Gearbox uniform load coefficient monitoring method based on optical fiber strain monitoring

Abstract

The invention provides a gearbox uniform load coefficient monitoring method based on optical fiber strain monitoring, and the method comprises the following steps: collecting a plurality of groups of dynamic strain signals through a plurality of grating optical fiber sensors which are uniformly distributed in the middle of the outer surface of an inner gear ring at intervals in the circumferential direction, the arrangement number of the grating fiber sensors is integral multiples of the number of the planet gears; calculating a uniform load coefficient of the gearbox according to the multiple groups of dynamic strain signals; the gear box uniform load coefficient comprises an average uniform load coefficient and an instantaneous uniform load coefficient. The technical problems that in the prior art, a resistance strain gauge is adopted to monitor the tooth root strain of a planetary gear train of a gearbox, long-term monitoring cannot be achieved, and the resistance strain gauge needs to be replaced regularly can be solved.

Description

Technical Field

[0001] This invention relates to the field of gearbox monitoring technology, and specifically to a method for monitoring the load sharing coefficient of a gearbox based on fiber optic strain monitoring. Background Technology

[0002] As a crucial component of the transmission chain, the gearbox smoothly and efficiently transmits power from the input shaft to the output shaft through gear meshing. By combining and matching different gears, the transmission ratio can be flexibly changed to meet the speed and torque requirements under various operating conditions. During actual operation, due to the combined effects of manufacturing errors, installation errors, and heavy-load deformation, the planetary gear train is prone to uneven meshing, reducing load-sharing performance. Therefore, accurately obtaining the load-sharing coefficient of the planetary gear train is of great significance for assessing the gearbox's health status, predicting remaining life, optimizing maintenance strategies, and improving the reliability and economy of the transmission chain.

[0003] In existing technologies, the method for testing the load sharing coefficient of planetary gear trains in gearboxes mainly involves attaching resistance strain gauges to the root of the sun gear or internal gear ring. The principle is to measure the periodic change in the bending strain at the tooth root during gear meshing, then extract the effective peak value of the strain signal to analyze the peak and valley values ​​and calculate the load sharing coefficient, thus evaluating the load distribution uniformity of the planetary gear train. However, this method has the following technical problems: the resistance strain gauges attached to the internal tooth root may detach from the gearbox due to adhesive aging over time and long-term corrosion from high-temperature oil, affecting gear meshing and limiting long-term monitoring. In this case, the transmission chain needs to be stopped after a period of operation, the gearbox opened, and the resistance strain gauges replaced, which is inconvenient and results in economic losses due to downtime. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a gearbox load-sharing coefficient monitoring method based on fiber optic strain monitoring. This method solves the technical problem that existing technologies, which use resistance strain gauges to monitor the tooth root strain of planetary gear trains in gearboxes, cannot achieve long-term monitoring and require periodic replacement of the resistance strain gauges.

[0005] The technical solution adopted in this invention is as follows: Firstly, a method for monitoring the load-sharing coefficient of a gearbox based on fiber optic strain monitoring is provided, comprising the following steps: Multiple sets of dynamic strain signals are acquired by a grating fiber optic sensor, which is deployed on the outer surface of the internal gear ring. The gearbox load-sharing coefficient is calculated based on multiple sets of dynamic strain signals.

[0006] Furthermore, the number of grating fiber optic sensors deployed is determined in the following manner: By conducting convergence analysis using the finite element method, a parameterized model was established. The number of measurement points was used as a variable, and the rate of change of the calculated load-sharing coefficient with the increase of measurement points was stabilized as the convergence criterion. This determined the optimal number of fiber optic grating sensors on the outer surface of the internal gear ring.

[0007] Furthermore, the number of grating fiber optic sensors deployed is an integer multiple of the number of planetary gears.

[0008] Furthermore, the number of grating fiber optic sensors deployed is twice the number of planetary gears.

[0009] Furthermore, the grating fiber optic sensors are arranged as follows: multiple grating fiber optic sensors are evenly spaced circumferentially along the middle of the outer surface of the inner toothed ring.

[0010] Furthermore, when acquiring multiple sets of dynamic strain signals using a grating fiber optic sensor, the sampling frequency... for: in, For the number of planetary gears, This refers to the rotational speed of the planetary carrier. Total acquisition time = Number of meshing cycles required / Meshing frequency.

[0011] Furthermore, the gearbox load sharing factor includes the average load sharing factor and the instantaneous load sharing factor.

[0012] Furthermore, the average load factor Calculate using the following formula: Furthermore, the first Planetary wheel Instantaneous load factor at any moment Calculate using the following formula: in, The number of planetary gears. For the first Planetary wheel The instantaneous peak and trough values ​​at any given moment.

[0013] In a second aspect, a gearbox load-sharing coefficient monitoring system based on fiber optic strain monitoring is provided to implement the gearbox load-sharing coefficient monitoring method based on fiber optic strain monitoring described in the first aspect, comprising: multiple grating fiber optic sensors, a fiber optic demodulator, and a host computer. Multiple grating fiber optic sensors are connected in series and share a single fiber optic demodulator test channel. The fiber optic demodulator processes the data collected by the multiple grating fiber optic sensors and then transmits it to a host computer to generate strain information. The host computer then calculates the gearbox load-sharing coefficient based on the strain information.

[0014] As can be seen from the above technical solution, the beneficial technical effects of the present invention are as follows: 1. The strain on the outer surface of the internal gear ring is monitored in real time by a grating fiber optic sensor to calculate the load sharing coefficient of the planetary gear train. This enables long-term online monitoring in situ without the need to periodically disassemble the gearbox to replace the sensor.

[0015] 2. A large number of fiber optic sensing points can be conveniently connected in series on the outer surface of the internal gear ring, which can quickly and accurately capture dynamic strain and obtain the instantaneous load-sharing coefficient of the planetary gear train under any rotating phase. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0017] Figure 1 This is a schematic diagram showing the placement of the grating fiber optic sensor in an embodiment of the present invention; Figure 2 This is a schematic diagram of the grating fiber strain monitoring system in an embodiment of the present invention; Figure 3 This is a graph showing the calculation results of the average load-sharing coefficient of the gearbox in an embodiment of the present invention; Figure 4 This is a diagram showing the calculation results of the instantaneous load-sharing coefficient of the gearbox in an embodiment of the present invention. Detailed Implementation

[0018] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0019] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0020] Example The inventors of this application constructed a finite element model of the gearbox, conducted strain analysis, and observed the strain distribution of the internal gear ring under meshing force. Specifically, they simulated the meshing state by applying a load to the tooth contraction point. This approach accurately reflects the effect of the meshing force and is also more efficient in computation. The inventors discovered through analysis that there is a significant and concentrated strain change on the outer surface of the internal gear ring near the planetary gear meshing point. This strain signal exhibits a good linear relationship with the applied load and has a high signal-to-noise ratio. Therefore, attaching a grating fiber optic sensor to the outer surface of the internal gear ring can effectively capture the strain signal. The dynamic strain signal acquired by the grating fiber optic sensor is essentially a tiny, rapid change in length at a point on the outer surface of the internal gear ring caused by the periodic action of the planetary gear meshing force. When the planetary gear and the teeth of the internal gear ring engage, transmit engagement, and disengage, the meshing force is applied to the internal gear ring. This force causes the internal gear ring to produce a tiny elastic deformation. The grating fiber optic sensor is attached to the outer surface of the internal gear ring and deforms synchronously with the internal gear ring, thus sensing this tiny "stretching" or "compression".

[0021] Based on the above research results, this embodiment provides a method for monitoring the load sharing coefficient of a gearbox based on fiber optic strain monitoring, including the following steps: Step 1: Determine the number and location of the grating fiber optic sensors to be deployed on the outer surface of the internal gear ring. For different gearboxes, the number of planetary gears and the number of planetary gears in each stage are different. When determining the number and location of fiber optic sensors on the outer surface of the internal gear ring, these are regarded as measurement points. The premise is to accurately calculate the load sharing coefficient, while taking into account economy. The number of measurement points should not be too many. At the same time, considering the difference in the stiffness of the internal gear ring structure, more measurement points can compensate for the impact of stiffness differences.

[0022] In this step, convergence analysis is performed using the finite element method to determine the optimal number of fiber optic strain measurement points on the surface of the internal gear ring. This analysis method establishes a parametric model of the gearbox in finite element software, using the number of measurement points as a variable. The convergence criterion is that the calculated load-sharing coefficient tends to stabilize with the increase of measurement points (rate of change < 5%). This minimizes the number of measurement points while ensuring calculation accuracy, effectively balancing the economy and reliability of the monitoring system. Preferably, the number of grating fiber optic sensors is an integer multiple of the number of planetary gears, with a minimum of 1 times the number of planetary gears.

[0023] For the measurement point location, multiple grating fiber optic sensors are evenly arranged circumferentially along the middle of the outer surface of the internal gear ring, such as... Figure 1 As shown, it can collect dynamic micro-strain at the measuring point position on the outer surface of the internal gear ring in real time.

[0024] Step 2: Based on the determined number and location of the grating fiber optic sensors, deploy the grating fiber optic sensors on the outer surface of the internal gear ring. Based on the determined number and location of the grating fiber optic sensors, the sensors are adhered to the outer surface of the inner toothed ring. Traditional resistance strain gauges, attached to the root of the tooth where deformation is severe, are prone to fatigue damage to the fragile grating wires and solder joints under repeated impacts of meshing forces; their sheet-like structure also makes the edges prone to lifting when adhered to complex curved surfaces, making long-term stable operation difficult. In contrast, the grating fiber optic sensor possesses inherent physical advantages: its linear structure allows for very close adhesion to curved surfaces and can withstand a certain degree of bending. Even with minor deformation, the fiber itself is not easily broken.

[0025] From an engineering practice perspective, the outer surface of the internal gear ring provides a high-quality, mild mechanical environment for the monitoring sensor, making it easy to protect and significantly improving the reliability of long-term monitoring. The advantages of fiber optic installation on the outer surface of the internal gear ring include: ample operating space, allowing technicians to easily perform standard procedures such as grinding, cleaning, applying adhesive, patching, and pressure curing, ensuring bonding quality; uniform adhesive layer, where the adhesive forms a uniform thickness on a smooth surface, resulting in good stress transfer and fewer internal defects; and easy protection, where silicone sealant or clamps can be easily applied after installation to secure the sensor and wires, preventing scratches.

[0026] In a specific implementation, a single optical fiber can integrate multiple sensors, meaning that each measuring point can be connected in series. The monitored signals share a single optical fiber demodulator test channel. The demodulator processes the data collected by multiple sensors and then transmits it to a host computer to generate strain information.

[0027] In this embodiment, the fiber optic strain monitoring system mainly consists of multiple grating fiber optic sensors, a fiber optic demodulator, and a host computer, such as... Figure 2 As shown.

[0028] Step 3: Acquire multiple sets of dynamic strain signals using multiple grating fiber optic sensors. Multiple sets of complete dynamic strain signals were simultaneously acquired under various operating conditions of the transmission chain containing the gearbox. The dynamic strain signal is a significant and concentrated strain change on the outer surface of the internal gear ring near the meshing point of the planetary gears.

[0029] During the data acquisition process, to ensure accurate capture of the strain generated by the meshing of each planetary gear with the internal gear ring, the sampling frequency must be set based on the passing frequency of the planetary gears. That is, the sensor sampling frequency must be greater than the frequency at which a single planetary gear passes through a certain meshing point on the internal gear ring twice. The formula for calculating the sampling frequency is: in, For the number of planetary gears, This refers to the rotational speed of the planetary carrier.

[0030] The acquisition time depends primarily on two core factors: ensuring signal stability and capturing sufficient engagement cycles for statistical analysis. To meet these requirements: Total acquisition time = Number of required meshing cycles / Meshing frequency For the storage format of data transmitted to the host computer, binary files (.tdms, .bin) can be used, which have the advantages of fast read and write speed, high compression rate and saving storage space, and are suitable for large data volumes generated by high-frequency collection; TXT text files can also be used, which have the advantages of strong universality and can be opened by any software.

[0031] Step 4: Calculate the gearbox load sharing coefficient based on multiple sets of dynamic strain signals. In this embodiment, the gearbox load sharing coefficient is divided into two types: the average load sharing coefficient and the instantaneous load sharing coefficient.

[0032] The average load sharing factor is an overall average index that measures the uniformity of load distribution in a planetary gear train over a complete working cycle. If the average load sharing factor deviates from the ideal value, it indicates that the system may have persistent problems such as manufacturing errors, installation errors, long-term wear, or structural load imbalances. Multiple sets of dynamic strain signals collected can be filtered and synchronously averaged to extract stable strain signals corresponding to the meshing cycle. Then, the difference between the maximum and minimum values ​​of each planetary gear in each meshing cycle under various working conditions is identified and defined as the peak-to-valley value. Then, the following formula is used to calculate the first... Average load distribution coefficient of each planetary gear : In one embodiment, the calculation result of the average load factor is as follows: Figure 3 As shown.

[0033] The instantaneous load-averaging factor of a planetary gear train is a key indicator for evaluating the uniformity of its dynamic load distribution. It reflects the load distribution at a specific instant, capturing dynamic changes and transient responses, and is used to analyze microscopic, real-time load fluctuations and dynamic characteristics. Fluctuations in the instantaneous load-averaging factor can effectively reveal dynamic events such as impact loads, localized transient faults, and transmission system vibrations. The peak and valley values ​​of multiple sets of acquired dynamic strain signals are extracted, and the instantaneous load-averaging factor is calculated. Planetary wheel Instantaneous load factor at any moment Calculate using the following formula: in, The number of planetary gears. For the first Planetary wheel The instantaneous peak and trough values ​​at any given moment.

[0034] In one embodiment, the calculation result of the instantaneous load-sharing factor is as follows: Figure 4 As shown.

[0035] The technical solution of this embodiment uses a grating fiber optic sensor to monitor the strain on the outer surface of the internal gear ring in real time to calculate the load-sharing coefficient of the planetary gear train. This enables long-term online monitoring in situ without the need to periodically disassemble the gearbox to replace the sensor. In contrast, using a resistance strain gauge to monitor tooth root strain has limitations: it allows for a limited number of measurement points, is susceptible to electromagnetic interference, and struggles to achieve high-density, high-precision instantaneous dynamic load capture. Therefore, it can only calculate the average load-sharing coefficient. The grating fiber optic sensor, on the other hand, has advantages such as small size and strong anti-interference capability. A large number of fiber optic sensing points can be conveniently connected in series on the outer surface of the internal gear ring, enabling rapid and accurate capture of dynamic strain and obtaining the instantaneous load-sharing coefficient of the planetary gear train under any rotational phase.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for monitoring the load-sharing coefficient of a gearbox based on fiber optic strain monitoring, characterized in that, Includes the following steps: Multiple sets of dynamic strain signals are acquired by a grating fiber optic sensor, which is deployed on the outer surface of the internal gear ring. The gearbox load-sharing coefficient is calculated based on multiple sets of dynamic strain signals.

2. The method for monitoring the load-sharing coefficient of a gearbox based on fiber optic strain monitoring according to claim 1, characterized in that, The number of grating fiber optic sensors deployed is determined in the following manner: By conducting convergence analysis using the finite element method, a parameterized model was established. The number of measurement points was used as a variable, and the rate of change of the calculated load-sharing coefficient with the increase of measurement points was stabilized as the convergence criterion. This determined the optimal number of fiber optic grating sensors on the outer surface of the internal gear ring.

3. The method for monitoring the load-sharing coefficient of a gearbox based on fiber optic strain monitoring according to claim 2, characterized in that, The number of grating fiber optic sensors deployed is an integer multiple of the number of planetary gears.

4. The method for monitoring the load-sharing coefficient of a gearbox based on fiber optic strain monitoring according to claim 3, characterized in that, The number of grating fiber optic sensors deployed is one times the number of planetary gears.

5. The method for monitoring the load-sharing coefficient of a gearbox based on fiber optic strain monitoring according to claim 1, characterized in that, The grating fiber optic sensors are arranged as follows: multiple grating fiber optic sensors are evenly spaced circumferentially along the middle of the outer surface of the inner tooth ring.

6. The method for monitoring the load-sharing coefficient of a gearbox based on fiber optic strain monitoring according to claim 1, characterized in that, When acquiring multiple sets of dynamic strain signals using a grating fiber optic sensor, the sampling frequency... for: in, For the number of planetary gears, This refers to the rotational speed of the planetary carrier. Total acquisition time = Number of meshing cycles required / Meshing frequency.

7. The method for monitoring the load-sharing coefficient of a gearbox based on fiber optic strain monitoring according to claim 1, characterized in that, The gearbox load sharing coefficient includes the average load sharing coefficient and the instantaneous load sharing coefficient.

8. The method for monitoring the load-sharing coefficient of a gearbox based on fiber optic strain monitoring according to claim 7, characterized in that, The average load factor Calculate using the following formula: The total average strain peak and valley values ​​of the star wheel during each meshing cycle.

9. The method for monitoring the load-sharing coefficient of a gearbox based on fiber optic strain monitoring according to claim 7, characterized in that, No. Planetary wheel Instantaneous load factor at any moment Calculate using the following formula: in, The number of planetary gears. For the first Planetary wheel The instantaneous peak and trough values ​​at any given moment.

10. A gearbox load-sharing coefficient monitoring system based on fiber optic strain monitoring, characterized in that, The gearbox load sharing coefficient monitoring method based on fiber optic strain monitoring as described in any one of claims 1-9 includes: multiple grating fiber optic sensors, a fiber optic demodulator, and a host computer. Multiple grating fiber optic sensors are connected in series and share a single fiber optic demodulator test channel. The fiber optic demodulator processes the data collected by the multiple grating fiber optic sensors and then transmits it to a host computer to generate strain information. The host computer then calculates the gearbox load-sharing coefficient based on the strain information.

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