of the torsional vibration sensor, removing the support vibration trend term T(t) that envelops the torsional vibration sensor, and obtaining the angular velocity signal of the torsional vibration sensor ,Right now .
[0029] In one embodiment of the present invention, the method comprises: Two magnetoelectric speed sensors are installed on the outer ring of the torsional vibration damper at 180 degrees relative to each other, and the two magnetoelectric speed sensors at 180 degrees relative to each other have opposite frequency modulation responses to the bending vibration of the low-speed diesel engine, thereby eliminating the influence of the bending vibration of the low-speed diesel engine; A photoelectric encoder is arranged on the inner ring of the torsional vibration damper, and the synthesized signals of the dual speed sensors of the inner ring and outer ring of the torsional vibration damper are fused and corrected to improve the torsional vibration signal acquisition accuracy of the low-speed diesel engine.
[0030] In the embodiment of the present invention, in order to eliminate the influence of the bending vibration of the rotating shaft, two magnetoelectric speed sensors with a relative angle of 180 degrees are installed on the outer ring of the torsional vibration damper. The bending vibration caused by mass imbalance can be decomposed into two directions, vertical and horizontal. The bending vibration in the horizontal direction has no effect on the modulation signal of the sensor, while the bending vibration in the vertical direction will cause the instantaneous linear velocity of the gear close to the sensor to be superimposed with an additional component formed by the vibration, affecting the frequency modulation signal of the sensor. The dual sensors facing each other at 180 degrees have opposite frequency modulation responses to the bending vibration. The signals of the dual sensors are synthesized to eliminate the influence of the bending vibration. At the same time, a photoelectric encoder is installed on the inner ring, and the synthesized signal of the dual speed sensors on the outer ring is fused and corrected. Combining the high-precision and high-resolution characteristics of the photoelectric encoder and the function of eliminating bending vibration of the dual magnetoelectric speed sensors, the accuracy of torsional vibration signal acquisition is improved from the sensor source.
[0031] In one embodiment of the present invention, the running state of the diesel engine often changes due to speed regulation, load changes, its own structural characteristics and other interferences. The instantaneous speed measured under the same working condition will also be distorted. In order to reduce errors, it is necessary to identify and eliminate them. Since external interference is discontinuous and random, and the influence of the diesel engine and its shaft system on the instantaneous speed within a certain period of time is continuous and periodic, the instantaneous speed fluctuation caused by external interference is suppressed by periodic averaging. The periodic averaging method is adopted, including: For a working cycle of a low-speed diesel engine, take the data of M cycles and average them to get the instantaneous speed after the whole cycle average. ,
[0032] in, , N is the number of teeth on the gear.
[0033] Taking a diesel engine as an example, the speed is 1000r / min, and the instantaneous speed is obtained under no-load conditions. After four periodic averaging, it can be concluded that after periodic averaging, the curve of the instantaneous speed becomes smooth.
[0034] The selection of the cycle and the averaging method in the cycle averaging have a great influence on the monitoring accuracy of the torsional vibration signal. In order to improve the measurement accuracy, a longer measurement cycle should be selected as much as possible so that the torsional vibration signal can be averaged over a longer period of time. However, a measurement cycle that is too long will increase the amount of calculation of the algorithm, and a trade-off needs to be made between accuracy and efficiency. The object of this technical solution is a four-stroke diesel engine. The crankshaft rotates twice in each working cycle. Based on the computing characteristics of the FPGA chip, a double averaging method is adopted without significantly increasing the amount of calculation. That is, the crankshaft is averaged every time it rotates one circle, and then averaged again in each working cycle to achieve a balance between accuracy and efficiency.
[0035] In yet another embodiment of the present invention, the method comprises: using a tooth averaging method; According to the calculation principle of instantaneous speed, the smaller the gear indexing, the more accurate the instantaneous speed and the more accurate the torsional vibration calculation result. Since there is a processing error in gear indexing, increasing the indexing introduces a larger processing error. It does not mean that the more gear indexing, the more accurate the torsional vibration measurement result.
[0036] The original signal collected by the magnetoelectric sensor is in positive and negative half cycles, corresponding to the reduction and increase of magnetic resistance, that is, the magnetoelectric signal corresponding to the tooth top and tooth root of the gear; The calculation cycle is the time it takes for the diesel engine crankshaft to rotate one index. Calculation based on uniform gear indexing will produce periodic errors. The error can be reduced by gear averaging, that is,
[0037] , N is the number of teeth of the gear, m is the average calculated number of teeth intervals, when m is taken, the calculated number of teeth intervals should try not to select divisors of the total number of teeth.
[0038] As you can see, The larger the value, the smaller the error caused by gear indexing will be, but there is also a limit to the tooth averaging process. If the value is too large, the calculation interval will increase, but the instantaneous speed will lose its "instantaneous" meaning. In order to ensure the appropriate calculation arc interval angle, the determination of the average tooth length (i.e. calculation interval) must also consider the total number of teeth in the gear ring. When calculating the value, the calculated interval teeth number should try not to select the divisor of the total number of teeth, so as to avoid the calculation of the fixed combination of teeth number.
[0039] Taking a diesel engine as an example, the speed is 1100r / min. The instantaneous speed before tooth averaging is obtained under no-load conditions. After the instantaneous speed of the four-time tooth average is tooth averaged, the burrs on the instantaneous speed curve become less, and the high-frequency fluctuations are significantly improved.
[0040] In another embodiment of the present invention, the method comprises: Among the various harmonic amplitudes of the torsional vibration of a low-speed diesel engine, the amplitude and phase characteristics of the 0.5 harmonic torsional vibration are most sensitive to the working state of each cylinder, and the quantitative analysis is accurate, which is suitable for monitoring and diagnosis of each cylinder of the diesel engine. The 0.5 harmonic torsional amplitude value in the normal state is taken as the characteristic threshold. If it is greater than the characteristic threshold, the operation of each cylinder of the diesel engine will increase unevenly, and the possibility of failure will increase. The oil temperature and oil pressure information of the torsional vibration damper is obtained in real time through the oil temperature and oil pressure sensors. Combined with the torsional vibration monitoring signal, multi-source data fusion technology is used to diagnose the state of the torsional vibration damper in real time.
[0041] In another embodiment of the present invention, the method comprises: If the low-speed diesel engine has no torsional vibration, the instantaneous speed of its shaft system is equal to its average speed, the shaft rotates at a constant speed, the angles rotated by the shaft in equal time are equal, and the time required for each gear to rotate is equal, that is, the period of the pulse signal is equal; When the low-speed diesel engine shaft system undergoes torsional vibration, when the two motion vectors of rotational motion and torsional vibration are in the same direction, the instantaneous angular velocity increases, and the pulse period formed by the gear teeth passing through the sensor measuring point position decreases; conversely, the instantaneous angular velocity component decreases, and the pulse period formed by the gear teeth passing through the sensor measuring point position increases.
[0042] The main advantage of the half-pulse period calculation of torsional vibration proposed in the technical solution of the present invention is that: using the same sensor system, when the number of speed pulse periods per unit time is equal, the torsion angle analysis dimension of this method is twice that of the traditional method, and the torsion angle sampling rate is doubled.
[0043] In another embodiment of the present invention, the method comprises: Perform equally spaced polynomial interpolation on the data between two points on the left and right of the zero-crossing moment, or perform equally spaced polynomial interpolation on the entire original data.
[0044] Accurate torsional vibration measurement results depend on accurate instantaneous rotation speed of the shaft system and accurate zero-crossing moment of the original signal. Accurate instantaneous rotation speed of the shaft system eliminates the influence of bending vibration of the shaft by collecting the sensing unit. In order to determine the precise zero-crossing moment, two methods can be used to interpolate the original data. One is to perform equally spaced polynomial interpolation on the entire original data; the other is to perform equally spaced polynomial interpolation on the data between two points on the left and right of the zero-crossing moment. Comparing the two methods, the amount of data calculation of the second method is much smaller than that of the first method. If interpolation is performed between all points, the amount of data calculation is very large, and the maximum number of interpolation polynomials can reach more than hundreds of thousands times, and it will be affected by the distorted points in the signal. Therefore, this technical solution adopts the second method for polynomial interpolation. In order to increase the interpolation speed, only a limited number of points near the zero point are taken to construct the interpolation function.
[0045] In another embodiment of the present invention, the method comprises: According to the original data, the moment when the rising edge crosses zero is taken, and the position where the signal "-" and "+" change is determined. K data acquisition points are taken before and after this position, and the interpolation function is constructed with 2k points. Interpolation processing is performed at equal intervals between ti and ti+1. The zero-crossing moment is searched for the interpolated data, that is, the two points where "-" and "+" change, and the two-point interpolation method is used to obtain the precise zero-crossing moment.
[0046] In addition, the selection of the cycle and the averaging method in the cycle average have a great influence on the monitoring accuracy of the torsional vibration signal. In order to improve the measurement accuracy, a longer measurement cycle should be selected as much as possible so that the torsional vibration signal can be averaged over a longer period of time. However, an excessively long measurement cycle will increase the amount of calculation of the algorithm, so a trade-off needs to be made between accuracy and efficiency. The object of this technical solution is a four-stroke diesel engine. The crankshaft rotates twice in each working cycle. Based on the calculation characteristics of the FPGA chip, a double averaging method is adopted without significantly increasing the amount of calculation. That is, the crankshaft is averaged every time it rotates one circle, and then averaged again in each working cycle to achieve a balance between accuracy and efficiency.
[0047] In an embodiment of the present invention, a fault diagnosis model of a torsional vibration damper is established based on historical fault data and normal operating condition data by using machine learning or deep learning algorithms. By continuously optimizing model parameters and algorithm structure, the recognition accuracy and generalization ability of the model are improved. The model can automatically identify and classify different vibration modes, thereby judging the health status of the torsional vibration damper. The real-time vibration signal is input into the established fault diagnosis model to monitor the operating status of the torsional vibration damper in real time. Once an abnormal vibration mode is found, the early warning mechanism is immediately triggered to remind the operator to take corresponding measures. Through real-time monitoring and early warning mechanisms, potential faults of the torsional vibration damper can be discovered and handled in a timely manner, providing an important basis for the maintenance and maintenance of the equipment.
[0048] like Figure 3 and Figure 4 As shown, Figure 3 A schematic diagram showing the torsional vibration monitoring principle of a method for eliminating errors in torsional vibration signals of a low-speed diesel engine according to an embodiment of the present invention; Figure 4 A schematic diagram of torsional vibration signal analysis and extraction showing a method for eliminating errors in torsional vibration signals of a low-speed diesel engine according to an embodiment of the present invention.
[0049] In the figure, a method for eliminating the error of torsional vibration signal of a low-speed diesel engine is shown. According to the development project of torsional vibration damper of a low-speed diesel engine, the torsional vibration damping effect of the torsional vibration damper and the characteristics of the torsional vibration damper itself are obtained through photoelectric encoder, magnetoelectric speed sensor, pressure sensor and temperature sensor. The hardware elimination and signal extraction and analysis methods are used to improve the accuracy of torsional vibration signal acquisition, and comprehensive monitoring and diagnosis are carried out in combination with the vibration reduction effect of the torsional vibration damper and the characteristics of the torsional vibration damper itself.
[0050] The technical solution of the present invention includes: a sensor unit, a signal processing unit, an error correction unit and a display unit. The sensor unit is used to collect the torsional vibration signal of the diesel engine and the oil temperature and oil pressure signal of the torsional vibration damper; the signal processing unit performs preprocessing and filtering processing on the collected signals, including real-time signal compensation processing; the error correction unit performs error correction on the preprocessed signals, mainly including the periodic average and tooth average of the signals; the display unit is used to display the corrected torsional vibration signal and related information. By optimizing the sensor selection and installation, signal processing and filtering, and introducing the error correction method, the accuracy and reliability of the measurement are improved.
[0051] Since the characteristics of the diesel engine torsional vibration signal itself are difficult to extract, and are affected by factors such as bending vibration, operating status, and sensor installation during the actual collection process, this technical solution eliminates errors through sensor installation, real-time signal compensation processing, dynamic signal processing, etc., to improve the monitoring accuracy of the diesel engine torsional vibration signal.
[0052] In another embodiment of the present invention, a system for eliminating the error of a torsional vibration signal of a low-speed diesel engine is provided, based on a method for eliminating the error of a torsional vibration signal of a low-speed diesel engine as described in any one of the above items, comprising: a frequency modulation processing module, a first processing module, a second processing module and an output module; The frequency modulation processing module is used for the amplitude modulation of the pulse train and the frequency modulation of the rectangular wave of the support vibration signal and the torsional vibration signal of the torsional vibration sensor of the low-speed diesel engine when the sensor support of the torsional vibration sensor vibrates, the torsional vibration sensor deviates from its original installation position, and the relative position between the torsional vibration sensor and the speed measuring gear changes; The first processing module is used to calculate the outer envelope of the original signal of the torsional vibration sensor of the low-speed diesel engine, and obtain its analytical signal z(t) by Hilbert transforming the original signal x(t) of the torsional vibration sensor: z(t)=x(t)+j
[0053] in, is the Hilbert transform of x(t); Then, the model of the analytical signal , which is the envelope of the analytical signal; The second processing module performs low-pass filtering on the envelope of the analytical signal of the torsional vibration sensor based on a low-pass filter to calculate the vibration trend item T(t) of the sensor support of the torsional vibration sensor; The output module uses the original signal x(t) of the torsional vibration sensor to envelop the support vibration trend term T(t) of the torsional vibration sensor to obtain the angular velocity signal of the torsional vibration sensor. ,Right now .
[0054] The technical solution of the present invention improves the accuracy of torsional vibration signal acquisition by obtaining the torsional vibration reduction effect of the torsional vibration damper and the characteristics of the torsional vibration damper itself, adopts methods such as hardware elimination and signal extraction analysis, and performs comprehensive monitoring and diagnosis in combination with the torsional vibration reduction effect of the torsional vibration damper and the characteristics of the torsional vibration damper itself.
[0055] The above are preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.
Claims
1. A method for eliminating errors in torsional vibration signals of a low-speed diesel engine, characterized in that: The method comprises: S101. For a low-speed diesel engine, when a sensor support of a torsional vibration sensor vibrates, the torsional vibration sensor deviates from its original installation position, and its relative position with the speed measuring gear changes, and the amplitude modulation of the pulse train and the frequency modulation of the rectangular wave by the support vibration signal of the torsional vibration sensor and the torsional vibration signal are determined; S102, calculating the outer envelope of the original signal of the torsional vibration sensor of the low-speed diesel engine, and obtaining its analytical signal z(t) by Hilbert transforming the original signal x(t) of the torsional vibration sensor: z(t)=x(t)+j in, is the Hilbert transform of x(t); Then, the model of the analytical signal , which is the envelope of the analytical signal; S103, performing low-pass filtering on the envelope of the analytical signal of the torsional vibration sensor based on a low-pass filter, and calculating a vibration trend item T(t) of a sensor support of the torsional vibration sensor; S104, using the original signal x(t) of the torsional vibration sensor, removing the support vibration trend term T(t) that envelops the torsional vibration sensor, and obtaining the angular velocity signal of the torsional vibration sensor ,Right now 。 2. The method for eliminating the error of the torsional vibration signal of a low-speed diesel engine according to claim 1, characterized in that: The method comprises: Two magnetoelectric speed sensors are installed on the outer ring of the torsional vibration damper at 180 degrees relative to each other, and the two magnetoelectric speed sensors at 180 degrees relative to each other have opposite frequency modulation responses to the bending vibration of the low-speed diesel engine, thereby eliminating the influence of the bending vibration of the low-speed diesel engine; A photoelectric encoder is arranged on the inner ring of the torsional vibration damper, and the synthesized signals of the dual speed sensors of the inner ring and outer ring of the torsional vibration damper are fused and corrected to improve the torsional vibration signal acquisition accuracy of the low-speed diesel engine.
3. The method for eliminating the error of the torsional vibration signal of a low-speed diesel engine according to claim 2, characterized in that: The method comprises: adopting a period averaging method; For a working cycle of a low-speed diesel engine, take the data of M cycles and average them to get the instantaneous speed after the whole cycle average. , in, , N is the number of teeth on the gear.
4. The method for eliminating the error of the torsional vibration signal of a low-speed diesel engine according to claim 2, characterized in that: The method comprises: using a tooth averaging method; The original signal collected by the magnetoelectric sensor is in positive and negative half cycles, corresponding to the reduction and increase of magnetic resistance, that is, the magnetoelectric signal corresponding to the tooth top and tooth root of the gear; The calculation cycle is the time it takes for the diesel engine crankshaft to rotate one index. Calculation based on uniform gear indexing will produce periodic errors. The error can be reduced by gear averaging, that is, , N is the number of teeth of the gear, m is the average calculated number of teeth intervals, when m is taken, the calculated number of teeth intervals should try not to select divisors of the total number of teeth.
5. The method for eliminating the error of the torsional vibration signal of a low-speed diesel engine according to claim 1, characterized in that: The method comprises: Among the various harmonic amplitudes of the torsional vibration of a low-speed diesel engine, the amplitude and phase characteristics of the 0.5 harmonic torsional vibration are most sensitive to the working state of each cylinder, and the quantitative analysis is accurate, which is suitable for monitoring and diagnosis of each cylinder of the diesel engine. The 0.5 harmonic torsional amplitude value in the normal state is taken as the characteristic threshold. If it is greater than the characteristic threshold, the operation of each cylinder of the diesel engine will increase unevenly, and the possibility of failure will increase. The oil temperature and oil pressure information of the torsional vibration damper is obtained in real time through the oil temperature and oil pressure sensors. Combined with the torsional vibration monitoring signal, multi-source data fusion technology is used to diagnose the state of the torsional vibration damper in real time.
6. The method for eliminating the error of the torsional vibration signal of a low-speed diesel engine according to claim 1, characterized in that: The method comprises: If the low-speed diesel engine has no torsional vibration, the instantaneous speed of its shaft system is equal to its average speed, the shaft rotates at a constant speed, the angles rotated by the shaft in equal time are equal, and the time required for each gear to rotate is equal, that is, the period of the pulse signal is equal; When the low-speed diesel engine shaft system undergoes torsional vibration, when the two motion vectors of rotational motion and torsional vibration are in the same direction, the instantaneous angular velocity increases, and the pulse period formed by the gear teeth passing through the sensor measuring point position decreases; conversely, the instantaneous angular velocity component decreases, and the pulse period formed by the gear teeth passing through the sensor measuring point position increases.
7. The method for eliminating the error of the torsional vibration signal of a low-speed diesel engine according to claim 1, characterized in that: The method comprises: Perform equally spaced polynomial interpolation on the data between two points on the left and right of the zero-crossing moment, or perform equally spaced polynomial interpolation on the entire original data.
8. The method for eliminating the error of the torsional vibration signal of a low-speed diesel engine according to claim 7, characterized in that: The method comprises: According to the original data, the moment when the rising edge crosses zero is taken to determine the position where the signal "-" and "+" change. K data acquisition points are taken before and after this position, and the interpolation function is constructed with 2k points. Interpolation processing is performed at equal intervals between ti and ti+1. The zero-crossing moment of the interpolated data is then searched, that is, the two points where "-" and "+" change, and the two-point interpolation method is used to obtain the precise zero-crossing moment.
9. A system for eliminating errors in torsional vibration signals of a low-speed diesel engine, based on a method for eliminating errors in torsional vibration signals of a low-speed diesel engine as claimed in any one of claims 1 to 8, characterized in that: The system comprises: a frequency modulation processing module, a first processing module, a second processing module and an output module; The frequency modulation processing module is used for the amplitude modulation of the pulse train and the frequency modulation of the rectangular wave of the support vibration signal and the torsional vibration signal of the torsional vibration sensor of the low-speed diesel engine when the sensor support of the torsional vibration sensor vibrates, the torsional vibration sensor deviates from its original installation position, and the relative position between the torsional vibration sensor and the speed measuring gear changes; The first processing module is used to calculate the outer envelope of the original signal of the torsional vibration sensor of the low-speed diesel engine, and obtain its analytical signal z(t) by Hilbert transforming the original signal x(t) of the torsional vibration sensor: z(t)=x(t)+j in, is the Hilbert transform of x(t); Then, the model of the analytical signal , which is the envelope of the analytical signal; The second processing module performs low-pass filtering on the envelope of the analytical signal of the torsional vibration sensor based on a low-pass filter to calculate the vibration trend item T(t) of the sensor support of the torsional vibration sensor; The output module uses the original signal x(t) of the torsional vibration sensor to remove the support vibration trend term T(t) of the torsional vibration sensor, thereby obtaining the angular velocity signal of the torsional vibration sensor. ,Right now 。