An industrial robot servo spot welding control method based on an integrated control system

Abstract

The application belongs to the field of industrial automation, and relates to a servo spot welding control method of an industrial robot based on an integrated control system.The method comprises the following steps: moving a robot body loaded with servo spot welding tongs to a predetermined welding starting position of a workpiece through a robot controller; controlling electrodes of the welding tongs to move towards the workpiece until it is considered that the electrodes of the welding tongs successfully contact the workpiece; controlling the electrodes of the welding tongs to contact the workpiece and apply a target welding pressure, calculating a measured plate thickness and comparing the measured plate thickness with a preset expected plate thickness, and sending a welding start signal to a spot welding machine when the comparison result meets a preset threshold condition; and after receiving a welding completion signal, controlling an output torque of a servo motor to be zero, and controlling the electrodes of the welding tongs to open to an end position at a preset second speed.The application can accurately control welding pressure, welding position and timing of servo spot welding tongs, can prevent poor welding spots caused by excessive gaps between workpieces or positioning errors, and improves welding quality and efficiency.

Description

Technical Field

[0001] This invention relates to the field of industrial automation, and specifically to a servo spot welding control method for industrial robots based on an integrated control system. Background Technology

[0002] In high-end manufacturing industries such as automobile manufacturing, body welding is one of the four core processes, characterized by its complexity and high technical difficulty. Industrial robot spot welding systems, as key equipment for automating this process, mainly consist of three core components: an industrial robot, a spot welding gun, and a spot welding machine. The spot welding gun is responsible for performing the specific welding actions, and its driving method has evolved from traditional pneumatic drive to high-precision, high-flexibility servo motor drive (i.e., servo welding gun). The servo welding gun can precisely control electrode pressure, achieve multi-stage pressurization, and synchronously open and close the electrodes during robot movement, significantly improving welding efficiency and quality. However, to fully leverage the advantages of the servo welding gun, a highly integrated, responsive, and logically rigorous spot welding control process is essential.

[0003] Currently, spot welding control systems on the market typically employ a "discrete" control architecture. In this architecture, the industrial robot controller, spot welding machine controller, and welding clamp driver (or PLC) operate as independent units. The robot controller is only responsible for planning and executing the robot's motion trajectory; the spot welding machine controller is responsible for outputting electrical parameters such as welding current and time; and the welding clamp's movements (such as opening and closing, applying pressure) are logically controlled by an independent PLC or a simple controller within the welding clamp itself via I / O signals. Communication and coordination between units are primarily achieved through hard-wired digital / analog I / O signals or simple fieldbuses. However, this discrete control scheme has the following drawbacks: low system integration and large response delay. Due to the dispersed control logic, coordination between the robot, welding clamp, and welding machine relies on I / O signal polling or interruption, resulting in inherent communication delays. This makes it impossible to achieve precise synchronization between the welding clamp's movements and the robot's motion on high-speed, high-paced production lines; for example, it is impossible to accurately control the opening and closing of the electrodes during robot movement. Limited control precision: The pressure control and position compensation functions of the welding clamp are usually handled by an independent PLC. Its computing power and real-time performance are far lower than those of a professional robot controller, making it difficult to implement complex dynamic compensation algorithms (such as deflection compensation based on real-time plate thickness measurement and high-precision electrode wear compensation), which affects the consistency and quality stability of welding. Summary of the Invention

[0004] To address the technical problems existing in the prior art, this invention provides an industrial robot servo spot welding control method based on an integrated control system. With the robot controller as the sole central hub, it highly coordinates the control of the industrial robot body and the servo spot welding clamp, enabling precise control of welding pressure, position, and timing, thereby improving welding quality and consistency.

[0005] The first objective of this invention can be achieved by adopting the following technical solution:

[0006] A servo spot welding control method for an industrial robot based on an integrated control system, wherein the integrated control system includes a robot body, a servo spot welding clamp, a spot welding machine, and a robot controller, and the servo spot welding clamp is installed at the end of the robot body, characterized in that the method includes:

[0007] S1. The robot controller sends position mode commands to the driver of the servo spot welding clamp and the robot body, controlling the robot body to move the servo spot welding clamp to the predetermined welding start position of the workpiece, and at the same time controlling the electrode of the servo spot welding clamp to move to the predetermined start position of the workpiece, generating a pre-contact signal.

[0008] S2. The robot controller sends a speed-torque composite mode command to the driver of the servo spot welding gun, controlling the electrode of the welding gun to move towards the workpiece at a preset first speed and apply a pre-pressure to the workpiece. The driver of the servo spot welding gun feeds back the current actual torque to the robot controller. When the actual torque reaches the preset torque threshold, it is considered that the electrode of the welding gun has successfully contacted the workpiece.

[0009] S3. The robot controller sends a torque mode command to the driver of the servo spot welding gun to control the electrode of the welding gun to contact the workpiece and apply the target welding pressure. The actual plate thickness is calculated based on the final position of the servo spot welding gun, the electrode head wear compensation amount, and the welding gun deflection compensation amount. The actual plate thickness is compared with the preset expected plate thickness. If the comparison result meets the preset threshold, a welding start signal is sent to the spot welding machine.

[0010] S4. After receiving the welding completion signal from the spot welding machine, the robot controller sends a control command with zero torque and a position mode command to the servo driver. After controlling the output torque of the servo motor to zero, it controls the welding clamp electrode to open to the end position at a preset second speed.

[0011] Specifically, the robot controller is connected to the driver of the servo spot welding clamp via a high-speed industrial bus. The robot sends mode switching commands, speed commands, and torque commands to the driver of the servo spot welding clamp, and receives position, speed, and torque signals fed back by the driver of the servo spot welding clamp. The robot controller is connected to the spot welding machine via a standard industrial interface. The robot controller sends welding start / stop commands and welding parameters to the spot welding machine. The spot welding machine feeds back the welding status to the robot controller. The spot welding machine is electrically connected to the servo spot welding clamp, and the spot welding machine provides DC welding current to the servo spot welding clamp.

[0012] Specifically, the position mode command package parameters include: target position, motion speed, acceleration / deceleration, position loop gain, velocity loop gain and torque limit, and contact speed threshold. The spot welding clamp servo driver drives the robot body to move towards the workpiece at a preset safe trajectory and safe speed according to the position mode command. After the robot body moves to the position, it stops and holds. The servo welding clamp driver continuously feeds back the actual position and actual speed to the robot controller. The robot controller adjusts the motor output according to the feedback of the actual position and actual speed, so that the electrode of the welding clamp smoothly approaches the workpiece. When the robot controller detects that the feedback of the actual speed has dropped to the preset contact speed threshold, it generates a pre-contact signal.

[0013] Specifically, step S3 includes:

[0014] Set the target welding pressure PC*, control the electrode of the welding gun to contact the workpiece and apply the target welding pressure PC*, the driver of the servo spot welding gun feeds back the actual torque to the robot controller, the robot controller performs real-time pressure closed-loop control based on the actual torque fed back by the driver, so that the electrode of the welding gun contacts the workpiece and the applied pressure reaches and is maintained within the range of ±5% of the target welding pressure PC*, then it is considered that the electrode of the welding gun contacts the workpiece and the applied pressure is in place, and the actual torque and actual position are continuously fed back through the driver of the servo spot welding gun.

[0015] The final position of the servo spot welding gun is obtained, the electrode head wear compensation amount is obtained based on historical measurement data, the pressure-deflection relationship table is queried according to the target welding pressure, the welding gun deflection compensation amount is calculated using linear fitting, and the actual plate thickness is calculated based on the final position of the welding gun, the electrode head wear compensation amount, and the welding gun deflection compensation amount.

[0016] The measured plate thickness is verified. When the absolute value of the difference between the actual plate thickness and the expected plate thickness is within the threshold range, the robot controller sends a welding start signal and welding parameter set to the spot welding machine via the bus.

[0017] After the spot welding machine completes the welding, it sends a welding completion signal to the robot controller.

[0018] Specifically, the formula for calculating the measured plate thickness is expressed as: TN_real = P - W - F;

[0019] Where TN_real represents the measured plate thickness, P represents the final position value of the welding clamp, W represents the electrode head wear compensation amount, and F represents the welding clamp deflection compensation amount.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] This invention provides an industrial robot servo spot welding control method based on an integrated control system. Using a robot controller as the sole central hub, it highly coordinates the control of the industrial robot body and the servo spot welding gun. Through integrated control and real-time compensation methods, the measured plate thickness is calculated based on the final position of the welding gun, electrode wear compensation, and welding gun deflection compensation. Precise control of welding pressure, position, and timing is then performed based on this measured plate thickness, significantly improving welding quality and consistency. The PLC intermediate link is eliminated, allowing for complete synchronization of robot and welding gun movements; for example, electrode opening and closing can be completed during robot movement, significantly shortening the cycle time for a single weld point. High integration and ease of use are achieved, with all control logic and parameter configuration completed on the robot teach pendant. Users do not need to learn multiple programming languages ​​and interface protocols, lowering the barrier to entry and simplifying engineering deployment and subsequent maintenance. Based on a modular software architecture, new process functions can be easily added or adapted to different brands of welding guns and welding machines, meeting diverse production needs. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] Figure 1 This is a flowchart of an industrial robot servo spot welding control method based on an integrated control system, according to an embodiment of the present invention.

[0024] Figure 2 This is a schematic diagram of the structure of the robot body and the servo spot welding clamp in an embodiment of the present invention;

[0025] Figure 3 This is a schematic representation of the pressure-deflection relationship in an embodiment of the present invention;

[0026] The numbers in the diagram are: 1 Industrial robot body, 2 Servo spot welding clamp, 3 Electrode of servo spot welding clamp. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of them. The implementation of the present invention is not limited thereto. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] Example 1:

[0029] This embodiment provides an industrial robot servo spot welding control method based on an integrated control system. The robot controller integrates the robot body movement, servo welding gun actions, and coordination with the spot welding machine. The control method can be divided into four stages: pre-positioning, contact pre-pressure, welding pressure holding, and rapid retraction. In the contact pre-pressure stage, the controller switches the control mode from position mode to speed-torque composite mode, applies pre-pressure, and reads the real-time opening of the welding gun. In the welding pressure holding stage, the controller reads the final position of the welding gun and calculates the measured plate thickness based on electrode head wear compensation and welding gun deflection compensation. Only when the comparison result between the measured plate thickness and the preset expected plate thickness meets a preset threshold condition is a welding start signal sent to the spot welding machine. This invention achieves pre-welding quality inspection, effectively preventing poor welds caused by excessive workpiece gaps or positioning errors, thus improving welding quality and efficiency.

[0030] like Figure 1 As shown, the present invention discloses an industrial robot servo spot welding control method based on an integrated control system. The integrated control system includes a robot body, a servo spot welding clamp, a spot welding machine, and a robot controller. The servo spot welding clamp is installed at the end of the robot body. The method includes the following steps:

[0031] S1, Pre-positioning stage: The robot controller sends position mode commands to the driver of the servo welding clamp and the robot body 1, controlling the robot to move the servo welding clamp 2 to the predetermined welding start position of the workpiece, and synchronously controlling the electrode 3 of the servo welding clamp to move to the predetermined welding start position of the workpiece and generate a pre-contact signal. For example... Figure 2 The diagram shown is a structural schematic of the robot body and the servo spot welding clamp.

[0032] Specifically, the robot controller is connected to the driver of the servo spot welding clamp via a high-speed industrial bus. The robot sends mode switching commands, speed commands, and torque commands to the driver of the servo spot welding clamp, and receives position, speed, and torque signals from the driver. The robot controller is connected to the spot welding machine via a standard industrial interface. The robot controller sends welding start / stop commands and welding parameters to the spot welding machine, and the spot welding machine provides feedback on the welding status to the robot controller. The spot welding machine is electrically connected to the servo spot welding clamp, and provides DC welding current to the servo spot welding clamp. The robot controller controls the welding robot body to rotate on the mounting base. The servo robot welding clamp is equipped with welding clamp electrodes. The robot controller controls the movement of the servo welding clamp, carrying the welding clamp, to the predetermined welding start position on the workpiece. The spot welding clamp also moves simultaneously, opening and closing to move the welding clamp electrodes to the predetermined welding start position. Subsequent steps can be performed by controlling the spot welding clamp to weld the workpiece.

[0033] In this embodiment, the servo spot welding gun uses a servo motor to achieve precise pressure and position control of the welding gun electrode, replacing the traditional pneumatic welding gun. This results in more precise pressure control and smoother movements. The spot welding machine can provide a stable DC welding current, offering advantages such as short welding time, small heat-affected zone, and energy saving. The robot controller communicates directly with the servo spot welding gun's driver via a high-speed industrial bus (GSKLINK), replacing the traditional PLC or independent controller and establishing a direct, real-time communication link with the servo spot welding gun's driver. This high-speed channel replaces traditional discrete I / O signals or slower network communication, achieving hard real-time synchronization and microsecond-level data exchange between robot motion control and welding gun pressure / position control. This allows each pressure application action of the welding gun to seamlessly coordinate with the robot's precise positioning, greatly improving cycle time and accuracy.

[0034] Specifically, the position mode command typically includes the following core parameters and auxiliary control parameters: target position, motion speed, acceleration / deceleration, position loop gain, velocity loop gain, torque limit, contact speed threshold, etc. The robot controller sends the position mode command to the robot body and the spot welding gun servo driver. The spot welding gun servo driver drives the robot body to move towards the workpiece at a preset safe trajectory and safe speed according to the position mode command. After the robot body moves into position, it stops and holds. The servo spot welding gun driver continuously feeds back the actual position and actual speed to the robot controller. The robot controller adjusts the motor output according to the feedback of the actual position and actual speed to ensure that the electrode smoothly approaches the workpiece. When the robot controller detects that the speed has dropped to the preset contact speed threshold, it generates a pre-contact signal, indicating that the servo welding gun has moved to the predetermined welding start position of the workpiece, and the welding gun electrode will attempt to contact the workpiece to enter the next stage.

[0035] Specifically, the target position is the final coordinate point (usually measured in pulses or millimeters) that the electrode of the servo spot welding clamp needs to reach. The movement speed is the speed at which the welding clamp electrode moves (usually set to a safe speed of 10-30 mm / s). Acceleration / deceleration is the rate of change of speed of the welding clamp electrode when it starts and stops, used to ensure smooth movement and prevent impact. Position loop gain: controls the response speed of position following; a higher gain results in a faster response, but excessive gain may cause jitter. Speed ​​loop gain: controls the stability of the speed, ensuring minimal speed fluctuations during movement. Torque limit sets the maximum torque output of the motor to prevent damage to the equipment or workpiece due to overload when the welding clamp electrode contacts the workpiece. Contact speed threshold: when the actual electrode speed drops to the preset contact speed (e.g., 1-5 mm / s), the system determines that the electrode has contacted the workpiece, triggers a contact signal, and automatically switches to the next stage (e.g., pressure control mode). The position mode command is used to allow the servo driver to take over the motion control of the welding clamp electrode, making it move strictly according to the preset path and speed until a pre-contact signal is detected.

[0036] In this embodiment, position commands are output based on instruction information and preset parameter information. Instruction information refers to a set of codes or commands used in the robot control system to control the robot's motion trajectory, set welding process parameters and actions, make logical judgments, and communicate with peripheral devices. Instruction information includes, but is not limited to: motion control commands (joint movement, linear movement, circular motion), welding process commands (spot welding parameter setting / change, spot welding action, grinding action, gun changing action), and logic and flow control commands (IO interaction, conditional judgment, jump, wait, loop), etc. In actual operation, these commands are usually written by engineers using a teach pendant, or generated by offline programming software and then imported into the robot controller. Preset parameter information refers to configuration parameters related to the robot body, spot welding machine, and servo welding gun control, typically including the following types of parameter information: motion direction, welding pressure threshold, pressure timeout time, etc. Among them, the direction of movement is used to set whether the electrode opening or closing represents a positive or negative direction in the controller, so that the controller can generate a control direction; the welding pressure threshold refers to setting the theoretical upper limit of the pressure that the spot welding clamp can withstand, which is used to protect the spot welding clamp from damage; the pressurization timeout time refers to the time to judge whether the pressure has reached the preset value during the pressurization process. If the pressure is not reached within the timeout, an alarm is generated to avoid process abnormality.

[0037] In this embodiment, all process parameters of the integrated control system can be uniformly configured and managed on the human-machine interface of the robot teach pendant, eliminating the need for operators to switch between different controllers (such as PLC touchscreens and welding machine panels). Key parameters include: target pressure (PC), end position (ED), and welding parameters (S). Target pressure (PC) refers to the precise pressure value applied by the electrode to the workpiece during welding. End position (ED) refers to the electrode position when the welding clamp pressure is applied or welding is completed, used to monitor the degree of weld compaction or changes in workpiece thickness. Welding parameters (S), such as welding current, time, and pulse, are used for the control of the spot welding machine. The opening and closing of the welding clamp, pressure application, and measurement can be manually controlled on the teach pendant, facilitating debugging and maintenance. Executing a tipdress command on the teach pendant automatically runs a preset tipdress path to remove oxides and impurities from the electrode surface. Users are allowed to perform online pressure calibration of the welding clamp's pressure sensor.

[0038] S2, in the contact pre-pressure stage, the robot controller sends a speed-torque composite mode command to the driver of the servo spot welding gun, controlling the electrode of the welding gun to move towards the workpiece at a preset first speed and apply a pre-pressure to the workpiece. The driver of the servo spot welding gun feeds back the current actual torque to the robot controller. When the actual torque reaches the preset torque threshold, it is considered that the electrode of the welding gun is in contact with the workpiece, and a contact signal is generated.

[0039] Specifically, after generating the pre-contact signal, the robot controller immediately switches the control mode from position mode to speed-torque composite mode. The robot controller sends speed and torque commands to the servo welding gun's driver, setting the welding gun's electrode to apply a small pre-pressure towards the workpiece at a low, preset speed, such as 5-10 mm / s, to gradually press the workpiece against it, confirming reliable contact and eliminating initial gaps. The servo welding gun's driver feeds back the current actual torque (i.e., current pressure) to the robot controller. The robot controller monitors whether the torque reaches a preset torque threshold. When the feedback indicates that the current actual torque has reached the preset torque threshold (usually preset by the command, with a range related to the specifications of the welding gun's servo drive and motor; a torque threshold within 10 N*M indicates successful contact between the welding gun's electrode and the workpiece). After the driver's feedback indicates that the actual torque has stabilized, a contact signal is generated, and the process proceeds to the next stage.

[0040] S3, during the welding pressure holding stage, the robot controller sends a torque mode command to the driver of the servo spot welding gun to control the electrode of the welding gun to contact the workpiece and apply the target welding pressure. The actual plate thickness is calculated based on the final position of the servo spot welding gun, the electrode head wear compensation amount, and the welding gun deflection compensation amount. The actual plate thickness is compared with the preset expected plate thickness. If the comparison result meets the preset threshold, a welding start signal is sent to the spot welding machine.

[0041] S31. The robot controller sends a torque mode command to the driver of the servo spot welding gun, sets the target welding pressure (PC*), controls the electrode of the welding gun to contact the workpiece and apply the target welding pressure, and the driver feeds back the actual torque to the robot controller. The robot controller performs real-time pressure closed-loop control based on the actual torque fed back by the driver, so that the electrode contacts the workpiece and the applied pressure is accurately reached and maintained within the range of PC*±5%. It is considered that the electrode of the welding gun contacts the workpiece and the applied pressure is in place. The actual torque and actual position are continuously fed back through the driver of the servo spot welding gun.

[0042] S32. Obtain the final position of the servo spot welding gun, obtain the electrode head wear compensation amount based on historical measurement data, query the pre-calibrated pressure-deflection relationship table according to the target welding pressure, calculate the welding gun deflection compensation amount using linear fitting, and calculate the actual plate thickness based on the final position of the welding gun, the electrode head wear compensation amount, and the welding gun deflection compensation amount.

[0043] The robot controller uses this data to verify the plate thickness. Once the pressure is applied, the robot controller immediately reads the final open position of the welding gun. Based on the electrode wear compensation (Wear Compensation) and the welding gun flex compensation (Flex Compensation) superimposed on the actual position, the actual plate thickness (TN_real) is calculated. The welding gun flex compensation (Flex Compensation) refers to the slight elastic deformation (bending) that occurs in the robotic arm and electrode arm when pressure is applied. This compensation is used to correct the positional error caused by this deformation. Typically, the pressure-flex relationship table is consulted using the pre-pressure; the greater the pressure, the greater the deformation, and the larger the compensation value. The electrode wear compensation (Wear Compensation) refers to the fact that the electrode tip gradually wears and shortens during welding. Without compensation, the welding gun will over-close to achieve the target pressure, resulting in a smaller actual clamped workpiece thickness (plate thickness).

[0044] like Figure 3 As shown, the pressure-deflection relationship is illustrated. Based on the target welding pressure, a pre-calibrated pressure-deflection relationship table is consulted, and the welding clamp deflection compensation is calculated using linear fitting. Assuming the target pressure is 120 kgf, which falls within the 100-150 kgf range according to the table, the welding clamp compensation for the target pressure can be calculated as: 120 * (1.68 - 1) ÷ (150 - 100) mm = 1.632 mm.

[0045] Specifically, the measured plate thickness is equal to the final position value of the welding clamp minus the electrode head wear compensation and the welding clamp deflection compensation. The formula for calculating the measured plate thickness is as follows:

[0046] TN_real = P - W - F;

[0047] Where TN_real represents the measured plate thickness, P represents the final position value of the welding clamp, W represents the electrode tip wear compensation, and F represents the welding clamp deflection compensation. For example, if the final position value of the welding clamp is 3.65mm, the electrode tip wear compensation is 0.11mm, and the welding clamp deflection compensation is 0.52mm, then the plate thickness (TN_real) = 5.25mm - 0.12mm - 0.52mm = 3.01mm.

[0048] S33. Verify the measured plate thickness. When the absolute value of the difference between the actual plate thickness and the expected plate thickness is within the threshold range, the robot controller sends a welding start signal and welding parameter set S* to the spot welding machine via the bus.

[0049] Specifically, the measured plate thickness TN_real is compared with the preset expected plate thickness (TN_set). If the absolute value of the difference between the actual plate thickness (TN_real) and the expected plate thickness (TN_set) is within the threshold range, the measured plate thickness verification passes. If the absolute value of the difference between the actual plate thickness (TN_real) and the expected plate thickness (TN_set) is greater than the threshold, i.e., |TN_real - TN_set| > Threshold (the threshold can be preset through system code, typically ±0.1mm), the verification fails, and the controller issues an alarm or shutdown signal to prevent poor welding. The welding parameter set S* refers to the standard parameter package for the welding process (such as resistance welding or laser welding), and the standard parameters include parameters such as current and time.

[0050] S34. After the spot welding machine completes the welding, it sends a welding completion signal (Weld DoneSignal) to the robot controller.

[0051] Specifically, during the welding process of the spot welding machine, the robot controller continuously maintains the torque command output of the target welding pressure PC*. After the welding current ends and the holding time is completed, the spot welding machine sends a "welding completed" signal to the robot controller, which can be a digital signal (such as a 24V high level). The robot controller continues to stop the torque command output of the target welding pressure PC* based on the received welding completed signal.

[0052] S4. In the rapid retraction phase, after receiving the welding completion signal from the spot welding machine, the robot controller sends a control command with zero torque and a position mode command to the servo driver, respectively, to control the output torque of the servo motor to be zero, and to control the welding clamp electrode to open to the end position at a preset second speed.

[0053] Specifically, upon receiving the welding completion signal from the welding machine, the robot controller system issues a zero-torque control command to depressurize. At this point, although the servo motor is still energized, its output torque is zero, and the welding electrode naturally releases under the action of the internal spring or its own weight, eliminating pressure on the workpiece. This step is to prevent the electrode from opening rapidly under pressure, causing impact damage to the workpiece or electrode. Immediately after depressurization, a position mode command is sent to the driver to switch to position mode. After receiving the position mode command, the driver preferably drives the welding electrode to open to the specified end position (ED*) at a relatively fast preset second speed (e.g., 30-50 mm / s). The driver reports the real-time position of the welding electrode to the robot controller, which monitors whether the position has reached the end position ED*. When the driver reports that the position has reached the end position ED*, the entire spot welding cycle is completed, and the robot can begin the next action.

[0054] This embodiment provides an industrial robot servo spot welding control method based on an integrated control system. Using a robot controller as the sole central hub, it highly coordinates the control of the robot body and the servo spot welding gun. Through integrated control and real-time compensation methods, the measured plate thickness is calculated based on the final position of the welding gun, electrode wear compensation, and welding gun deflection compensation. Precise control of welding pressure, position, and timing based on the measured plate thickness significantly improves welding quality and consistency. By eliminating the intermediate PLC step, the movements of the robot body and the servo spot welding gun can be completely synchronized. For example, the electrode opening and closing of the servo spot welding gun can be completed simultaneously during robot movement, significantly shortening the cycle time of a single weld point. High integration and ease of use are achieved because all control logic and parameter configuration are completed on the robot teach pendant. Users do not need to learn multiple programming languages ​​and interface protocols, lowering the barrier to entry, simplifying engineering deployment and subsequent maintenance. New process functions can be easily added or adapted to different brands of welding guns and welding machines, meeting diverse production needs.

[0055] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A servo spot welding control method for an industrial robot based on an integrated control system, wherein the integrated control system includes a robot body, a servo spot welding clamp, a spot welding machine, and a robot controller, the servo spot welding clamp being mounted at the end of the robot body, characterized in that, The method includes: S1. The robot controller sends position mode commands to the driver of the servo spot welding clamp and the robot body, controlling the robot body to move the servo spot welding clamp to the predetermined welding start position of the workpiece, and at the same time controlling the electrode of the servo spot welding clamp to move to the predetermined start position of the workpiece, generating a pre-contact signal. S2. The robot controller sends a speed-torque composite mode command to the driver of the servo spot welding gun, controlling the electrode of the welding gun to move towards the workpiece at a preset first speed and apply a pre-pressure to the workpiece. The driver of the servo spot welding gun feeds back the current actual torque to the robot controller. When the actual torque reaches the preset torque threshold, it is considered that the electrode of the welding gun has successfully contacted the workpiece. S3. The robot controller sends a torque mode command to the driver of the servo spot welding gun to control the electrode of the welding gun to contact the workpiece and apply the target welding pressure. The actual plate thickness is calculated based on the final position of the servo spot welding gun, the electrode head wear compensation amount, and the welding gun deflection compensation amount. The actual plate thickness is compared with the preset expected plate thickness. If the comparison result meets the preset threshold, a welding start signal is sent to the spot welding machine. S4. After receiving the welding completion signal from the spot welding machine, the robot controller sends a control command with zero torque and a position mode command to the servo driver. After controlling the output torque of the servo motor to zero, it controls the welding clamp electrode to open to the end position at a preset second speed.

2. The control method for servo spot welding of an industrial robot according to claim 1, characterized in that, The robot controller is connected to the driver of the servo spot welding clamp via a high-speed industrial bus. The robot sends mode switching commands, speed commands, and torque commands to the driver of the servo spot welding clamp, and receives position, speed, and torque signals fed back by the driver of the servo spot welding clamp. The robot controller is connected to the spot welding machine via a standard industrial interface. The robot controller sends welding start / stop commands and welding parameters to the spot welding machine. The spot welding machine feeds back the welding status to the robot controller. The spot welding machine is electrically connected to the servo spot welding clamp, and the spot welding machine provides DC welding current to the servo spot welding clamp.

3. The control method for servo spot welding of an industrial robot according to claim 2, characterized in that, The position mode command package parameters include: target position, motion speed, acceleration / deceleration, position loop gain, velocity loop gain and torque limit, and contact speed threshold. The spot welding clamp servo driver moves towards the workpiece at a preset safe trajectory and safe speed according to the position mode command. After the robot body moves to the position, it stops and holds. The servo welding clamp driver continuously feeds back the actual position and actual speed to the robot controller. The robot controller adjusts the motor output according to the feedback of the actual position and actual speed, so that the electrode of the welding clamp smoothly approaches the workpiece. When the robot controller detects that the feedback of the actual speed has dropped to the preset contact speed threshold, it generates a pre-contact signal.

4. The control method for servo spot welding of an industrial robot according to claim 3, characterized in that, The preset first speed in step S2 is 5-10 mm / s, and the torque threshold is less than or equal to 10 N*M.

5. The control method for servo spot welding of an industrial robot according to claim 3, characterized in that, Step S3 includes: Set the target welding pressure PC*, control the electrode of the welding gun to contact the workpiece and apply the target welding pressure PC*, the driver of the servo spot welding gun feeds back the actual torque to the robot controller, the robot controller performs real-time pressure closed-loop control based on the actual torque fed back by the driver, so that the electrode of the welding gun contacts the workpiece and the applied pressure reaches and is maintained within the range of ±5% of the target welding pressure PC*, then it is considered that the electrode of the welding gun contacts the workpiece and the applied pressure is in place, and the actual torque and actual position are continuously fed back through the driver of the servo spot welding gun. The final position of the servo spot welding gun is obtained, the electrode head wear compensation amount is obtained based on historical measurement data, the pressure-deflection relationship table is queried according to the target welding pressure, the welding gun deflection compensation amount is calculated using linear fitting, and the actual plate thickness is calculated based on the final position of the welding gun, the electrode head wear compensation amount, and the welding gun deflection compensation amount. The measured plate thickness is verified. When the absolute value of the difference between the actual plate thickness and the expected plate thickness is within the threshold range, the robot controller sends a welding start signal and welding parameter set to the spot welding machine via the bus. After the spot welding machine completes the welding, it sends a welding completion signal to the robot controller.

6. The control method for servo spot welding of an industrial robot according to claim 5, characterized in that, The formula for calculating the measured plate thickness is expressed as: TN_real = P - W - F; Where TN_real represents the measured plate thickness, P represents the final position value of the welding clamp, W represents the electrode head wear compensation amount, and F represents the welding clamp deflection compensation amount.

7. The control method for servo spot welding of an industrial robot according to claim 5, characterized in that, The preset second speed is 30-50 mm / s.

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