Integrated ultrasonic composite high-frequency pulse MIG welding power source and control method

Abstract

The invention discloses an integrated ultrasonic composite high-frequency pulse MIG welding power source and a control method, the integrated ultrasonic composite high-frequency pulse MIG welding power source comprises a low-frequency pulse power source module, a high-frequency pulse power source module, an ultrasonic power source module and a digital control system, and the output end of the low-frequency pulse power source module and the output end of the high-frequency pulse power source module are connected in parallel and then connected to an arc load; the current source is used for forming hybrid welding current; the ultrasonic power module is connected to an ultrasonic piezoelectric transducer load and used for generating ultrasonic mechanical vibration, and the digital control system adopts a double-DSP cooperative control framework to achieve accurate synchronous control over welding arc energy and ultrasonic mechanical energy. The integrated design is adopted, the system structure is remarkably simplified, the equipment size and cost are reduced, communication delay and interference between split systems are eliminated, through accurate cooperative control over multiple energy forms, weld forming can be effectively improved, grains can be refined, welding defects can be effectively reduced, and the welding quality and reliability are improved.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to an integrated ultrasonic composite high-frequency pulse MIG welding power supply and control method. Background Technology

[0002] Metal Inert-gas Welding (MIG) is a high-efficiency and highly automated welding process, and is one of the main welding processes for aluminum alloys. However, aluminum alloys and other materials are prone to defects such as humps, undercut, weld collapse, porosity, and burn-through during welding. At the same time, problems such as poor molten pool fluidity and coarse grains also limit the improvement of the mechanical properties and forming quality of the welded joint.

[0003] To improve welding quality, various waveform control methods have been introduced in existing technologies. Among them, high-frequency pulsed MIG welding, by superimposing a high-frequency pulse component onto the welding current, can significantly improve arc stability, energy density, and stiffness. The high-frequency pulsed current concentrates the arc force, increases the vertical pressure of the arc, thereby deepening the weld penetration, reducing porosity, refining the weld microstructure, and improving overall mechanical properties. Furthermore, the high-frequency pulse helps stabilize the droplet transfer process, reduces spatter, and optimizes weld formation. However, a single high-frequency pulsed current still has limitations in controlling molten pool fluidity and grain refinement, especially for thick plates or high-reflectivity materials, where welding defects are difficult to completely avoid.

[0004] On the other hand, the application of ultrasonic vibration technology in the welding field is gradually attracting attention. Ultrasonic vibration acts on the welding wire or workpiece through mechanical vibration, which can effectively break dendrites in the molten pool, promote the escape of bubbles, improve the fluidity of the molten pool, thereby reducing porosity and cracks, refining the grain structure, and reducing welding residual stress. The combined effect of ultrasonic vibration and electric arc can also enhance the stability of droplet transfer and improve welding efficiency. However, traditional ultrasonic vibration systems are usually used as independent accessories in conjunction with the welding power source, which has problems such as low system integration, poor control coordination, and large size. It is also difficult to achieve precise synchronous control with the arc parameters, which limits the full realization of its advantages.

[0005] Current research has attempted to combine pulsed current with ultrasonic vibration, but most studies focus on low-frequency pulses or conventional pulse waveforms. Furthermore, the ultrasonic power supply and welding power supply are often separate designs, leading to system complexity, high communication latency, and insufficient precision in coordinated control. In addition, existing technologies lack integrated solutions that combine high-frequency pulse power supplies and ultrasonic vibration power supplies, failing to fully leverage the synergistic advantages of high-frequency pulses in arc control and ultrasonic vibration in molten pool modification. Summary of the Invention

[0006] In order to achieve a stable and efficient ultrasonic composite high-frequency pulse MIG welding process and overcome the shortcomings and deficiencies of existing technologies such as single-function welding power sources, large size when multiple systems are combined, and difficulty in achieving coordinated energy control, the purpose of this invention is to provide an integrated ultrasonic composite high-frequency pulse MIG welding power source and control method.

[0007] This invention integrates low-frequency pulse power supply, high-frequency pulse power supply and ultrasonic power supply into a unified design. Through a unified digital control system, it realizes the coupling and coordinated control of multiple energy forms, simplifies the system structure, reduces equipment costs, and improves the stability of the welding process and the overall performance of the welded joint.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] An integrated ultrasonic composite high-frequency pulse MIG welding power supply includes a low-frequency pulse power supply module, a high-frequency pulse power supply module, an ultrasonic power supply module, and a digital control system.

[0010] The output terminals of the low-frequency pulse power supply module and the high-frequency pulse power supply module are connected in parallel and then connected to the arc load.

[0011] The output of the ultrasonic power module is connected to the ultrasonic piezoelectric transducer.

[0012] The digital control system is connected to the low-frequency pulse power module, the high-frequency pulse power module, and the ultrasonic power module respectively, and is used to coordinate and control the energy output of the low-frequency pulse power module, the high-frequency pulse power module, and the ultrasonic power module.

[0013] Furthermore, the digital control system includes a first DSP control chip and a second DSP control chip that communicate with each other; the first DSP control chip is used to control the generation of welding current waveforms of the low-frequency pulse power supply module and the high-frequency pulse power supply module; the second DSP control chip is used to control the ultrasonic energy generation and frequency tracking of the ultrasonic power supply module.

[0014] Furthermore, the first DSP control chip and the second DSP control chip are connected via an I / O communication interface for transmitting synchronization control signals.

[0015] Furthermore, the low-frequency pulse power supply module includes an input rectifier and filter circuit, a phase-shifted full-bridge inverter circuit, a transformer, and an output rectifier and filter circuit connected in sequence; the phase-shifted full-bridge inverter circuit is composed of IGBT switching transistors.

[0016] Furthermore, the high-frequency pulse power supply module includes an input rectifier and filter circuit, an inverter circuit, a transformer, an output rectifier and filter circuit, and a high-frequency chopper circuit connected in sequence; the high-frequency chopper circuit is connected in series in the DC output circuit of the output rectifier and filter circuit.

[0017] Furthermore, the inverter circuit is specifically a phase-shifted full-bridge inverter circuit composed of IGBTs; the high-frequency chopper circuit is composed of MOSFET switching transistors.

[0018] Furthermore, the ultrasonic power supply module includes an input rectifier and filter circuit, a high-frequency full-bridge inverter circuit composed of MOSFETs, a transformer, and an LC impedance matching network connected in sequence. The LC impedance matching network is connected between the secondary winding of the transformer and the ultrasonic piezoelectric transducer.

[0019] A control method for an integrated ultrasonic composite high-frequency pulse MIG welding power supply includes the following steps:

[0020] Step 1: The first DSP control chip controls the low-frequency pulse power supply module to output a DC or low-frequency pulse form of basic current, and at the same time controls the high-frequency chopper circuit of the high-frequency pulse power supply module to work and output a high-frequency pulse current. The two are superimposed to form a composite welding current.

[0021] Step 2: The second DSP control chip controls the full-bridge inverter circuit of the ultrasonic power module to work and output ultrasonic vibration energy.

[0022] Step 3: The first DSP control chip sends a synchronization signal to the second DSP control chip according to the welding process program. The second DSP control chip controls the ultrasonic power module to turn on the output during the peak phase, base phase, or the entire process of the low-frequency pulse current according to the synchronization signal.

[0023] The first DSP control chip calculates the acquired output current signal and current reference value through the PI controller to generate a PWM control signal, which adjusts the phase shift angle of the phase-shifted full-bridge inverter circuit in the low-frequency pulse power supply module and the high-frequency pulse power supply module, and controls the on / off of the high-frequency chopper circuit, so as to accurately control the amplitude and waveform of the output current and form a composite high-frequency pulse welding current.

[0024] The second DSP control chip uses a phase-locked loop (PLL) frequency tracking algorithm. By acquiring the output voltage and current signals of the ultrasonic power module, it calculates and adjusts the switching frequency of its full-bridge inverter circuit in real time to ensure that the output frequency always tracks the resonant frequency of the ultrasonic piezoelectric transducer, thereby achieving efficient and stable energy output.

[0025] The second DSP control chip receives a synchronization signal from the first DSP control chip and, according to the welding process requirements, selectively turns on or off the output of the ultrasonic power module during the peak phase, base phase, or the entire process of the low-frequency pulse current, so as to apply ultrasonic vibration energy to the weld pool.

[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0027] (1) This invention integrates three power supply modules—low frequency, high frequency, and ultrasonic—into one unit and adopts a unified digital control system. Compared with the scheme of multiple independent power supply combinations, it significantly reduces the size of the equipment and the space occupied, reduces manufacturing costs and system complexity, and improves the reliability of the system.

[0028] (2) This invention adopts a dual-DSP collaborative control architecture, which realizes synchronous collaborative control of welding arc energy and ultrasonic mechanical energy through internal high-speed communication. Among them, PI closed-loop control ensures stable output of welding current, while PLL automatic frequency tracking technology ensures efficient and stable application of ultrasonic energy. This control architecture avoids the delay and interference problems caused by bus communication between traditional split systems, and can accurately control the timing and intensity of ultrasonic intervention according to the instantaneous requirements of welding process, so as to achieve efficient energy coupling.

[0029] (3) This invention stabilizes the arc and improves the arc stiffness by using high-frequency pulsed current, while utilizing the cavitation and acoustic flow effects of ultrasound on the molten pool to effectively promote bubble escape, refine weld grains, and improve metal fluidity. The synergistic effect of the two energies can significantly reduce weld defects such as porosity and cracks, and improve weld density and mechanical properties, making it particularly suitable for high-quality welding of difficult-to-weld materials such as aluminum alloys and magnesium alloys.

[0030] (4) The present invention has many adjustable parameters. According to the needs of different welding processes, the low-frequency pulse module can output a stable DC or pulse welding current. The high-frequency pulse and ultrasound can be flexibly turned on or off at the peak stage, base stage or throughout the entire process of the low-frequency pulse current, which can finely control the welding process. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0032] Figure 2 This is the main circuit schematic diagram of the present invention;

[0033] Figure 3 This is a schematic diagram of the high-frequency pulse welding current waveform of the present invention;

[0034] Figure 4This is a flowchart of the phase-locked loop frequency tracking control method for the ultrasonic power supply module of the present invention. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0036] like Figure 1 As shown in the figure, this embodiment discloses an integrated ultrasonic composite high-frequency pulse MIG welding power supply, including a low-frequency pulse power supply module, a high-frequency pulse power supply module, an ultrasonic power supply module, and a digital control system. The three power supply modules share a single input stage circuit.

[0037] like Figure 2 As shown, the input stage circuit consists of a three-phase rectifier bridge BR1 and filter capacitors C1, C3, and C5. External three-phase AC power is rectified by BR1 and filtered by the capacitors, converting it into relatively smooth high-voltage DC power, which serves as the common DC bus for the three subsequent power modules, providing energy to the entire system.

[0038] The digital control system adopts a dual-DSP collaborative control architecture, mainly consisting of a first DSP control chip and a second DSP control chip. The first DSP control chip is responsible for controlling the low-frequency pulse power supply module and the high-frequency pulse power supply module, and processes peripheral control signals such as the welding torch switch, wire feed drive circuit, fan, and air valve. The second DSP control chip is dedicated to power control and frequency tracking of the ultrasonic power supply module. The two DSP control chips communicate with each other via I / O to achieve synchronous coordination between the welding process and the application of ultrasonic vibration.

[0039] The low-frequency pulse power supply module's main circuit topology is a phase-shifted full-bridge inverter circuit, which consists of IGBT switches Q5, Q6, Q7, and Q8. Q5 and Q6 form the leading arm, and Q7 and Q8 form the lagging arm, with both arms connected in parallel to the DC bus. The midpoints of the arms are sequentially connected to resonant inductor L3, the primary winding of transformer T3, and filter capacitor C6. The secondary winding of transformer T3 undergoes full-wave rectification via diodes D3 and D4, and the waveform is smoothed by filter inductor L5 before being output to the arc load. The function of the low-frequency pulse power supply module is to provide the base current during the welding process. By adjusting the phase shift angle, a stable DC current or a preset low-frequency pulse current can be output.

[0040] The high-frequency pulse power supply module adopts a two-stage conversion structure. The first stage is a constant current source circuit, which is also a phase-shifted full-bridge inverter circuit. It consists of IGBT switching transistors Q1, Q2, Q3, and Q4, transformer T2, rectifier diodes D1 and D2, and filter inductor L2. Its function is to output a DC power supply with stable and controllable amplitude.

[0041] In the output circuit of this DC power supply, a high-frequency chopper circuit is connected in series as the second stage. This chopper circuit consists of two MOSFET switches, V5 and V6. The first DSP control chip, through a high-speed drive circuit, controls the alternating switching of V5 and V6 at an extremely high frequency and an adjustable duty cycle, thereby chopping the stable DC current output from the previous stage into a high-frequency pulse current. This high-frequency pulse current is ultimately superimposed in parallel with the output current of the low-frequency pulse power supply module and jointly delivered to the welding arc.

[0042] The ultrasonic power supply module's main circuit consists of a high-frequency full-bridge inverter circuit composed of MOSFET switching transistors V1, V2, V3, and V4. A filter capacitor C2 and a transformer T1 are connected at the midpoint of the bridge arm. An inductor L is connected between the secondary winding of transformer T1 and the ultrasonic piezoelectric transducer (PZT). p and capacitor C p An LC impedance matching network is constructed. This matching network is used on the one hand to match the inverter output impedance with the purely resistive load presented by the ultrasonic piezoelectric transducer at resonance, so as to maximize power transmission efficiency; on the other hand, it filters the square wave voltage output of the high-frequency full-bridge inverter circuit to make it closer to a sine wave, so as to adapt to the operating characteristics of the transducer and make it operate near the resonant frequency.

[0043] The series inductance L of the LC impedance matching network p With parallel capacitor C p The selection steps are as follows:

[0044] First, set the operating frequency f and obtain the generator output impedance R. s And such as Figure 2 The transducer equivalent circuit model parameters are shown, where R m L m C m C1 represents the equivalent resistance, inductance, and capacitance of the dynamic branch of the transducer, and C2 represents the static parallel capacitance of the transducer.

[0045] Dynamic branch reactance:

[0046]

[0047] Transducer conductance:

[0048]

[0049] Transducer susceptance:

[0050]

[0051] The conditions for satisfying real solutions are:

[0052]

[0053] And it satisfies the positive capacitance condition:

[0054]

[0055] The matching inductor can then be obtained. :

[0056]

[0057] With matching capacitor

[0058]

[0059] The working principle of the power supply system of this invention is as follows:

[0060] The three-phase AC power is rectified and filtered by the three-phase rectifier bridge BR1 and filter capacitors C1, C3, and C5 to provide DC bus voltage for the three power modules.

[0061] During the welding process, the first DSP control chip, based on the acquired output current feedback signal, compares and calculates with the set current reference value using a PI control algorithm to generate a PWM signal. This PWM signal acts on the IGBT drive circuit, precisely controlling the amplitude of the output current by adjusting the phase shift angle of the phase-shifted full-bridge in the low-frequency pulse power supply module, thus forming a stable DC or low-frequency pulse current. Simultaneously, the first DSP control chip controls the chopper circuit of the high-frequency pulse power supply module, superimposing a high-frequency pulse current onto the low-frequency pulse at specific stages (such as the peak stage).

[0062] like Figure 3 The diagram shown is a schematic representation of the composite welding current waveform output by this invention. Wherein, I b I is the base current. p The peak current and the low-frequency pulse waveform together constitute the basic waveform of the low-frequency pulse, generated by the low-frequency pulse power supply module. At the peak current t... p During this period, an amplitude of I is superimposed. h The frequency is f h The high-frequency pulsed current is generated by a high-frequency pulsed power supply module. This composite current waveform allows for precise control of the arc morphology and droplet transition.

[0063] Meanwhile, the second DSP control chip performs closed-loop control of the ultrasonic power supply module. For example... Figure 4The diagram shows the flowchart of the phase-locked loop (PLL) frequency tracking control method for the ultrasonic power supply module. After system initialization, an initial ultrasonic frequency is set, and the second DSP control chip controls the ultrasonic power supply module to perform soft start and frequency scanning. When the transducer loop current reaches a preset threshold, indicating that it is close to the resonant point, the system enters the PLL tracking stage. In this stage, the ADC synchronously samples the transducer's terminal voltage and loop current, and calculates the phase difference ΔΦ between them. Based on the value of ΔΦ, the following judgments are made: if ΔΦ=0, it indicates that the inverter output frequency is completely consistent with the transducer resonant frequency, and the current frequency remains unchanged; if ΔΦ>0, the inverter switching frequency is increased through the PI controller; if ΔΦ<0, the switching frequency is decreased through the PI controller. Through this closed-loop feedback adjustment, the PWM frequency is continuously updated, ensuring that the ultrasonic power supply always operates at the optimal resonant point, guaranteeing efficient and stable ultrasonic energy output.

[0064] The first DSP control chip sends start / stop synchronization signals to the second DSP control chip via I / O communication according to the welding process settings. After receiving the signal, the second DSP control chip controls the ultrasonic power module to apply ultrasonic vibration during the peak phase, base phase, or throughout the welding process of the low-frequency pulse, thereby achieving precise synergy between arc energy and ultrasonic mechanical energy to improve weld formation, refine grains, and reduce defects.

[0065] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above. 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. An integrated ultrasonic composite high-frequency pulse MIG welding power source, characterized in that, It includes a low-frequency pulse power supply module, a high-frequency pulse power supply module, an ultrasonic power supply module, and a digital control system; The output terminals of the low-frequency pulse power supply module and the high-frequency pulse power supply module are connected in parallel and then connected to the arc load. The output of the ultrasonic power module is connected to the ultrasonic piezoelectric transducer. The digital control system is connected to the low-frequency pulse power module, the high-frequency pulse power module, and the ultrasonic power module respectively, and is used to coordinate and control the energy output of the low-frequency pulse power module, the high-frequency pulse power module, and the ultrasonic power module.

2. The integrated ultrasonic composite high-frequency pulse MIG welding power supply according to claim 1, characterized in that, The digital control system includes a first DSP control chip and a second DSP control chip that communicate with each other; the first DSP control chip is used to control the generation of welding current waveforms of the low-frequency pulse power supply module and the high-frequency pulse power supply module; the second DSP control chip is used to control the ultrasonic energy generation and frequency tracking of the ultrasonic power supply module.

3. The integrated ultrasonic composite high-frequency pulse MIG welding power supply according to claim 2, characterized in that, The first DSP control chip and the second DSP control chip are connected through an I / O communication interface for transmitting synchronization control signals.

4. The integrated ultrasonic composite high-frequency pulse MIG welding power supply according to claim 1, characterized in that, The low-frequency pulse power supply module includes an input rectifier and filter circuit, a phase-shifted full-bridge inverter circuit, a transformer, and an output rectifier and filter circuit connected in sequence; the phase-shifted full-bridge inverter circuit is composed of IGBT switching transistors.

5. The integrated ultrasonic composite high-frequency pulse MIG welding power supply according to claim 1, characterized in that, The high-frequency pulse power supply module includes an input rectifier and filter circuit, an inverter circuit, a transformer, an output rectifier and filter circuit, and a high-frequency chopper circuit connected in sequence; the high-frequency chopper circuit is connected in series in the DC output circuit of the output rectifier and filter circuit.

6. The integrated ultrasonic composite high-frequency pulse MIG welding power supply according to claim 5, characterized in that, The inverter circuit is specifically a phase-shifted full-bridge inverter circuit composed of IGBTs; the high-frequency chopper circuit is composed of MOSFET switching transistors.

7. The integrated ultrasonic composite high-frequency pulse MIG welding power supply according to claim 1, characterized in that, The ultrasonic power supply module includes an input rectifier and filter circuit, a high-frequency full-bridge inverter circuit composed of MOSFETs, a transformer, and an LC impedance matching network connected in sequence. The LC impedance matching network is connected between the secondary winding of the transformer and the ultrasonic piezoelectric transducer.

8. A control method for an integrated ultrasonic composite high-frequency pulse MIG welding power source as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: The first DSP control chip controls the low-frequency pulse power supply module to output a DC or low-frequency pulse form of basic current, and at the same time controls the high-frequency chopper circuit of the high-frequency pulse power supply module to work and output a high-frequency pulse current. The two are superimposed to form a composite welding current. Step 2: The second DSP control chip controls the full-bridge inverter circuit of the ultrasonic power module to work and output ultrasonic vibration energy. Step 3: The first DSP control chip sends a synchronization signal to the second DSP control chip according to the welding process program. The second DSP control chip controls the ultrasonic power module to turn on the output during the peak phase, base phase, or the entire process of the low-frequency pulse current according to the synchronization signal.

9. The control method according to claim 8, characterized in that, In step one, the first DSP control chip, through a PI controller, adjusts the PWM signal of the inverter circuit in the low-frequency pulse power supply module and the high-frequency pulse power supply module according to the difference between the collected output current signal and the current reference value, thereby realizing closed-loop control of the composite welding current.

10. The control method according to claim 8, characterized in that, In step two, the second DSP control chip uses a phase-locked loop frequency tracking algorithm to collect the output voltage and current signals of the ultrasonic power module and calculate their phase difference. It then adjusts the switching frequency of the high-frequency full-bridge inverter circuit of the ultrasonic power module in real time to achieve automatic tracking control of the resonant frequency of the ultrasonic piezoelectric transducer.

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