Real-time control method and system for welding current of inverter resistance welding machine

Abstract

The application provides a kind of real-time control method and system for welding current of inverter resistance welding machine, comprising: welding and collecting transformer primary side current signal;Current signal of current cycle is segmented;Processing and calculating fast rising section;Determine the starting point of slope section;Calculate the target peak current of slope section;Calculate the current statistical value of current cycle;Adjust the target peak current of next cycle.The application collects the primary side current signal of inverter welding machine in real time, processes and extracts the current signal, determines the starting point of slope section, calculates the target peak current of slope section according to the current target value;When the current of slope section reaches the target peak current, the welding current is turned off;Calculate the current statistical value in current cycle and compare it with the current target value, and then adjust the target peak current of next cycle;Repeat the above steps until the welding power-on time reaches the preset value, so as to realize the real-time fine control of welding current.

Description

Technical Field

[0001] This invention relates to the technical field of real-time control of welding current in resistance spot welding, specifically to a method and system for real-time control of welding current in inverter resistance welding machines, and more particularly to a method for real-time control of welding current in inverter resistance welding machines based on primary-side current control. Background Technology

[0002] In resistance spot welding, the control of welding current plays a crucial role in welding quality. Traditional welding current control methods often rely on preset welding parameters and fixed control strategies. However, in practical applications, the actual value of the welding current often deviates from the preset value, leading to unstable welding quality. In particular, as the workpiece temperature rises during welding, its resistance changes accordingly. When the load resistance changes, the control effect of the welding current is significantly affected. Furthermore, interference factors such as welding spatter and transformer magnetization may occur during welding, making it impossible to achieve real-time and accurate control of the welding current.

[0003] This invention proposes a novel real-time welding current control method to improve the above-mentioned technical problems. The method first acquires the primary current signal and processes it into a rapid rise segment, a ramp segment, and a current shut-off segment. Then, it calculates the characteristic quantities of the current signal to determine the starting point of the ramp segment. Subsequently, it continuously adjusts the target peak current of the next cycle according to the target current value and the measured statistical value until the welding energization time reaches the preset value, thereby achieving fine control of the welding current. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method and system for real-time control of welding current in an inverter resistance welding machine.

[0005] According to the present invention, a method for real-time control of welding current in an inverter resistance welding machine includes the following steps:

[0006] Step a1: Perform resistance spot welding, collect the primary current signal and obtain a curve of current change over time;

[0007] Step a2: Based on the curve of current changing with time, the current signal is divided into different cycles according to the inverter cycle. The current signal of each cycle is divided into a rapid rise segment T1, a ramp segment T2, and a current cut-off segment T3 based on the welding current conduction and cut-off.

[0008] Step a3: For the current signal of the current cycle, process and calculate the fast rising segment T1. By averaging the primary current sampling value, extract the feature quantity of the current signal to obtain the feature quantity curve. Determine the fast rising segment based on the feature quantity curve.

[0009] Step a4: Determine the starting point of slope segment T2. Based on the characteristic quantity curve, determine the starting point of slope segment T2 and set the characteristic quantity thresholds, including the high threshold D. H Low threshold D L The feature quantity is higher than the high threshold D for the first time. H And it is below the low threshold D L The moment when the current is below the low threshold is the starting point of ramp segment T2, and is denoted as the current value I corresponding to the starting point of ramp segment T2. V ;

[0010] Step a5: Calculate the target peak current of the slope section T2, based on the target current value I. T and the current value I at the starting point of the slope section T2 V Calculate the target peak current I in the slope section T2. P That is, the current value at the moment of conduction and turn-off; when the current in the ramp section T2 reaches the target peak current I. P The primary welding current is switched from the on state to the off state to control the welding current of the current cycle in real time.

[0011] Step a6: Calculate the current statistics for the current cycle. From the start of ramp segment T2 to the current turn-off time, perform a point-by-point weighted summation of the current sampled values ​​within the time range from the start of ramp segment T2 to the current turn-off time to obtain the ramp segment T2 statistics I. A ;

[0012] Step a7: According to I A and I T Adjust the target peak current I for the next cycle P The calculation formula;

[0013] Step a8: Repeat the above steps until the welding energizing time reaches the preset value.

[0014] Preferably, in step a1: the primary current signal of the inverter resistance welding machine is acquired in real time, and the primary current signal refers to the rated current of the high-voltage side winding of the transformer in the inverter welding machine, i.e., the power input side winding.

[0015] Preferably, in step a2: the rapid rise segment T1 refers to the stage where the welding current conduction current value increases rapidly; the ramp segment T2 refers to the stage where the welding current is basically stable but increases slowly due to changes in workpiece resistance; and the current shut-off segment T3 refers to the stage from the welding current being shut off to its re-conduction.

[0016] Preferably, in step a3: the characteristic quantity is the first-order difference of the current signal with respect to time, and the first-order difference curve of the current signal with respect to time is obtained.

[0017] Preferably, in step a5: the peak value of the target slope segment I P The calculation formula is: Among them: I T For the target current value, I V The value is the current at the starting point of the slope section, where α and β are both percentage parameters.

[0018] Preferably, the collected current values ​​and characteristic quantities, i.e., the first-order difference data of the current values ​​versus time, are input into the calculation and analysis module. A point-by-point weighted calculation is performed using the slope segment statistical value calculation formula. The calculation and analysis module includes: a microprocessor, industrial computer, PLC, monitoring instrument, welding controller, desktop computer, laptop computer, server, or workstation. The calculation formula for the point-by-point weighted cumulative calculation is: Among them I i Let w be the sampled value at point i. i Let be the weight coefficient for point i, n be the total number of sampling points, and m be the power weight coefficient.

[0019] Preferably, in step a7: according to I A and I T The difference is adjusted to the percentage parameter β of the next wave, i.e., β←β+f(I A -I T ), where f is the specific adjustment method, and PID control is adopted.

[0020] The present invention also provides a real-time control system for welding current of an inverter resistance welding machine, the system comprising the following modules:

[0021] Module m1: Performs resistance spot welding, collects the primary current signal, and obtains a curve of current changing over time;

[0022] Module m2: Based on the curve of current changing with time, the current signal is divided into different cycles according to the inverter cycle. The current signal of each cycle is divided into a rapid rise segment T1, a ramp segment T2, and a current cut-off segment T3 according to the welding current conduction and cut-off.

[0023] Module m3: For the current signal of the current cycle, process and calculate the fast rising segment T1. By averaging and filtering the primary current sample value, extract the feature quantity of the current signal to obtain the feature quantity curve. Determine the fast rising segment based on the feature quantity curve.

[0024] Module m4: Determines the starting point of slope segment T2 based on the characteristic quantity curve, and sets characteristic quantity thresholds, including a high threshold D. H Low threshold D L The feature quantity is higher than the high threshold D for the first time. H And it is below the low threshold D LThe moment when the current is below the low threshold is the starting point of ramp segment T2, and is denoted as the current value I corresponding to the starting point of ramp segment T2. V ;

[0025] Module m5: Calculates the target peak current of the slope section T2, based on the target current value I. T and the current value I at the starting point of the slope section T2 V Calculate the target peak current I in the slope section T2. P That is, the current value at the moment of conduction and turn-off; when the current in the ramp section T2 reaches the target peak current I. P The primary welding current is switched from the on state to the off state to control the welding current of the current cycle in real time.

[0026] Module m6: Calculates the current statistics for the current cycle. From the start of ramp segment T2 to the current turn-off time, it performs a point-by-point weighted summation of the current sampled values ​​within this time range to obtain the ramp segment T2 statistics I. A ;

[0027] Module m7: According to I A and I T Adjust the target peak current I for the next cycle P The calculation formula;

[0028] Module m8: Repeat the above module until the welding energization time reaches the preset value.

[0029] Preferably, in module m1: the primary current signal of the inverter resistance welding machine is acquired in real time, and the primary current signal refers to the rated current of the high-voltage side winding of the transformer in the inverter welding machine, i.e., the power input side winding.

[0030] In module m2: the rapid rise segment T1 refers to the stage where the welding current conduction current value increases rapidly; the ramp segment T2 refers to the stage where the welding current is basically stable but increases slowly due to changes in workpiece resistance; the current shut-off segment T3 refers to the stage from the welding current being shut off to being turned on again.

[0031] In module m3: the characteristic quantity is the first-order difference of the current signal with respect to time, which yields the first-order difference curve of the current signal with respect to time.

[0032] Preferably, in module m5: the peak value I of the target slope segment P The calculation formula is: Among them: I T For the target current value, I V α represents the current value at the starting point of the slope section, where α and β are both percentage parameters.

[0033] The collected current values ​​and characteristic quantities, i.e., the first-order difference data of current values ​​versus time, are input into the calculation and analysis module. A point-by-point weighted calculation is performed using the slope segment statistical value calculation formula. The calculation and analysis module includes: a microprocessor, industrial computer, PLC, monitoring instrument, welding controller, desktop computer, laptop computer, server, or workstation. The calculation formula for the point-by-point weighted cumulative calculation is as follows: Among them I i Let w be the sampled value at point i. i Let be the weight coefficient for the i-th point, n be the total number of sampling points, and m be the power weight coefficient.

[0034] In module m7: according to I A and I T The difference is adjusted to the percentage parameter β of the next wave, i.e., β←β+f(I A -I T ), where f is the specific adjustment method, and PID control is adopted.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. This invention acquires the primary current signal of an inverter welding machine in real time and processes it in segments, namely a rapid rise segment, a ramp segment, and a current shut-off segment; it uses characteristic quantities to determine the starting point of the ramp segment and calculates the target peak current of the ramp segment based on the target current value; when the ramp segment current reaches the target peak current, the welding current is shut off, thereby controlling the welding current of the current cycle in real time; it calculates the current statistics of the current cycle and compares them with the current target value, and then adjusts the target peak current of the next cycle; it repeats the above steps until the welding energization time reaches the preset value, thereby achieving precise control of the welding current;

[0037] 2. This invention effectively reduces welding current fluctuations caused by welding spatter, transformer magnetization, load changes, etc., by real-time monitoring and control of welding current, thereby improving the consistency of the welding process, ensuring the strength and reliability of the joint, reducing the scrap rate during the welding process, and improving production efficiency.

[0038] 3. This invention overcomes the shortcomings of traditional methods that only measure but do not adjust the current frequency, and realizes real-time control of the welding current of the current frequency, thus improving the timeliness of control; by iteratively adjusting the target peak current of the next frequency, it achieves self-adaptation to different loads; it can be widely applied to welding plates of different materials and thicknesses, thus improving the versatility and adaptability of current control. Attached Figure Description

[0039] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0040] Figure 1 This is a flowchart of the present invention;

[0041] Figure 2 This is a schematic diagram of the system of the present invention;

[0042] Figure 3 This is a schematic diagram of the primary-side current signal acquisition method of the present invention;

[0043] Figure 4 This is a schematic diagram of the current-cycle current signal segmentation processing of the present invention;

[0044] Figure 5 This is a schematic diagram illustrating the determination of the starting point of the slope section according to the present invention;

[0045] The components include: 1. Electrode cap; 2. Electrode rod; 3. Workpiece to be tested; 4. Current sensor; 5. Current signal acquisition module; 6. Calculation and analysis module; and 7. Current control module. Detailed Implementation

[0046] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0047] Example 1:

[0048] According to the present invention, a method for real-time control of welding current in an inverter resistance welding machine includes the following steps:

[0049] Step a1: Perform resistance spot welding, collect the primary current signal and obtain the current change curve over time; collect the primary current signal of the inverter resistance welding machine in real time, wherein the primary current signal refers to the rated current of the high-voltage side winding of the transformer in the inverter welding machine, i.e., the power input side winding.

[0050] Step a2: Based on the curve of current change over time, the current signal is divided into different cycles according to the inverter cycle. The current signal of each cycle is divided into a rapid rise segment T1, a ramp segment T2, and a current cut-off segment T3 based on the welding current conduction and cut-off. The rapid rise segment T1 refers to the stage where the welding current conduction current value increases rapidly. The ramp segment T2 refers to the stage where the welding current is basically stable but increases slowly due to the change in workpiece resistance. The current cut-off segment T3 refers to the stage from the welding current being cut off to its re-conduction.

[0051] Step a3: For the current signal of the current cycle, process and calculate the fast rising segment T1. By averaging the primary current sample value, extract the feature quantity of the current signal to obtain the feature quantity curve. Determine the fast rising segment based on the feature quantity curve. The feature quantity is the first-order difference of the current signal with respect to time, and obtain the first-order difference curve of the current signal with respect to time.

[0052] Step a4: Determine the starting point of slope segment T2. Based on the characteristic quantity curve, determine the starting point of slope segment T2 and set the characteristic quantity thresholds, including the high threshold D. H Low threshold D L The feature quantity is higher than the high threshold D for the first time. H And it is below the low threshold D L The moment when the current is below the low threshold is the starting point of ramp segment T2, and is denoted as the current value I corresponding to the starting point of ramp segment T2. V ;

[0053] Step a5: Calculate the target peak current of the slope section T2, based on the target current value I. T and the current value I at the starting point of the slope section T2 V Calculate the target peak current I in the slope section T2. P That is, the current value at the moment of conduction and turn-off; when the current in the ramp section T2 reaches the target peak current I. P The primary welding current is switched from on to off state to achieve real-time control of the welding current for the current cycle; the target ramp peak value I P The calculation formula is: Among them: I T For the target current value, I V The value is the current at the starting point of the slope section, where α and β are both percentage parameters.

[0054] Step a6: Calculate the current statistics for the current cycle. From the start of ramp segment T2 to the current turn-off time, perform a point-by-point weighted summation of the current sampled values ​​within the time range from the start of ramp segment T2 to the current turn-off time to obtain the ramp segment T2 statistics I. A The collected current values ​​and characteristic quantities, i.e., the first-order difference data of the current values ​​versus time, are input into the calculation and analysis module. A point-by-point weighted calculation is performed using the slope segment statistical value calculation formula. The calculation and analysis module includes: a microprocessor, industrial computer, PLC, monitoring instrument, welding controller, desktop computer, laptop computer, server, or workstation. The calculation formula for the point-by-point weighted cumulative calculation is as follows: Among them I i Let w be the sampled value at point i. i Let be the weight coefficient for point i, n be the total number of sampling points, and m be the power weight coefficient.

[0055] Step a7: According to I A and I T Adjust the target peak current I for the next cycle P The calculation formula; according to I A and I T The difference is adjusted to the percentage parameter β of the next wave, i.e., β←β+f(I A -I T ), where f is the specific adjustment method, and PID control is adopted.

[0056] Step a8: Repeat the above steps until the welding energizing time reaches the preset value.

[0057] The present invention also provides a real-time control system for the welding current of an inverter resistance welding machine. The real-time control system for the welding current of an inverter resistance welding machine can be implemented by executing the process steps of the real-time control method for the welding current of an inverter resistance welding machine. That is, those skilled in the art can understand the real-time control method for the welding current of an inverter resistance welding machine as a preferred embodiment of the real-time control system for the welding current of an inverter resistance welding machine.

[0058] Example 2:

[0059] The present invention also provides a real-time control system for welding current of an inverter resistance welding machine, the system comprising the following modules:

[0060] Module m1: Performs resistance spot welding, collects primary current signal and obtains current-time curve; collects primary current signal of inverter resistance welding machine in real time, the primary current signal refers to the rated current of the high voltage side winding of transformer in inverter welding machine, i.e., power input side winding.

[0061] Module m2: Based on the current-time curve, the current signal is divided into different cycles according to the inverter cycle. Each cycle's current signal is divided into a rapid rise segment T1, a ramp segment T2, and a current shutdown segment T3, based on the welding current's on and off states. The rapid rise segment T1 refers to the stage where the welding current value increases rapidly when it is on. The ramp segment T2 refers to the stage where the welding current is basically stable but increases slowly due to changes in workpiece resistance. The current shutdown segment T3 refers to the stage from when the welding current is off until it is turned on again.

[0062] Module m3: For the current signal of the current cycle, process and calculate the fast rise segment T1. By averaging and filtering the primary current sample value, extract the feature quantity of the current signal to obtain the feature quantity curve. Based on the feature quantity curve, determine the fast rise segment. The feature quantity is the first difference of the current signal with respect to time, and obtain the first difference curve of the current signal with respect to time.

[0063] Module m4: Determines the starting point of slope segment T2 based on the characteristic quantity curve, and sets characteristic quantity thresholds, including a high threshold D. H Low threshold D L The feature quantity is higher than the high threshold D for the first time. H And it is below the low threshold D L The moment when the current is below the low threshold is the starting point of ramp segment T2, and is denoted as the current value I corresponding to the starting point of ramp segment T2. V ;

[0064] Module m5: Calculates the target peak current of the slope section T2, based on the target current value I. T and the current value I at the starting point of the slope section T2 V Calculate the target peak current I in the slope section T2. P That is, the current value at the moment of conduction and turn-off; when the current in the ramp section T2 reaches the target peak current I. P The primary welding current is switched from on to off state to achieve real-time control of the welding current for the current cycle; the target ramp peak value I P The calculation formula is: Among them: I T For the target current value, I V α represents the current value at the starting point of the slope section, where α and β are both percentage parameters.

[0065] Module m6: Calculates the current statistics for the current cycle. From the start of ramp segment T2 to the current turn-off time, it performs a point-by-point weighted summation of the current sampled values ​​within this time range to obtain the ramp segment T2 statistics I. A The collected current values ​​and characteristic quantities, i.e., the first-order difference data of the current values ​​versus time, are input into the calculation and analysis module. A point-by-point weighted calculation is performed using the slope segment statistical value calculation formula. The calculation and analysis module includes: a microprocessor, industrial computer, PLC, monitoring instrument, welding controller, desktop computer, laptop computer, server, or workstation. The calculation formula for the point-by-point weighted cumulative calculation is as follows: Among them I i Let w be the sampled value at point i. i Let be the weight coefficient for the i-th point, n be the total number of sampling points, and m be the power weight coefficient.

[0066] Module m7: According to I A and I T Adjust the target peak current I for the next cycle P The calculation formula; according to I A and I T The difference is adjusted to the percentage parameter β of the next wave, i.e., β←β+f(I A -I T), where f is the specific adjustment method, and PID control is adopted.

[0067] Module m8: Repeat the above module until the welding energization time reaches the preset value.

[0068] Example 3:

[0069] like Figure 2 As shown, the workpieces to be welded in this embodiment are divided into three types: no load, light load (0.8mm steel plate + 0.8mm steel plate), and heavy load (1.6mm steel plate + 1.6mm steel plate). The inverter frequency is 1kHz, the transformer ratio is 40:1, and the current is set to 4-12kA. The welding current of the inverter resistance welding machine is adjusted in real time through the following steps.

[0070] Step S1: Taking a small load as an example, resistance spot welding is performed. The welding current is selected as 8kA, therefore the target current I is... T =200A, real-time acquisition and recording of current signals during resistance spot welding process, obtaining a curve of current change over time, such as... Figure 3 As shown.

[0071] Step S2: Based on the curve of current change over time, the current signal is divided into different cycles according to the inverter cycle. The current signal of each cycle is divided into a rapid rise segment T1, a ramp segment T2, and a current cut-off segment T3 based on the welding current conduction and cut-off.

[0072] Step S3: For the current signal of the current cycle, process and calculate the rapid rise segment. By averaging and filtering the primary current sample values, extract the feature quantities of the current signal during the resistance spot welding process to obtain the feature quantity curve, as shown in the figure. Figure 5 As shown, the rapid rise segment is determined based on the characteristic quantity diagram. At time t1 = 0.65ms, the characteristic quantity changes from zero to greater than zero. Therefore, time t1 is the starting point of the rapid rise segment. In this example, the rise segment time is 16.12μs.

[0073] Step S4: Determine the starting point of the slope segment based on the characteristic quantity diagram, such as... Figure 5 As shown in Table 1, the feature thresholds are set, where the high threshold D... H 2×10 5 A·S -1 Low threshold D L 10 5 A·S -1 At time t2 = 0.66 ms, the feature value first exceeds the high threshold D. H And it is below the low threshold D L The time t2 is the starting point of the slope section. Figure 3 Find the current value I at time t2 V=125A.

[0074] Table 1 Recommended Table for Selecting High and Low Thresholds

[0075] <![CDATA[I T / A]]> <![CDATA[D H / A·S -1 ]]> <![CDATA[D L / A·S -1 ]]> 0-75 <![CDATA[3×10 4 ]]> <![CDATA[1×10 4 ]]> 75-150 <![CDATA[5×10 4 ]]> <![CDATA[2×10 4 ]]> 150-300 <![CDATA[1×10 5 ]]> <![CDATA[5×10 4 ]]> 300-600 <![CDATA[2×10 5 ]]> <![CDATA[1×10 5 ]]> 600-1200 <![CDATA[3×10 5 ]]> <![CDATA[2×10 5 ]]> 1200-2400 <![CDATA[3×10 5 ]]> <![CDATA[4×10 5 ]]>

[0076] Step S5: Based on the target current value I T and the current value I at the starting point of the slope section V Calculate the target peak current I P Target peak current I P The calculation formula is: Among them I T For the target current value, I V The valley value of the slope section is the current value at the starting point of the slope section. α and β are both percentage parameters. In this example, α = 0.5, and the initial value of β is 1, i.e., Ivalley. P =2I T -I V When the target current value I T When the current is 200A, the corresponding target peak current I can be obtained according to the formula. P =275A, and the corresponding time t3=0.84ms is the current cut-off time, the welding current is turned off, thus realizing real-time control of the welding current.

[0077] Step S6: From the starting point of ramp segment T2 to the current turn-off time, perform a point-by-point weighted summation of the current sampling values ​​within this time range to obtain the statistical value I of ramp segment T2. A Statistical value I of the slope section A The calculation formula is: Where w i Let be the weight coefficient for point i, in this example I i Let I be the sampled value at point i, and n be the total number of sampled points. In this embodiment, n = 180. The statistical value I of the slope section is calculated. A =195A.

[0078] Step S7: According to I A and I T Adjust the percentage parameter β for the next wave. This example uses proportional control with a proportional coefficient of 0.01, i.e., β←β+0.01(I A -I T After 5 cycles, the statistical value I of the slope section A =198A, with an error rate of 1.0%, achieving precise control of welding current.

[0079] As can be seen from Table 2, when the set current is 4-12kA, the measured current also changes with the size of the load. Compared with the traditional method, the new method has less fluctuation under different loads, thus verifying the effectiveness of the present invention.

[0080] Table 2 Comparison of Errors Between Actual Current and Set Current for Different Loads

[0081]

[0082] Example 4

[0083] Compared to Example 3, this example uses a 2mm aluminum plate + 2mm aluminum plate as the workpiece to be welded, a welding current of 30kA, an inverter frequency of 2kHz, and a transformer ratio of 30:1. Therefore, the target current I... T =1000A, and the welding current of the inverter resistance welding machine is adjusted in real time using the same steps.

[0084] In this embodiment, the feature threshold is selected as a high threshold D. H 3×10 5 A·S -1 Low threshold D L 2×10 5 A·S -1 .

[0085] In this embodiment, the starting time of the rapid ascent segment is t1 = 0.56 ms, and the ascent period is 60.36 μs. Based on the aforementioned high and low thresholds, the starting time of the ramp segment is determined to be t2 = 0.62 ms, and the current value I corresponding to the starting time of the ramp segment is... V =923A.

[0086] The target peak current I in this embodiment P Using the target current value I A The current value I corresponding to the starting point of the slope section V In this example, α = 0.5, and the initial value of β is 1. The calculation formula is: I P =2I T -I V I T The target current value is 1000A in this example, and the target peak current I is calculated. P =1079A, corresponding to the welding current being turned off at time t3=0.88ms.

[0087] In this embodiment, the slope section statistical value I A The calculation formula is: in I iThe sampled value is the i-th point, and the total number of sampled points is n = 260. The statistical value I of the slope section is calculated. A =988.6A. According to I A and I T Adjust the proportion factor β for the next cycle. This example uses proportional-integral control with a proportional factor of 0.01 and an integral time constant of 0.002. After 6 cycles, the current ramp segment statistical value I... A =998.3A, with an error rate of 0.17%, achieving precise control of welding current.

[0088] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0089] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for real-time control of welding current in an inverter resistance welding machine, characterized in that, The method includes the following steps: Step a1: Perform resistance spot welding, collect the primary current signal and obtain a curve of current change over time; Step a2: Based on the current-time curve, divide the current signal into different cycles according to the inverter cycle. Each cycle of the current signal is divided into a rapid rise segment based on the on and off states of the welding current. T1 sloping section T2 and current shut-off section T3 ; Step a3: For the current signal of the current cycle, process and calculate the fast rise segment. T1 By averaging and filtering the primary current sample values, feature quantities are extracted from the current signal to obtain a feature quantity curve. The rapid rising segment is then determined based on the feature quantity curve. Step a4: Determine the slope section T2 Starting point, determine the slope section based on the characteristic quantity curve. T2 Starting point, setting feature thresholds, including high thresholds. D H low threshold D L The feature value is higher than the high threshold for the first time. D H And it is below the low threshold. D L The moment when the value is below the low threshold is the slope section. T2 The starting point is denoted as the slope section. T2 Current value corresponding to the starting point I V ; Step a5: Calculate the slope section T2 Target peak current, based on target current value I T and slope section T2 Starting point current value I V Calculate the slope section T2 Target peak current I P That is, the current value at the moment of conduction and the moment of turn-on; When the slope section T2 Current reaches target peak current I P The primary welding current is switched from the on state to the off state to control the welding current of the current cycle in real time. Step a6: Calculate the current statistics for the current cycle, starting from the ramp segment. T2 From the starting point to the current cutoff time, for the ramp section T2 The current sampling values ​​within the time range from the starting point to the current turn-off point are weighted and accumulated point by point to obtain the slope section. T2 Statistical value I A ; Step a7: According to I A and I T Adjust the target peak current for the next cycle I P The calculation formula; Step a8: Repeat the above steps until the welding energizing time reaches the preset value.

2. The method for real-time control of welding current in an inverter resistance welding machine according to claim 1, characterized in that, In step a1: the primary current signal of the inverter resistance welding machine is acquired in real time. The primary current signal refers to the rated current of the high-voltage side winding of the transformer in the inverter welding machine, i.e., the power input side winding.

3. The method for real-time control of welding current in an inverter resistance welding machine according to claim 1, characterized in that, In step a2: the rapid ascent segment T1 This refers to the stage where the welding current conduction current value increases rapidly; the slope section T2 This refers to the stage where the self-welding current is stable but the resistance of the workpiece increases slowly; the current shut-off section. T3 This refers to the period from when the welding current is turned off to when it is turned on again.

4. The method for real-time control of welding current in an inverter resistance welding machine according to claim 1, characterized in that, In step a3: the characteristic quantity is the first-order difference of the current signal with respect to time, and the first-order difference curve of the current signal with respect to time is obtained.

5. The method for real-time control of welding current in an inverter resistance welding machine according to claim 1, characterized in that, In step a5: the peak value of the target slope segment I P The calculation formula is: ,in: I T For the target current value, I V This represents the current value at the starting point of the slope section. α , β All of these are percentage parameters.

6. The method for real-time control of welding current in an inverter resistance welding machine according to claim 1, characterized in that, The collected current values ​​and characteristic quantities, i.e., the first-order difference data of current values ​​versus time, are input into the calculation and analysis module. A point-by-point weighted calculation is performed using the slope segment statistical value calculation formula. The calculation and analysis module includes: a microprocessor, industrial computer, PLC, monitoring instrument, welding controller, desktop computer, laptop computer, server, or workstation. The calculation formula for the point-by-point weighted cumulative calculation is as follows: ,in I i For the first i Point sample value, w i For the first i The weighting coefficient of the point. n This is the total number of sampling points. m It is a power-order weighting coefficient.

7. The method for real-time control of welding current in an inverter resistance welding machine according to claim 1, characterized in that, In step a7: according to I A and I T The difference will be adjusted to determine the percentage of the next wave. β ,Right now ,in f For specific adjustment methods, PID control is adopted.

Images