RESISTANCE POINT WELDING CONTROL SYSTEM AND CORRESPONDING PROCEDURE

Abstract

System (100) for controlling welding parameters of a spot welding machine that joins a plurality of plates (P1, P2), wherein the system comprises: an ultrasonic sensor (110) installed in an electrode (11, 12) of a welding gun (10), the application of an ultrasonic wave to a welding part of the plate (P1, P2) and the detection of a reflected ultrasonic signal; an ultrasound analyzer (120) capable of generating ultrasound analysis information by analyzing the ultrasound signal in real time; and a welding control (130) that receives the ultrasonic analysis information from the ultrasonic analyzer (120), performs adaptive welding control with the welding parameters set on the basis of the information about the plate (P1, P2), and compensates in real time for one or more welding parameters according to the received ultrasonic analysis information, the welding control (130) includes: a communication module (131) for communication with a server (200) of a manufacturing execution system, which centrally manages the ultrasonic analyzer (120) and the welding process via a multi-channel communication interface; an information collection module (132) that analyzes the message type and reception time of the ultrasound analysis information received by the ultrasound analyzer (120); a timer module (133) for performing a time-division-based counting in milliseconds (ms) during the welding process; a current conversion module (134) for converting the current for spot welding according to an applied signal; a memory module (135) that stores at least one program and setting data for the welding control (130) and stores information generated according to the welding process, and a control module (136) that receives the information about the present plate (P1, P2), transmits the information about the present plate (P1, P2) to the ultrasonic analyzer (120), sets the welding parameters according to the information about the plate (P1, P2) and then starts the welding process, wherein the control module (136) is able to set the welding parameters, including a base current at the welding start time, a base current increase rate, a current increase start time, a current increase end time, a base welding time at the welding start time, a maximum welding time, a time increase start time and a time increase end time.

Description

[Technical subject area]

[0001] The present disclosure relates to a resistance spot welding control system and a corresponding method. In particular, the present disclosure relates to a control system for regulating welding parameters of a resistance spot welding machine that joins a plurality of metal plates, and a corresponding method. [Background]

[0002] In general, a welding robot in a vehicle factory is used to join numerous elements (hereinafter referred to as plates) to form a vehicle body using resistance spot welding. Resistance spot welding (hereinafter referred to as spot welding) is a process in which two electrodes, attached to opposite ends of a welding gun, are clamped onto overlapping metal plates, and a high-current current is applied to the overlapping metal plates under pressure. The electrical contact resistance between the metal plates creates a localized weld. Since spot welding is typically performed thousands of times per vehicle in the vehicle factory, the quality of the spot welds is a critical factor in the impact safety of a vehicle's body structure.

[0003] Generally, a vehicle body uses panels of various materials and thicknesses, including a roof, pillars, side panels, and door opening flanges. This necessitates a range of different welding plans and settings, facilitated by a welding control system. Conventionally, spot welding control is achieved by applying a predetermined time and current when joining panels with varying geometric features.

[0004] A conventional welding control system may not be able to handle even the slightest variation in the strength and physical properties of mass-produced plates caused by changes within a batch, during punching, and in the contact conditions of the joints. This can lead to potential defects in the final product.

[0005] Welding control systems and procedures are known from the documents JP 2013 - 215 748 A, DE 103 56 978 A1 and JP 2006 - 95 542 A.

[0006] The production of high-quality products therefore requires an adaptive welding control process based on monitoring variations in spot welding parameters.

[0007] The information disclosed in this background section is provided solely for a better understanding of the background of the invention and may therefore contain information that is not part of the prior art and is already known to a person with normal technical knowledge in this country. [DETAILED DESCRIPTION OF THE INVENTION][Technical Task]

[0008] Exemplary embodiments of the present disclosure should provide an adaptive resistance spot welding control system and a corresponding method capable of controlling a welding time and current of a welding gun based on ultrasonic monitoring of the spot welding process in real time. [Means of solving the problem]

[0009] According to one aspect of the present disclosure, a system for regulating welding parameters of a spot welding machine that joins a plurality of plates includes an ultrasonic sensor installed within an electrode of a welding gun, the application of an ultrasonic wave to a welding part of the plate and the detection of a reflected ultrasonic signal; an ultrasonic analyzer capable of generating ultrasonic analysis information by analyzing the ultrasonic signal in real time; and a welding controller that receives the ultrasonic analysis information from the ultrasonic analyzer, performs adaptive welding control with the welding parameters set on the basis of information about the plate, and compensates in real time for one or more welding parameters according to the received ultrasonic analysis information.

[0010] Furthermore, the ultrasonic analyzer can generate the ultrasonic wave with a frequency band that is selected based on the information received from the welding control about the plate, in order to perform an ultrasonic analysis of the weld part.

[0011] Furthermore, based on the ultrasonic signal transmitted in real time, the ultrasonic analyzer can capture at least one of the following as ultrasonic analysis information: steel-to-steel interface (SSI), steel-to-steel interface disappearance (SSID), weld heat of a weld (α), liquid penetration depth (LPD), and end of melting (EOM).

[0012] In addition, the ultrasonic analyzer can generate an ultrasonic image, perform the ultrasonic analysis from a welding start time to a welding end time to obtain the ultrasonic analysis information, and transmit the obtained ultrasonic analysis information to the welding control system.

[0013] Furthermore, the welding parameters can include welding time and current.

[0014] Furthermore, the welding control system compensates for welding time and current using factors from ultrasonic analysis information, which are evaluated sequentially to ensure welding quality.

[0015] The welding control system includes: a communication module for communicating with a server of the manufacturing execution system, which centrally manages the ultrasonic analyzer and the welding process via a multi-channel communication interface; an information collection module that analyzes the message type and reception time of the ultrasonic analysis information received from the ultrasonic analyzer; a timing module for performing a time-division-based count in milliseconds (ms) during the welding process; a current conversion module for converting the current for spot welding according to an applied signal; and a memory module that stores at least one program and setting data for the welding control system and stores information generated according to the welding process.and a control module that receives the information about the present plate, transmits the information about the present plate to the ultrasonic analyzer, sets the welding parameters according to the information about the plate and then starts the welding process, wherein the control module is able to set the welding parameters, including a base current at the welding start time, a base current increase rate, a current increase start time, a current increase end time, a base welding time at the welding start time, a maximum welding time, a time increase start time and a time increase end time.

[0016] Furthermore, the information collection module can transmit the reception time of the ultrasound analysis information, divided into milliseconds (ms), from the welding start time to the welding end time to the control module.

[0017] Furthermore, the setting data can include position information of a weld point and control parameters for the basic welding, which are variably set according to the material and thickness of the plates and the serial information of the plates.

[0018] Furthermore, the control module is able to store information on the kinematic position control for the welding process of a robot equipped with a welding gun and to control the movement and operation of the welding gun by means of a position control of the robot according to each set process.

[0019] Furthermore, the control module determines a total welding time based on the base welding time, the time increase rate at the time of receiving the SSID, and information about the plate.

[0020] Furthermore, the control module can limit a current increase according to the α of the received ultrasonic analysis information and terminate the welding process when the total welding time is reached.

[0021] Furthermore, the control module can interrupt the power supply if the LPD received by the ultrasound analyzer corresponds to a reference value according to the information about the plate.

[0022] Furthermore, the control module can terminate the welding process by canceling any welding force acting on the plate from the electrode when the EOM is received from the ultrasonic analyzer.

[0023] A welding control method for connecting a plurality of plates to a welding control system of a spot welding machine according to one aspect of the present disclosure comprises: step (a) setting basic welding parameters corresponding to serial information of a given plate and starting welding based on the set basic welding parameters; step (b) monitoring ultrasonic analysis information in real time using an ultrasonic sensor installed in an electrode of a welding gun; step (c) starting a current increase according to a set basic current increase rate upon reaching a predetermined current increase start time from a welding start time;Step (d) to identify a time increase rate corresponding to the time of receiving a disappearance of the steel-steel interface (SSID) as the ultrasonic analysis information, and to determine a final welding time based on the set base welding time and the time increase rate; and step (e) to limit the current increase when a welding heat of a weld part (α), received as the ultrasonic analysis information, reaches a predetermined threshold angle, and to maintain a current as the maximum current for a remaining welding time before welding is completed.

[0024] Furthermore, step (b) may include a step to transfer the serial information to an ultrasonic analyzer at the start of welding, for the purpose of synchronizing an ultrasonic wave generation time and generating an ultrasonic wave with a frequency band corresponding to information about the plate.

[0025] Furthermore, step (e) may include a step of calculating the remaining welding time based on the final welding time and a receiving time of α.

[0026] Furthermore, step (e) may include: a step to terminate the power supply to the welding gun based on a determination that a liquid penetration depth (LPD) received as ultrasonic analysis information meets a welding quality requirement; and a step to cancel any welding force of the electrode acting on the plate when an end of melting (EOM) is received as ultrasonic analysis information in order to terminate the welding.

[0027] Furthermore, after step (e), the welding control procedure may include a further step to receive an ultrasonic image, which has been analyzed by the ultrasonic analyzer according to the welding control, to compare the ultrasonic analysis information with adaptive ultrasonic control information to build a database, and to check the weld quality. [Effect of the invention]

[0028] An exemplary embodiment of the present disclosure can prevent defective welding by receiving real-time ultrasonic analysis information about a weld part during the welding process and compensating for welding time and current using an adaptive control algorithm, thus producing products with reliable weld quality.

[0029] Furthermore, an exemplary embodiment of the present disclosure can prevent the occurrence of splashes by limiting an excessive increase in current by ultrasonic monitoring of α, which represents heat generation of a plate. [BRIEF DESCRIPTION OF THE DRAWINGS] Fig. Figure 1 shows an example of a production line system to which a welding control system according to an exemplary embodiment of the present disclosure is applied. Fig. Figure 2 shows a design of a welding control system according to an exemplary embodiment of the present disclosure. Fig. Figure 3 is a diagram showing the time sequence of information exchange between an ultrasonic analyzer and a welding control system according to an exemplary embodiment of the present disclosure. Fig. Figure 4 shows B-scan information analyzed by an ultrasound analyzer according to an exemplary embodiment of the present disclosure. Fig. Figure 5 is a schematic diagram showing a detailed design of a welding control system according to an exemplary embodiment of the present disclosure. Fig. Figure 6 shows an example of control parameters of a basic welding process and ultrasonic analysis information received by an ultrasonic analyzer according to an exemplary embodiment of the present disclosure. Fig. Figure 7 shows an example of compensating for welding time and current based on information from a [unclear] in Fig. The ultrasound analyzer shown in section 6 can be received. Fig. Figure 8 is a flowchart showing a welding control method according to an exemplary embodiment of the present disclosure. [Details on the implementation of the invention]

[0030] The present disclosure is described in more detail below with reference to the accompanying drawings, which illustrate exemplary embodiments of the disclosure for those skilled in the art. However, the present disclosure can be implemented in many different forms and should not be understood as being limited to the embodiments set forth herein. Accordingly, the drawings and explanations are to be regarded as illustrative and not limiting, and identical reference numbers denote identical elements throughout the entire description.

[0031] Throughout this description, unless explicitly stated otherwise, the word "include" and variations such as "includes" or "comprehensive" are to be understood as signifying the inclusion of the elements mentioned, but not the exclusion of other elements. Furthermore, the terms "-er", "or", and "module" as described here denote units for processing at least one function and one operation and can be implemented by hardware components or software components and combinations thereof.

[0032] Throughout the description, terms such as the first, the second, A, B, (a), (b), etc., may be used to describe different elements, but the elements should not be considered restricted by such terms. These terms are only used to distinguish the elements from one another, so the nature, order, or sequence of the elements is not restricted by the terms.

[0033] When a component is described as being "connected" or "coupled" to another component, it may be directly connected or coupled to that other component, or connected or coupled to that component with another component in between. Conversely, when a component is described as being "directly connected or coupled to another component," it is understood that it may be connected or coupled to that other component without any other component in between.

[0034] Throughout this description, unless otherwise defined herein, all terms, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art in the technical field to which this disclosure belongs. Terms defined in a commonly used dictionary should be interpreted in accordance with their meanings in the context of the technical field and, unless expressly defined otherwise herein, should not be interpreted as having an ideal or overly formal meaning.

[0035] A welding control system and a corresponding method according to an exemplary embodiment of the present disclosure are described in detail below with reference to the drawings.

[0036] Fig. Figure 1 shows an example of a production line system to which a welding control system according to an exemplary embodiment of the present disclosure is applied.

[0037] In Fig. 1 Several articulated welding robots 20 are arranged in a production line of a vehicle factory for assembling a product, and a welding gun 10 for spot welding is installed at a front end of an arm of each welding robot 20.

[0038] A Server 200 assigns to a welding control system 100 information about a vehicle body transported by a conveyor, information about the vehicle specification that corresponds to the information about the vehicle body, and task information for each welding robot that corresponds to the information about the vehicle specification, and centrally controls the processes in the production line.

[0039] The welding control system 100 is a system for controlling the spot welding of the welding robot 20 and includes a welding control 130 as a main element.

[0040] The welding controller 130 automatically performs the welding of a large number of weld points in coordination with the server 200 of a manufacturing control system that centrally manages the processes in the factory. The welding controller 130 automatically moves the welding gun 10 to the weld points by controlling the posture of the articulated welding robot 20 according to the task information set by the server 200, and then controls the spot welding according to an adaptive control algorithm.

[0041] Here, the adaptive control algorithm refers to the compensation of time and current, which are the main factors in spot welding control, depending on the welding status. For example, the welding controller 130 can compensate for welding control conditions by receiving time and current feedback from a sensor if a given plate is thicker or thinner than a reference value during welding.

[0042] However, even with plates made of the same material and with the same thickness, adaptive control is limited by variations in strength or physical properties depending on the manufacturer or production quantity, so more accurate adaptive control requires additional information.

[0043] Therefore, an interpretation of an improved welding control system according to an exemplary embodiment of the present disclosure is presented below with reference to Fig. 2 described in detail.

[0044] Fig. Figure 2 shows a design of a welding control system according to an exemplary embodiment of the present disclosure.

[0045] As in Fig. As shown in Figure 2, the welding control system 100 according to the exemplary embodiment of the present disclosure includes an ultrasonic sensor 110, an ultrasonic analyzer 120 and the welding control 130.

[0046] The ultrasonic sensor 110 is installed in an upper electrode 11 of the welding gun 10, applies ultrasonic waves to a weld part of plates P1 and P2, and detects a reflected signal. In the following description, it is assumed that the ultrasonic sensor 110 is installed in the upper electrode 11 of the welding gun 10, but an exemplary embodiment of the present disclosure is not limited to this, so that the ultrasonic sensor 110 can also be installed in a lower electrode 12. Depending on the welding system, the ultrasonic sensor 110 can be installed on a welding gun of type C or type X, but an exemplary embodiment of the present disclosure is not limited to this. Since the ultrasonic sensor 110 is installed inside the electrode, it also supports real-time monitoring of the welding status of a weld part during welding, even after the welding gun 10 has been moved.

[0047] The ultrasonic sensor 110 is able to transmit the detected ultrasonic signals in real time to the ultrasonic analyzer 120 via the wired or wireless communication means available for the welding gun 10.

[0048] The ultrasonic analyzer 120 includes wired or wireless communication means for communication with the ultrasonic sensor 110 and communication means for interaction with the welding control 130. Furthermore, the ultrasonic analyzer 120 may include an information communication device with at least one program, data, memory, input / output interface, and a processor for ultrasonic analysis, which will be described later.

[0049] When serial information for plates P1 and P2 is received by the welding control system 130, the ultrasonic analyzer 120 generates ultrasonic waves with a frequency band that takes into account the material and thickness of the plates to initiate the ultrasonic analysis of the welded part. This serial information can be used as unique identification (ID) information to specify welding details and the part of a product (e.g., vehicle body) to which the plates are attached. The serial information can include at least one of the following characteristics: material, thickness, manufacturer, and storage date, or it can be matched with data containing such information. The serial information is managed by the server 200 and shared with the welding control system 100, allowing the serial information to be recognized via barcode / tag during loading.

[0050] The ultrasonic analyzer 120 samples the ultrasonic signals received by the ultrasonic sensor 110 and transmits the real-time analyzed ultrasonic information about the weld area of ​​plates P1 and P2 to the welding controller 130. This ultrasonic analysis information can also be referred to as weld status information about the weld area, collected during spot welding. The timing of the real-time transmission of the ultrasonic analysis information (i.e., the weld status information) is considered crucial for supporting the adaptive ultrasonic control performed by the welding controller 130.

[0051] In Fig. Figure 3, for example, shows a time sequence for the exchange of information between the ultrasonic analyzer and the welding control according to the exemplary embodiment of the present disclosure.

[0052] Fig. Figure 4 shows B-scan information analyzed by the ultrasound analyzer according to the exemplary embodiment of the present disclosure.

[0053] According to Fig. 3 and Fig. 4. The ultrasonic analyzer 120 is able to acquire the ultrasonic analysis information, including at least one of a steel-steel interface (SSI), a steel-steel interface disappearance (SSID), a weld heat of the weld (α), a liquid penetration depth (LPD) and an end of melting (EOM) in time series based on ultrasonic detection signals and to transmit the ultrasonic analysis information in real time.

[0054] For example, with reference to Fig. 4. The ultrasound analysis information can have the following meanings.

[0055] The SSI refers to the point in time when a boundary line between the upper plate P1 and the lower plate P2 is detected by the ultrasonic waves. In this case, the actual thickness of the upper plate P1 can be determined from the boundary line, which can then be used to calculate the difference between the actual thickness and the thickness based on the plate's serial information. The serial information is information used to specify the plate's welding process and can include, or be matched with, at least one of the unique identification (ID) information, the material, the thickness, and the weld part.

[0056] The SSID refers to the point in time when melting begins at the welded part, as well as the point in time when the disappearance of the SSI from the welded part is detected. The SSID can vary depending on the material or thickness of the plate. Therefore, the SSID can be used as a control factor for determining the final welding time.

[0057] The value of α refers to an angle of inclination that represents the amount of heat generated in the weld as a function of the current. Since the ultrasonic signals slow down with increasing heat, an increase in the value of α means an increase in the amount of heat. Therefore, the value of α can be used as a control factor to prevent spatter by limiting excessive current.

[0058] The LPD is the depth of a weld joint in which molten material is present and can be used to determine an interruption of a welding current and welding time.

[0059] The end of melting (EOM) refers to a point in time at which melting ceases due to a decrease in welding heat caused by the interruption of the welding current, whereby a welding force acting on the plate by electrodes 11 and 12 can be eliminated.

[0060] Meanwhile, the ultrasonic analyzer 120 generates a B-scan ultrasonic image and corresponding analysis information from the start to the end of the welding process. It can then transmit this information and the B-scan image to the welding controller 130, enabling the controller to determine the quality of the spot weld. Furthermore, this data can be used to verify or modify suitability by comparing it with information from the adaptive control system, which is implemented to account for subtle variations in the plates.

[0061] The welding controller 130 performs adaptive welding control using basic welding control values ​​set according to the serial information of the plates. Ultrasonic analysis information is received by the ultrasonic analyzer 120 as additional information for real-time compensation of the welding time and current of the welding gun 10. For example, welding time and current compensation can be achieved within 1 ms.

[0062] Fig. Figure 5 is a schematic diagram showing a detailed design of a welding control system according to an exemplary embodiment of the present disclosure.

[0063] As in Fig. As shown in Figure 5, the welding control 130 according to the exemplary embodiment of the present disclosure includes a communication module 131, an information collection module 132, a timer module 133, a current conversion module 134, a storage module 135 and a control module 136.

[0064] The communication module 131 includes a multi-channel communication device and can communicate with the ultrasound analyzer 120 or the server 200.

[0065] The information collection module 132 analyzes the message type and reception time of the ultrasonic analysis information from the ultrasonic analyzer 120 during welding in order to transmit the analyzed data to the control module 136. In addition, the information collection module 132 can use a sensor to detect the actual current / voltage values ​​applied to the electrodes 11 and 12 of the welding gun 10 during welding and transmit this information to the control module 136.

[0066] The timer module 133 counts the spot welding operating time of the welding gun 10 in milliseconds (ms). Thus, the information collection module 132 can transmit the reception time of the ultrasonic analysis information, divided into milliseconds (ms), from the welding start time to the welding end time to the control module 136.

[0067] The current conversion module 134 generates the current for spot welding and converts the welding current according to a signal applied by the control module 136.

[0068] The memory module 135 stores at least one program and setting data for spot welding control according to the exemplary embodiment of the present disclosure and stores information generated during the welding process. The setting data can include the positions of the welding points and the basic welding control parameters, which are variably set for the materials and the thickness of the plates according to the serial information (ID) of the plate.

[0069] The control module 136 can include at least one processor that controls the overall operation of the welding control 130 for welding control according to the exemplary embodiment of the present disclosure and controls the welding gun 10 on the basis of the execution of the program and the setting data.

[0070] The control module 136 stores information on the kinematic position control for the welding process of the welding robot 20 and controls the movement and operation of the welding gun 10 by means of a position control of the welding robot 20 according to the respective set process.

[0071] The control module 136 records the serial information (ID) of the plate supplied by the conveyor, transmits the serial information (ID) to the ultrasonic analyzer 120 and sets the basic welding control parameters according to the serial information to start welding.

[0072] For example, it shows Fig. 6 An example of the basic welding control parameters and the ultrasonic analysis information received by the ultrasonic analyzer according to an exemplary embodiment of the present disclosure.

[0073] Furthermore, it shows Fig. 7. An example of the compensation of welding time and current based on the information provided by the Fig. The ultrasound analyzer shown in section 6 can be received.

[0074] According to Fig. 6 and Fig. 7. The control module 136 sets the basic welding control parameters, including a base current at welding start time, a base current increase rate, a current increase start time, a current increase end time, a base welding time, a maximum welding time, a time increase start time, and a time increase end time, based on the serial information (ID) of the plate.

[0075] The control module 136 starts welding with the set base current of 7.0 kA when welding is performed according to the base welding control parameters of a scenario shown above.

[0076] The control module 136 begins to increase the current by 10% 30 ms after the welding start time, which corresponds to the set base current increase rate.

[0077] At this point, the control module 136 identifies the SSID detected by the ultrasonic analyzer 120 during welding, as shown in Fig. Figure 7 shows a time increment rate (105%), as shown in the welding time control diagram A. Additionally, the control module 136 can determine the final welding time (210 ms) by multiplying the set base welding time (200 ms) by the time increment rate (105%) (200 ms * 105% = 210 ms).

[0078] As described above, the control module 136 performs an adaptive control algorithm to compensate for the welding time, which increases from the set base welding time by the time increase rate detected at the time the SSID is received, which has the advantage of preventing faulty welds.

[0079] Furthermore, when the α detected by the ultrasonic analyzer 120 is received, the control module 136 limits a current increase, as in Fig. Figure 7, which shows a current control diagram B, determines a current increase as the maximum current and applies this maximum current for the remaining welding time until welding is complete. At this point, the control module 136 can calculate the remaining welding time (70 ms) by subtracting the reception time (140 ms) of the α from the final welding time (210 ms). Furthermore, the control module 136 can limit the current increase and determine the maximum current when the received α reaches a predetermined threshold angle.

[0080] As described above, the control module 136 executes the adaptive control algorithm that prevents splash formation by limiting excessive current increase according to the α detected by ultrasonic analysis, thus preventing contamination of product surfaces even if the base current increase end time set according to the serial information is not reached.

[0081] Furthermore, the control module 136 can interrupt the application of the welding current if the LPD received by the ultrasonic analyzer 120 corresponds to a reference value taking into account the thickness of the plates.

[0082] Furthermore, the control module 136 can cancel the welding force of the electrodes 11 and 12 acting on the plates in order to terminate the welding process if the EOM is received from the ultrasonic analyzer 120 during welding or if a certain period of time has elapsed after the welding current has been applied.

[0083] Furthermore, the control module 136 can verify the acquisition of the LPD and EOM to determine weld quality by receiving the B-scan image from the ultrasonic analyzer 120 during the welding process. If the LPD and EOM are acquired at this time and the criteria for the material and thickness of the plates are met, the weld quality requirement is considered fulfilled.

[0084] The welding control method using the adaptive control algorithm is now described on the basis of the design of the welding control system 100 according to the exemplary embodiment of the present disclosure described above.

[0085] Fig. Figure 8 is a flowchart showing the welding control method according to an exemplary embodiment of the present disclosure.

[0086] The welding control method according to the exemplary embodiment of the present disclosure is illustrated by a sequence in which the ultrasonic analyzer 120 and the welding control system 130 exchange information. Based on this sequence, the welding control system 100 can be described in more detail. To simplify the explanation, reference can also be made to the scenarios in Fig. 6 and Fig. 7 are referred to.

[0087] As in Fig. As shown in Figure 8, the welding controller 130 identifies the serial information of the plates P1 and P2 fed by the conveyor and, in step S1, sets the basic welding control parameters corresponding to this serial information. The welding controller 130 can identify the task information assigned by the server 200 and the ID of the fed vehicle body to determine the serial information of the plates attached to the vehicle body.

[0088] The welding control 130 starts the welding process by moving the welding gun 10 to the welding points on the plates and, in step S2, applying the base current, which has been set according to the basic welding control parameters. Simultaneously, the welding control 130 synchronizes the welding start time by transmitting the serial information to the ultrasonic analyzer 120 in step S3.

[0089] At this point, in step S4, the ultrasonic analyzer 120 operates the ultrasonic sensor 110 using the serial information received from the welding controller 130 as a trigger signal. The ultrasonic analyzer 120 can generate the ultrasonic waves of the band frequency, taking into account the material and thickness of the plates according to the serial information. Subsequently, in step S5, the ultrasonic analyzer 120 can transmit the ultrasonic analysis information in real time. Here, the ultrasonic analysis information, such as SSID, α, LPD, and EOM, may or may not be detected depending on the welding status of the welded part or the sensitivity of the detection conditions.

[0090] When the predetermined current increase start time (30 ms) has elapsed since the welding start time, the welding control 130 begins in step S6 to increase the current by the set basic current increase rate (e.g. 10%).

[0091] When the welding controller 130 receives the SSID detected by the ultrasonic analyzer 120 (“Yes” in step S7), the time increase rate (105%) at the time of SSID reception is identified in step S8, as shown in Fig. 7 shown with the welding time control diagram A.

[0092] In step S9, the welding control unit 130 determines the compensated final welding time (210 ms) by multiplying the set base welding time (200 ms) by the specified time increase rate (105%). This means the welding control time is adjusted so that the current increase can continue according to the base current increase rate (e.g., 10%) for the final welding time (210 ms), which is increased from the base welding time (200 ms).

[0093] The welding controller 130 receives the α detected by the ultrasonic analyzer 120 ("Yes" in step S7), and when the received α reaches the predetermined threshold angle ("Yes" in step S11), the current increase is limited (suspended) in step S12, and the currently increased current is determined as the maximum current. In this case, reaching the predetermined threshold angle α indicates sufficient melting, and an excessive increase in current can lead to spatter formation, which is why the current is limited according to the adaptive control algorithm.

[0094] The welding controller 130 controls the welding current so that the maximum current is maintained without increasing it (“No” in step S13) until the final welding time is reached after the remaining welding time (70 ms) has elapsed, and in step S14, upon reaching the final welding time (“Yes” in step S13), it interrupts the power supply to the welding gun 10. However, an exemplary embodiment of the present disclosure is not limited to this, and the welding controller 130 can immediately interrupt the power supply to the welding gun 10 in step S14 when the LPD, detected by the ultrasonic analyzer 120, is received and determines that the received LPD meets the welding quality requirements.

[0095] The welding control 130 terminates the welding process by canceling the welding force of the electrodes 11 and 12 acting on the plates P1 and P2 after the predetermined time has elapsed following the interruption of the power supply in step S16. However, an exemplary embodiment of the present disclosure is not limited to this, and the welding control 130 can immediately interrupt the power supply to the welding gun 10 in step S16 when the EOM is received, which is detected by the ultrasonic analyzer 120.

[0096] If the SSID is not received in step S7 ("No" in step S7) or the α is not received in step S10 ("No" in step S10), the welding control 130 does not need to perform the adaptive ultrasonic algorithm corresponding to each step, but can perform normal adaptive control in steps S15 and S16 according to the basic welding control parameters and then terminate the welding process.

[0097] Then the welding control can be 130, albeit in Fig. 8 not shown, the B-SCAN image from the ultrasonic analyzer 120 is received according to the welding control, the ultrasonic analysis information of the B-SCAN image is compared with the adaptive ultrasonic control information to build the database in the storage module 35, and the suitability of the welding quality and the welding control is determined.

[0098] In addition, the welding control 130 controls the welding gun 10 and repeats the welding control process until the welding operations are completed for all welding points included in the welding information.

[0099] As described above, the welding control method according to the exemplary embodiment of the present disclosure can have an effect in that it prevents defective welding and contributes to the production of products with good weld quality by compensating the welding time and current using the adaptive control algorithm for the plates after the ultrasonic analysis information of a weld part has been received in real time.

[0100] Furthermore, the welding control method can limit an excessive increase in current by means of ultrasonic monitoring of the α, which represents the heat value of the plates, and thus prevent the formation of spatter.

[0101] An exemplary embodiment of the present disclosure can be implemented not only by the device and / or method described above, but also by a program for implementing a function corresponding to the design of an embodiment of the present disclosure, or by a medium on which programs are recorded, and such an implementation can be easily carried out by persons skilled in the art based on the exemplary embodiment described above.

[0102] Although this disclosure has been described in connection with exemplary embodiments currently considered practical, it should be clear that the disclosure is not limited to the disclosed embodiments, but on the contrary is intended to include various modifications and equivalent arrangements that are included within the spirit and scope of the attached claims. Reference numeral Fig. 2 Melting start / end time information, splash information, quality determination information B Welding series information Welding start / end information Current / voltage real-time information (unit 1 ms) C Real-time current / time control based on welding status information according to ultrasonic analysis

Claims

[1] System (100) for controlling welding parameters of a spot welding machine joining a plurality of plates (P1, P2), the system comprising: an ultrasonic sensor (110) installed in an electrode (11, 12) of a welding gun (10), the application of an ultrasonic wave to a welding part of the plate (P1, P2) and the detection of a reflected ultrasonic signal; an ultrasound analyzer (120) capable of generating ultrasound analysis information by analyzing the ultrasound signal in real time; and a welding control (130) that receives the ultrasonic analysis information from the ultrasonic analyzer (120), performs adaptive welding control with the welding parameters set on the basis of the information about the plate (P1, P2), and compensates in real time for one or more welding parameters according to the received ultrasonic analysis information, the welding control (130) includes: a communication module (131) for communication with a server (200) of a manufacturing execution system, which centrally manages the ultrasonic analyzer (120) and the welding process via a multi-channel communication interface; an information collection module (132) that analyzes the message type and reception time of the ultrasound analysis information received by the ultrasound analyzer (120); a timer module (133) for performing a time-division-based counting in milliseconds (ms) during the welding process; a current conversion module (134) for converting the current for spot welding according to an applied signal; a memory module (135) that stores at least one program and setting data for the welding control (130) and stores information generated according to the welding process, and a control module (136) that receives the information about the present plate (P1, P2), transmits the information about the present plate (P1, P2) to the ultrasonic analyzer (120), sets the welding parameters according to the information about the plate (P1, P2) and then starts the welding process, wherein the control module (136) is able to set the welding parameters, including a base current at the welding start time, a base current increase rate, a current increase start time, a current increase end time, a base welding time at the welding start time, a maximum welding time, a time increase start time and a time increase end time. [2] System according to claim 1, wherein the ultrasonic analyzer (120) generates the ultrasonic wave with a frequency band selected on the basis of the information received from the welding control (130) about the plate (P1, P2) to perform an ultrasonic analysis of the weld part. [3] System according to claim 2, wherein the ultrasonic analyzer (120) detects at least one of the following as the ultrasonic analysis information based on the ultrasonic signal transmitted in real time: steel to steel interface (SSI), steel to steel interface disappearance (SSID), welding heat of a weld part (α), liquid penetration depth (LPD) and end of melting (EOM). [4] System according to claim 3, wherein the ultrasonic analyzer (120) generates an ultrasonic image, performs the ultrasonic analysis from a welding start time to a welding end time to obtain the ultrasonic analysis information and transmits the obtained ultrasonic analysis information to the welding control (130). [5] System according to claim 1, wherein the welding parameters include a welding time and a current. [6] System according to claim 1, wherein the welding control (130) controls a compensation of the welding time and current with factors of the ultrasonic analysis information, which are evaluated sequentially, to ensure welding quality. [7] System according to any one of claims 1 to 6, wherein the information collection module (132) transmits the reception time of the ultrasonic analysis information, divided into milliseconds (ms), from the welding start time to the welding end time to the control module (136). [8] System according to any one of claims 1 to 6, wherein the setting data includes position information of a welding point and basic welding control parameters, which are variably set according to the material and thickness of the plates (P1, P2) according to serial information (ID) of the plates (P1, P2). [9] System according to one of claims 1 to 6, wherein the control module (136) is able to store information for the kinematic position control for the welding process of a robot (20) equipped with the welding gun (10) and to control the movement and operation of the welding gun (10) by means of a position control of the robot (20) according to each set process. [10] System according to any one of claims 1 to 6, wherein the control module (136) determines a total welding time based on the base welding time, the time increase rate at the time of receiving the SSID and the information about the plate (P1, P2). [11] System according to claim 10, wherein the control module (136) limits a current increase corresponding to a welding heat of a weld part (α) of the received ultrasonic analysis information and terminates the welding process when the total welding time is reached. [12] System according to any one of claims 1 to 6, wherein the control module (136) interrupts the power supply when the LPD received from the ultrasonic analyzer (120) reaches a reference value according to the information about the plate (P1, P2). [13] System according to any one of claims 1 to 6, wherein the control module (136) terminates the welding by canceling a welding force of the electrode (11, 12) acting on the plate (P1, P2) when the EOM is received from the ultrasonic analyzer (120). [14] Welding control method for joining a plurality of plates (P1, P2) with a welding control system (100) of a spot welding machine, the method comprising: Step (a) to set basic welding parameters corresponding to the serial information (ID) of an existing plate (P1, P2) and to start a welding process based on the set basic welding parameters; Step (b) to monitor ultrasonic analysis information in real time using an ultrasonic sensor (110) installed inside an electrode (11, 12) of a welding gun (10); Step (c) to start increasing a current according to a set base current increase rate upon reaching a predetermined current increase start time from a welding start time; Step (d) to identify a time increment rate corresponding to a time of receiving a disappearance of the steel-steel interface (SSID) as the ultrasonic analysis information, and to determine a final welding time based on the set base welding time and the time increment rate; and Step (e) to limit the current increase when a welding heat of a weld part (α), received as the ultrasonic analysis information, reaches a predetermined threshold angle, and to maintain a current as the maximum current for a remaining welding time before welding is terminated. [15] Method according to claim 14, wherein step (b) includes a step for transferring the serial information to an ultrasonic analyzer (120) at the start of welding, for the purpose of synchronizing an ultrasonic wave generation time and generating an ultrasonic wave with a frequency band corresponding to information about the plate (P1, P2). [16] Method according to claim 14, wherein step (e) includes a step of calculating the remaining welding time based on the final welding time and a receiving time of welding heat of a weld part (α). [17] Method according to claim 14, wherein step (e) comprises: a step to terminate the power supply to the welding gun (10) based on a determination that a liquid penetration depth (LPD) received as ultrasonic analysis information meets a weld quality requirement; and a step to cancel a welding force of the electrode (11, 12) acting on the plate (P1, P2) when a melting end (EOM) is received as the ultrasonic analysis information to terminate the welding. [18] Method according to claim 14 or claim 17, further comprising, after step (e), a step of receiving an ultrasonic image which has been analyzed by the ultrasonic analyzer (120) according to the welding control (130), for comparing the ultrasonic analysis information with adaptive ultrasonic control information to build a database, and to verify the welding quality.

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