A ring-shaped strain sensor for load measurement, a roller and a roller bearing

Abstract

The application relates to a ring-shaped strain sensor for load measurement, a roller and a roller bearing, which comprises a ring-shaped base arranged in an axial through hole of a bearing roller and abutting against an inner circumferential surface of the through hole, a 360-degree outer circumferential surface of the ring-shaped base is divided into four or six strain gauges arranged uniformly in a range of 135 degrees or 150 degrees of the outer circumferential surface; the strain gauges are divided into two groups, the strain gauges of the first group are connected in series on one bridge arm of a Wheatstone bridge, and the strain gauges of the other group are connected in series on the bridge arm opposite to the bridge arm where the strain gauges of the first group are located. The application can eliminate the influence of the rotation of the roller as much as possible when measuring the load of the roller, improves the measurement precision, and can be used for measuring the load distribution of the raceway of various types of large roller bearings under the action of complex loads.

Description

TECHNICAL FIELD

[0001] The present application relates to a ring-shaped strain sensor for load measurement, a roller and a roller bearing, and belongs to the technical field of intelligent monitoring of bearings. Specifically, the present application relates to a flexible ring-shaped strain sensor for measuring periodic strain signals and an intelligent roller for measuring the load distribution of the raceway of a large roller bearing, which has the sensor built-in, as well as a bearing using the intelligent roller, and provides a calibration method for the intelligent roller. BACKGROUND

[0002] Large roller bearings are widely used in large mechanical equipment such as shield tunneling machines, cranes and wind turbines, and are the core components of large mechanical equipment. They have a huge structure and are expensive, and play a role in supporting the rotation of two components and transmitting loads. Common large roller bearings include single-row tapered roller bearings and three-row cylindrical roller slewing bearing. Due to the special application field of large roller bearings, large roller bearings are often used in low-speed heavy-load working conditions and harsh environments, and bear complex loads such as large impact, partial load, heavy load, variable load and overturning moment. The complex load is borne by the rollers in the bearing and the raceway in contact with the rollers.

[0003] Once a large roller bearing fails, it will affect the normal operation of the large mechanical equipment, and is likely to cause major safety accidents and huge economic losses. The load distribution of the raceway of a large roller bearing has an important influence on the design of the bearing and the operation of the large mechanical equipment. Therefore, in order to ensure the normal and safe operation of the large mechanical equipment and provide data support for the design of the large roller bearing, it is necessary to invent a measuring method for measuring the load distribution of the raceway of a large roller bearing. At present, the various large roller bearings manufactured in China and applied in large mechanical equipment such as tunnel boring machines, cranes and wind power machinery still have a large gap with foreign countries. The main reason is that there is a lack of relevant experimental parameters, and there is currently no good measuring method for the load distribution of the raceway, which plays an important role in the design of the bearing.

[0004] In recent years, research on embedding sensors in bearings to monitor the state of the bearing, diagnose faults, etc. has become a hot topic. Through the intelligentization of bearings, the load, speed, temperature and vibration of the bearing are measured. Among them, there are also researches on modifying the bearing rollers and embedding various sensors to realize the intelligentization of the rollers. For example, the Chinese patent publication with the publication number CN107542758A discloses a sensorized roller. The roller is hollowed along the circumference, and a strain sensor is placed in it to measure the load on the outer surface of the roller. However, this patent does not consider the influence of the rotation of the roller on the strain output, and cannot obtain the load change on the outer surface of the roller when the large roller bearing bears the load containing partial load and overturning moment.

[0005] In order to improve the design level of large roller bearings, monitor the load of large roller bearings in real time, thereby guaranteeing the operation safety of large mechanical equipment and improving economic benefits, it is necessary to invent an intelligent roller capable of acquiring the load distribution of the raceway of the large roller bearing in real time and a new strain sensor capable of eliminating the influence of the rotation angle of the roller and acquiring the load distribution information of the raceway of the bearing under complex load in cooperation with the intelligent roller. SUMMARY

[0006] The purpose of the present application is to provide a ring-shaped strain sensor, a roller and a roller bearing for load measurement, which solves the problem of low precision caused by the influence of the rotation angle of the roller in the monitoring of the load of the large roller bearing.

[0007] To achieve the above-mentioned purpose, the scheme of the present application includes:

[0008] The technical scheme of a ring-shaped strain sensor of the present application includes a ring-shaped base body arranged in the axial through hole of the roller and attached to the inner circumferential surface of the through hole, the outer circumferential surface of the ring-shaped base body is divided into 360 degrees, and four strain gauges are evenly arranged in the range of 135 degrees of the outer circumferential surface; in the two pairs of adjacent strain gauges, the first pair of adjacent strain gauges are connected in series in one bridge arm of the Wheatstone bridge, and the other pair of adjacent strain gauges are connected in series in the bridge arm opposite to the bridge arm where the first pair of strain gauges are located.

[0009] This scheme eliminates all odd harmonics and part of even harmonics in the output under unit load, to some extent, avoiding the influence of the rotation angle of the roller.

[0010] And this scheme only needs four strain gauges to form a bridge circuit to measure the contact load from the raceway on a radial slice of the intelligent roller, the distance between the strain gauges can be relatively far, and the flexible ring-shaped strain sensor of this scheme has low cost and the intelligent roller has low energy consumption.

[0011] Further, resistors for temperature compensation are connected in series on the remaining two bridge arms of the Wheatstone bridge.

[0012] The temperature compensation resistors are arranged in the axial through hole of the roller, which is used to compensate the influence of temperature change on the measurement during the working process of the bearing roller.

[0013] Further, the ring-shaped base body adopts a ring-shaped flexible circuit board, and the strain gauges adopt one or more of a foil strain gauge, a semiconductor piezoresistive strain gauge or a wire-wound strain gauge.

[0014] Further, the annular strain sensor is made by the following method: firstly, an insulating layer film is formed on the inner hole wall by deposition or ion sputtering process; then, a resistance film is added on the insulating layer film by deposition or ion sputtering; and finally, the resistance and the corresponding bridge connection circuit are etched on the resistance film by photoetching process.

[0015] Further, rotation monitoring strain gauges for obtaining the rotation angular velocity and the rotation angle are arranged outside the 135-degree range of the outer circumferential surface.

[0016] The load measuring roller of the present application can still realize the measurement of the rotation angle and the rotation angular velocity by arranging the strain gauges.

[0017] The technical scheme of the annular strain sensor of the present application comprises an annular base arranged on the axial through hole of the roller and attached to the inner circumferential surface of the through hole, the outer circumferential surface of the annular base is divided into 360 degrees, and six strain gauges are evenly arranged within the 150-degree range of the outer circumferential surface; the circumferentially adjacent first three strain gauges are connected in series on one bridge arm of the Wheatstone bridge, and the circumferentially adjacent last three strain gauges are connected in series on the bridge arm opposite to the bridge arm on which the first three strain gauges are arranged.

[0018] The flexible annular strain sensor of the present application eliminates all odd harmonics, and the sum of the remaining even harmonics becomes very small. The output of the bridge is further reduced in the influence of the roller angle, and the measurement accuracy is improved.

[0019] Further, resistors for temperature compensation are connected in series on the remaining two bridge arms of the Wheatstone bridge.

[0020] Further, the annular base adopts a flexible circuit board, and the strain gauges adopt one or more of a foil strain gauge, a semiconductor piezoresistive strain gauge and a wire-wound strain gauge.

[0021] Further, the annular strain sensor is made by the following method: firstly, an insulating layer film is formed on the inner hole wall by deposition or ion sputtering process; then, a resistance film is added on the insulating layer film by deposition or ion sputtering; and finally, the resistance and the corresponding bridge connection circuit are etched on the resistance film by photoetching process.

[0022] Further, rotation monitoring strain gauges for obtaining the rotation angular velocity and the rotation angle are arranged outside the 150-degree range of the outer circumferential surface.

[0023] The technical scheme of the intelligent roller with load measurement of the present application comprises a through hole opened along the axis, and at least one annular strain sensor as described above is arranged on the inner circumferential surface of the through hole.

[0024] The technical solution of the roller bearing with load measurement of the application comprises at least one intelligent roller with load measurement as described above.

[0025] The application greatly reduces the influence of the self-rotation of the intelligent roller on the measurement results when collecting the contact load between the raceway and the roller using the intelligent roller, and the operation is convenient when the flexible ring-shaped strain sensor is pasted or prepared on the inner hole wall of the intelligent roller. The flexible ring-shaped strain sensor of the application can not only obtain the load value affected little by the self-rotation of the roller, but also obtain the self-rotation angular velocity and the self-rotation angle of the intelligent roller, thereby avoiding the manufacturing difficulty of embedding multiple types of sensors into the intelligent roller. The unevenly distributed linear load between the roller and the raceway is obtained by dividing the intelligent roller into multiple slices, the measurement can be directly performed inside the bearing, the bearing does not need to be disassembled or the structure of the bearing does not need to be changed, the measurement result is more in line with the actual situation, the load distribution on the raceway of the bearing can be monitored in real time, and adjustment can be timely performed. The application can realize the measurement of the load distribution of the raceway of multiple types of large roller bearings under complex load. BRIEF DESCRIPTION OF DRAWINGS

[0026] Fig. 1(a) is a schematic diagram of the load form borne by a cylindrical roller when simultaneously bearing radial force and overturning moment;

[0027] Fig. 1(b) is a schematic diagram of the equivalent uniformly distributed load on the roller slice after the cylindrical roller is divided into three slices;

[0028] Fig. 2(a) is a bridge connection principle diagram of the strain gauge group bridge scheme A of the flexible ring-shaped strain sensor in the intelligent roller of the application;

[0029] Fig. 2(b) is a position diagram of the strain gauge of the strain gauge group bridge scheme A of the flexible ring-shaped strain sensor in the intelligent roller of the application on the inner hole wall of the intelligent roller slice;

[0030] Fig. 3(a) is a bridge connection principle diagram of the strain gauge group bridge scheme B of the flexible ring-shaped strain sensor in the intelligent roller of the application;

[0031] Fig. 3(b) is a position diagram of the strain gauge of the strain gauge group bridge scheme B of the flexible ring-shaped strain sensor in the intelligent roller of the application on the inner hole wall of the intelligent roller slice;

[0032] Fig. 4(a) is a bridge connection principle diagram of the load measurement strain gauge in the strain gauge group bridge scheme of the flexible ring-shaped strain sensor in the intelligent roller of the application, which can realize the measurement of the self-rotation angular velocity and the self-rotation angle of the intelligent roller (the same as Fig. 2(a));

[0033] Figure 4(b) is a strain gauge bridge connection principle diagram of the strain gauges for measuring the rotation angular velocity and rotation angle of the flexible annular strain sensor in the smart roller of the present application;

[0034] Figure 4(c) is a position diagram of the strain gauges of the flexible annular strain sensor for measuring the rotation angular velocity and rotation angle of the smart roller on the inner hole wall of the smart roller slice of the present application;

[0035] Figure 5 Figure 4(c) is a position diagram of the strain gauges of the flexible annular strain sensor for measuring the rotation angular velocity and rotation angle of the smart roller on the inner hole wall of the smart roller slice of the present application;

[0036] Figure 6 Figure 4(c) is a position diagram of the strain gauges of the flexible annular strain sensor for measuring the rotation angular velocity and rotation angle of the smart roller on the inner hole wall of the smart roller slice of the present application;

[0037] Figure 7 Figure 4(c) is a position diagram of the strain gauges of the flexible annular strain sensor for measuring the rotation angular velocity and rotation angle of the smart roller on the inner hole wall of the smart roller slice of the present application;

[0038] Figure 8 Figure 4(c) is a position diagram of the strain gauges of the flexible annular strain sensor for measuring the rotation angular velocity and rotation angle of the smart roller on the inner hole wall of the smart roller slice of the present application;

[0039] Figure 9 Figure 4(c) is a position diagram of the strain gauges of the flexible annular strain sensor for measuring the rotation angular velocity and rotation angle of the smart roller on the inner hole wall of the smart roller slice of the present application; DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application is further described in detail below with reference to the drawings and examples.

[0041] The present application realizes the monitoring of the raceway load distribution information and the like by installing several smart rollers at different positions in the large roller bearing and the raceway load distribution monitoring software in the upper computer. The smart roller should meet the scene including the large cylindrical roller turntable bearing and the large tapered roller bearing commonly used in the wind driven generator and the shield machine, so the structure of the smart roller is a hollow cylindrical roller or a hollow tapered roller. The sensor module, the wireless transmission module, the power supply module, the embedded controller and the three-layer structure circuit board bearing each module are integrated in the inner hole of the roller, which are used for collecting and sending the strain values on the inner hole wall of the roller. The sensor module includes a platinum thermal resistance temperature sensor for measuring the roller temperature and several flexible annular strain sensors capable of realizing continuous force measurement and eliminating the influence of the roller rotation angle. The raceway load distribution monitoring software in the upper computer is used for denoising, inverse calculation and display of the continuous strain values collected by the several smart rollers in the large roller bearing and the corresponding raceway load values and temperatures which are not affected by the roller rotation angle.

[0042] For the structural design of the intelligent roller, the intelligent roller should have the functions and features of measuring the strain value on the inner hole wall of the roller which is not affected by the rotation angle of the roller, the roller temperature, data storage, data timing wireless transmission, power feedback, roller hibernation, low power consumption, and similar load capacity as the solid roller.

[0043] For the inner hole of the intelligent roller, the inner hole axis coincides with the roller axis, the inner hole is a cylinder, the inner hole diameter is related to the roller diameter of the measured bearing, and at least there needs to be space in the inner hole to place related electrical components without affecting the load capacity of the roller, and the diameter of the space can be selected from 50mm-30mm.

[0044] For the sensor module of the intelligent roller, it contains several flexible ring-shaped strain sensors for measuring the strain value on the inner hole wall and a platinum resistance temperature sensor for measuring the roller temperature. The flexible ring-shaped strain sensor is composed of several foil strain gauges distributed at a specific angle and connected in a specific bridge mode, and a ring-shaped flexible circuit board for bearing and connecting the foil strain gauges. The composition of the flexible ring-shaped strain sensor described here is only an example of one, where the foil strain gauges can be replaced by semiconductor strain gauges or wire-wound strain gauges. The strain gauges can also be in the form of resistance strain gauges made directly on the inner hole wall of the intelligent roller by deposition or ion sputtering, but the number and relative position of these types of strain gauges on the inner hole wall of the intelligent roller and the bridge mode are uniform.

[0045] For the wireless transmission module of the intelligent roller, the circuit board of the wireless transmission module is placed near the edge of the inner hole of the intelligent roller to improve the transmission efficiency as much as possible. The wireless transmission module of the present application should meet the requirements of strong penetration, energy saving, reliability, low cost, short delay, large network capacity, safety, etc. Therefore, Zig-Bee communication technology is selected to build the wireless transmission module. Zig-Bee wireless transmission technology can transmit a distance of 100 meters with a baud rate of 115200.

[0046] For the embedded controller of the intelligent roller, a single-chip microcomputer and related components are arranged to control the work and sleep of each sensor and complete the processing and transmission of sensor data. An STM32 single-chip microcomputer is used as the control and data processing center of the system. The STM32 single-chip microcomputer is mainly a microcontroller designed by the STMicroelectronics Company, which has the characteristics of low power consumption, low cost and high performance, and is suitable for embedded applications. The embedded controller is located on an embedded controller circuit board. Among them, a microcontroller with an integrated ADC function is arranged on the embedded controller circuit board. The voltage signal of the power supply is collected by using a differential input method, and then the measurement of the residual power signal is realized to master the residual power of the intelligent roller. According to the residual power of the intelligent roller, the working time of the intelligent roller is determined to prolong the service life of the intelligent roller.

[0047] For the power supply unit of the intelligent roller, the battery is used as the energy source of the intelligent roller, which is affected by the size of the measured bearing roller. The size and type of the battery should be selected according to different types of bearings. The principle of selecting the battery is to improve the battery capacity as much as possible, prolong the working time of the intelligent roller, and at least meet the use time of 2-3 years. When designing the link, as much space as possible should be left for the battery to increase the battery volume as much as possible.

[0048] For the three-layer structure circuit board of the intelligent roller, the three layers are wireless transmission module circuit board, embedded controller circuit board and sensor module circuit board. For the sensor module circuit board, a platinum resistance temperature sensor and related circuits for processing flexible ring-shaped strain sensors are arranged thereon. The shape of each layer of the circuit board is circular, which is arranged radially along the inner hole of the roller, and the diameter is restricted by the inner hole radius of the intelligent roller, and the thickness is 2mm. The three layers of circuit boards are connected through circuits, and the distance between the three layers of circuit boards should be as compact as possible. The three layers of circuit boards are placed in the inner hole of the intelligent roller close to the gap on one side of the large roller bearing structure. The wireless transmission module circuit board is placed on the side closest to the roller end face. Arranging the circuit board into the above three-layer structure can reduce the space occupied by the circuit board as much as possible and increase the battery volume as much as possible.

[0049] For the fixation of electronic components of the intelligent roller, the battery is placed in a semi-cylindrical battery sleeve made of plastic material. The several flexible ring-shaped strain sensors in the intelligent roller are evenly pasted, and the battery sleeve with various components installed is placed in the specified position in the hollow roller of the intelligent roller. Then the epoxy resin glue is filled in the inner hole of the intelligent roller to fix the electronic components in the intelligent roller and protect the electronic components from being damaged and invaded by foreign matters.

[0050] The structure of the intelligent roller of the application is specifically as follows Figure 8As shown in the figure, wherein the number 16 is the outer wall of the roller, 17 is the battery cover, 18 is the battery, 19 is one of the flexible ring-shaped strain sensors, 20 is the circuit board connecting column, 21 is the sensor module circuit board; 22 is the embedded controller circuit board, 23 is the wireless transmission module circuit board, 24 is the STM32 single-chip microcomputer, 25 is the flexible ring-shaped strain sensor processing module, 26 is the platinum resistance-based temperature sensor, 27 is the second flexible ring-shaped strain sensor, 28 is the third flexible ring-shaped strain sensor. After the assembly of the intelligent roller is completed, as shown in the figure. Figure 9 As shown in the figure.

[0051] Design of flexible ring-shaped strain sensor:

[0052] For the design of the flexible ring-shaped strain sensor in the intelligent roller, the purpose is to reduce the influence of the roller rotation angle on the output strain value as much as possible to achieve the goal of continuous force measurement, and the key lies in the number and position of the strain gauge and the bridge connection method. This flexible ring-shaped strain sensor can realize continuous measurement of the periodic strain signal varying with the angle, and the measurement result is affected very little by the angle. The structure of the flexible ring-shaped strain sensor of the embodiment is mainly determined by the periodic variation law of the measured signal and the size of the measured signal, and is restricted by the size of the inner hole wall of the intelligent roller and the size of the foil strain sensor. For different periods and different sizes of strain signals, the distribution form and bridge connection method of the foil strain sensor in the flexible ring-shaped strain sensor should be changed accordingly. The calibration method provided in the embodiment is mainly for the calibration of the flexible ring-shaped strain sensor.

[0053] Theoretical basis for the design of the flexible ring-shaped strain sensor: build a three-dimensional model of the intelligent roller in the measured bearing of the large cylindrical roller and the large conical roller and part of the upper and lower raceways at the joint with the intelligent roller. Use finite element simulation software to simulate the real bearing constraint condition and the load condition of the roller in reality to perform finite element statics simulation on the built intelligent roller model, and obtain the strain distribution cloud diagram of the inner hole wall of the intelligent roller in the axial direction, the ring direction and the radial direction of the intelligent roller. By observing the strain distribution cloud diagram on the inner hole wall of the intelligent roller section, it is found through analysis and comparison that the ring direction strain value on the inner hole wall of the cylindrical intelligent roller and the conical intelligent roller is the largest, that is, the ring direction strain value has the largest sensitivity to the load bearing of the intelligent roller, and the strain value along the ring direction of the intelligent roller inner hole wall has a clear periodic distribution, that is, the ring direction strain value of the measured point will show a clear periodic variation law with the rotation of the intelligent roller. Therefore, the ring direction strain on the inner hole wall is selected as the measured object.

[0054] Because intelligent rollers are used in harsh working environments such as wind turbines and tunnel boring machines, where bearings are subjected to complex loads, and considering that the outer surface of the rollers in large bearings has a large convexity, the load applied to the intelligent roller by the raceway is unevenly distributed along the roller generatrix. Taking a cylindrical intelligent roller as an example, due to the influence of the roller surface convexity, when a uniformly distributed radial force is applied to the simulation model, it is found that the force distribution at the contact point between the intelligent roller and the raceway is smaller at both ends and larger in the middle along the roller axis, with the maximum value appearing in the middle position. When a non-uniformly distributed radial force under the simulated overturning moment is applied to the simulation model, it is found that the force distribution at the contact point between the intelligent roller and the raceway increases from small to large and then decreases again, as shown in Figure 1(a), which illustrates the load form borne by the cylindrical intelligent roller when simultaneously subjected to radial force and overturning moment. In the figure, the rectangle represents the roller cross-section, and the up and down arrows and lengths represent the distribution, direction, and magnitude of the radial force on the roller. The circumferential strain distribution along the generatrix of the intelligent roller's inner bore wall is positively correlated with the force distribution at the contact point of the intelligent roller's raceway. Therefore, when using flexible annular strain sensors to obtain the load distribution on the raceway of large roller bearings, the uneven loading on the outer surface of the intelligent roller should be considered to obtain more accurate results.

[0055] To obtain more accurate results, the intelligent roller with an effective length of L is equally divided into n pieces along the roller axis. The non-uniformly distributed load on the intelligent roller by the inner and outer raceways is equivalent to a pair of uniformly distributed loads acting in opposite directions along a certain diameter on each intelligent roller slice, as shown in Figure 1(b), which is a simplified diagram of the equivalent uniformly distributed load on the roller slice after dividing the intelligent roller into three slices. In the figure, the roller is divided into 3 slices along the axial direction, with slice lengths of l1, l2, and l3, and equivalent loads of Q1, Q2, and Q3, respectively. Taking the i-th intelligent roller slice as an example, the uniformly distributed load value is equivalent to the load value borne by the intelligent roller slice, and the circumferential strain around the center of the inner hole wall of this slice is equivalent to the circumferential strain value on the inner hole wall of this intelligent roller. A mathematical model is established between the circumferential strain on the inner hole wall of the slice, the load, and the roller rotation angle.

[0056] ε(F i ,θ)=F i f(θ)

[0057] Wherein: F i ε(F) is the equivalent uniformly distributed load acting on the i-th slice. i When the measured point on the inner wall of the intelligent roller slice i is θ away from the contact position of the upper raceway, the intelligent roller is subjected to an equivalent load F. i The circumferential strain value under action, f(θ) is a function coefficient with the rotation angle of the intelligent roller as the independent variable.

[0058] Any function with a period of 2T can be expanded into a Fourier series as follows, which is a constant term plus n harmonics.

[0059]

[0060] where the coefficients a n and b n are calculated as follows:

[0061]

[0062]

[0063] From the above simulation analysis, it can be seen that the hoop strain on the inner hole wall of the intelligent roller slice is an even function with a period of π, and the coefficient b n in the Fourier series expansion is 0, so the Fourier series expansion of the hoop strain on the inner hole wall of the intelligent roller slice after being subjected to a unit load is:

[0064]

[0065] where a n is calculated as follows:

[0066]

[0067] The hoop strain can be expressed as:

[0068]

[0069] If a resistance strain sensor is used to measure the strain value at this point, the theoretical output of the sensor is:

[0070]

[0071] where K is the sensitivity coefficient of the strain sensor.

[0072] The load measured by the strain sensor is:

[0073]

[0074] where u out is the output of the strain sensor, K is the sensitivity coefficient of the strain sensor, is the ramp term of the periodic strain, the existence of this term causes the measured load value to be affected by the angle, and the purpose of the bridge assembly scheme described below is to minimize the size of this term and thus obtain a load value that is approximately free of angle influence.

[0075] It can be found that the relationship between the circumferential strain of the inner hole wall of the smart roller and the equivalent uniform load borne by the roller slice is affected by the angle θ between the roller and the contact line of the raceway, and the influence is through the n-th harmonic of the periodic function. If there is a function that can eliminate the n-th harmonic in the function relationship, the relationship between the circumferential strain and the equivalent uniform load will be linear and no longer affected by the rotation angle of the roller. For the above purpose, the embodiment provides such a flexible annular strain sensor. The harmonic analysis of the strain gauge output result is performed to determine the appropriate number, position and bridge connection mode of the strain gauges, which can greatly eliminate the influence of the rotation angle on the output of the strain gauges, that is, under the same load, the strain gauge group will output an approximately straight line with small fluctuations around a certain value when the roller rotates arbitrarily. Then, the calibration experiment is performed to determine the linear relationship between the load and the output of the strain gauge group, so that the continuous measurement of the force borne by the smart roller can be realized.

[0076] The bridge connection scheme and principle of the present application are illustrated by taking foil strain gauges as an example, but the bridge connection scheme is not limited to foil strain gauges. The conventional method of using strain gauges is to build a Wheatstone bridge, and select full-bridge, half-bridge or single-bridge mode for measurement. When two strain gauges A and A' are arranged on opposite bridge arms of the bridge, according to the principle of the Wheatstone bridge, the output of the bridge at this time is:

[0077]

[0078] wherein u out is the output voltage of the bridge; K is the sensitivity coefficient of the bridge; ε A is the strain value output by strain gauge A; and ε A' is the output result of strain gauge A'.

[0079] Suppose that the position of strain gauge A is the position closest to the contact position on the inner hole wall of the smart roller when the smart roller is in contact with the upper raceway at a certain moment, that is, the position of maximum normal strain at a certain moment, and the position of strain gauge A at this moment is defined as the 0° position on the inner hole wall, clockwise as positive, and the angle change range is [0, 2π]. Strain gauge A' is located at π / 2. Two strain gauges are arranged on opposite bridge arms of the bridge to form a Wheatstone bridge, and the resistors R on the other two opposite bridge arms in the Wheatstone bridge are used for temperature compensation and are arranged in the sensor module circuit board. When a unit load is applied to the smart roller, the output of the bridge at this time is:

[0080]

[0081] It can be found from the above formula that the outputs of the two strain gauges are periodic functions with a phase difference of π / 2. The bridge output of this bridge connection scheme eliminates all odd harmonics of the two periodic functions, leaving only the constant term a0 and even harmonics and, but still cannot well eliminate the influence of the angle on the output result.

[0082] Further, based on the above principle, the present application provides the following bridge connection schemes as the flexible ring-shaped strain sensor is prepared according to the actual application scene and needs. The purpose of the bridge connection scheme is to connect the plurality of strain gauges in a certain bridge connection manner so that the output of the bridge connection circuit is the cumulative sum of the output results of the strain gauges, to eliminate the harmonic components as much as possible and to reduce the influence of the angle on the result as much as possible, and finally to make the output result of the bridge connection circuit fit a linear relationship with the load value.

[0083] ① Bridge connection scheme A

[0084] In order to eliminate the influence of the even harmonics as much as possible, four strain gauges are taken to be connected in the manner shown in Fig. 2(a), the interval angle of the four strain gauges is π / 4, the strain gauges A and A' arranged on the opposite bridge arms of the bridge have an interval of π / 2, and the strain gauges B and B' have an interval of π / 2. The positions of the strain gauges on the inner hole wall of the intelligent roller are shown in Fig. 2(b), and the resistors R in the other two opposite bridge arms of the Wheatstone bridge are arranged in the sensor module circuit board for temperature compensation. The output of the flexible ring-shaped strain sensor formed by this bridge connection scheme under the action of a unit load is:

[0085]

[0086] It can be found that the flexible ring-shaped strain sensor formed by this bridge connection scheme eliminates all odd harmonics and part of even harmonics, and still leaves the fourth harmonic, the eighth harmonic and other integer multiple of four harmonics. Therefore, the strain value of the sensor output will still be affected by the angle of rotation of the intelligent roller.

[0087] For the Fourier series expansion term of a periodic function, generally speaking, the larger the n is, the higher the corresponding harmonic frequency is, that is, the smaller the spatial period is. Correspondingly, the larger the n is, the more detailed the corresponding waveform change will be, and therefore the influence on the overall periodic function waveform will be more intense. However, it should be noted that although the high-order cosine term may be more localized and more detailed in the influence on the periodic function than the low-order term, the weight coefficient a n of the high-order cosine term will generally decrease rapidly with the increase of n, and therefore the overall effect may not be more significant than that of the low-order term.

[0088] In the application example, since the intelligent roller is a standard axisymmetric structure, the circumferential strain variation on the inner hole wall is very close to a trigonometric function with a period of π, and the first three terms of the Fourier series expansion can be used to approximate the original function. Therefore, this group of bridge schemes eliminates the first three harmonics, and the uneliminated harmonics have little effect on the measurement results. But there will still be some fluctuations, and whether the error brought by it can meet the demand needs to be determined through the calibration test of the intelligent roller.

[0089] The feature of this group of bridge schemes is that only four strain gauges are needed to form a bridge circuit for an intelligent roller slice to measure the contact load from the raceway. The distance between the strain gauges can be relatively far. The advantage of using this group of bridge schemes to make flexible ring-shaped strain sensors is low cost and low energy consumption of the intelligent roller. The disadvantage is that the measurement accuracy may not be high enough.

[0090] ②Bridge scheme B

[0091] Six strain gauges are used to form a bridge as shown in Fig. 3(a). The interval angle between the six strain gauges is π / 6. The strain gauges A and A' arranged on opposite arms of the bridge have an interval of π / 2, B and B' have an interval of π / 2, and C and C' have an interval of π / 2. The positions of the strain gauges on the inner hole wall of the intelligent roller are shown in Fig. 3(b). The resistance R in the other two opposite arms of the Wheatstone bridge is used for temperature compensation and is arranged in the sensor module circuit board. The output of the flexible ring-shaped strain sensor formed by this group of bridge schemes under unit load is:

[0092]

[0093] It can be found that the flexible ring-shaped strain sensor formed by this group of bridge schemes eliminates all odd harmonics, and even harmonics are not eliminated, but the sum of all even harmonics will be very small, with a value of 10 -14 order. Such a small harmonic sum makes the output of the bridge very small. The degree of influence of this group of bridge schemes on the output of the intelligent roller is smaller than that of the bridge scheme A. However, it does not completely eliminate the harmonics, and the output strain value of the sensor will still be affected by the rotation angle of the intelligent roller, i.e. the output of the sensor still has a certain error in theory. Whether the error brought by it can meet the demand needs to be determined through the calibration test of the intelligent roller.

[0094] The bridge scheme features that six strain gauges are needed for one intelligent roller slice, and the interval angle between the strain gauges is relatively small. Due to the limited space in the inner hole wall of the intelligent roller, the bridge scheme requires higher strain gauge size. The flexible ring-shaped strain sensor prepared by the bridge scheme has the advantages of higher measurement accuracy than the bridge scheme A, and the disadvantages of relatively high cost and relatively large energy consumption, which is not conducive to the low energy consumption design of the intelligent roller.

[0095] Further, the self-rotation angular velocity and the self-rotation angle of the intelligent roller are also obtained by using the flexible ring-shaped strain sensor. A strain gauge is arranged on the ring-shaped flexible circuit board of the flexible ring-shaped strain sensor, and the sampling frequency of the strain gauge is set to be above 1 kHz. The periodic signal output by the strain gauge can be used to calculate the self-rotation angular velocity and the self-rotation angle of the intelligent roller. The higher the sampling frequency is, the more accurate the calculated angular velocity and angle are. The principle of the calculation algorithm is as follows: the average self-rotation angular velocity in a short period of time is equal to twice the average frequency of the periodic signal output by the strain gauge in the period of time; and the rotation angle of the intelligent roller can be obtained by integrating the continuously measured angular velocity. For example, the bridge scheme A is increased with the measurement of the self-rotation angular velocity and the self-rotation angle of the intelligent roller, and the bridge scheme of the flexible ring-shaped strain sensor for measuring the rotation angle and the angular velocity of the intelligent roller is increased. The relative positions of the strain gauges in the flexible ring-shaped strain sensor on the inner hole wall of the intelligent roller are shown in FIGS. 4(a), 4(b) and 4(c), wherein the strain gauge D is used to measure the self-rotation angular velocity and the self-rotation angle of the intelligent roller by the strain change rule.

[0096] Further, for the preparation of the above flexible ring-shaped strain sensor, the strain gauges can be selected from various types, and then the strain gauges are fixed on a ring-shaped flexible circuit board as a ring-shaped substrate according to the bridge scheme. The diameter of the ring-shaped flexible circuit board should comprehensively consider the thickness of the selected strain sensor, the thickness of the flexible circuit board itself, the diameter of the inner hole of the intelligent roller, and the pasting method of the flexible ring-shaped strain sensor on the inner hole wall of the intelligent roller, and the diameter can be generally between 27 mm and 28 mm. The following four preparation schemes are provided in the embodiment:

[0097] Preparation scheme A: foil strain gauge and ring-shaped flexible circuit board combination preparation; a micro foil strain gauge with a size less than 2 mm, such as 1-LY11-0.3 / 120 micro strain gauge, is selected, and the thickness of the ring-shaped flexible circuit board can be selected from 0.2-0.5 mm.

[0098] Preparation scheme B: semiconductor piezoresistive strain gauge is combined with ring-shaped flexible circuit board; the semiconductor piezoresistive strain gauge is manufactured on a wafer by microelectronic processing technology, and its size parameters are sufficient to meet the requirements of the flexible ring-shaped strain sensor on the size of the strain unit, and the thickness of the ring-shaped flexible circuit board can be selected as 0.2-0.5 mm.

[0099] Preparation scheme C: wire-wound strain gauge is combined with ring-shaped flexible circuit board; the wire-wound strain gauge can be selected from thin wire-wound strain gauges, M-DSR series micro wire-wound strain gauges and 1N series micro wire-wound strain gauges, and the thickness of the ring-shaped flexible circuit board can be selected as 0.2-0.5 mm.

[0100] Preparation scheme D: the ring-shaped strain sensor is prepared by using in-situ measurement technology. First, an insulating layer film is formed on the inner hole wall by deposition or ion sputtering process, then a resistance film is formed on the insulating layer film by deposition or ion sputtering, then a photoetching process is used to etch the resistance and the corresponding bridge connection circuit on the required position of the resistance film, and finally a protective film is added to prepare the sensor on the smart roller.

[0101] Figure 5 A structure schematic diagram of the flexible ring-shaped strain sensor constructed by using the bridge combination scheme A and the preparation scheme C of the present application is shown, wherein 1 is a strain gauge A, 2 is a strain gauge B, 3 is a strain gauge A', 4 is a strain gauge B', 5 is a ring-shaped flexible circuit board, 6 is a connection head for outputting signals of the circuit board.

[0102] Figure 6 A structure schematic diagram of the flexible ring-shaped strain sensor constructed by using the bridge combination scheme A and the preparation scheme D of the present application is shown, and the thickness of each layer structure is only schematic and does not represent the actual thickness, wherein 7 is a strain resistance A, 8 is an inner hole wall of a smart roller, 9 is a strain resistance B, 10 is an insulating layer, 11 is a resistance layer, 12 is a strain resistance A', 13 is a protective layer, and 14 is a strain resistance B'.

[0103] Figure 7 A structure schematic diagram of the flexible ring-shaped strain sensor with angular velocity and angle measurement function constructed by using the bridge combination scheme A and the preparation scheme C of the present application is shown, wherein 15 is an angle measurement strain gauge, and 151 is a load measurement strain gauge.

[0104] Further, for the calibration of the smart roller with the built-in flexible ring-shaped strain sensor, the calibration of the smart roller includes the selection of the bridge connection scheme of the flexible ring-shaped strain sensor; the selection of the preparation scheme; the calibration of the sensor-related parameters such as the sensitivity, zero-point drift, nonlinearity, and temperature compensation range of the flexible ring-shaped strain sensor; the degree of influence of the output result of the flexible ring-shaped strain sensor on the self-rotation angle of the smart roller; the linear coefficient and nonlinearity between the output result of the flexible ring-shaped strain sensor and the load received by the smart roller, i.e., the linear relationship between the output result of the flexible ring-shaped strain sensor and the contact load between the smart roller and the raceway. The principles for the selection of the bridge connection scheme and the preparation scheme are as follows: 1) the number of strain gauges should be reduced as much as possible to reduce the cost and power consumption of the sensor; 2) the selected bridge connection scheme should be able to meet the installation requirements in the limited inner hole of the smart roller; and 3) the parameters of the sensor formed by the bridge connection scheme should be as good as possible.

[0105] The calibration test bench for the calibration test of the smart roller should have the ability to cause the smart roller to rotate, i.e., to realize the dynamic calibration of the smart roller, and the ability to apply a non-uniformly distributed load perpendicular to the outer surface of the smart roller to the outer surface of the smart roller.

[0106] The overall process of the calibration test of the smart roller with the built-in flexible ring-shaped strain sensor is as follows: first, the dynamic calibration of the smart roller with the flexible ring-shaped strain sensor made by the bridge connection scheme B is performed under a certain constant load to obtain the degree of influence of the angle, and it is determined whether the error caused by the angle can meet the requirements according to the actual requirements. If the error can meet the requirements, the calibration of the related parameters of the flexible ring-shaped strain sensor and the linear coefficient and nonlinearity between the output result of the flexible ring-shaped strain sensor and the contact load between the smart roller and the raceway is performed. If the error cannot meet the requirements, the bridge connection scheme C is used.

[0107] Further, for the determination of the number of ring-shaped strain sensors when the smart roller is used to measure the load distribution of the raceway, since the application scenarios of the smart roller are harsh working environments such as wind turbines and shield machines, and the bearing load conditions are complex, and considering that a large convexity is arranged on the outer surface of the large bearing roller, the load perpendicular to the roller is not uniformly distributed along the roller generatrix, and therefore as many flexible ring-shaped strain sensors as possible should be pasted on the inner hole wall of the smart roller, i.e., as many slices of the smart roller as possible are described above, and a flexible ring-shaped strain sensor is pasted on each slice to realize the measurement of the non-uniformly distributed load between the smart roller and the bearing raceway. However, due to the space limitation of the inner hole of the smart roller and the requirement of low energy consumption during the design of the smart roller, the number of strain rings should be reasonably selected. Generally, three to five strain rings can meet the use requirements.

[0108] Further, for the determination of the number of smart rollers when measuring the raceway load distribution with smart rollers: the best way to obtain the raceway load distribution is to replace all the rollers in the large cylindrical roller bearing with smart rollers, but considering the cost and the problem of weakening the bearing capacity, 12 rollers spaced 30 degrees apart can be replaced with smart rollers or 24 rollers spaced 15 degrees apart can be replaced with smart rollers. The more the number of smart rollers, the more accurate and timely the measured raceway load distribution will be. In specific applications, the relationship between the accuracy, real-time performance, cost and safety of the raceway load distribution should be considered, and the number of replacement should be selected according to the actual situation, but it is recommended that at least 12 rollers should be replaced with smart rollers.

[0109] Further, for the measurement method of the raceway load distribution, taking the replacement of 12 rollers with equal angle distribution in the large roller bearing with smart rollers as an example, the way of measuring the raceway load distribution of the large roller bearing with smart rollers is illustrated. When obtaining the raceway load distribution of the bearing with smart rollers, it includes the load distribution of each smart roller at the instant position on the raceway of the large roller bearing in the instantaneous state and the complete raceway load distribution obtained by the 12 smart rollers together walking around the raceway of the large roller bearing, i.e. each roller obtains the load distribution of the raceway in the time period of 30° rotation of the shaft of the large roller bearing on the raceway. For the load of a single smart roller, several groups of flexible ring-shaped strain sensors are set, i.e. the smart roller is divided into several slices, and several load values can be obtained. The equivalent uniform load on the outer surface of the smart roller is accumulated, which is the load value of the raceway of the large roller bearing at the contact position of the smart roller measured by the smart roller.

[0110] Further, for the construction of the raceway load distribution monitoring software in the upper computer, which is used to display the temperature, strain and angle of several smart rollers collected at different positions in the large cylindrical roller bearing and the corresponding raceway load value of the smart roller, and to display the raceway load distribution diagram composed of the load values at different positions on the raceway obtained by several smart rollers, and finally to realize the real-time measurement and display of the raceway load distribution of the large cylindrical roller bearing under complex load.

[0111] The application greatly reduces the influence of the self-rotation of the intelligent roller on the measurement result when the contact load of the intelligent roller collecting the raceway and the roller is used, and the flexible annular strain sensor is convenient to stick or prepare on the inner hole wall of the intelligent roller, the flexible annular strain sensor of the application can not only obtain the load value affected little by the self-rotation of the roller, but also obtain the self-rotation angular velocity and the self-rotation angle of the intelligent roller, and the manufacturing difficulty of embedding multiple types of sensors into the intelligent roller is avoided. The unevenly distributed linear load between the roller and the raceway is obtained by dividing the intelligent roller into multiple slices, the measurement can be directly carried out in the bearing, the bearing does not need to be disassembled or the bearing structure does not need to be changed, the measurement result is more close to the real situation, the load distribution on the bearing raceway can be monitored in real time, and adjustment can be carried out in time. The application can realize the measurement of the load distribution of various types of large roller bearings under the action of complex load.

Claims

1. A ring strain sensor, characterized in that, It includes an annular base for being installed in the axial through hole of the roller and fitting against the inner circumferential surface of the through hole. The outer circumferential surface of the annular base is divided into 360 degrees, and four strain gauges are uniformly arranged within a 135-degree range on the outer circumferential surface. In two pairs of adjacent strain gauges, the first pair of adjacent strain gauges is connected in series on one arm of a Wheatstone bridge, and the other pair of adjacent strain gauges is connected in series on the arm opposite to the arm where the first pair of strain gauges are located.

2. The ring strain sensor according to claim 1, characterized in that, The annular substrate is a ring-shaped flexible circuit board, and the strain gauge is one or more of the following: foil strain gauge, semiconductor piezoresistive strain gauge, or wire-wound strain gauge.

3. The ring strain sensor according to claim 1, characterized in that, The ring strain sensor is manufactured by the following method: first, an insulating layer is formed on the inner wall of the hole using deposition or ion sputtering process; then, a resistive film is added on the insulating layer using deposition or ion sputtering; and finally, the resistor and the corresponding bridge connection circuit are etched on the resistive film at the required positions using photolithography.

4. The annular strain sensor according to claim 1, characterized in that, Outside the 135-degree range of the outer circumference, a rotation monitoring strain gauge for obtaining the rotation angular velocity and rotation angle is also provided, and the rotation monitoring strain gauge is set on the bridge arm of another Wheatstone bridge.

5. A ring strain sensor, characterized in that, It includes an annular base for being installed in the axial through hole of the roller and fitting against the inner circumferential surface of the through hole. The outer circumferential surface of the annular base is divided into 360 degrees, and six strain gauges are uniformly arranged within a 150-degree range on the outer circumferential surface. The first three adjacent strain gauges in the circumferential direction are connected in series on one arm of a Wheatstone bridge, and the last three adjacent strain gauges are connected in series on the arm opposite to the arm where the first three strain gauges are located.

6. The ring strain sensor according to claim 5, characterized in that, The annular substrate is a ring-shaped flexible circuit board, and the strain gauge is one or more of the following: foil strain gauge, semiconductor piezoresistive strain gauge, or wire-wound strain gauge.

7. The annular strain sensor according to claim 5, characterized in that, The ring strain sensor is manufactured by the following method: first, an insulating layer is formed on the inner wall of the hole using deposition or ion sputtering process; then, a resistive film is added on the insulating layer using deposition or ion sputtering; and finally, the resistor and the corresponding bridge connection circuit are etched on the resistive film at the required positions using photolithography.

8. The annular strain sensor according to claim 5, characterized in that, Outside the 150-degree range of the outer circumference, a rotation monitoring strain gauge for obtaining the rotation angular velocity and rotation angle is also provided, and the rotation monitoring strain gauge is set on the bridge arm of another Wheatstone bridge.

9. A smart roller with load measurement, characterized in that, A through hole is provided along the axis, and at least one annular strain sensor as described in any one of claims 1 to 8 is provided on the inner circumferential surface of the through hole.

10. A roller bearing with load measurement, characterized in that, Includes at least one smart roller with load measurement as described in claim 9.

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