CN115722797A - Laser welding signal analysis method based on machine learning - Google Patents

Laser welding signal analysis method based on machine learning Download PDF

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CN115722797A
CN115722797A CN202211369035.3A CN202211369035A CN115722797A CN 115722797 A CN115722797 A CN 115722797A CN 202211369035 A CN202211369035 A CN 202211369035A CN 115722797 A CN115722797 A CN 115722797A
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laser welding
analysis method
sample signals
signal analysis
welding signal
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欧红师
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Shenzhen Microspectral Sensing Intelligent Technology Co ltd
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Abstract

The invention belongs to the technical field of computers, and discloses a laser welding signal analysis method based on machine learning, which comprises the following steps: carrying out data normalization on the sampling parameters, setting acquisition parameters, and acquiring positive sample signals and negative sample signals; partitioning the whole signal according to the data distribution characteristics of each point, and removing a detection area from an area with a large fluctuation range; selecting an optimal standard area generation method and a detection model based on machine learning, and carrying out hyper-parameter optimization on the detection model; and training the detection model to obtain a target model, and inputting the laser welding signal into the target model to obtain an analysis result. The laser welding signal analysis method provided by the invention adopts the machine learning technology to construct the detection model, provides feedback and data support for the laser system, and analyzes and processes the laser welding signal through the detection model, thereby judging the quality of the welding quality and avoiding the influence of personnel on the welding quality judgment standard.

Description

Laser welding signal analysis method based on machine learning
Technical Field
The invention belongs to the technical field of computers, and particularly relates to a laser welding signal analysis method based on machine learning.
Background
Laser welding is a new processing technology, has the advantages of high welding point quality, small deformation of a welding area, high production efficiency, easy realization of automation, flexibility, non-contact processing and the like, and is widely applied to the industrial manufacturing fields of 3C electronics, automobile industry, new energy and the like. The principle of laser welding is that a laser generates laser, the laser is focused on the surface of a material to be processed through optical fiber conduction and a lens, the material is heated, melted and gasified, the welding process is an extremely complex physical and chemical process, a molten pool is formed by melting the material, a keyhole is generated by melting the material, metal vapor is formed by gasifying the metal, and plasma is generated.
The stability of the laser welding process is also affected by many factors, such as the change of the material surface, the change of the laser optical system, the deformation or deviation of the welding mechanism, etc., which may cause welding defects. However, unlike the traditional welding method which can monitor the current and voltage or the penetration to monitor the welding process, the welding quality can only be judged by vision and spot check, and the welding quality can not be confirmed or real-time online monitoring can not be realized by the method, so that the welding quality can not be guaranteed in percentage, and the monitoring effect is not ideal.
Many researches show that various signals such as optical signals, acoustic signals, electric field signals, heat radiation and the like can be generated in the laser welding process, and the judgment of welding defects can be realized through the change of the signals. Along with the development of detection technology, the real-time detection technology of the laser welding process makes great progress and development, but the existing real-time detection product of the laser welding process is low in integration level, complex in system, incapable of generating feedback to the laser welding process, weak in autonomous learning capacity of the system, and large in influence of human factors on monitoring results.
Disclosure of Invention
The present invention aims to solve the above technical problem at least to some extent. Therefore, the invention aims to provide a laser welding signal analysis method based on machine learning.
The technical scheme adopted by the invention is as follows:
a laser welding signal analysis method based on machine learning comprises the following steps:
s1, carrying out data normalization on sampling parameters; initializing acquisition parameters, acquiring multiple groups of positive sample signals, judging whether the acquired positive sample signals are in an optimal linear region according to standard deviations of the acquired positive sample signals, if so, saving the acquisition parameters, otherwise, setting new acquisition parameters, and acquiring multiple groups of positive sample signals again and judging;
s2, collecting a positive sample signal and a negative sample signal;
s3, partitioning the whole signal through the data distribution characteristics of each point, and removing a detection area from an area with a large fluctuation range;
s4, selecting an optimal standard region generation method and a detection model based on machine learning, and carrying out hyper-parameter optimization on the detection model;
and S5, training the detection model to obtain a target model, and inputting a laser welding signal into the target model to obtain an analysis result.
Preferably, in step S1, the initialized acquisition parameters include a circuit analog amplification coefficient, a depolarizer angle in a light intensity continuously adjustable structure, a digital amplification factor, a sampling frequency, and a sampling time.
Preferably, the continuously adjustable structure for light intensity comprises a polarizer and an analyzer.
Preferably, in step S1, when the acquired normal sample signal is not in the optimal linear region, a new acquisition parameter is set according to a deviation value of the real data from the optimal linear region.
Preferably, in step S2, more than 50 positive-sample signals and more than 30 negative-sample signals are collected.
Preferably, step S3 further comprises: and (4) counting the average value of the normal sample signals, and if a certain area of the normal sample signals seriously deviates from the average value, rejecting the normal sample signals.
Preferably, in step S4, the standard region is generated by using the positive sample signal, where the time t is an X axis and the sampling value is a Y axis, and the standard region generation method on the Y axis may adopt a gaussian mixture method, a percentage method, an average value method, a median method or a maximum/minimum value method.
The invention has the beneficial effects that:
the laser welding signal analysis method based on machine learning provided by the invention adopts the machine learning technology to construct the detection model, provides feedback and data support for the laser system, and analyzes and processes the laser welding signal through the detection model, so that the quality of welding is judged, the influence of personnel on the welding quality judgment standard is avoided, and the stability of the welding system is tracked and fed back for a long time.
Drawings
Fig. 1 is a flow chart of a laser welding signal analysis method of the present invention.
Fig. 2 is a schematic diagram of a light intensity continuously adjustable structure according to the present invention.
Fig. 3 is a flow chart of the present invention for setting acquisition parameters.
Fig. 4 is a diagram of the general format of the signal of the present invention.
Fig. 5 is a flow chart of step S4 of the present invention.
FIG. 6 is a schematic diagram of the hyper-parametric optimization of the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it is to be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, the laser welding signal analysis method based on machine learning of this embodiment specifically includes the following steps:
s1, data normalization is carried out on sampling parameters, continuous adjustment of signal intensity is achieved, the signal distribution ranges of different processes are consistent, standardization of reference data is achieved, and effective and rapid learning of a model (linear discriminant, SVM) in the subsequent step S5 can be promoted based on a small number of samples.
The data normalization of the sampling parameters adopts a formula:
Figure BDA0003924245690000041
setting acquisition parameters, as shown in fig. 3, specifically includes: initializing acquisition parameters, acquiring multiple groups of positive sample signals, judging whether the acquired positive sample signals are in an optimal linear region according to standard deviation of the acquired positive sample signals, if so, saving the acquisition parameters, otherwise, setting new acquisition parameters according to deviation values of real data and the optimal linear region, and acquiring multiple groups of positive sample signals again and judging.
The initialized acquisition parameters comprise circuit analog amplification coefficients, the angle of the depolarizer in the light intensity continuous adjustable structure, digital amplification times, sampling frequency and sampling time. As shown in fig. 2, the continuously adjustable light intensity structure includes a polarizer and an analyzer, and the continuously adjustable light intensity structure is used for realizing continuous adjustment of light intensity. The same data distribution can be obtained under different processes.
And S2, collecting more than 50 positive sample signals and more than 30 negative sample signals, wherein the negative sample signals are not necessarily equal to the positive sample signals due to the high cost of processing materials. When the cost is not considered, the same number of positive-sample signals and negative-sample signals can be collected.
And S3, counting the average value of the normal sample signals, and rejecting the normal sample signals if a certain region of the normal sample signals deviates from the average value seriously. Due to the various complexity of laser welding, the center of the normal signal also has data that the signal distribution deviates greatly from the normal signal distribution. The elimination of abnormal signals is realized by counting the average value of the positive signals: if a certain area of the positive sample signal is seriously deviated from the average value, the signal is not taken as the positive sample signal. Through the data cleaning, the problem of model overfitting in the step S5 is solved under the condition of less sample data, namely, the risk of model overfitting is reduced by ensuring the correctness of the sample.
Partitioning the whole signal according to the data distribution characteristics of each point, and removing a detection area from an area with a large fluctuation range; as shown in fig. 4, if the fluctuation value of the edge portion on the left side of the signal is large, the edge portion is removed from the detection area.
S4, as shown in FIG. 5, selecting an optimal standard area generation method and a detection model based on machine learning, and carrying out hyper-parameter optimization on the detection model;
the method specifically comprises the following steps:
and generating a standard area by using the positive sample signal, wherein the time t is an X axis, the sampling value is a Y axis, and the standard area generation method on the Y axis can adopt a Gaussian mixture method, a percentage method, an average value method, a median method or a maximum/minimum value method to realize the selection of the optimal standard area generation method.
Gaussian mixture method:
Figure BDA0003924245690000051
assuming that the sampling value of each signal at a certain time is in normal distribution (time t is X axis, the sampling value is Y axis), the value within 3 standard deviations is taken as the standard range.
The percentage method comprises the following steps:
Figure BDA0003924245690000052
the Y-axis calibration area is obtained by subtracting the upper and lower percentages considered to be defined from the original sample value.
Method of averaging
Figure BDA0003924245690000053
The Y-axis standard area is given by the mean value as the center, plus the artificially defined upper and lower fluctuation values.
Median method
Figure BDA0003924245690000054
The Y-axis is obtained by taking the median as the center of the standard area and adding the artificially defined upper and lower fluctuation values.
Maximum/minimum method
Figure BDA0003924245690000055
The Y-axis acquisition criteria area is given by the raw acquisition data.
The detection method of the detection model can adopt the following methods:
local area characterization method
Defect definition: the actual signal exceeds a certain area of the standard region and the duration exceeds the specified time
Learning the target: defining top/bottom area and time by hyper-parametric optimization automated machine learning
Signal value characterization method
Defect definition: the actual signal exceeding the limit value and the permissible time given according to the standard range
Learning the target: the upper/lower limit values and the tolerance times are defined by hyperparametric optimization automated machine learning.
Average offset characterization method
Defect definition: the signal mean shift exceeds a limit value which is considered to be defined
Learning the target: defining average offset limit values by hyper-parametric optimization automated machine learning
As shown in fig. 6, the iterative process of hyper-parameter optimization includes:
initializing and training a Bayesian agent model;
selecting a new super parameter group:
Figure BDA0003924245690000061
and updating the agent model.
S5, training the detection model to obtain a target model:
training set: t = { (x) 1 ,y 1 ),(x 2 ,y 2 ),…,(x N ,y N )},
Figure BDA0003924245690000063
y i ∈Y={-1,1};
A classifier: detection model G after hyper-parameter optimization 0 (x) G' (x) is SVM;
training process:
1) Initializing training data weight distribution:
Figure BDA0003924245690000062
(a) The training is carried out by the user,
(b) Calculation of G 0 (x) Classification error rate of (2):
Figure BDA0003924245690000071
(c) Calculation of G 0 (x) Coefficient (c):
Figure BDA0003924245690000072
(d) Updating the weight of the training data, increasing the error class weight, decreasing the correct class weight, focusing on the error class attention,
Figure BDA0003924245690000073
2) Using G' (x) as classifier, D 1 Repeating the steps (a), (b), (c) and (d) for the initial data weight distribution;
3) Constructing a linear combination of basic classifiers:
Figure BDA0003924245690000074
and (4) a final classifier:
Figure BDA0003924245690000075
and inputting the laser welding signal into a target model to obtain an analysis result. And the target model can calculate and compare the laser welding signal with the good product signal so as to judge the welding quality. And according to the signal trend of welding, the laser controller is fed back, and the special reasons such as defocusing and power change are corrected to be deteriorated, so that the welding system is always in a stable state. Based on the characteristic of machine learning, the full automation can be realized, the influence of personnel on the welding quality judgment standard is avoided, and great convenience is provided for a production line.
The invention is not limited to the above alternative embodiments, and any other various forms of products can be obtained by anyone in the light of the present invention, but any changes in shape or structure thereof, which fall within the scope of the present invention as defined in the claims, fall within the scope of the present invention.

Claims (9)

1. A laser welding signal analysis method based on machine learning is characterized by comprising the following steps:
s1, carrying out data normalization on sampling parameters; initializing acquisition parameters, acquiring multiple groups of positive sample signals, judging whether the acquired positive sample signals are in an optimal linear region according to standard deviations of the acquired positive sample signals, if so, saving the acquisition parameters, otherwise, setting new acquisition parameters, and acquiring multiple groups of positive sample signals again and judging;
s2, collecting a positive sample signal and a negative sample signal;
s3, partitioning the whole signal through the data distribution characteristics of each point, and removing a detection area from an area with a large fluctuation range;
s4, selecting an optimal standard region generation method and a detection model based on machine learning, and carrying out hyper-parameter optimization on the detection model;
and S5, training the detection model to obtain a target model, and inputting a laser welding signal into the target model to obtain an analysis result.
2. The laser welding signal analysis method according to claim 1, characterized in that: in step S1, the initialized acquisition parameters include a circuit analog amplification coefficient, a depolarizer angle in a light intensity continuously adjustable structure, a digital amplification factor, a sampling frequency, and a sampling time.
3. The laser welding signal analysis method according to claim 2, characterized in that: the light intensity continuously adjustable structure comprises a polarizer and an analyzer.
4. The laser welding signal analysis method according to claim 1, characterized in that: in step S1, when the collected normal sample signal is not in the optimal linear area, new collection parameters are set according to the deviation value of the real data and the optimal linear area.
5. The laser welding signal analysis method according to claim 1, characterized in that: in step S2, more than 50 positive-sample signals and more than 30 negative-sample signals are collected.
6. The laser welding signal analysis method according to claim 1, characterized in that: step S3 further includes: and (4) counting the average value of the positive sample signals, and if a certain region of the positive sample signals deviates from the average value seriously, rejecting the positive sample signals.
7. The laser welding signal analysis method according to claim 1, characterized in that: in step S4, a standard region is generated by using the sample signal, where time t is an X axis, a sampling value is a Y axis, and a gaussian mixture method, a percentage method, an average value method, a median method, or a maximum/minimum value method may be used as a method for generating the standard region on the Y axis.
8. The laser welding signal analysis method according to claim 1, characterized in that: in step S4, the iterative process of the hyper-parameter optimization includes:
initializing and training a Bayesian agent model;
selecting a new super-parameter group:
Figure FDA0003924245680000021
and updating the agent model.
9. The laser welding signal analysis method according to claim 1, characterized in that: in the step S5, the process is carried out,
training set:
Figure FDA0003924245680000022
a classifier: detection model G after hyper-parameter optimization 0 (x) G' (x) is SVM;
a training process:
1) Initializing training data weight distribution:
Figure FDA0003924245680000023
(a) The training is carried out by the user,
(b) Calculation of G 0 (x) Classification error rate of (2):
Figure FDA0003924245680000024
(c) Calculation of G 0 (x) Coefficient (c):
Figure FDA0003924245680000025
(d) Updating the weight of the training data, increasing the error weight, decreasing the correct weight, focusing on the error attention,
Figure FDA0003924245680000031
2) Using G' (x) as a classifier, D 1 Repeating the steps (a), (b), (c) and (d) for the initial data weight distribution;
3) Constructing a linear combination of basic classifiers:
Figure FDA0003924245680000032
and (4) a final classifier:
Figure FDA0003924245680000033
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