Monitoring linkage control high-precision resistance spot welding equipment

Abstract

The invention discloses monitoring linkage control high-precision resistance spot welding equipment, and relates to the technical field of resistance spot welding, and the equipment comprises a main control circuit board which takes a TDA4VM chip as a control core and comprises an integrated power supply module, an IGBT driving module, an ADC analog signal processing unit, a communication interface and a digital I / O isolation driving module, all the modules and units are in electric signal connection with the main control circuit board; the TDA4VM chip controls an inverter direct-current welding power source of the spot welder through the IGBT driving module, receives signals of a sensor system through the ADC analog signal processing unit, interacts with the visual monitoring unit and external equipment through a communication interface, and achieves safety control and actuating mechanism driving through digital I / O isolation driving. Multi-signal real-time monitoring, process parameter intelligent optimization and post-welding quality prediction in the welding process are achieved, and the method is particularly suitable for precise welding of tiny parts such as aviation relay reeds.

Description

Technical Field

[0001] This invention belongs to the field of resistance spot welding technology, and in particular relates to a high-precision resistance spot welding device with monitoring and linkage control. Background Technology

[0002] Tiny components such as aviation relay springs (approximately 0.3 mm thick) are often connected using resistance spot welding. Due to the small size of the components and the asymmetrical shape of the electrodes (the upper electrode is conical, and the lower electrode is a backing plate), problems such as spatter, unstable weld nugget size, and difficulties in post-weld inspection are prone to occur during the welding process. Traditional methods often employ destructive post-weld testing (such as tensile and peel tests) or ultrasonic testing, which are inefficient, costly, and cannot achieve real-time monitoring and closed-loop process control during welding.

[0003] Currently, although some resistance spot welding monitoring systems exist, most are designed for welding of conventional plate thicknesses. When welding small parts, they suffer from problems such as low signal acquisition accuracy, difficulty in sensor installation, and poor anti-interference capabilities. Furthermore, process parameters are mostly set based on experience, lacking system optimization methods based on simulation and data analysis. Summary of the Invention

[0004] To address the problems of severe spatter in energy storage welding and insufficient precision in medium-frequency inverter welding control in existing technologies, this invention provides a resistance spot welding equipment with an integrated real-time monitoring system. This system enables real-time monitoring of multiple signals during the welding process, intelligent optimization of process parameters, and prediction of post-weld quality. It is particularly suitable for precision welding of small parts such as aviation relay springs.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A high-precision resistance spot welding device with monitoring and linkage control includes a spot welding machine, a sensor unit, a data acquisition and processing unit, a vision monitoring unit, a fixture and positioning mechanism, and a main control circuit board.

[0007] The main control circuit board uses the TDA4VM chip as the control core and includes an integrated power module, an IGBT drive module, an ADC analog signal processing unit, a communication interface, and a digital I / O isolation drive module. Each module and unit is electrically connected to the main control circuit board.

[0008] The TDA4VM chip controls the inverter DC welding power supply of the spot welding machine through the IGBT drive module, receives signals from the sensor system through the ADC analog signal processing unit, interacts with the vision monitoring unit and external devices through the communication interface, and realizes safety control and actuator drive through digital I / O isolation drive. The external devices include a display screen integrated controller with control functions.

[0009] Furthermore, the spot welding machine includes a frame support, a pressure device fixed on the frame support, an upper electrode and a lower electrode located on one side of the pressure device, and a high-frequency transformer. The high-frequency transformer is electrically connected to the integrated controller of the display screen. The upper electrode is connected to the negative terminal of the high-frequency transformer, and the lower electrode is connected to the positive terminal of the high-frequency transformer.

[0010] Furthermore, the sensor system includes a Rogowski coil sleeved on the lower electrode cable, a laser displacement sensor installed near the upper electrode, a voltage acquisition circuit that acquires the voltage between the electrodes through an isolation amplification circuit, and a temperature sensor. The signals from each sensor are input to the ADC analog signal processing unit after passing through an isolated power supply.

[0011] Furthermore, the visual monitoring unit uses an AcutEye high-speed camera, which is connected to the TDA4VM chip via a network interface to receive synchronous trigger signals and realize synchronous analysis of electrical and visual signals.

[0012] Furthermore, the fixture and positioning device includes a 3D-printed fixture for fixing the eddy current sensor and a precision positioning stage. The TDA4VM chip controls the position of the positioning stage by outputting a signal from a solenoid valve driven by digital I / O isolation. Combined with the feedback signal from the laser displacement sensor, closed-loop control with an assembly accuracy of ≤0.05mm is achieved.

[0013] In summary, the beneficial technical effects of the present invention are as follows:

[0014] 1. This equipment utilizes Rogowski coils, laser displacement sensors, voltage acquisition circuits, and a high-speed visual monitoring unit to achieve real-time, multi-dimensional monitoring of welding current, electrode displacement, inter-electrode voltage, weld nugget formation, and spatter behavior. The TDA4VM chip, through a synchronous triggering mechanism, ensures strict alignment of the electrical signal and visual image on the time axis. Combined with second-order Butterworth filtering and median filtering algorithms, it effectively eliminates noise interference, achieving a current monitoring accuracy of ±1% and a displacement resolution of 0.1μm. Simultaneously, electrical isolation design and multiple signal verification mechanisms avoid electromagnetic interference in industrial environments, significantly improving the stability and reliability of the monitoring data and providing a solid foundation for accurate analysis of the welding process.

[0015] 2. Based on multi-dimensional synchronously acquired experimental data, a high-precision welding process simulation model is constructed, enabling this equipment to predict weld nugget formation, stress distribution, and spatter behavior. For micro-parts such as aviation relay springs, the optimal process parameters (e.g., 2500A current, 80N pressure, and 2ms time for a 0.3mm spring) can be quickly determined through a combination of simulation iteration and experimental verification. This transforms the extensive trial-and-error experiments in traditional process development into efficient simulation iteration, shortening the process development cycle by more than 60% while reducing material waste and labor costs.

[0016] 3. The equipment adopts a highly integrated main control circuit board and modular design, resulting in a compact overall structure suitable for welding small parts in confined spaces. The combination of 3D-printed fixtures and a precision positioning stage allows for flexible adjustment of the mounting positions of key components such as laser displacement sensors, achieving an assembly accuracy of ≤0.05mm. This ensures precise positioning and welding of thin plates, foils, and dissimilar materials ranging from 0.1 to 0.5mm. Furthermore, the modular sensor design supports rapid replacement and expansion, allowing for flexible configuration of monitoring solutions to meet diverse welding requirements.

[0017] 4. Based on a multi-signal fusion machine learning model, this equipment can analyze current waveforms, electrode displacement curves, and visual image features during the welding process in real time, enabling accurate prediction of key quality indicators such as weld nugget diameter and welding strength. When the predicted value deviates from the preset threshold (e.g., weld nugget diameter < 0.525mm), the system will immediately trigger an alarm and output a fault signal through the digital I / O interface, promptly terminating the unqualified welding process. This function reduces the proportion of post-weld destructive inspections by more than 80%, preventing unqualified products from flowing into the next process and significantly improving production efficiency and product qualification rate. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification, but do not constitute a limitation thereof. In the drawings:

[0019] Figure 1 This is a monitoring and control block diagram of a high-precision resistance spot welding equipment with monitoring and linkage control according to this embodiment;

[0020] Figure 2 This is a structural schematic diagram of a high-precision resistance spot welding device with monitoring and linkage control according to this embodiment.

[0021] In the diagram: 1. Base; 2. Current sensor; 3. Lower electrode; 4. High-speed camera; 5. Upper electrode; 6. Displacement sensor; 7. Pressure sensor; 8. Pressurization device; 9. Support column; 10. High-frequency transformer; 11. Display screen integrated controller. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings.

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Please see Figure 1-2 The present invention provides a technical solution: a high-precision resistance spot welding equipment with monitoring and linkage control includes a spot welding machine, a sensor unit, a data acquisition and processing unit, a vision monitoring unit, a fixture and positioning mechanism, and a main control circuit board;

[0025] The main control circuit board uses the TDA4VM chip as the control core and includes an integrated power module, an IGBT driver module, an ADC analog signal processing unit, a communication interface, and a digital I / O isolation driver module. Each module and unit is electrically connected to the main control circuit board.

[0026] The TDA4VM chip controls the inverter DC welding power supply of the spot welding machine through the IGBT driver module, receives signals from the sensor system through the ADC analog signal processing unit, interacts with the vision monitoring unit and external devices through the communication interface, and realizes safety control and actuator drive through digital I / O isolation drive. External devices include an integrated controller with a display screen and control functions.

[0027] The TDA4VM chip outputs PWM signals to the IGBT driver module (4–8 modules) to drive the power stage of the external IGBT module and control the output current and time of the inverter DC welding power supply.

[0028] The high voltage detection and current detection module collects the voltage and current signals of the IGBT module and feeds them back to the TDA4VM chip to form a current closed-loop control.

[0029] The power supply modules (±3.3V, ±5V, ±12V, ±15V, ±24V) on the main control circuit board supply power to each sub-module, while the isolation power supply provides electrical isolation for the sensor signals.

[0030] A Rogowski coil is connected to the lower electrode cable to acquire welding current signals (measurement range 0–5000A, frequency response 1Hz–1MHz, accuracy ±1%); a laser displacement sensor is installed near the upper electrode to monitor electrode displacement (measurement range 0–2mm, resolution 0.1μm); a voltage acquisition circuit acquires the voltage between electrodes (range 0.1–0.5V) through an isolation amplifier circuit; a temperature sensor acquires the temperature of key parts of the equipment; the above sensor signals are isolated by an isolation power supply and then input to the ADC analog signal processing unit, converted into digital signals, and transmitted to the TDA4VM chip.

[0031] The AcutEye high-speed camera connects to the TDA4VM chip via a network interface; the TDA4VM chip sends a synchronization trigger signal to the vision unit, which is synchronized with the welding current and voltage signals to ensure that the image and electrical signals are aligned in time; the vision unit transmits the image data of the weld nugget formation and spattering process, as well as the synchronous electrical signal data, to the TDA4VM chip for process analysis and quality judgment.

[0032] The 3D-printed fixture fixes the laser displacement sensor to ensure stable monitoring position; the precision positioning stage adjusts its position by outputting a signal from a solenoid valve driven by digital I / O isolation, and the displacement signal from the laser displacement sensor is fed back to the control unit to form a positioning closed-loop control, ensuring assembly accuracy ≤0.05mm; after the spring is clamped, the position signal of the positioning stage serves as one of the welding trigger conditions to ensure accurate welding position.

[0033] The external PLC / HMI connects to the ARM core processing unit via RS232, RS485, or network interface to realize process parameter setting, data monitoring, and remote control; the input signals of the digital I / O isolated drive (emergency stop / normally closed, cooling water detection, welding adjustment switch, temperature detection switch, start button) are used for safety interlocking and mode selection; the output signals (READY signal, fault output, welding electrode request, reserved, weld point / production monitoring output, solenoid valve output) are used for status indication and actuator control.

[0034] Based on the above structure, in this embodiment, for the aviation relay spring with a thickness of 0.3mm, the optimization target is a weld nugget diameter ≥ 0.525mm, and the optimized process parameters are: current 2500A, electrode pressure 8N, and welding time 2ms.

[0035] This equipment is suitable for resistance spot welding of thin plates or foils with a thickness of 0.1–0.5 mm, as well as precision welding scenarios involving dissimilar materials and asymmetric electrode structures.

[0036] The core monitoring and control principle of this invention is as follows: Figure 2 As shown, by integrating high-precision sensors and signal processing circuits, synchronous and accurate measurement of key physical quantities in the welding process is achieved, as detailed below:

[0037] (1) Electrode pressure measurement

[0038] A gasket-type flat diaphragm strain gauge pressure sensor with a range of 0–20N is clamped between the spot-welded electrode holder and the positioning stage. The sensor has a sensitivity of 2mV / V and an operating voltage of 5V. The existing +15V on the control board is regulated to 5V by an LT3042LDO and used as the bridge excitation. The differential output of the bridge is amplified by an AD8421 instrumentation amplifier (RG=470Ω, gain 100), and then a 0.5V offset is superimposed on the REF pin by a 10-bit TLV5616 DAC, so that 0N corresponds to 0.5V and 20N corresponds to 2.5V. The amplified signal P_FB is sent to the ADC-A0 channel of the DSP, and the pressure value is calculated according to...

[0039] P(N)=(ADC_CODE / 4095)×2.0V×(20N / 2.0V)

[0040] The calculations were performed, and a two-point calibration was used to achieve a repeatability accuracy better than ±0.1N.

[0041] (2) Electrode displacement measurement

[0042] A KD-2300-2S laser displacement sensor is fixed to the side of the upper electrode handle. The target aluminum sheet is attached to the surface of the electrode insulating handle with a static gap of 0.5mm. The sensor is powered by +15V and has an output sensitivity of 0.5V / mm. The 0–0.15V signal corresponding to the 0–0.3mm displacement is differentially amplified 10 times by an AD8429 and superimposed with a 0.5V offset, so that 0mm→0.5V and 0.3mm→2.0V. The amplified signal DI1_DT is then divided and input to the ADC-A1 channel of the DSP. The displacement value is calculated according to...

[0043] d(mm)=[(ADC_CODE / 4095)×3.0V–0.5V] / (0.5V / mm×10)

[0044] Calculations were performed with a resolution of 0.1µm and noise ≤1µm.

[0045] (3) Welding current measurement

[0046] A Rocoil 1012 Rogowski coil with a sensitivity of 50mV / kA is connected to the lower electrode cable; the coil output ±250mV is amplified 6 times by an AD8476 fully differential amplifier and boosted by a 1.5V level to form a 0–3V single-ended signal I_S, which is then input to the ADC-A2 channel of the DSP. The current value is set according to...

[0047] I(kA)=(ADC_CODE / 4095×3.0V–1.5V) / (0.3V / kA)

[0048] Calculations, with an accuracy of ±1%.

[0049] (4) Multi-interface resistance measurement

[0050] During the interval when the main welding current stops, a 100mA injection source is formed by expanding the PMOS through the built-in 0–20mA constant current unit of the control board, and a 10Ω sampling resistor with 0.1% accuracy is connected in series to form a closed loop;

[0051] a) Upper interface resistance R1: A 0.05mm platinum wire is led out between the upper electrode and the upper workpiece, differentially connected to the isolation amplifier VO_FB5, and the output V1 is sampled by ADC-B0 and calculated according to R1=V1 / 0.1A;

[0052] b) Workpiece body resistance R2: 0.1mm nickel wire is laser welded to the sides of the upper and lower workpieces, differentially connected to UAL1, and the output V2 is sampled by ADC-B1 and calculated according to R2=V2 / 0.1A;

[0053] c) Lower interface resistance R3: A platinum wire is led out between the lower workpiece and the lower electrode pad, differentially connected to UAL2, and the output V3 is sampled by ADC-B2 and calculated according to R3=V3 / 0.1A;

[0054] d) Total dynamic resistance Rtot: The voltage Vele across the electrodes is synchronously acquired (after gain 6 by the isolation amplifier) ​​and the Rogowski current Iw. The result is calculated according to Rtot = Vele / Iw. The result is compared with the redundancy of R1 + R2 + R3, and the error is ≤5%.

[0055] The timing of the 100mA injection, sampling, and IGBT switching is completed by the DSP+CPLD within ≤1ms, without affecting the normal welding cycle.

[0056] By simultaneously acquiring electrode pressure, displacement, current, and the resistance of three interfaces and the total dynamic resistance, real-time monitoring and quality prediction of the resistance spot welding process can be achieved.

[0057] Example 1

[0058] In this embodiment, the integrated monitoring and control resistance spot welding equipment described in this invention is used to conduct spot welding connection tests on aviation relay springs with thicknesses of 0.15 mm and 0.3 mm, respectively. During the welding process, the monitoring system is fully activated to achieve simultaneous acquisition and real-time analysis of multiple signals during the welding process.

[0059] The process parameters are set as follows:

[0060] Welding current: 2500A;

[0061] Electrode pressure: 80N;

[0062] Welding time: 2ms.

[0063] The monitoring system workflow is as follows:

[0064] 1. Welding current monitoring

[0065] The Rogowski coil acquires the welding current signal in real time, which is then amplified and level-upped by the AD8476 fully differential amplifier before being input to the DSP for analog-to-digital conversion and calculation. The current waveform is then displayed in real time with an accuracy of ±1%.

[0066] 2. Electrode displacement monitoring

[0067] The laser displacement sensor detects the minute displacement of the electrode during the welding process in real time. The signal is differentially amplified by AD8429 and then sent to the DSP. The displacement resolution reaches 0.1µm and the noise is less than 1µm, which can accurately reflect the formation of the weld nugget and the material deformation process.

[0068] 3. Inter-electrode voltage monitoring

[0069] The voltage between electrodes is collected in real time by an isolation amplifier circuit, and the dynamic resistance change is calculated by combining the current signal to determine the stability of the welding process and the quality of the weld nugget.

[0070] 4. Multi-interface resistance measurement

[0071] During welding intervals, the system automatically injects a constant current of 100mA to measure the resistance of the upper interface, the resistance of the workpiece, and the resistance of the lower interface, and performs redundant comparisons with the dynamic resistance. The error does not exceed 5%, thus achieving multi-dimensional interface status monitoring.

[0072] 5. Visual monitoring

[0073] The AcutEye high-speed camera captures the welding process at 5000fps, simultaneously recording current, voltage, and displacement signals, enabling time alignment and joint analysis of multimodal signals in "power vision".

[0074] Welding results:

[0075] The monitoring system operated stably throughout the entire process, with clear and interference-free signals. Post-weld inspection revealed a weld nugget diameter of approximately 0.53 mm, no spatter, and consistent weld quality. The system successfully recorded the current, displacement, voltage, and resistance changes throughout the welding process, providing comprehensive data support for process optimization and quality traceability.

[0076] Example 2

[0077] This embodiment further verifies the applicability of the monitoring system in welding dissimilar materials with different thicknesses. The welding objects are dissimilar metal foils of 0.15mm and 0.5mm.

[0078] The optimized process parameters are as follows:

[0079] Welding current: 3000A;

[0080] Electrode pressure: 100N;

[0081] Welding time: 3ms.

[0082] The monitoring system performs as follows:

[0083] 1. Precise displacement monitoring: The eddy current sensor successfully captures the asymmetric deformation caused by material differences during the welding process, and the displacement curve reflects the fusion difference between the two sides of the material;

[0084] 2. Voltage Anomaly Warning: If the system detects an abnormal voltage drop during the welding process, it will trigger an "Incomplete Fusion Risk" alarm in real time, thus preventing the generation of defective weld joints;

[0085] 3. Multi-signal synchronous analysis: The weld nugget formation process captured by the high-speed camera is highly synchronized with the current and displacement curves, clearly showing the weld nugget expansion behavior in dissimilar material welding;

[0086] 4. Strong anti-interference capability: Even in environments with strong electromagnetic interference, the data acquisition system maintains signal stability, and the filtering algorithm effectively suppresses noise.

[0087] Welding quality:

[0088] The weld nugget is uniform, the interface bonding is good, and there is no spatter, meeting the quality standards for welding dissimilar materials. The monitoring system provides a reliable data foundation for process debugging and quality control.

[0089] Comparative Example 1

[0090] Welding tests were conducted on the same batch of 0.15mm+0.3mm spring sheets using a traditional resistance spot welding machine (without an integrated monitoring system) and empirical process parameters (current 2800A, pressure 6N, time 4ms). During the welding process, it was impossible to obtain key signals such as current, displacement, and voltage in real time; post-weld quality could only be inspected through destructive sampling tests.

[0091] The results are as follows:

[0092] 1. Approximately 35% of solder joints have issues with insufficient weld nugget size or spatter.

[0093] 2. The welding process cannot be monitored in real time, and quality problems cannot be detected and intervened in a timely manner;

[0094] 3. Process adjustments rely on experience, resulting in high trial-and-error costs and low efficiency.

[0095] This invention integrates high-precision sensors, high-speed vision units, and an intelligent data processing system to achieve simultaneous acquisition and real-time analysis of multiple signals, including current, displacement, voltage, resistance, and visual images, during resistance spot welding. This system is not only suitable for welding minute parts such as aviation relay springs, but also enables stable monitoring and quality early warning in complex scenarios involving dissimilar materials and asymmetrical structures, fundamentally improving the controllability, traceability, and quality consistency of the welding process.

[0096] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0097] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-precision resistance spot welding device with monitoring and linkage control, characterized in that, It includes a spot welding machine, sensor unit, data acquisition and processing unit, vision monitoring unit, fixture and positioning mechanism, and main control circuit board; The main control circuit board uses the TDA4VM chip as the control core and includes an integrated power module, an IGBT drive module, an ADC analog signal processing unit, a communication interface, and a digital I / O isolation drive module. Each module and unit is electrically connected to the main control circuit board. The TDA4VM chip controls the inverter DC welding power supply of the spot welding machine through the IGBT drive module, receives signals from the sensor system through the ADC analog signal processing unit, interacts with the vision monitoring unit and external devices through the communication interface, and realizes safety control and actuator drive through digital I / O isolation drive. The external devices include a display screen integrated controller with control functions.

2. The high-precision resistance spot welding equipment with monitoring and linkage control according to claim 1, characterized in that, The spot welding machine includes a frame support column, a pressure device fixed on the frame support column, an upper electrode and a lower electrode located on one side of the pressure device, and a high-frequency transformer. The high-frequency transformer is electrically connected to the integrated controller of the display screen. The upper electrode is connected to the negative terminal of the high-frequency transformer, and the lower electrode is connected to the positive terminal of the high-frequency transformer.

3. The high-precision resistance spot welding equipment with monitoring and linkage control according to claim 2, characterized in that, The sensor system includes a Rogowski coil sleeved on the lower electrode cable, an eddy current displacement sensor and a laser displacement sensor installed near the upper electrode, a voltage acquisition circuit that acquires the voltage between the electrodes through an isolation amplification circuit, and a temperature sensor. The signals from each sensor are input to an ADC analog signal processing unit after passing through an isolated power supply.

4. The high-precision resistance spot welding equipment with monitoring and linkage control according to claim 1, characterized in that, The visual monitoring unit uses an AcutEye high-speed camera, which is connected to the TDA4VM chip via a network interface to receive synchronous trigger signals and realize synchronous analysis of electrical and visual signals.

5. The high-precision resistance spot welding equipment with monitoring and linkage control according to claim 1, characterized in that, The fixture and positioning device includes a 3D printed fixture for fixing the eddy current sensor and a precision positioning stage. The TDA4VM chip controls the position of the positioning stage by outputting a signal from a solenoid valve driven by digital I / O isolation. Combined with the feedback signals from the eddy current displacement sensor and the laser displacement sensor, closed-loop control with an assembly accuracy of ≤0.05mm is achieved.

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