A method for detecting the change in the length of a rotating electric arc based on the characteristics of rotating electric arc sensing signals.

Abstract

This invention discloses a method for detecting the change in the length of a rotating arc based on the characteristics of a rotating arc sensing signal. The method includes: the working principle of the rotating arc length change detection method; the relationship between the rotating arc length change coefficient and the welding current and its change; establishing a relationship model between the rotating arc length change coefficient and the characteristic quantities of the rotating arc sensing signal; and the method for detecting the change in the length of the rotating arc. The change in the length of the rotating arc affects the stability of the rotating arc. A larger change in arc length results in poorer arc stability, while a smaller change in arc length results in better arc stability. Using the method of this invention, the change in the length of the rotating arc can be detected based on the characteristics of the rotating arc sensing signal, laying the foundation for automated machine control of the change in arc length. This enables intelligent control of robotic welding quality, improving welding quality and efficiency.

Description

Technical Field

[0001] This invention relates to the field of electronic information technology, and in particular to a method for detecting the change in the length of a rotating arc based on the characteristics of a rotating arc sensing signal. Background Technology

[0002] During welding, the magnitude of the arc length change affects the welding current and voltage, thus influencing arc stability and ultimately weld quality. In actual welding, a small arc length change results in a stable arc shape, stable arc heat and resistance heat, leading to better weld formation. Therefore, it is necessary to develop a method for detecting the change in rotating arc length, enabling automated machine detection of this change. This would facilitate automated machine control of the rotating arc length change and improve the quality of robotic automated welding. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a method for analyzing arc sensing signals, enabling automatic detection of changes in the length of the rotating arc. This facilitates automatic machine adjustment of the changes in the length of the rotating arc, ensuring that the changes meet requirements and improving the level of intelligent robotic welding and welding quality.

[0004] To achieve this objective, the present invention adopts the following technical solution:

[0005] The method for detecting the change in the length of a rotating arc based on the characteristics of a rotating arc sensing signal is characterized by comprising four parts: the working principle of the method for detecting the change in the length of a rotating arc, the relationship between the coefficient of change in the length of the rotating arc and the welding current and its change, the establishment of a relationship model between the coefficient of change in the length of the rotating arc and the characteristic quantities of the rotating arc sensing signal, and the method for detecting the change in the length of the rotating arc.

[0006] Furthermore, the working principle of the rotating arc length change detection method establishes the relationship between the arc length change value and the characteristics of the rotating arc sensing signal. Specifically, when the arc is more stable, due to the effect of the arc length self-adjustment system, the arc length recovery value is larger, resulting in smaller changes in adjacent welding currents. When the arc is unstable, the arc length recovery value is small, resulting in large changes in adjacent welding currents. The arc length change coefficient is used to evaluate the magnitude of the arc length change value; the larger the arc length change value, the larger the arc length change coefficient. A relationship model between the arc length change coefficient and the characteristics of each group of rotating arc sensing signals can be established. Therefore, by using the acquired welding current waveform to identify the characteristics of the rotating arc sensing signal, the change value of the rotating arc length can be identified based on these characteristics.

[0007] Furthermore, the relationship between the rotating arc length change coefficient and the welding current and its change allows for the identification of the rotating arc length change coefficient based on the welding current and its change. The specific details are as follows: The relationship between the rotating arc length change coefficient and the welding current and its change is as follows...

[0008]

[0009] In the formula, This represents the change in arc length. Let ρ(l) be the change in welding current, l be the total length of the arc, ρ(l) be the resistivity of the arc at length l, s(l) be the cross-sectional area of ​​the arc at length l, U be the welding voltage, and I be the welding current. From this formula, it can be seen that the coefficient for the change in current consists of three parts. The negative sign of the first term indicates that when the arc length decreases while other conditions remain unchanged, the welding current will increase; the second term indicates that when the welding voltage increases while other conditions remain unchanged, the arc length will increase; and the third term indicates that when the welding current increases while other conditions remain unchanged, the arc length will decrease.

[0010] During arc rotation, if the arc length recovery value is large, the change in arc length is small, and the magnitude of the arc length change coefficient is also small. Therefore, the magnitude of the arc length change coefficient and the arc length change satisfy the following relationship.

[0011]

[0012] In the formula, K represents the magnitude of the arc length change coefficient, and the meanings of other physical quantities have been introduced in the above formula. The change in current in the formula contains two coefficients. Because the welding voltage is relatively small, generally less than 35V, and the welding current is generally greater than 100A, and ρ(l) / s(l) does not change significantly, the first coefficient is much smaller than the square of the current in the second coefficient. Therefore, the coefficient preceding the change in current is relatively small, and its absolute value is generally less than 1. Thus, a slight change in the arc length results in a large change in the welding current. Therefore, the arc length change coefficient is mainly related to the welding current and its change.

[0013] Furthermore, the established model relating the rotating arc length change coefficient to the characteristic quantities of the rotating arc sensing signal enables the identification of the rotating arc length change coefficient based on the characteristic quantities of the rotating arc sensing signal. The specific details are as follows: The arc length change coefficient K and its magnitude K are related to the characteristic quantities P(η) of the rotating arc sensing signal. i ,β i ,α i ,γ i The relationship between ) satisfies the following equation:

[0014]

[0015]

[0016] In the formula, K is the arc length change coefficient, and |K| is the magnitude of the arc length change coefficient K, denoted by K. η i β is a characteristic quantity representing the number of times an arc is interrupted or nearly interrupted. i This is a characteristic quantity describing the number of times the sampling welding current direction changes within the same rotating arc. `n` represents the number of filtered currents used to determine the number of times the sampling welding current direction changes within the same rotating arc; in the experiment, its value was 61. α i α is a characteristic quantity describing the magnitude variation of welding current in adjacent samples within the same rotating arc. max When the arc is unstable, α i The value, represented by α i Divide by α max α can be i The range of values ​​for γ is normalized to [0, 1]. i γ is a characteristic quantity used to describe the magnitude change of sampled welding current at the same position in two adjacent rotating arcs. max When the arc is unstable, γ i The value of γ i Divide by γ max γ can i The value range of is normalized to [0,1]. w1, w2, w3, and w4 are the weights of each item. Based on the importance of each item and the experimental results, their values ​​are as follows: w1 = 1, w2 = 1, w3 = 0.8, and w4 = 0.2.

[0017] In the above formula, α max The calculation method is as follows:

[0018]

[0019] Similarly, γ max The calculation method is as follows:

[0020]

[0021] In the formula, α max When the arc is unstable, α i The value of γ max When the arc is unstable, γ i The values ​​of η are: median() (the function to find the median), max[] (the function to find the maximum value), and min{} (the function to find the minimum value). i η represents the number of times the arc is broken or nearly broken in the i-th calculation. i-1 η represents the number of times the arc is broken or nearly broken in the (i-1)th calculation.i-2 This represents the number of times the arc is broken or nearly broken in the (i-2)th calculation. b1 is the amplification factor, with a value of 1.3. η i >0orη i-1 >0orη i-2 >0 indicates that there was an arc break or near-arc break within the last three sampling periods, and the arc is in an unstable state. η i =0andη i-1 =0andη i-2 =0 indicates that there was no arc breakage or near arc breakage in the last three sampling periods, and the arc is in a stable or understable state.

[0022] Furthermore, the method for detecting the change in the length of the rotating arc establishes rules for identifying the change in the length of the rotating arc, the specific contents of which are as follows.

[0023] Rule 1: If the magnitude K of the arc length change coefficient is small, the recovery value of the rotating arc length is large, and the change value of the rotating arc length is small.

[0024] Rule 2: If the magnitude K of the arc length change coefficient is large, the recovery value of the rotating arc length is small, and the change value of the rotating arc length is large.

[0025] The beneficial effects of this invention are as follows:

[0026] The advantage of this invention lies in that it provides a method for detecting the change in the length of a rotating arc based on the characteristics of a rotating arc sensing signal. This method enables online machine monitoring of the change in the length of the rotating arc in strong arc light environments, which is beneficial for achieving precise control of the change in the length of the rotating arc, improving the level of automated robotic welding, reducing manual welding costs, and improving the quality of robotic welding. Attached Figure Description

[0027] Figure 1 This is the working principle of the rotating arc length change detection method of the present invention;

[0028] Figure 2 This is the equivalent circuit diagram of the welding circuit of the present invention;

[0029] Figure 3 The present invention provides a robot for tracking the fillet weld after welding when the electric arc is stable;

[0030] Figure 4 This invention provides a robot for tracking fillet welds after welding when the electric arc is unstable.

[0031] Figure 5 This refers to the magnitude of the arc length change coefficient detected by the present invention;

[0032] In the diagram: 1. Resistance of the electric arc; 2. Welding wire; 3. Electric arc; 4. Steel plate; 5. Resistance of the welding wire. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0034] The method of this invention mainly includes four parts: the working principle of the rotating arc length change detection method, the relationship between the rotating arc length change coefficient and the welding current and its change, the establishment of a relationship model between the rotating arc length change coefficient and the characteristic quantities of the rotating arc sensing signal, and the detection method of the rotating arc length change value. These will be introduced separately below.

[0035] (1) Working principle of the rotating arc length change detection method

[0036] Figure 1 The working principle of the rotating arc length change detection method is as follows. During the rotation of the arc (3), the arc length changes according to a certain pattern after being modulated by the welding groove. However, due to the effect of the arc length self-adjustment system, the arc length recovery value resists the change of arc length. After passing through the welding circuit, the arc length recovery value is converted into a change in the welding current waveform. When the arc (3) is more stable, the arc length recovery value is larger due to the effect of the arc length self-adjustment system, resulting in smaller changes in adjacent welding current. When the arc (3) is unstable, the arc length recovery value is very small, resulting in large changes in adjacent welding current. The arc length change coefficient K is used to evaluate the magnitude of the arc length change value. The larger the arc length change value, the larger the arc length change coefficient K. A relationship model between the arc length change coefficient K and the characteristics of each group of rotating arc sensing signals can be established. Therefore, as long as the collected welding current waveform is used, the rotating arc sensing signal characteristics P(η) can be identified. i ,β i ,α i ,γ i ), then the change in the length of the rotating arc can be identified based on the characteristics of the rotating arc sensing signal, where η i β is a characteristic quantity representing the number of times an arc is interrupted or nearly interrupted. i α is a characteristic quantity describing the number of times the direction of the sampling welding current changes within the same rotating arc. i γ is a characteristic quantity used to describe the magnitude variation of welding current in adjacent samples within the same rotating arc. i This is a characteristic quantity used to describe the change in the magnitude of the sampled welding current at the same position between two adjacent rotating arcs.

[0037] Therefore, the welding circuit converts non-electrical quantities into electrical quantities, transforming the change in arc length into a rotating arc sensing signal characteristic, that is, the change characteristic of each welding current waveform. This establishes a connection between the arc length and the welding current. Furthermore, the welding current is an easily measurable electrical quantity, facilitating subsequent signal transmission, storage, and analysis.

[0038] (2) Relationship between the coefficient of change of rotating arc length and welding current and its change

[0039] Figure 2 The equivalent circuit diagram of the welding circuit is shown. The welding power source outputs welding voltage and welding current, generating an electric arc (3) between the end of the welding wire (2) and the steel plate (4). The welding wire (2) melts through the heat of the electric arc and resistance heat. The resistance (5) of the welding wire is R1, and the resistance (1) of the electric arc is R... t R t It changes with the shape and length of the electric arc (3). Taking the end of the welding wire (2) as the origin, Figure 2 The resistivity ρ of the arc (3) at different cross-sections is plotted in the figure. ( l t) and cross-sectional area s ( l t) The curve shows the change of the arc, where the value of point K is determined by the resistivity of the welding wire (2), and the value of point J is determined by the cross-sectional area of ​​the welding wire (2). The arc length corresponding to the BC section of the arc (3) is l. BC The arc length corresponding to the DE section of the electric arc (3) is l.

[0040] The arc (3) region is equivalent to a conductor. When the arc length is l, its equivalent resistance R t The following formula must be satisfied:

[0041]

[0042] In the formula, R t Let l be the resistance of the electric arc (1), and l be... Figure 2 The total length of the electric arc (3), l t Let ρ be the arc length corresponding to a certain cross section of the arc (3). ( l t) The arc length is l t The resistivity of the corresponding arc (3), s ( l t) The arc length is l t The cross-sectional area of ​​the electric arc (3) at the corresponding location.

[0043] right Figure 2 The welding circuit in the diagram can be obtained using Ohm's law.

[0044]

[0045] In the formula, U is the welding voltage, I is the welding current, R1 is the resistance of the welding wire (5), R t Let be the resistance of the electric arc (1), and other physical quantities are introduced in equation (1).

[0046] Equation (2) simultaneously applies to both sides of the arc length l t After taking the derivative, we can obtain...

[0047]

[0048] After simplification, we get:

[0049]

[0050] After further simplification, we can obtain:

[0051]

[0052] In equation (3-5), the meanings of each physical quantity have been introduced in equation (1-2). In equation (5), the coefficient of current change consists of three parts. The negative sign of the first term of the coefficient indicates that when the arc length is shortened, the welding current will increase while other conditions remain unchanged; the second term of the coefficient indicates that when the welding voltage is increased, the arc length will increase while other conditions remain unchanged; the third term of the coefficient indicates that when the welding current is increased, the arc length will decrease while other conditions remain unchanged.

[0053] During the rotation of the electric arc (3), if the arc length recovery value is large, the change in arc length is small, and the magnitude of the arc length change coefficient is also small. Therefore, the magnitude of the arc length change coefficient and the arc length change satisfy the following relationship:

[0054]

[0055] In equation (6), K is the magnitude of the arc length change coefficient, and the meanings of other physical quantities have been introduced in equation (1-2).

[0056] The change in current in formula (6) contains two coefficients. Since the welding voltage is relatively small, generally less than 35V, and the welding current is generally greater than 100A, and ρ(l) / s(l) does not change much, the first coefficient is much smaller than the square of the current in the second coefficient. Therefore, the coefficient before the change in current is small, and its absolute value is generally less than 1. Thus, when the arc length changes slightly, the welding current changes significantly. Therefore, the arc length change coefficient is mainly related to the welding current and its change. Based on this characteristic, some characteristic quantities of the rotating arc sensing signal will be proposed below using the welding current and its change, which will help to establish a relationship model between the arc length change coefficient and the characteristic quantities of the rotating arc sensing signal.

[0057] (3) Establish a model relating the coefficient of change of the rotating arc length to the characteristic quantities of the rotating arc sensing signal.

[0058] The welding circuit establishes a relationship between the arc length change coefficient and the welding current, while the rotating arc sensor establishes a relationship between the welding current and the characteristics of the rotating arc sensing signal. Therefore, there is a relationship between the arc length change coefficient and the characteristics of the rotating arc sensing signal. The more times the arc is interrupted or nearly interrupted, the more times the direction of the sampled welding current changes within the same rotating arc, the greater the magnitude change of adjacent sampled welding currents within the same rotating arc, and the greater the magnitude change of the sampled welding current at the same position between two adjacent rotating arcs. This results in a smaller arc length recovery value and a larger corresponding arc length change coefficient. Therefore, the arc length change coefficient K is related to the characteristics P(η) of the rotating arc sensing signal. i ,β i ,α i ,γ i The relationship between ) satisfies the following equation:

[0059]

[0060] The magnitude of the arc length change coefficient K satisfies the following formula.

[0061]

[0062] In equation (7-8), K is the arc length change coefficient, and |K| is the magnitude of the arc length change coefficient K, denoted by K. η i β is a characteristic quantity representing the number of times an arc is interrupted or nearly interrupted. i This is a characteristic quantity describing the number of times the sampling welding current direction changes within the same rotating arc. `n` represents the number of filtered currents used to determine the number of times the sampling welding current direction changes within the same rotating arc; in the experiment, its value was 61. α i α is a characteristic quantity describing the magnitude variation of welding current in adjacent samples within the same rotating arc. max When the arc (3) is unstable, α i The value, represented by α i Divide by α max α can be i The range of values ​​for γ is normalized to [0, 1]. i γ is a characteristic quantity used to describe the magnitude change of sampled welding current at the same position in two adjacent rotating arcs. max When the arc (3) is unstable, γ i The value of γ i Divide by γ max γ can iThe value range of is normalized to [0,1]. w1, w2, w3, and w4 are the weights of each item. Based on the importance of each item and the experimental results, their values ​​are as follows: w1 = 1, w2 = 1, w3 = 0.8, and w4 = 0.2.

[0063] In equation (7-8), α max The calculation method is as follows:

[0064]

[0065] Similarly, γ max The calculation method is as follows:

[0066]

[0067] In equation (9-10), α max When the arc (3) is unstable, α i The value of γ max When the arc (3) is unstable, γ i The values ​​of η are: median() (the function to find the median), max[] (the function to find the maximum value), and min{} (the function to find the minimum value). i η represents the number of times the arc is broken or nearly broken in the i-th calculation. i-1 η represents the number of times the arc is broken or nearly broken in the (i-1)th calculation. i-2 This represents the number of times the arc is broken or nearly broken in the (i-2)th calculation. b1 is the amplification factor, with a value of 1.3. η i >0orη i-1 >0orη i-2 >0 indicates that there is an arc break or near arc break within the last three sampling periods, and the arc (3) is in an unstable state. η i =0andη i-1 =0andη i-2 =0 indicates that there is no arc breakage or near arc breakage in the last three sampling periods, and the arc (3) is in a stable or understable state.

[0068] (4) Detection method for change in the length of rotating electric arc

[0069] Therefore, using formula (7-10) and the previously calculated characteristic quantities of the rotating arc sensing signal, the arc length change coefficient K and its magnitude K can be calculated, and the following two rules can be used to identify the change value of the rotating arc length.

[0070] Rule 1: If the magnitude K of the arc length change coefficient is small, the recovery value of the rotating arc length is large, and the change value of the rotating arc length is small.

[0071] Rule 2: If the magnitude K of the arc length change coefficient is large, the recovery value of the rotating arc length is small, and the change value of the rotating arc length is large.

[0072] To verify the effectiveness of the method of the present invention, a rotating arc sensing robot was used to perform tracking welding on fillet welds, and the experimental data were analyzed using the method of the present invention.

[0073] Figure 3 When the robot tracks the fillet weld after welding to ensure the arc is stable, it can be observed that the weld size is uniform and the weld formation is aesthetically pleasing. Therefore, the arc stability is good during the welding process. Figure 4 When a robot tracks a fillet weld after welding when the arc is unstable, it can be found that the weld size changes greatly and the weld formation is very poor. Therefore, the arc stability is not good during the welding process.

[0074] right Figure 3 and Figure 4 The experimental data were analyzed, and the magnitude of the arc length change coefficient was detected as follows: Figure 5 As shown in the diagram. When the arc is stable, the magnitude of the detected arc length change coefficient is represented by the solid red line. It can be observed that after a period of arc initiation, the detected arc length change coefficient is less than 0.6. At this time, the recovery value of the rotating arc length is relatively large, therefore, the change value of the rotating arc length is small. When the arc is unstable, the magnitude of the detected arc length change coefficient is represented by the dashed blue line. It can be observed that the detected arc length change coefficient is greater than 0.8, the recovery value of the rotating arc length is relatively small, therefore, the change value of the rotating arc length is relatively large.

[0075] The method of this invention can detect the change in the length of the rotating arc and can be used to help determine the stability of the rotating arc. This helps in the monitoring and control of the change in the length of the rotating arc during the welding process, and can improve welding quality and the intelligence level of robotic welding.

[0076] The above are embodiments of the present invention. The above embodiments and specific parameters are only for clearly illustrating the invention verification process and are not intended to limit the patent protection scope of the present invention. The patent protection scope of the present invention shall still be determined by its claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the protection scope of the present invention.

Claims

1. A method for detecting the change in length of a rotating electric arc based on the characteristics of a rotating electric arc sensing signal, characterized in that, The detection method includes establishing a relationship model between the coefficient of change of rotating arc length and the characteristic quantities of rotating arc sensing signals based on the relationship between the change in rotating arc length and the welding current and its change. The relationship between the change in the rotating arc length and the welding current and its change allows for the identification of the rotating arc length change coefficient based on the welding current and its change. The specific details are as follows: The relationship between the change in the rotating arc length and the welding current and its change is as follows. In the formula, This represents the change in arc length. This represents the change in welding current. The total length of the electric arc. The arc length is The resistivity of the corresponding electric arc at that location. The arc length is The cross-sectional area of ​​the electric arc at that location. For welding voltage, This refers to the welding current. During the rotation of the electric arc, the magnitude of the arc length change coefficient and the amount of arc length change satisfy the following relationship. In the formula, The magnitude of the coefficient is changed to represent the arc length. This is the coefficient for changing the arc length; The change in current in the formula contains two coefficients: welding voltage less than 35 V and welding current greater than 100 A.

2. The method for detecting the change in length of a rotating arc based on the characteristics of a rotating arc sensing signal as described in claim 1, characterized in that, The specific details of the model establishing the relationship between the coefficient of change of the rotating arc length and the characteristic quantities of the rotating arc sensing signal are as follows: Arc length change coefficient K and its magnitude The characteristic P of the rotating arc sensing signal , , , The relationship between ) satisfies the following equation: In the formula, K is the arc length variation coefficient. To change the magnitude of the coefficient K for the arc length, use express, This is a characteristic quantity representing the number of times the arc is interrupted or nearly interrupted. This is a characteristic quantity used to describe the number of times the direction of the sampled welding current changes within the same rotating arc. This indicates the number of filtered currents used to determine the number of times the direction of the sampled welding current changes within the same rotating arc; in the experiment, its value was 61. This is a characteristic quantity used to describe the variation in the magnitude of welding current between adjacent samples within the same rotating arc. When the electric arc is unstable The value, using Divide by Can The range of values ​​for is normalized to [0, 1]. This is a characteristic quantity used to describe the change in the magnitude of the sampled welding current at the same position between two adjacent rotating arcs. When the electric arc is unstable The value, using Divide by Can The range of values ​​for is normalized to [0, 1]. , , and These are the weights of each item, and their values ​​are as follows, based on the importance of each item and the experimental results. , , and ; In the above formula, The calculation method is as follows: Similarly, The calculation method is as follows: In the formula, When the electric arc is unstable The value, When the electric arc is unstable The values ​​of , median() is the function to find the median, max[] is the function to find the maximum value, and min{} is the function to find the minimum value; Let be the number of times the arc is broken or nearly broken in the i-th calculation. This represents the number of times the arc is broken or nearly broken in the (i-1)th calculation. This represents the number of times the arc is broken or nearly broken in the (i-2)th calculation. This is the magnification factor, with a value of 1.

3. This indicates that there was an arc break or near arc break within the last three sampling periods, and the arc is in an unstable state. This indicates that there was no arc breakage or near arc breakage in the last three sampling periods, and the arc is in a stable or understable state.

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