[0075] The present invention will be further described below in conjunction with specific embodiments.
[0076] The dual-wire arc welding power supply system based on sine wave modulated pulses in this embodiment includes:
[0077] Mathematical model for sine wave modulated pulse, used to change the welding pulse current I i The peak value and the base value change according to the sine wave law to form the peak and base current sequence value;
[0078] The control detection circuit with DSP as the control core is used to realize the closed-loop control of the double-wire arc welding power supply system to ensure that the output current and voltage of the system have stable closed-loop controllability. DSP is used for flexible programming to realize the digitalization of the control process of the system. At the same time, on the basis of the above mathematical model, the sine wave modulated pulse technology is realized to make the welding pulse current I i The peak and base value changes are controlled by sine waves;
[0079] The intelligent expert welding panel with LM3S818 as the control core is used to realize the human-computer interaction function of the dual-wire arc welding power system, which can adjust the sine wave modulated pulse welding parameters in the mathematical model, and adopts CPLD (complex programmable logic device) , Complex Programmable Logic Device) or FPGA (Field Programmable Gate Array), cooperate with ARM-Cortex M3 to realize the selection, unification and optimization of welding parameters to build a sine wave control pulse current welding expert database. In this embodiment, CPLD (Complex Programmable Logic Device) is used.
[0080] The control detection circuit is mainly composed of a DSP controller with a model of TMS320F2808 and a peripheral circuit. The peripheral circuit includes a current and voltage feedback circuit, a wire feeder circuit, an inverter input current and voltage detection module, a PWM drive module, and a voltage supply Overvoltage and undervoltage protection module. Such as figure 1 As shown, when performing sine wave modulated pulse MIG welding, the power supply system adopts a constant current strategy, and through two-stage current feedback, a stable double closed-loop control is formed.
[0081] Such as figure 2 with image 3 As shown, the function of the CPLD is to receive the command sent by the MCU through the SSI bus, drive two 3-digit common anode digital tubes and 26 LEDs to display welding parameters and status, and to deburr the encoder input signal , And then send the processed signal to the QEI interface of the MCU. To this end, the CPLD logic is divided into five modules: SPI interface module, instruction decoding module, nixie tube control module, LED blinking control module, and encoder signal processing module. The specific implementation of each module adopts VerilogHDL hardware description language Design.
[0082] In this embodiment, as time changes, each welding pulse current I i The peak value and the base value change are controlled by a sine wave, and the duration of each pulse current peak and base value t i The magnitude change of is also controlled by a sine wave, so in the mathematical model, the relationship between the pulse peak current and its time is:
[0083] I pi =I p0 +A I Sin(2πt i /T) (i=1,2,…,N) (1)
[0084] t pi =t p0 +A tp Sin(2πt i /T) (i=1,2,…,N) (2)
[0085] Among them, the pulse peak current is I pi , The initial value is I p0 , The pulse peak width is t pi , The initial value is t p0;
[0086] The relationship between the pulse base current and its time is:
[0087] I bi =I b0 +A I Sin(2πt i /T) (i=1,2,…,N) (3)
[0088] t bi =t b0 -A tb Sin(2πt i /T) (i=1,2,…,N) (4)
[0089] Among them, the pulse base current is I bi , The initial value is I b0 , The width of the pulse base value is t bi , The initial value is t b0;
[0090] N is the number of pulse currents in a sine wave cycle, A I Is the amplitude of sine wave pulse peak current and pulse base current, A tp Is the amplitude of the peak value of the sine wave pulse current, A tb It is the wide amplitude of the sine wave pulse current base value. The establishment of the mathematical model includes the following steps:
[0091] 1) Set the number of pulse current peaks in each sine wave period T to N, and the number of pulse current peaks in the positive and negative half cycles of each sine wave are n'and n, n, n', respectively And N is a natural number greater than 0, n'≥n, the ratio of the number of pulse current values in the positive half cycle of the sine wave to the negative half cycle is denoted as m, then n'=mn, N=mn+n=n (m+1), and it is called symmetrical sine wave modulated pulse MIG welding when m=1, when m> 1 hour is asymmetrical sine wave modulated pulse MIG welding;
[0092] 2) Suppose the amplitude of the sine wave pulse current peak value and the base value duration are both A t And set: A t /t p0 Is the time amplitude coefficient, denoted as k At , 0≤k At <1; t b0 /t p0 Is the energy coefficient, denoted as k t , K t 0, then
[0093] t b0 =k t ×t p0 (5)
[0094] Since the product of the current value of each pulse and its duration represents the energy intensity of the pulse, the amplitude coefficient k of the modulated sine wave At And k AI The modulation target and effect are the same, so for the unified control of the parameters in the welding process, set the time amplitude coefficient and the current amplitude coefficient to be the same, referred to as the amplitude coefficient, denoted as k A , That is
[0095] k At =k AI =k A (6);
[0096] 3) Pulse peak current I pi The value of is mainly determined by its initial value I p0 Determined, the peak size change is determined by the sinusoidal function Sin(2πt i /T) modulation, its variation amplitude is affected by amplitude A I Limit; pulse base current I bi The size is mainly determined by its initial value I b0 Determine, the change of the base value is also determined by the sinusoidal function Sin(2πt i /T) modulation, its variation amplitude is also affected by amplitude A I Limit, because –1≤Sin(2πt i /T)≤1, then there is
[0097] I p0 -A I ≤I pi ≤I p0 +A I (i=1,2,…,N) (7)
[0098] I b0 -A I ≤I bi ≤I b0 +A I (i=1,2,…,N) (8);
[0099] 4) Select the initial value I b0 , Must make I b0 -A I Meet the minimum dimensional arc current value, pulse current base value I bi Selection and pulse current peak value I pi Same sinusoidal modulation amplitude A I , Which doubles the adjustable range of the energy change between the peak value of the pulse current and the base value, so as to adjust to a greater extent, which is beneficial to the application of welding materials and welding conditions with large differences. The formulas (2) and (4) are cited
[0100] t pi +t bi =t p0 +t b0 +(A tp -A tb )Sin(2πt i /T) (9)
[0101] then T = X i = 1 N ( t pi + t bi ) , Available
[0102] T = N ( t p 0 + t b 0 ) + ( A tp - A tb ) X i = 1 N Sin ( 2 π t i / T ) - - - ( 10 ) ;
[0103] 5) Since –1≤Sin(2πt i /T)≤1, then there is
[0104] t p0 -A tp ≤t pi ≤t p0 +A tp (i=1,2,…,N)
[0105] t b0 -A tb ≤t bi ≤t b0 +A tb (i=1,2,…,N)
[0106] If the amplitude A of the peak time of the sine wave pulse current is selected tp And the amplitude A of the sine wave pulse current base value time tb Same, both are A t , which is
[0107] A tp =A tb =A t
[0108] Then T=N(t p0 +t b0 )
[0109] t pi =t p0 +A t Sin(2πt i /T),(i=1,2,…,N) (11)
[0110] t bi =t b0 -A t Sin(2πt i /T),(i=1,2,…,N) (12)
[0111] t p0 -A t ≤t pi ≤t p0 +A t (i=1,2,…,N) (13)
[0112] t b0 -A t ≤t bi ≤t b0 +A t (i=1,2,…,N) (14)
[0113] When the amplitude A of the peak time of the sine wave pulse current is selected tp When it is zero, that is, A tp =0, there are
[0114] T = N ( t p 0 + t b 0 ) - A tb X i = 1 N Sin ( 2 π t i / T ) - - - ( 15 )
[0115] t pi =t p0 =t 0 (i=1,2,…,N) (16)
[0116] That is, the peak time of the sine wave pulse current is a constant value, which is always equal to the initial value t p0 , Set to a constant initial value t 0;
[0117] 6) When A tp =A tb =A t =0, t p0 =t 0 ≠t b0 When, the pulse peak current and its time are:
[0118] I pi =I p0 +A I Sin(2πt i /T) (i=1,2,…,N)
[0119] t pi =t p0 =t 0 (i=1,2,…,N)
[0120] The pulse base current and time are:
[0121] I bi =I b0 +A I Sin(2πt i /T) (i=1,2,…,N)
[0122] t bi =t b0 (i=1,2,…,N)
[0123] If t b0 =t b0+ (0≤Sin(2πt i /T)时), t b0 =t b0﹣ (Sin(2πt i /T)<0), t b0+ b0﹣ , Then this special case is equivalent to the double pulse welding currently being applied to lightweight materials such as aluminum alloys, and due to the use of sine wave modulation, there is a smooth transition between pulses. Compared with pure double pulse welding, The stability is significantly improved.
[0124] 7) When A I =0, A tp =A tb =A t =0, t p0 =t b0 =t 0 When, the pulse peak current and time are:
[0125] I pi =I p0 (i=1,2,…,N)
[0126] t pi =t p0 =t 0 (i=1,2,…,N)
[0127] The pulse base current and its time are:
[0128] I bi =I b0 (i=1,2,…,N)
[0129] t bi =t b0 =t 0 (i=1,2,…,N)
[0130] The special case of this situation is equivalent to the current single-pulse welding applications that need to reduce energy input.
[0131] One pulse and one drop is considered the best state of pulse welding. In the actual production process, it was found that the welding state of the droplet transition can also produce high-quality welds. Therefore, when selecting the initial value of the pulse peak current, it is only necessary to ensure that it meets the minimum current value of each pulse and drop according to the pulse-by-drop critical current curve chart of different welding wires, which is the smallest of all current pulses with sinusoidal waveform changes. When the pulse current value meets the minimum critical value of one pulse one drop, an ideal welding process can be realized in which one pulse one drop and one pulse multi-drop jet state are intertwined. Through the modulation of the sine wave, the process of interweaving and changing the jet state of one pulse with one drop and one pulse with multiple drops presents a smooth and stable characteristic. Such as Figure 4 As shown, the current waveform of aluminum alloy sine wave modulated pulse MIG welding is shown.
[0132] Now use the established mathematical model to test the actual double-wire welding process. In the test, the waveform is collected and analyzed by the welding arc dynamic wavelet analyzer. The test piece is an aluminum plate with a thickness of 3.0mm; the welding wire grade is ER1070 pure aluminum. The diameter is Φ1.2mm; the shielding gas is high-purity argon; the gas flow rate is 20L/min, and the dry wire elongation is 15mm; flat surfacing welding; the pulse peak time is 2ms.
[0133] In a sine wave cycle T, set the number of pulse current peaks to N, and keep the positive and negative half cycles equal to T/2, and the number of pulse current peaks in the positive half cycle of the sine wave is its negative half cycle When the peak number of pulse current is 1 times, and when N is 45, the experimental results are as follows Figure 5 to Figure 8 Shown.
[0134] Observed in the experiment Figure 7 By Figure 5 Original welding current combined Image 6 The U-I graph drawn in real time by the original welding voltage has clear and neat edge lines, and the U-I graph has high repeatability. It can be considered that the peak energy is stable and the welding quality is good.
[0135] Figure 8 It is a real-time waveform diagram of welding energy obtained after filtering by a dynamic wavelet analyzer. With the real-time change of the sine waveform current, it also has an approximate sine wave shape. Through the modulation of the sine wave parameters, it is very convenient to adjust the welding energy input.
[0136] It can be seen that sine wave modulated pulse welding has the characteristics of stable welding process and effective and accurate control of welding energy. This also fully shows that the dual-wire arc welding power supply system is particularly suitable for the welding needs of light alloys such as aluminum and magnesium. It has a good market prospect and is worthy of promotion.
[0137] The embodiments described above are only preferred embodiments of the present invention, and are not intended to limit the scope of implementation of the present invention. Therefore, all changes made in accordance with the shape and principle of the present invention should be covered by the protection scope of the present invention.
