阅读说明：本技术 一种短路过渡焊接的稳定性检测方法 (Stability detection method for short circuit transition welding ) 是由 朱路生 李良军 其他发明人请求不公开姓名 于 2021-09-07 设计创作，主要内容包括：本发明公开了一种短路过渡焊接的稳定性检测方法,对焊接过程的电压和电流进行同步采集；找到短路区间、燃弧区间、短路开始点、短路结束点、燃弧开始点和燃弧结束点,相邻两个短路开始点之间的区域为一个短路周期；在每个短路周期内,对波形特征进行提取；将不同短路周期内的相同特征值组成数组,分别进行变异系数计算,变异系数＝标准差/平均值,再将各个波形特征的数值与对应的变异系数相乘后求和,得到波形一致性。本发明以焊接波形特征抓取为基础,解决短路焊接稳定性评定无法量化的问题。(The invention discloses a stability detection method for short circuit transition welding, which is used for synchronously collecting voltage and current in a welding process; finding a short circuit interval, an arcing interval, a short circuit starting point, a short circuit ending point, an arcing starting point and an arcing ending point, wherein an area between two adjacent short circuit starting points is a short circuit period; extracting waveform characteristics in each short circuit period; and forming arrays of the same characteristic values in different short circuit periods, respectively calculating the variation coefficient, wherein the variation coefficient is the standard deviation/average value, multiplying the numerical value of each waveform characteristic by the corresponding variation coefficient, and summing to obtain the waveform consistency. The method is based on welding waveform characteristic grabbing, and solves the problem that short-circuit welding stability evaluation cannot be quantized.)

1. A method for detecting the stability of short circuit transition welding is characterized by comprising the following steps:

step S100, synchronously collecting voltage and current in a welding process according to a preset sampling frequency; defining a sampling threshold value, a first slope critical value and a second slope critical value;

step S200, marking a first sampling point of which the voltage value is lower than a sampling threshold value and the slope is smaller than a first slope critical value in the collected data as a short circuit starting point, marking a first sampling point of which the voltage value exceeds the sampling threshold value and the slope is larger than a second slope critical value in the collected data as a short circuit end point, namely an arc starting point, marking a first sampling point of which the voltage value is lower than the sampling threshold value and the slope is smaller than the first slope critical value in the collected data as an arc end point, namely a short circuit starting point, and setting an area between two adjacent short circuit starting points as a short circuit period;

step S300, extracting waveform characteristics in each short circuit period;

step S400, similar waveform characteristics in different short circuit periods form an array, variation coefficients are calculated respectively, the variation coefficients are equal to standard deviation/average value, the numerical values of the waveform characteristics are multiplied by the corresponding variation coefficients and then summed to obtain waveform consistency, the smaller the value of the waveform consistency is, the smaller the waveform difference of each transition period in the same welding process is, and the larger the waveform consistency is otherwise.

2. The method of claim 1, wherein the waveform characteristics comprise a short circuit peak current, an arcing peak current, a short circuit current first segment slope, a short circuit current second segment slope, a short circuit time, and an arcing time.

3. The method for detecting the stability of short-circuit transition welding according to claim 2, wherein the step S300 specifically comprises:

respectively acquiring the positions and amplitudes of short-circuit peak current and arcing peak current of a short-circuit period;

the amplitude of the short circuit peak current value is 1/m₁The current point of the short-circuit current is used as a calculation point of the slope of the first section of the short-circuit current and the slope of the first section of the short-circuit current is calculated; the first m of the short circuit peak position₂The point is used as a calculation point of the slope of the second end of the short-circuit current and the slope of the second section of the short-circuit current is calculated; m is₁And m₂Is a positive integer and m₁≠1；

The short-circuit time is the subtraction of the abscissa of the short-circuit starting point from the abscissa of the short-circuit ending point;

the arcing time is the abscissa of the arcing end point minus the abscissa of the arcing start point.

4. The method for detecting the stability of the short circuit transition welding according to claim 3, characterized in that m is a positive integer₁＝2，m₂＝3。

5. The method of claim 2, wherein the waveform characteristics further comprise any one or more of a secondary switch off current minimum, an arc current falling slope, an arc current rising slope, a short circuit current knee current, a secondary advanced off time, a secondary switch on time, and joule heat.

6. The method for detecting the stability of short-circuit transfer welding according to claim 5, wherein the step S300 specifically comprises:

acquiring the position and amplitude of the arcing peak current of the short-circuit period; m after the position of the arcing peak current₃The point is used as an arc current descending slope calculation point and an arc current descending slope is calculated;

after the sampling point of the lowest value of the turn-off current of the secondary switch and the short-circuit peak current value amplitude value is 1/m₁The current point of the arc-burning current is used as an arc-burning current rising slope calculation point and an arc-burning current rising slope is calculated;

respectively acquiring the positions and amplitudes of short-circuit peak current and arcing peak current of a short-circuit period; the amplitude of the short circuit peak current value is 1/m₁The current point of (2) is used as a calculation point of the slope of the first section of the short-circuit current; intercepting a region between a calculation point of a first section slope of the short-circuit current and a sampling point of the short-circuit peak current, carrying out secondary derivation on the region to obtain a lowest point position of a trough, namely a short-circuit current inflection point position, and obtaining an inflection point current amplitude; wherein m is₁、m₂、m₃Is a positive integer and m₁≠1；

Respectively acquiring the positions of short-circuit peak current and arcing peak current of a short-circuit period, wherein the continuous turn-off time of a secondary switch is the abscissa of the arcing peak current minus the abscissa of the short-circuit peak current;

the secondary advanced turn-off time is the abscissa of the short-circuit end point minus the abscissa of the short-circuit peak current;

joule heat is the average current of arcing x the average voltage of arcing x the time of arcing, wherein the average current of arcing is the average value of all arcing amplitude points in the arcing interval in the current curve; the average arcing voltage is the average value of all arcing amplitude points in an arcing region in a voltage curve; the average arcing current is the average value of all arcing amplitude points in an arcing region in a current curve.

7. The method for detecting the stability of the short circuit transition welding according to claim 6, wherein m is a positive integer₁＝2，m₂＝m₃＝3。

8. The method for detecting the stability of the short circuit transition welding according to claim 1, wherein the sampling threshold value satisfies: the sampling threshold value is more than or equal to 5V and less than or equal to 15V, and the first slope critical value meets the following conditions: -0.5v/n ≦ first slope threshold ≦ -2v/n, the second slope threshold satisfying: the second slope critical value is less than or equal to 2v/n and less than or equal to 0.5v/n, wherein n is a sampling point.

Technical Field

The invention relates to the technical field of short-circuit transition welding, in particular to a stability detection method of short-circuit transition welding.

Background

Different from jet flow transition and particle transition welding, short circuit transition welding has a short circuit behavior, current and voltage waveforms fluctuate continuously, and the short circuit process and the arc burning process are accompanied with the control of a welding machine on the waveforms, so that the stability of electric arcs can not be judged by a simple current and voltage variation coefficient. The stability of the short circuit transition is not quantified at present. The traditional evaluation method is to judge through the operation feeling of a welder, and has great human factors, so a scientific and effective method is needed to quantitatively judge the stability of the welding process.

Disclosure of Invention

The invention aims to provide a method for detecting the stability of short-circuit transition welding, which is used for solving the problem that the stability of electric arc cannot be quantitatively judged in the prior art.

The invention solves the problems through the following technical scheme:

a method for detecting the stability of short circuit transition welding comprises the following steps:

step S100, synchronously collecting voltage and current in a welding process according to a preset sampling frequency; defining a sampling threshold value, a first slope critical value and a second slope critical value;

step S200, marking a first sampling point of which the voltage value is lower than a sampling threshold value and the slope is smaller than a first slope critical value in the collected data as a short circuit starting point, marking a first sampling point of which the voltage value exceeds the sampling threshold value and the slope is larger than a second slope critical value in the collected data as a short circuit end point, namely an arc starting point, marking a first sampling point of which the voltage value is lower than the sampling threshold value and the slope is smaller than the first slope critical value in the collected data as an arc end point, namely a short circuit starting point, and setting an area between two adjacent short circuit starting points as a short circuit period;

step S300, extracting waveform characteristics in each short circuit period;

step S400, similar waveform characteristics in different short circuit periods form an array, variation coefficients are calculated respectively, the variation coefficients are equal to standard deviation/average value, the numerical values of the waveform characteristics are multiplied by the corresponding variation coefficients and then summed to obtain waveform consistency, the smaller the value of the waveform consistency is, the smaller the waveform difference of each transition period in the same welding process is, and the larger the waveform consistency is otherwise.

The waveform characteristics comprise short circuit peak current, arcing peak current, short circuit current first-stage slope, short circuit current second-stage slope, short circuit time and arcing time.

The step S300 specifically includes:

respectively acquiring the positions and amplitudes of short-circuit peak current and arcing peak current of a short-circuit period;

the amplitude of the short circuit peak current value is 1/m₁The current point of the short-circuit current is used as a calculation point of the slope of the first section of the short-circuit current and the slope of the first section of the short-circuit current is calculated; the first m of the short circuit peak position₂The point is used as a calculation point of the slope of the second end of the short-circuit current and the slope of the second section of the short-circuit current is calculated; m is₁And m₂Is a positive integer and m₁≠1；

The short-circuit time is the subtraction of the abscissa of the short-circuit starting point from the abscissa of the short-circuit ending point;

the arcing time is the abscissa of the arcing end point minus the abscissa of the arcing start point.

Preferably, said m₁＝2，m₂＝3。

The waveform characteristics further comprise any one or more of a secondary switch turn-off current minimum value, an arcing current descending slope, an arcing current ascending slope, a short-circuit current inflection point current, secondary advanced turn-off time, secondary switch continuous turn-off time and joule heat. The step S300 specifically includes:

acquiring the position and amplitude of the arcing peak current of the short-circuit period; m after the position of the arcing peak current₃The point is used as an arc current descending slope calculation point and an arc current descending slope is calculated;

after the sampling point of the lowest value of the turn-off current of the secondary switch and the short-circuit peak current value amplitude value is 1/m₁The current point of the arc-burning current is used as an arc-burning current rising slope calculation point and an arc-burning current rising slope is calculated;

respectively acquiring the positions and amplitudes of short-circuit peak current and arcing peak current of a short-circuit period; the amplitude of the short circuit peak current value is 1/m₁The current point of (2) is used as a calculation point of the slope of the first section of the short-circuit current; intercepting the calculation point of the first segment slope of the short-circuit current to shortPerforming secondary derivation on an area between sampling points of the peak current of the path to obtain the lowest point position of a trough, namely the position of a short circuit current inflection point, and obtaining the current amplitude of the inflection point; wherein m is₁、m₂、m₃Is a positive integer and m₁≠1；

And respectively acquiring the positions of the short-circuit peak current and the arcing peak current of the short-circuit period, wherein the continuous turn-off time of the secondary switch is the abscissa of the arcing peak current minus the abscissa of the short-circuit peak current.

The secondary advanced turn-off time is the abscissa of the short-circuit end point minus the abscissa of the short-circuit peak current;

joule heat is the average current of arcing x the average voltage of arcing x the time of arcing, wherein the average current of arcing is the average value of all arcing amplitude points in the arcing interval in the current curve; the average arcing voltage is the average value of all arcing amplitude points in an arcing region in a voltage curve; the average arcing current is the average value of all arcing amplitude points in an arcing region in a current curve. Preferably, m₁＝2，m₂＝m₃＝3。

The sampling threshold value is more than or equal to 5V and less than or equal to 15V, the first slope critical value is more than or equal to-0.5V/n and less than or equal to-2V/n, the second slope critical value is more than or equal to 0.5V/n and less than or equal to 2V/n, and n is a sampling point. The expression-2V/n means that the voltage of each sampling point is decreased by 2V, and the expression-2V/n means that the voltage of each sampling point is increased by 2V. The slope critical value selection is changed when the sampling frequency is different, the number of the sampling points in the same section is increased when the sampling frequency is increased, and the value change between each sampling point is reduced, for example, when the sampling frequency is increased by 10 times, the first slope critical value is-0.05 to-0.2 v/n, and the second slope critical value is 0.05 to 0.2 v/n.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) the invention provides a stability detection method for short circuit transition welding based on welding waveform characteristic capture, which solves the problem that short circuit welding stability evaluation cannot be quantized, can evaluate the quality stability of a single welding seam and even a welding machine, and provides a scientific reference basis for welding machine users.

(2) The invention can also be used as an evaluation index of skill level of welder MIG welding and secondary welding protection operation; meanwhile, as the method also extracts a plurality of characteristic parameters of the waveform, scientific research can be well carried out on the waveform control and some physical phenomena of the electric welding machine.

Drawings

FIG. 1 is a block diagram of the system of the present invention;

FIG. 2 is a schematic diagram of determining a short circuit interval and an arcing interval according to a voltage curve;

FIG. 3 is a current raw graph;

FIG. 4 is an enlarged view of A in FIG. 3;

FIG. 5 is a schematic representation of a waveform signature;

FIG. 6 is a schematic diagram illustrating a secondary lead interval in the process of determining a location of a short-circuit current inflection point;

FIG. 7 is a schematic diagram illustrating a secondary pilot interval and a secondary pilot trough;

FIG. 8 is a schematic diagram of an early turn-off time;

FIG. 9 is a schematic diagram of the current of a sample containing all features, wherein (a) is a sample No. 1 macro-graph; (b) is a sample No. 1 microscopic picture; (c) is a No. 2 sample macro graph; (d) is a sample No. 2 microscopic picture;

FIG. 10 is a schematic current diagram of a sample containing 6 features, wherein (a) is a No. 3 sample macro-graph; (b) is a No. 3 sample microscopic picture; (c) is a No. 4 sample macro graph; (d) is a microscopic picture of sample No. 4;

fig. 11 is a schematic current diagram of a sample containing 8 features, wherein (a) is a sample No. 5 macro diagram; (b) is a microscopic picture of sample No. 5; (c) is a No. 6 sample macro graph; (d) is a sample No. 6 microscopic picture;

FIG. 12 is a schematic current diagram of a sample containing 3 features, where (a) is a No. 7 sample macro-graph; (b) is a microscopic picture of sample No. 7; (c) is a No. 8 sample macro graph; (d) is a microscopic picture of sample No. 8;

wherein, 1-short circuit peak current; 2-arcing peak current; 3-the lowest point of the turn-off current of the secondary switch; 4-slope of first segment of short circuit current; 5-slope of second segment of short circuit current; 6-arc current decline slope; 7-arc current rising slope; 8-short circuit current inflection point position; and 9-secondary switch continuous off time.

Detailed Description

The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.

Example 1:

referring to fig. 1, a method for detecting stability of short-circuit transition welding includes placing a welding machine at a welding station, where the welding station may be a welding robot or a welder, and starting synchronous acquisition of voltage and current during short-circuit transition welding. And sending the acquired data to an industrial personal computer for storage and data processing. If the data has interference signals or clutter, the waveform is filtered by adopting a filtering method such as a sliding mean filtering method; the data analysis module on the industrial personal computer comprises a short-circuit time arcing time calculation module, a microscopic waveform feature extraction module and a result calculation module, wherein the microscopic waveform feature extraction module comprises a slope calculation module, a peak value calculation module, a joule heat calculation module and a secondary switching time action module.

The data analysis module executes the following steps:

the sampling frequency of the current and the voltage is set to be 25K/s, the sampling frequency is not specially specified in the text, the following steps are set on the basis of the sampling frequency of 25K/s, and if the sampling frequency changes, the selection of part of parameters is also adjusted correspondingly.

When the sampling threshold is selected, the method is to determine the voltage threshold of the welding short-circuit process, namely, when the program judges that the voltage is lower than the threshold, the welding is judged to enter a short-circuit state, the short-circuit voltage is generally between 0V and 15V, and therefore the threshold is selected as the numerical value of the interval. The maximum short-circuit voltage of the invention is generally around 5V, namely the threshold value can be selected from the number between 5V and 15V, so the invention selects 8V as the threshold value for short-circuit judgment. The purpose of the selection of the critical values of the first slope critical value and the second slope is to determine a voltage drop point (a short circuit starting point, an arc burning ending point) and a voltage rise point (a short circuit ending point, an arc burning ending point), and as can be seen from a waveform diagram, the rate of the voltage drop and the rate of the voltage rise are generally greater than 5V/n, so that the value of the critical slope is selected to be less than 5V/n, and since some abnormal values may occur in the waveform, such as a process of slowly dropping or rising the voltage, the critical values of the first slope critical value and the second slope are selected to be too small, and the tolerance to the judgment of the conditions is too large, so that the abnormal changes are counted, the selection of the critical slope is not too small, and the selection of the value in the range of 1-5V/n is more suitable. The scheme selects 2V/n.

Judging an arcing interval and a short-circuit interval according to the voltage according to a sampling threshold and a curve slope; the voltage interval below 8V is marked as a short-circuit interval, and the voltage interval above 8V is marked as an arcing interval. The method for judging the short circuit starting point comprises the steps of reading data points in sequence, when the voltage of the data points is lower than a threshold value of 8V, calculating whether the slope of the points is lower than a first slope critical value, setting the slope critical value to be-2V/n, and if the two conditions are met, recording the points as the short circuit starting point; when the amplitude voltage of the data point is higher than 8V and the voltage rising slope is greater than the second slope threshold (+2V/n), the point is recorded as the short end position. The same approach can find the start and end points of the arc: the critical value of the slope of the arcing is consistent with the threshold value and the magnitude of the short circuit setting, except that the slope of the arcing starting point must be greater than +2V/n and the slope of the arcing ending point must be less than-2V/n. The region between two adjacent short circuit starting points is a curve interval of one short circuit period, and when one period is found, the waveform feature of each period can be subjected to subsequent feature extraction, as shown in fig. 2, 3 and 4.

And extracting and mining the waveform characteristics of the current in one period, and searching the values of the short-circuit peak current 1, the arcing peak current 2 and the secondary switch turn-off current lowest point 3 by using a signal. The current point of the short circuit peak current value 1/2 is selected as the calculation point of the short circuit current first segment slope 4. The first three points of the short circuit peak position are taken as calculation points of the short circuit current second slope 5. Three points after the position of the arc-burning peak current are taken as the calculation points of the arc-burning current descending slope 6. The current point after the secondary switch off current minimum point 3 and short circuit peak current value 1/2 is calculated as the arcing current rising slope 7 point. The calculation of the short-circuit current inflection point position 8 is to intercept the region from the calculation point of the first slope 4 of the short-circuit current to the position of the short-circuit peak current 1, as shown in fig. 6, solve the quadratic derivative for the region, and then find the lowest point of the trough by using a signal. The secondary on-off duration 9 can be calculated by subtracting the abscissa of the short-circuit peak current 1 from the abscissa of the arcing peak current 2.

In order to prevent the necking from exploding and breaking, a secondary switch is added in part of welding machines at present, and the current is turned off in advance when the necking is finished, so that the liquid bridge energy at the necking position is reduced, and the probability of electromagnetic explosion and breaking of the liquid bridge is reduced (namely the lowest point 3 of the turn-off current of the secondary switch is manually controlled). Since this control is important, the advanced off time of this control is captured. As shown in fig. 8, the early turn-off time is a time t when the short-circuit peak current reaches the short-circuit end point position (voltage rapid rise position), and the time t is the early turn-off time, that is, t is the short-circuit end time abscissa-short-circuit current peak value abscissa;

the arc burning process is the main supply stage of welding heat input, determines the metallurgical process and the thermal cycle of the welding process, the physical quantities such as heat diffusion and the like, and has great correlation with the arc burning form and the continuity of the weldment heat, so the stability of the heat input value is also important, the joule heat in the arc burning process is calculated, and the formula is as follows:

W＝I_{average current of arc}×U_{Average voltage of arcing}×t_{Time of arcing}

The characteristic values of all short circuit periods in one welding process can be uniformly processed by independently extracting each transition period of welding, calculating the characteristics of the waveform of each period and putting each calculated characteristic value into a corresponding array for storage.

The saved feature array comprises: short circuit peak current array, arcing peak current array, secondary switch off current minimum array, short circuit current first section slope array, short circuit current minimum arrayA current second segment slope array, an arc current falling slope array, an arc current rising slope array, a short circuit current inflection point array, a secondary advanced turn-off time array, a short circuit time array, an arc time array, a secondary switch continuous turn-off time array and a joule heating array. The 13 variables are uniformly calculated, because the 13 characteristics describe the integral appearance of a periodic waveform, the uniformity of a welding waveform is reflected by the dispersion of the 13 characteristic data, and because the characteristic units are different and the numerical value is greatly different, the 13 characteristics (v) are subjected to the uniform calculation₁～v₁₃) And calculating a variation coefficient (the variation coefficient is equal to a standard deviation/average value), weighting and summing the numerical values of the 13 characteristics to obtain waveform characteristic consistency, wherein the waveform consistency can be effectively quantified and judged through the calculated waveform characteristic consistency value, and the smaller the value is, the smaller the waveform difference of each transition period in the same welding process is, namely, the better the transition consistency is.

The standard deviation is the arithmetic square root of the variance, which is the sum of the squares of the numerical minus the mean. The standard deviation can reflect the degree of dispersion of a data set. The coefficient of variation is the standard deviation/average value, the coefficient of variation can smooth out the influence brought by different data units and data types, and different types of data can be compared or operated at the same latitude.

The sampling threshold is used when calculating the short circuit and arcing start time and the short circuit and arcing end time, and the sampling threshold is selected as long as it can be ensured that a threshold line (y is a threshold) can intersect with a voltage rapidly falling section and a voltage rapidly rising section, which is shown in fig. 2, where y is a threshold line 8. The first slope threshold is to find the point of the voltage drop, and the value is selected to ensure that the absolute value of the slope of the voltage drop during all short circuits is higher than the set value, i.e. the slope of the voltage drop during short circuits < the first slope threshold < 0. The second slope threshold is selected to ensure that the slope of the voltage rise during all short circuits is above a predetermined value, i.e., 0< the second slope threshold < the short circuit voltage rise slope.

At a rising slope for the first and second segments of the short-circuit current and at the arcing currentM is respectively used in the slope reduction solving process₁，m₂，m₃Wherein m is₁Is the position of the calculated point of the first segment of the short-circuit current, such as m₁When the short circuit first section slope is 2, the calculation position of the short circuit first section slope is that the current value is at the short circuit peak current/2, namely, the calculation point threshold line is that the short circuit peak current/2 is y, and m is₁The larger, the lower the threshold line, m₁The smaller the threshold line, the higher when m₁At 1, the threshold line height just intersects the short circuit peak point. m is₂Is the calculated point position for determining the slope of the second segment of the short circuit, e.g. when m₂When 3, the second step slope is (short-circuit peak value — current value at point 3 before the short-circuit peak value)/3, and the larger this value, the larger the calculation range of the slope before short-circuit. m is₃Same m₂Very similarly, the arc peak current reduction slope is calculated, for example, when m₃When the value is 3, the second slope is (current value at the 3 rd point after the arcing peak value — arcing peak value)/3, and the larger the value is, the larger the calculation range of the slope after the arcing peak value is.

The method for detecting the stability of the short circuit transition welding is suitable for adopting 13 waveform characteristics, 6 waveform characteristics and 8 waveform characteristics, can solve the problem that the evaluation of the short circuit welding stability cannot be quantized, and adopts experimental data to verify the effect of the method.

Experiment one:

table 1 waveform consistency test sample data containing all features

Table 1 summarizes the data obtained from all the features, and it can be seen from table 1 that the waveform feature consistency of sample No. 1 is 7.7567, while the waveform feature consistency of sample No. 2 is only 1.3381, the current-voltage diagrams corresponding to sample No. 1 are shown in (a) and (b) of fig. 9, and the current diagrams corresponding to sample No. 2 are shown in (c) and (d) of fig. 9, and it can be seen that the current fluctuation of sample No. 1 is much better than the current fluctuation of sample No. 2, the transition uniformity of sample No. 2 is much better, and the welding process is also much more stable. Practice proves that the quality of the welded joint corresponding to the sample No. 1 and the sample No. 2 is also obviously different, the sample No. 1 is obviously poor in quality, discontinuous in welding seams, continuous in welding seams of the sample No. 2 and good in regularity.

Experiment two:

table 2 waveform consistency test sample data containing 6 features

Wave form characteristics	Sample No. 3	Sample No. 4
			Coefficient of variation of short circuit peak current	0.1119	0.0550
Coefficient of variation of arc peak current	0.1903	0.0226
			Slope coefficient of variation of first segment of short-circuit current	0.9407	0.0763
Slope coefficient of variation of second stage of short-circuit current	0.1500	0.1209
			Coefficient of variation of short circuit time	0.9591	0.0754
Coefficient of variation of arcing time	0.3408	0.1860
			Waveform feature uniformity	2.6928	0.5362

Table 2 records 6 important waveform characteristics, and it can be seen from table 2 that the value of the waveform characteristic consistency of sample No. 3 is 2.6928, while the value of the waveform characteristic consistency of sample No. 4 is only 0.5362, the current-voltage graphs corresponding to sample No. 3 are shown in (a) and (b) of fig. 10, and the current graphs corresponding to sample No. 4 are shown in (c) and (d) of fig. 10, and it can be seen that the transition uniformity of sample No. 4 is much better and the welding process is much more stable compared with the current fluctuation of sample No. 3 and sample No. 4. Practice proves that the quality of the welded joint corresponding to the sample No. 3 and the sample No. 4 is also obviously different, the sample No. 3 is obviously poorer in quality, discontinuous in welding seam, continuous in welding seam of the sample No. 4 and good in regularity.

Experiment three:

table 3 waveform consistency test sample data containing 8 features

Table 3 records that 6 important waveform characteristics are added with the variation coefficient of the secondary switch off-break point distance short-circuit end time and the variation coefficient of joule heat, and it can be seen from table 3 that the value of the waveform characteristic consistency of sample No. 5 is 3.8491, while the value of the waveform characteristic consistency of sample No. 6 is only 1.7724, the current-voltage diagram corresponding to sample No. 5 is shown in (a) and (b) of fig. 11, and the current diagram corresponding to sample No. 6 is shown in (c) and (d) of fig. 11, and it can be seen that the transition uniformity of sample No. 6 is much better and the welding process is also much more stable compared with the current fluctuation of sample No. 6. Practice proves that the quality of the welded joint corresponding to the sample No. 5 and the sample No. 6 is also obviously different, the sample No. 5 is obviously poorer in quality, discontinuous in welding seam, continuous in welding seam of the sample No. 6, and good in regularity. The welding voltage adopted by the sample No. 5 is 12.5V, the welding voltage adopted by the sample No. 6 is 16.5V, and the welding seam forming quality of the sample No. 5 is poor, while the welding seam forming quality of the sample No. 6 is good.

Experiment four:

table 4 waveform consistency test sample data containing 3 features

Table 4 only records 3 important waveform features, when 3 features are adopted, the judgment and the drawing of waveform data are very insufficient, and a waveform diagram is shown in (c) and (d) in fig. 12, it can be seen that the current short circuit peak current of the sample No. 7 is more stable than that of the sample No. 8, but because the coefficient of variation does not calculate the index, the results of two sample data are very close, the final forming of the two samples is different, the sample No. 7 is welded by 90A current, the forming effect is good, and the sample No. 8 is welded by 120A current, so that the burn-through problem occurs. It follows that imperfect statistics of waveform features can lead to errors in results. In the waveform characteristics, the 6 important characteristic parameters mentioned above are absent, and if only 1-5 of the 6 parameters are counted, the counted results have errors to a certain degree.

According to the experiment, the method for detecting the stability of the short circuit transition welding is suitable for 6 waveform features, 8 waveform features and 13 waveform features, can solve the problem that the short circuit welding stability cannot be quantitatively evaluated, can evaluate a single welding seam and even the quality stability of a welding machine, and provides a scientific reference basis for users of the welding machine.

The method can also be used in other aspects with periodic fluctuation statistics, such as pulse consistency of pulse welding, periodic motion consistency of industrial robots and the like.

Although the present invention has been described herein with reference to the illustrated embodiments thereof, which are intended to be preferred embodiments of the present invention, it is to be understood that the invention is not limited thereto, and that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure.