Planetary gearbox sun gear tooth root wireless stress test system

Abstract

The invention discloses a planetary gearbox sun gear tooth root wireless stress test system, which comprises a test computer, a wireless gateway and a plurality of emergency test modules, and is characterized in that each emergency test module comprises an antenna, a plurality of wireless strain testers and a plurality of strain gauges; the wireless strain tester obtains stress data of the tooth root of the corresponding sun gear through the strain gauge and transmits the obtained stress data to the test computer through the antenna and the wireless gateway. According to the planetary gear box sun gear tooth root wireless stress test system disclosed by the invention, a complex slip ring structure and complex wiring are not needed on site, the stress of the sun gear tooth root is acquired through the plurality of wireless strain testers, and data are transmitted to the external wireless gateway through wireless signals; wireless, multi-channel, distributed, high-precision and high-time-synchronization sun gear tooth root stress data acquisition is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of wind power gearboxes, and in particular relates to a wireless stress testing system for sun gear tooth roots of planetary gearboxes, which can realize stress testing of sun gear tooth roots of multi-stage planetary gearboxes. Background Art

[0002] Wind turbine gearboxes are a crucial component of wind turbine generators. Their primary function is to transmit the wind power generated by the rotor to the generator, achieving the desired rotational speed. Gear teeth are subject to repeated alternating stresses. When a pair of gears mesh, errors in pitch and tooth profile can cause meshing shock during operation, generating noise corresponding to the meshing frequency. Since tooth root stress is often a key indicator of gear force during gear transmission, understanding the stress level and distribution at the ring gear root provides valuable insights into strain gauge placement.

[0003] During the development of new wind turbine gearboxes, gear stress testing of the sun gear and ring gear is required. Since the ring gear is relatively stationary, stress testing is relatively easy and can be performed using traditional methods. However, the sun gear is located at the center of the gearbox transmission and rotates continuously during operation, making it impossible to measure using conventional wiring methods. Therefore, collecting sun gear root strain data while the gearbox is operating has become a pressing technical challenge for those skilled in the art.

[0004] Currently published wind turbine gearbox sun gear root stress testing methods (CN 116989926 A, CN218444459U, CN 117825043A) generally involve designing a test fixture and using a slip ring structure to guide the strain cable of the sun gear root to a data acquisition device outside the gearbox.

[0005] First, the slip ring and test fixture have complex structures. Each model of sun gear may require a separate test fixture, and the internal and external wiring is complicated.

[0006] Second, since the strain signals are all tiny resistance changes at the milliohm level, when converted into small voltage signals at the microvolt level, they are easily affected by external electromagnetic signals and power frequency interference after being connected through long cables and slip rings, resulting in unsatisfactory data noise.

[0007] Third, since there are many measuring points on the sun gear, a quarter-bridge two-wire system is often used in engineering to simplify wiring. This is very susceptible to the additional resistance caused by long cables, which can affect the linearity of the measured data.

[0008] Fourth, the slip ring contact has the disadvantage of short life. After long-term wear, the contact resistance changes or even fails completely. The strain signal is also an electrical signal generated by the change of strain gauge resistance. The change of slip ring contact resistance has a great impact on the data. Therefore, in actual testing, the test data of certain measuring points often cannot be used due to problems with the slip ring structure.

[0009] Therefore, further improvements are made to the above problems. Summary of the Invention

[0010] The main purpose of the present invention is to provide a planetary gearbox sun gear root wireless stress testing system, which does not require complex slip ring structures and complex wiring on site. The stress of the sun gear root is collected by multiple wireless strain testers, and the data is transmitted to an external wireless gateway via wireless signals, realizing wireless, multi-channel, distributed, high-precision, and high-time synchronized sun gear root stress data collection.

[0011] To achieve the above objectives, the present invention provides a planetary gearbox sun gear root wireless stress testing system, comprising a test computer, a wireless gateway, and several levels of emergency test modules, wherein:

[0012] Each of the emergency test modules includes an antenna, several wireless strain testers and several strain gauges. The wireless strain testers are fixedly installed on the sun gear of the corresponding planetary gearbox. The wireless strain testers obtain stress data of the tooth root of the corresponding sun gear through the strain gauges and transmit the obtained stress data to the test computer through the antenna and the wireless gateway.

[0013] As a further preferred technical solution of the above technical solution, it is assumed that the emergency test module includes N wireless strain gauges and M strain gauges, wherein:

[0014] The number N of wireless strain gauges required on each level of sun gear is consistent with the number N of teeth that need to be monitored. The value of N is equal to the number of sun gears in the planetary gearbox at that level.

[0015] The strain gauges are installed on each tooth root of the corresponding sun gear, and it is assumed that each tooth root of the sun gear adopts Nt strain measurement points.

[0016] As a further preferred technical solution of the above technical solution, the wireless strain tester includes a single-chip microcomputer, a battery pack, a storage module, a first wireless module, a second wireless module and several test channels, each test channel includes a strain conditioning unit and an AD acquisition unit, wherein:

[0017] Each strain conditioning unit is connected to the corresponding strain gauge, conditions and amplifies the strain gauge signal and converts the resistance signal into a voltage signal, and transmits the voltage signal to the corresponding AD acquisition unit, so that the AD acquisition unit converts the voltage signal into analog-to-digital and transmits it to the microcontroller, which stores the obtained stress data in the storage module.

[0018] As a further preferred technical solution of the above technical solution, in the wireless strain gauge, dual-mode wireless communication is performed through the first wireless transmission module and the second wireless transmission module and operates in the same frequency band. The dual-mode wireless communication is specifically implemented as follows:

[0019] S21: The wireless strain gauge enters the sleep mode by default when it is turned on. In the sleep mode, the second wireless transmission module is turned off and the first wireless transmission module is periodically enabled. The first wireless transmission module is awakened for a time T1 at intervals of T0. When the wireless strain gauge receives a wake-up command from the wireless gateway within the wake-up time T1, the wireless strain gauge enters the standby mode.

[0020] S22: Standby mode, turn on the first wireless transmission module, turn off the second wireless transmission module, if a collection control instruction is received from the wireless gateway, enter the data collection mode; if a data download instruction is received, enter the data download mode; if no instruction is received in the first time, re-enter the sleep mode;

[0021] S23: In the data acquisition mode, the first wireless transmission module is turned on, the second wireless transmission module is turned off, and the collected stress data is stored in the storage module; the stress data is sent to the wireless gateway in a manner of sampling one point out of Ns points to realize data waveform monitoring. At the same time, in the data acquisition mode, the wireless gateway sends a time synchronization data packet every T2 time interval. After receiving the time synchronization data packet, each wireless strain gauge adjusts its local clock to keep it consistent with the clock of the wireless gateway, thereby realizing wireless synchronous data acquisition;

[0022] S24: After the test collection is completed, in the data download mode, the second wireless transmission module is enabled to achieve high-speed data download. If the second wireless transmission module fails, the first wireless transmission module is continued to be used for data download;

[0023] S25: After the data collection of a certain working condition is completed, the wireless gateway controls the wireless strain gauge to be in a dormant state, and the entire device is in a low-power dormant state;

[0024] S26: After the test is completed and the download is completed, the wireless gateway controls the wireless strain gauge to be in a dormant state, and the entire device is in a low-power dormant state.

[0025] As a further preferred technical solution of the above technical solution, the wireless gateway includes a first control module and a second control module, the first control module and the first wireless module are connected to each other through a first wireless protocol, and the second control module and the second wireless module are connected to each other through a second wireless protocol, wherein:

[0026] Wireless synchronization is achieved when the first control module communicates with the first wireless module. The wireless gateway uses a crystal oscillator as the system clock and sends wireless synchronization instructions at regular intervals. After receiving the wireless synchronization instructions, the wireless strain tester adjusts the internal timer clock to achieve synchronization with the wireless gateway clock, thereby realizing distributed wireless synchronous data collection within the entire wireless local area network.

[0027] As a further preferred technical solution of the above technical solution, the test computer analyzes the stress data and uses the following steps to calculate the (helical) load distribution coefficient K when calculating the internal bending strength of the tooth: Fβ and the (helical) load distribution coefficient K for contact strength calculation Hβ , the specific implementation is:

[0028] Step S31: For each strain gauge on the sun gear tooth root, find the peak points P(1), P(2), P(3), ..., P(Ny) of each strain measurement point under Ny consecutive cycles collected within a period of time;

[0029] Step S32: for the Nt strain test points on the root tooth, calculate the average value of each strain test point under Ny cycles;

[0030] Step S33: Find the maximum value max_P of the average strain values ​​of the Nt strain test points in step S32;

[0031] Step S34: finding the average value ave_P of the average strain values ​​of the Nt strain test points in step S32;

[0032] Step S35: Calculate the load distribution coefficient K within the tooth Fβ :

[0033] K Fβ =max_P / ave_P;

[0034] Step S36: According to the formula:

[0035]

[0036] Calculate the load distribution coefficient K within the tooth Hβ , h is the planet gear tooth height, b is the planet gear tooth width, N F is the power exponent.

[0037] The beneficial effects of the present invention are:

[0038] (1) Wireless sun gear stress testing is achieved, which greatly reduces the installation complexity of slip ring fixtures and wiring, and improves work efficiency. A wireless, multi-channel, distributed conductivity acquisition system can realize wireless, distributed, and synchronous conductivity data acquisition and wireless transmission. The wireless transmission distance is better than 500 meters, which greatly simplifies on-site wiring. While reducing on-site wiring cables, it also reduces signal crosstalk between long cables and the impact of additional impedance brought by long cables on conductivity test accuracy.

[0039] (2) High reliability and higher precision. Since the slip ring structure and complex wiring are eliminated, the risks caused by the slip ring structure and wiring are greatly reduced. The cable length between the strain gauge and the data acquisition instrument is greatly reduced, the collected data is more accurate, and the probability of electromagnetic and power frequency interference is lower.

[0040] (3) Dual-mode wireless communication technology is used to balance power consumption, wireless synchronization, and data download. One wireless module realizes low-power, long-distance, synchronous data acquisition and control, while the other wireless module realizes high-speed data download. The advantages of the two wireless modules can be combined to ensure low power consumption and wireless synchronous acquisition of the acquisition system, while ensuring high-speed data download of the collected data, thus avoiding users from wasting too much time in the data download stage and completing data download without disassembling the gearbox.

[0041] (4) Multi-channel strain data acquisition. A single wireless strain gauge has 8 channels. A single system can support up to 64 wireless strain gauges working simultaneously, achieving a maximum of 64 × 8 = 512 channels of strain data acquisition, which can meet more complex application requirements.

[0042] (5) Parallel synchronous acquisition. A dedicated wireless synchronization algorithm ensures that the data acquisition synchronization accuracy between multiple wireless strain gauges is within 10us, ensuring the synchronous acquisition of the entire wireless stress test system and facilitating real-time data analysis.

[0043] (6) Small size and light weight. The wireless strain gauge can collect strain from 8 channels. Its dimensions are only 76mm×55mm×16mm, making it very small and thin. It can be installed on the side end face of various sun gears. It is small, light and easy to install. It weighs less than 70g and can withstand the centrifugal force under high-speed rotation, which provides high safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of a planetary gearbox sun gear tooth root wireless stress testing system of the present invention.

[0045] Figure 2 This is a diagram of the installation method of the first-stage sun gear of the present invention.

[0046] Figure 3 This is a diagram of the installation method of the secondary sun gear of the present invention.

[0047] Figure 4 This is a diagram of the installation method of the three-stage sun gear of the present invention.

[0048] Figure 5 It is a structural schematic diagram of the wireless strain tester of the present invention.

[0049] Figure 6 It is a schematic diagram of the dual-mode wireless communication process of the wireless strain tester of the present invention.

[0050] Figure 7 It is a structural diagram of the wireless gateway of the present invention. DETAILED DESCRIPTION

[0051] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are for illustrative purposes only, and those skilled in the art will readily appreciate other obvious variations. The basic principles of the present invention defined in the following description may be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the present invention.

[0052] In the preferred embodiment of the present invention, those skilled in the art should note that the sun gear tooth root of the planetary gearbox involved in the present invention can be regarded as prior art.

[0053] Preferred embodiment.

[0054] like Figure 1-7 As shown, the present invention takes a three-stage gearbox as an example, but the present invention is not limited to three-stage gearboxes. The present invention discloses a planetary gearbox sun gear root wireless stress testing system, including a test computer, a wireless gateway and several levels of emergency test modules, wherein:

[0055] Each of the emergency test modules includes an antenna, several wireless strain testers and several strain gauges. The wireless strain testers are fixedly installed on the sun gear of the corresponding planetary gearbox (on the side end face of the tooth root, move and rotate with the sun gear, and communicate with the antenna fixed in the box through wireless signals). The wireless strain tester obtains the stress data of the tooth root of the corresponding sun gear through the strain gauge and transmits the obtained stress data to the test computer through the antenna and the wireless gateway (the wireless gateway is installed outside the gearbox and is directly connected to the antenna fixed in each level of the gearbox through a dedicated antenna connection line. In this way, wireless transmission and data acquisition are realized. The test software runs inside the test computer, and is connected to the wireless gateway through a cable. The wireless gateway is controlled to realize wireless node control and data transmission).

[0056] The 1N wireless strain gauges installed in the first-stage gearbox communicate wirelessly with antenna 1, which is also installed in the first gearbox. The 2N wireless strain gauges installed in the second-stage gearbox communicate wirelessly with antenna 2, which is also installed in the second gearbox. The 3N wireless strain gauges installed in the third-stage gearbox communicate wirelessly with antenna 3, which is also installed in the third gearbox. Antennas 1, 2, and 3 are installed inside the first, second, and third gearboxes, respectively. The specific installation locations depend on the actual structure, but the general guideline is to ensure good line-of-sight communication with the wireless strain gauges installed on the respective sun gear ends. Antennas 1, 2, and 3 are connected to the wireless gateway through holes drilled in the gearbox using dedicated antenna cables. This allows a single wireless gateway to collect and control data from the 1N, 2N, and 3N wireless strain gauges in the third gearbox.

[0057] The wireless strain gauges are installed on the sun gear side end face of the multi-stage planetary gearbox. Generally, the sun gear side end area in the first-stage gearbox is larger, so the wireless strain gauges and battery packs can be installed along the circumference, such as Figure 2 As shown. The side end area of ​​the sun gear in the secondary gearbox is small, so the wireless strain gauge and battery pack can be installed tangentially, as shown. Figure 3 As shown. The side end area of ​​the sun gear in the three-stage gearbox cannot be directly installed with a wireless strain gauge and a battery pack. You can process a test fixture to expand the cross-sectional area of ​​the three-stage sun gear, and then install the wireless strain gauge and a battery pack on the fixture, as shown. Figure 4 shown.

[0058] The wireless strain gauge and battery pack are mounted to the sun gear side face or fixture using screws and threaded adhesive to ensure strong and reliable mounting. All mounting pins within the wireless strain gauge and battery pack are located on the back to prevent screws from falling out and damaging the gearbox during operation.

[0059] In a planetary gearbox sun gear tooth root wireless stress testing system, strain gauges are attached to specific locations on the sun gear tooth root using specialized glue. A wireless strain gauge is electrically connected to the strain gauges installed on the tooth root via a cable. The strain gauge cable at the sun gear tooth root is routed through a groove between two teeth to the side face of the sun gear, and protective adhesive is used to protect the strain gauge routing.

[0060] Specifically, it is assumed that the emergency test module includes N wireless strain gauges and M strain gauges, wherein:

[0061] The number N of wireless strain gauges required on each sun gear stage is consistent with the number N of teeth that need to be monitored. The value of N is equal to the number of sun gears in the planetary gearbox at that stage (for example, if the first-stage gearbox has 7 planet gears, then 7 teeth should be evenly selected on the first-stage sun gear for monitoring. The number of wireless strain gauges required for the first-stage sun gear, 1N, is also 7. For example, if the second-stage gearbox has 6 planet gears, then 6 teeth should be evenly selected on the second-stage sun gear for monitoring. The number of wireless strain gauges required for the second-stage sun gear, 2N, is also 6).

[0062] Strain gauges are installed on each tooth root of the corresponding sun gear. It is assumed that each tooth root of the sun gear adopts Nt strain measurement points (generally, for the first-stage sun gear, Nt=8, for the second-stage sun gear, Nt=6, for the third-stage sun gear, Nt=6).

[0063] More specifically, the wireless strain gauge includes a single-chip microcomputer (MCU), a battery pack (the battery pack is a disposable external large-capacity battery pack that can support long-term battery life and far exceeds the capacity requirements of a single sun gear tooth root stress test), a storage module, a first wireless module (i.e., wireless module 1), a second wireless module (i.e., wireless module 2), and several test channels. Each test channel includes a strain conditioning unit and an AD acquisition unit, wherein:

[0064] Each strain conditioning unit is connected to the corresponding strain gauge, conditions and amplifies the strain gauge signal and converts the (weak) resistance signal into a (larger) voltage signal, and transmits the voltage signal to the corresponding AD acquisition unit, so that the AD acquisition unit converts the voltage signal into analog-to-digital and transmits it to the microcontroller, which stores the obtained stress data in the storage module.

[0065] The strain conditioning unit contains three standard resistors, which form a bridge circuit with the external strain gauge. Generally, a 120 ohm strain gauge or a 350 ohm strain gauge is used.

[0066] The wireless strain gauge uses a quarter-bridge, two-wire connection method, simplifying on-site strain gauge installation and connection. Because the wireless strain gauge is mounted on the sun gear end face, close to the tooth root strain gauge installation location, it avoids the cable errors associated with traditional long cable connections such as slip rings, which often affect the linearity of the measured data.

[0067] The strain conditioning unit of the wireless strain gauge has a strain balancing circuit to eliminate the error caused by manually attaching strain gauges and adjust the strain value to near zero when no-load. This is achieved by adjusting the voltage at the reference terminal of the instrumentation amplifier. The specific implementation method is as follows:

[0068] The MCU reads the data from the AD acquisition unit. If the current value is greater than the zero position of the AD, the voltage at the reference end of the instrumentation amplifier is reduced through the DA.

[0069] On the contrary, if the current value is less than the zero position of AD, the voltage of the reference terminal of the instrumentation amplifier is increased through DA.

[0070] In this way, the strain value at no-load is adjusted to be near zero, so that the range of AD acquisition can be applied to the maximum extent.

[0071] The wireless strain gauge's AD acquisition unit performs analog-to-digital conversion on the voltage signal output by the strain conditioning unit. It uses the AD4010, an 18-bit, low-power SAR AD acquisition chip. Each signal channel utilizes a separate AD chip to prevent cross-channel interference. The AD acquisition unit is electrically connected to the MCU via SPI signals.

[0072] The MCU of the wireless strain gauge reads the data from the AD acquisition unit and stores the data in a storage module. The storage module uses a large-capacity SD NAND of 8GB as a storage medium.

[0073] Furthermore, in the wireless strain tester, dual-mode wireless communication is performed through the first wireless transmission module and the second wireless transmission module and operates in the same frequency band (such as the 2.4G band or the 433M band, etc., and can share the same set of antennas to simplify wiring). The wireless transmission module 1 mainly realizes the wireless control function and has the characteristics of low power consumption, long distance, and high clock synchronization. The wireless transmission module 2 has the characteristics of high-speed data transmission and is mainly used for subsequent high-speed data download. Since the power consumption of the wireless transmission module 2 is relatively high, it will interfere with the analog signal acquisition when the wireless transmission module 2 transmits data. Therefore, the wireless transmission module 2 is only used for subsequent data download. The use of dual-mode wireless communication technology can combine the low power consumption, long distance, high clock synchronization advantages of the wireless transmission module 1 and the high-speed data download advantages of the wireless transmission module 2. The dual-mode wireless communication is specifically implemented as follows:

[0074] S21: The wireless strain gauge enters the sleep mode by default when it is turned on. In the sleep mode, the second wireless transmission module is turned off and the first wireless transmission module is periodically enabled. The first wireless transmission module is awakened for a time T1 at intervals of T0. When the wireless strain gauge receives a wake-up command from the wireless gateway within the wake-up time T1, the wireless strain gauge enters the standby mode.

[0075] S22: Standby mode, turn on the first wireless transmission module, turn off the second wireless transmission module, if the collection control instruction of the wireless gateway is received, enter the data collection mode; if the data download instruction is received, enter the data download mode; if no instruction is received within the first time (a longer time, such as 10 minutes), re-enter the sleep mode;

[0076] S23: In the data acquisition mode, the first wireless transmission module is turned on and the second wireless transmission module is turned off (to achieve low-power consumption and long-distance wireless transmission). The collected (original) stress data is stored in the storage module (because each first wireless transmission module is a low-speed module, the total bandwidth is limited and real-time data transmission cannot be achieved); the stress data is sent to the wireless gateway in a manner of sampling one point out of Ns points to achieve data waveform monitoring. At the same time, in the data acquisition mode, the wireless gateway sends a time synchronization data packet every T2 time interval. After receiving the time synchronization data packet, each wireless strain gauge adjusts its local clock to be consistent with the clock of the wireless gateway, thereby achieving wireless synchronous data acquisition;

[0077] S24: After the test collection is completed, in the data download mode, the second wireless transmission module is enabled to achieve high-speed data download (generally, the data download speed of the second wireless transmission module is better than 150 kB / s, which can achieve faster data transmission). If the second wireless transmission module fails, the first wireless transmission module is continued to be used for data download (using this method, the test data can be downloaded without disassembling the gearbox);

[0078] S25: After the data collection of a certain working condition is completed (the wireless strain gauge tester may not need to work), the wireless gateway controls the wireless strain gauge tester to be in a dormant state, and the entire device is in a low-power dormant state;

[0079] S26: After the test is completed and the download is completed, the wireless gateway controls the wireless strain gauge to be in a dormant state, and the entire device is in a low-power dormant state.

[0080] The power consumption calculation and long-term monitoring method of the wireless strain gauge are as follows:

[0081] In sleep mode, the current is <10uA; in data acquisition mode, the current is approximately 60mA; and in data download mode, the current is approximately 200mA. Using a two-cell ER18505M battery pack with a total capacity of approximately 6400mAh, the device can continuously collect data for approximately 100 hours in data acquisition mode. In sleep mode, the device theoretically offers a battery life of over 10 years, fully meeting current wind turbine gearbox stress testing application scenarios. Using a periodic sampling mode—for example, collecting data for one minute every two hours—the device can achieve a battery life of 500 days, enabling early-stage condition monitoring of new gearbox products.

[0082] Furthermore, a wireless gateway in a planetary gearbox sun gear root wireless stress test system can wirelessly control multiple wireless strain gauges in a multi-stage gearbox to achieve wireless synchronous acquisition. Figure 7 As shown, the wireless gateway includes a first control module (i.e., control module 1) and a second control module (i.e., control module 2), the first control module and the first wireless module are connected to each other via a first wireless protocol, and the second control module and the second wireless module are connected to each other via a second wireless protocol, wherein:

[0083] Wireless synchronization is achieved when the first control module communicates with the first wireless module. The wireless gateway uses a (high stability) crystal oscillator as the system clock and sends wireless synchronization instructions at regular intervals. After receiving the wireless synchronization instructions, the wireless strain tester adjusts the internal timer clock to achieve synchronization with the wireless gateway clock, thereby realizing distributed wireless synchronous data collection within the entire wireless local area network.

[0084] Preferably, the test computer analyzes the stress data and runs the test software to realize the functions of wireless node control, data reading, waveform display, etc. After the stress data of each test point is downloaded and read by the test software, the following steps are used to calculate the (helical) load distribution coefficient K when calculating the internal bending strength of the tooth: Fβ and the (helical) load distribution coefficient K for contact strength calculation Hβ , the specific implementation is:

[0085] Step S31: For each strain gauge on the sun gear tooth root, find the peak points P(1), P(2), P(3), ..., P(Ny) of each strain measurement point under Ny consecutive cycles collected within a period of time;

[0086] Step S32: for Nt strain test points on the root tooth (eight strain test points A, B, C, ..., H in this example), calculate the average value of each strain test point under Ny cycles;

[0087] ave(P(A))=ave(Pa(1),Pa(1),Pa(1),...,Pa(Ny));

[0088] ave(P(B))=ave(Pb(1),Pb(1),Pb(1),...,Pb(Ny))

[0089] …

[0090] ave(P(H))=ave(Ph(1),Ph(1),Ph(1),...,Ph(Ny))

[0091] Step S33: Find the maximum value max_P of the average strain values ​​of the Nt strain test points in step S32;

[0092] max_P=max(ave(P(A)),ave(P(B)),ave(P(C)),…,ave(P(H)))

[0093] Step S34: finding the average value ave_P of the average strain values ​​of the Nt strain test points in step S32;

[0094] ave_P=ave(ave(P(A)),ave(P(B)),ave(P(C)),…,ave(P(H)))

[0095] Step S35: Calculate the load distribution coefficient K within the tooth Fβ :

[0096] K Fβ =max_P / ave_P;

[0097] Step S36: According to the formula:

[0098]

[0099] Calculate the load distribution coefficient K within the tooth Hβ , h is the planet gear tooth height, b is the planet gear tooth width, N F is the power index. The tooth internal load distribution coefficient K Hβ The closer it is to 1, the smaller the influence of the corresponding planetary gear tooth width load distribution on the tooth surface contact stress.

[0100] Compared with previous methods, a planetary gearbox sun gear root wireless stress testing system has the characteristics of wireless, simple structure, high reliability, small size, high precision, and synchronous acquisition. It can meet the environment of wind turbine gearbox sun gear root stress testing. There are currently no similar products on the domestic market. It can fill the domestic market gap in this field and can be promoted in the production and manufacturing of large gearboxes such as marine gearboxes and engineering machinery gearboxes, as well as in the field of long-term gearbox load status monitoring. It has extremely high scientific research value and application value.

[0101] It is worth mentioning that the technical features such as the planetary gearbox sun gear root involved in the patent application of this invention should be regarded as prior art. The specific structure, working principle and possible control method and spatial layout method of these technical features can be selected by conventional means in the field and should not be regarded as the inventive point of this patent. This patent will not be further elaborated.

[0102] For those skilled in the art, it is still possible to modify the technical solutions described in the aforementioned embodiments, or to make equivalent replacements for some of the technical features therein. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A planetary gearbox sun gear tooth root wireless stress testing system, characterized in that: It includes a test computer, a wireless gateway and several levels of emergency test modules, including: Each of the emergency test modules includes an antenna, several wireless strain testers and several strain gauges. The wireless strain testers are fixedly installed on the sun gear of the corresponding planetary gearbox. The wireless strain testers obtain stress data of the tooth root of the corresponding sun gear through the strain gauges and transmit the obtained stress data to the test computer through the antenna and the wireless gateway.

2. A planetary gearbox sun gear tooth root wireless stress testing system according to claim 1, characterized in that: Assume that the emergency test module includes N wireless strain testers and M strain gauges, wherein: The number N of wireless strain gauges required on each level of sun gear is consistent with the number N of teeth that need to be monitored, and the value of N is equal to the number of sun gears of the planetary gearbox at that level; The strain gauges are installed at each tooth root of the corresponding sun gear, and it is assumed that each tooth root of the sun gear adopts Nt strain measurement points.

3. A planetary gearbox sun gear tooth root wireless stress testing system according to claim 2, characterized in that: The wireless strain tester includes a single chip microcomputer, a battery pack, a storage module, a first wireless module, a second wireless module and a plurality of test channels, each of which includes a strain conditioning unit and an AD acquisition unit, wherein: Each strain conditioning unit is connected to the corresponding strain gauge, conditions and amplifies the strain gauge signal and converts the resistance signal into a voltage signal, and transmits the voltage signal to the corresponding AD acquisition unit, so that the AD acquisition unit converts the voltage signal into an analog-to-digital signal and transmits it to the single-chip microcomputer, which stores the obtained stress data in the storage module.

4. A planetary gearbox sun gear tooth root wireless stress testing system according to claim 3, characterized in that: In the wireless strain tester, dual-mode wireless communication is performed through the first wireless transmission module and the second wireless transmission module and operates in the same frequency band. The dual-mode wireless communication is specifically implemented as follows: S21: The wireless strain gauge enters the sleep mode by default when it is turned on. In the sleep mode, the second wireless transmission module is turned off, and the first wireless transmission module is periodically enabled. The first wireless transmission module is awakened for a time T1 at intervals of T0. When the wireless strain gauge receives a wake-up command from the wireless gateway within the wake-up time T1, the wireless strain gauge is in the standby mode. S22: Standby mode, turn on the first wireless transmission module, turn off the second wireless transmission module, if a collection control instruction from the wireless gateway is received, enter the data collection mode; if a data download instruction is received, enter the data download mode; if no instruction is received at the first time, re-enter the sleep mode; S23: In the data acquisition mode, the first wireless transmission module is turned on, the second wireless transmission module is turned off, and the collected stress data is stored in the storage module; The stress data is sent to the wireless gateway in the manner of sampling one point out of Ns points to realize the monitoring of the data waveform. At the same time, in the data acquisition mode, the wireless gateway sends a time synchronization data packet every T2 time interval. After receiving the time synchronization data packet, each wireless strain tester adjusts the local clock to keep consistent with the clock of the wireless gateway, thereby realizing wireless synchronous data acquisition; S24: After the test collection is completed, in the data download mode, the second wireless transmission module is enabled to achieve high-speed data download. If the second wireless transmission module fails, the first wireless transmission module is continued to be used for data download; S25: After the data collection of a certain working condition is completed, the wireless gateway controls the wireless strain gauge to be in a dormant state, and the entire device is in a low-power dormant state; S26: After the test is completed and the download is completed, the wireless gateway controls the wireless strain gauge to be in a dormant state, and the entire device is in a low-power dormant state.

5. A planetary gearbox sun gear tooth root wireless stress testing system according to claim 4, characterized in that: The wireless gateway includes a first control module and a second control module, the first control module is connected to the first wireless module through a first wireless protocol, and the second control module is connected to the second wireless module through a second wireless protocol, wherein: Wireless synchronization is achieved when the first control module communicates with the first wireless module. The wireless gateway uses a crystal oscillator as the system clock and sends wireless synchronization instructions at regular intervals. After receiving the wireless synchronization instructions, the wireless strain tester adjusts the internal timer clock to achieve synchronization with the wireless gateway clock, thereby realizing distributed wireless synchronous data acquisition in the entire wireless local area network.

6. A planetary gearbox sun gear tooth root wireless stress testing system according to claim 5, characterized in that: The test computer analyzes the stress data and uses the following steps to calculate the load distribution factor K for the internal bending strength calculation of the tooth: Fβ Load distribution factor K when calculating contact strength Hβ , the specific implementation is: Step S31: for each strain gauge on the sun gear tooth root, find the peak points P(1), P(2), P(3), ..., P(Ny) of each strain measurement point under Ny consecutive cycles collected within a period of time; Step S32: for the Nt strain test points on the root tooth, calculate the average value of each strain test point under Ny cycles; Step S33: Find the maximum value max_P of the strain average values ​​of the Nt strain test points in step S32; Step S34: Find the average value ave_P of the average values ​​of the strains of the Nt strain test points in step S32; Step S35: Calculate the load distribution coefficient K in the tooth Fβ : K Fβ =max_P / ave_P; Step S36: According to the formula: Calculate the load distribution coefficient K inside the tooth Hβ , h is the planet gear tooth height, b is the planet gear tooth width, N F is the power index.

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