Method and system for monitoring internal gear mesh wear in a harmonic reducer

Abstract

The application discloses a kind of harmonic reducer internal gear meshing wear monitoring method and system, the method includes the following steps: using the vibration sensor that is symmetrically installed in the inside of steel wheel along radial direction obtains two groups of vibration data under the stable health state of harmonic reducer, the similarity of corresponding data points of two groups of data is solved;Using similarity, the maximum distance difference D max Of two groups of data is calculated;Using the vibration sensor that is symmetrically installed in the inside of steel wheel along radial direction obtains the data under actual operation;The similarity Dr of data under actual operation is calculated;Contrast Dmax and Dr, judge whether the wear exists in the meshing of internal gear of reducer;The degree of wear is calculated and monitoring conclusion is given according to the degree of wear.The application obtains the wear condition of gear at gear meshing by comparing the differentiated information of vibration signals detected by symmetric vibration sensors in stable health state and actual operation, algorithm is simple;Common external interference can be removed, and monitoring is more accurate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of gear wear monitoring, and particularly relates to a monitoring method and system for gear meshing wear inside a harmonic reducer. BACKGROUND

[0002] A harmonic reducer is composed of three basic components: a fixed inner tooth rigid gear, a flexible gear, and a wave generator that causes radial deformation of the flexible gear. As a new type of reducer, the harmonic reducer has the characteristics of high transmission efficiency, large transmission ratio, and smooth operation, and is widely used in electronic industry, aerospace field, robot joint transmission and other fields. The control accuracy of the harmonic reducer is high, therefore, it is very important to understand the running status of the harmonic reducer, and the key point is to master the gear meshing condition between the flexible gear and the steel gear inside the harmonic reducer and the wear condition of the gear.

[0003] In order to obtain the meshing condition of the gear, most of the speed measuring devices install sensors on the output part, which is complex to operate, inconvenient to install, and easy to affect the original reducer operation performance.

[0004] In order to obtain the wear condition of the gear, CN111611946A discloses a micro-milling cutter wear online monitoring method based on principal component analysis and BP neural network, vibration signals in the gear meshing process are collected through a vibration sensor installed on the main shaft of the machine tool, frequency domain features are obtained through time domain and frequency domain analysis methods, and the micro-milling vibration signals are dimensionally reduced by using principal component analysis method, and the features after dimension reduction are input into a support vector machine model based on particle swarm optimization to realize micro-milling cutter wear feature classification. However, the vibration sensor will also collect external interference signals, which will affect the monitoring result, and the principal component analysis method for feature dimension reduction may cause loss of some important information. SUMMARY

[0005] The present application aims to solve the technical problems existing in the prior art, and the purpose of the present application is to provide a monitoring method and system for gear meshing wear inside a harmonic reducer.

[0006] In order to achieve the above purpose, according to the first aspect of the present application, a monitoring method for gear meshing wear inside a harmonic reducer is disclosed, which comprises the following steps:

[0007] Two groups of vibration data in a stable and healthy state of the harmonic reducer are obtained by using a first vibration sensor and a second vibration sensor symmetrically installed on the inner side of the steel gear along the radial direction,

[0008] The similarity of the data points corresponding to the two groups of data is calculated;

[0009] The maximum distance difference D is calculated by using the similarity max ;

[0010] The first vibration sensor and the second vibration sensor symmetrically installed on the inner side of the steel wheel are used to obtain the data under actual operation of the harmonic reducer;

[0011] The similarity Dr of the data under actual operation is calculated;

[0012] The wear and tear of the gear engagement inside the reducer is judged by comparing Dmax and Dr.

[0013]

[0014] The wear degree W is calculated.

[0015]

[0016] The monitoring conclusion is given according to the range size of the wear degree W.

[0017] The vibration sensor is symmetrically installed on the steel wheel to obtain the gear engagement signal, the differential information of the vibration signals detected by the symmetric vibration sensors under the stable healthy state and the actual operation is compared, the wear and tear of the gear at the gear engagement is obtained, the algorithm is simple, the common external interference can be removed, and the monitoring is more accurate. The implementation logic of the method is closer to the engineering application and the actual situation, and the method has very high practical value in online monitoring.

[0018] According to a preferred embodiment of the present application, the maximum distance difference D max is calculated by using the first vibration sensor and the second vibration sensor symmetrically installed on the inner side of the steel wheel to obtain two groups of vibration data under the stable healthy state of the harmonic reducer, each group of data including n data samples, respectively Data A-1, Data A-2, …, Data A-n, Data B-1, Data B-2, …, Data B-n; each sample containing m data points.

[0019] The similarity D j of the corresponding data Data A-j and Data B-j between the two groups of data is calculated, j = 1, 2, …, n.

[0020] After obtaining D = {D1, D2, …, D n}, the maximum distance difference D max is calculated.

[0021]

[0022] By calculating the maximum distance difference, the maximum difference of the detection data of the symmetric first vibration sensor and the second vibration sensor is obtained, and the gear engagement wear and tear is more accurately obtained.

[0023] According to another preferred embodiment of the present application, the similarity D is calculated using JS divergence j :

[0024] Set i statistical intervals, and count each group of data respectively to obtain the number of data points of each sample in the statistical interval, fit the statistical distribution using a normal curve to obtain the parameters of the curve, the parameters including mean and variance;

[0025]

[0026] Wherein, A and B represent the normal distribution of sample points Data A-j and Data B-j, M is the average distribution of the two groups of data, and KL represents Kullback-Leibler divergence.

[0027] Thus, the similarity is calculated quickly and accurately.

[0028] According to still another preferred embodiment of the present application, when W is less than 10%, the internal gear engagement of the harmonic reducer is slightly worn; when W is greater than or equal to 10% and less than or equal to 50%, the internal gear engagement of the harmonic reducer is moderately worn; and when W is greater than 50%, the internal gear engagement of the harmonic reducer is severely worn. Thus, the wear degree is more preferably identified.

[0029] To achieve the above-mentioned purpose, according to a second aspect of the present application, a harmonic reducer internal gear engagement wear monitoring system is disclosed, which comprises symmetric vibration sensors arranged on the inner side of the steel wheel near the engagement position of the flexspline and the steel wheel along the axial direction, the vibration sensors acquire gear engagement signals in stable and healthy states and actual running states and transmit the signals to a controller, and the controller monitors the gear engagement wear condition according to the method of the present application.

[0030] The present application acquires the gear engagement signals by symmetrically installing vibration sensors on the steel wheel, acquires the wear condition of the gear at the gear engagement position by comparing the differential information of the vibration signals detected by the symmetric vibration sensors in stable and healthy states and actual running states, the vibration sensors are installed close to the engagement position, and more real and accurate signals can be obtained, the signal transmission path of the system is short, the noise interference is small, the common external interference can be removed, the signal is reliable, and the number of sensors arranged is small.

[0031] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0032] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, taken in conjunction with the following drawings in which:

[0033] Figure 1 is a front view of a harmonic reducer in a preferred embodiment of the present application;

[0034] Figure 2 is a schematic diagram of the connection structure of a steel wheel, a flexible wheel and a wave generator of a sensor in a preferred embodiment of the present application;

[0035] Figure 3 is a flow chart of a monitoring method of internal gear meshing wear of a harmonic reducer in a preferred embodiment of the present application. DETAILED DESCRIPTION

[0036] Embodiments of the present application are described in detail below with reference to the accompanying drawings, in which the same or similar elements or elements having the same or similar functions are denoted by the same or similar reference numerals throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and cannot be understood as a limitation of the present application.

[0037] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "vertical", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0038] In the description of the present application, unless otherwise specified and limited, it should be noted that the terms "mounting", "connection" and "connection" should be understood broadly, for example, it can be a mechanical connection or an electrical connection, it can be a communication between two elements, it can be directly connected or indirectly connected through an intermediate medium, and the specific meaning of the above terms can be understood by a person of ordinary skill in the art according to the specific circumstances.

[0039] As shown in Figure 1 and Figure 2 The present application installs a first vibration sensor (located at a first measuring point) and a second vibration sensor (located at a second measuring point) on both sides of the steel wheel symmetrically, and the installation position is on the fixed rigid wheel, which is close to the position where the flexible wheel engages with the steel wheel. Get the gear meshing signal, and get the wear condition of the gear at the gear meshing position by comparing the differential information of the vibration signals on both sides. With this monitoring structure, the gear meshing signal of the flexible wheel and the steel wheel inside the harmonic reducer can be directly measured by the sensor, the transmission path is short, the noise interference is small, the signal is reliable, and the number of sensors arranged is small.

[0040] The symmetrical vibration signals are monitored, the information distribution difference threshold of the symmetrical points of gear engagement in the stable healthy state is acquired, the signal distribution difference of the two symmetrical sensors at the running time is calculated, the wear degree is calculated by comparing the signal distribution difference with the distribution difference threshold in the stable healthy state, and finally the monitoring conclusion is given.

[0041] As shown in Figure 3 The application discloses a kind of harmonic reducer internal gear engagement wear monitoring method, it includes the following steps:

[0042] Two groups of vibration data of harmonic reducer stable healthy row state are acquired using first vibration sensor, second vibration sensor symmetrically installed in the inside of steel wheel along radial direction.Each group of data includes n data samples, respectively Data A-1, DataA-2, …, Data A-n;Data B-1, Data B-2, …, Data B-n;Each sample contains m data points, for example: Data A-n=(x1, x2, …, xm), m, n are positive integers.

[0043] The similarity of the corresponding data points of the two groups of data is obtained.In the embodiment, the specific method is as follows:

[0044] Set i statistical intervals, and count each group of data respectively to obtain the number of data points of each sample in the statistical interval, i is a positive integer, for example SData A-n=(Data A-n1, Data A-n2, …, Data A-ni), Data A-ni is the number of data point distribution of data sample Data A-n in interval i, the normal curve is fitted to the statistical distribution, and the parameters of the curve are obtained, including mean, variance.

[0045] The similarity D j Of the corresponding data samples Data A-j and Data B-j between the two groups of data is calculated, j=1, 2, …, n, and the similarity can be calculated by using, but not limited to, Euclidean distance, cosine similarity, cross entropy, maximum mean difference, Mahalanobis distance, JS divergence and other methods, and the JS divergence is preferably used for calculation.

[0046]

[0047] Wherein, A and B represent the normal distribution of sample points Data A-j and Data B-j, M is the average distribution of the two groups of data;KL represents Kullback-Leibler divergence.

[0048] Specifically, assuming that the mean of two normal distributions A and B is μ1, μ2 respectively, and the variance is σ1, σ2 respectively, the mean of the average distribution M is (μ1+μ2) / 2, and the variance is (σ12 +σ2 2 ) / 2.

[0049] The average distribution M and two normal distributions A, B are brought into the above formula, and the JS divergence between them is obtained, wherein the calculation of the KL distance is calculated as follows again by taking the two normal distributions A and B as examples:

[0050]

[0051] After obtaining the distance array D={D1, D2, …, D n}, the maximum distance difference D max is calculated.

[0052]

[0053] wherein represents the average value of the distance array D, and 3σ D represents 3 times the variance of the distance array D.

[0054] By calculating the maximum distance difference, the maximum difference of the detection data of the symmetrical first vibration sensor and the second vibration sensor is obtained, and the gear meshing wear condition is more accurately obtained.

[0055] Then, the data Data A-r, Data B-r under the actual operation of the harmonic reducer are obtained by using the first vibration sensor and the second vibration sensor symmetrically installed on the inner side of the steel wheel in the radial direction;

[0056] The similarity Dr of the data Data A-r, Data B-r under the actual operation is calculated, and the calculation method is the same as that of the similarity D j , which will not be repeated here;

[0057] By comparing Dmax and Dr, it is judged whether the gear meshing inside the reducer is worn;

[0058]

[0059] The wear degree W is calculated.

[0060]

[0061] According to the range size of the wear degree W, a monitoring conclusion is given.

[0062] Preferably, when W is less than 10%, the gear meshing inside the harmonic reducer is slightly worn; when W is greater than or equal to 10% and less than or equal to 50%, the gear meshing inside the harmonic reducer is moderately worn; and when W is greater than 50%, the gear meshing inside the harmonic reducer is severely worn.

[0063] The application obtains the gear wear condition at the gear meshing position by symmetrically installing vibration sensors on the steel wheel, acquiring gear meshing signals, and comparing the differentiated information of the vibration signals detected by the symmetric vibration sensors in the stable healthy state and the actual operation, and the algorithm is simple; the common external interference can be removed, and the monitoring is more accurate.

[0064] The application also discloses a harmonic reducer internal gear meshing wear monitoring system, which comprises symmetric vibration sensors arranged on the inner side of the steel wheel close to the meshing position of the flexspline and the steel wheel along the axial direction, the vibration sensors acquire gear meshing signals in the stable healthy state and the actual operation and transmit the signals to a controller, and the controller monitors the gear meshing wear condition according to the method of the application.

[0065] The application obtains the gear wear condition at the gear meshing position by symmetrically installing vibration sensors on the steel wheel, acquiring gear meshing signals, and comparing the differentiated information of the vibration signals detected by the symmetric vibration sensors in the stable healthy state and the actual operation, and the algorithm is simple; the common external interference can be removed, and the monitoring is more accurate.

[0066] In the description of the present specification, the description of the terms "preferred embodiment", "one embodiment", "some embodiments", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are contained in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily mean the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0067] Although the embodiments of the present application have been shown and described, those skilled in the art can understand that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and purposes of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A method of monitoring internal gear mesh wear in a harmonic reducer, comprising: It comprises the following steps: Two groups of vibration data of the harmonic reducer in a stable and healthy running state are acquired by using a first vibration sensor and a second vibration sensor symmetrically installed on the inner side of the steel wheel in the radial direction, The similarity of the corresponding data points of the two groups of data is calculated; Using the similarity, the maximum distance difference D is calculated max ; Data in actual operation is acquired by using a first vibration sensor and a second vibration sensor symmetrically installed on the inner side of the steel wheel in the radial direction; The similarity Dr of the data in actual operation is calculated; Whether the gear meshing inside the reducer is worn is judged by comparing Dmax and Dr. The wear degree W is calculated. A monitoring conclusion is given according to the size of the wear degree W.

2. The method of claim 1, wherein the method further comprises: Calculate the maximum distance difference D max The method is as follows: Two groups of vibration data of the harmonic reducer in a stable and healthy running state are acquired by using a first vibration sensor and a second vibration sensor symmetrically installed on the inner side of the steel wheel in the radial direction, each group of data comprising n data samples, respectively Data A-1, Data A-2, …, Data A-n, Data B-1, Data B-2, …, Data B-n; each sample containing m data points. The similarity D between corresponding data Data A-j and Data B-j in the two groups of data is calculated j j = 1, 2, …, n; D = {D1, D2,..., D n} is obtained, the maximum distance difference D max is calculated. wherein, represents the average of the distance array D, 3σ D represents the 3 times standard deviation of the distance array D.

3. The method of claim 2, wherein the method further comprises: The similarity D is calculated using the JS divergence j : i statistical intervals are set, and each group of data is counted to obtain the number of data points of each sample in the statistical interval, the normal curve is fitted to the statistical distribution to obtain the parameters of the curve, including the mean and the variance. Wherein, A and B represent the normal distribution of sample points Data A-j and Data B-j, M is the average distribution of the two groups of data; KL represents Kullback-Leibler divergence.

4. The method of claim 1, wherein When W is less than 10%, the gear meshing inside the harmonic reducer is slightly worn; when W is greater than or equal to 10% and less than or equal to 50%, the gear meshing inside the harmonic reducer is moderately worn; when W is greater than 50%, the gear meshing inside the harmonic reducer is severely worn.

5. A system for monitoring internal gear mesh wear in a harmonic reducer, comprising: Symmetrical vibration sensors are arranged on the inner side of the steel wheel near the meshing position of the flexspline and the steel wheel in the axial direction, the vibration sensors acquire gear meshing signals in stable and healthy operation and actual operation and transmit them to a controller, and the controller monitors the gear meshing wear condition according to the method of any one of claims 1-4.

Images