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Digital welding machine

Digital signal processing has great advantages over analog signal processing, and it is characterized by high precision, high flexibility, good reliability and easy dog scale integration. therefore. Digital signal processing technology in the communications, voice processing, graphics / image processing, automatic control, consumer electronics and many other areas have been widely used. As a digital signal processing technology and arc welding process of the product, the emergence of digital welding machine has aroused widespread concern in the industry. This paper will discuss the concept, characteristics, realization and future prospects of the word-making machine.


1.Digital welding machine and its characteristics

Because the digital out of the machine appeared relatively late, for example, nD "m in 1998 began to digital port machine production, so cut out so far has not formed the application of the welding machine uniform, get all aspects of the definition of identity. The so-called digital welding machine should refer to some of these welding machine, their main control circuit by the traditional analog technology directly by the digital technology on behalf of the control circuit in the control signal also by the analog signal transition to 0 / L encoded digital signal.

In the development of computational control technology has experienced two key stages, namely, the creation of the period and the direct effect of the word compensation period. In the excavation period, the computer system is slow, high price, not reliable, so this stage of the calculation and control mainly in two ways. One way is that the computer prints out instructions to the operator; the other is the computer that modifies the settings of the analog adjuster. After entering the direct digital control period, the task of the computer is no longer limited to sending instructions to the operator and setting the value of the controller, but instead replacing the function of the analog adjuster. "J. In the digital welding The morning of the machine is also similar to the two stages. ∞ maggot or ∞ c196 as the representative of the single-chip control arc welding inverter power is basically a digital welding machine to create the product.The main feature is the single-chip in the welder In the welding process of constant pressure, constant current control through the simulation of the PI (proportional integral) controller to complete.Of course, this is not absolute. In some of the thyristor controlled thyristor, from the parameter setting, welding parameter feedback sampling, Pl control, to the thyristor trigger pulse are generated by the single chip. In this case the single-chip control of the arc welding The power supply should belong to the product of the direct digital control period.Only in a sense, only in the digital welding machine into the direct digital stage really realized the digital, only fully embodies the advantages of digital control.

It goes without saying that digital control has good system flexibility. For analog systems, the system of the amount and gain by the resistance of the network and other hardware parameters determined, once determined to be difficult to change. And for the digital system, all this is just to change the software only. For the digital welding machine, the flexibility of the meaning of the same set of hardware circuit can achieve a different welding process control, for different welding methods and different wire materials, diameter can use different control strategies, control parameters, so that the welder In the realization of multi-functional integration at the same time, each of the welding process of the process will also be greatly improved. Taking the waveform control of c0, short circuit transition as an example, the current waveform at short circuit determines the size of the welding splash and the shape of the weld, and for different wire diameter and welding process interval. The best current waveform will be different. In the use of analog control, often in accordance with the principle of taking into account the entire process interval to select the current waveform, which will inevitably result in part of the process effect is not ideal. The flexibility of digitally controlled lanthanum is also reflected in the online upgrade function of the digital welding machine. As a result of the use of n ∞ h as a memory, while the circuit design to increase the online n * h programming function, therefore, digital welding machine control program upgrades or online debugging changes, simply through the Rs232 serial communication interface.

The second advantage of a digital welder is that it has better stability. In the simulation system. Signal processing is through a flood or passive power network, the processing parameters set by the resistance, the choice of capacitance parameters to complete. In this way, the tolerance of the capacitive parameters in the simulation system, the drift must lead to the change of the controller parameters. On the one hand, the temperature stability of the simulated control is poor, and the product consistency is difficult to be guaranteed on the other hand. In the digital control, the implementation of signal processing or control algorithm is through the software to add / base, multiply / divide operation to complete, so its stability is good, product consistency has also been a very good guarantee. Digital welding machine has a higher control accuracy. The accuracy of the analog control is generally determined by the error caused by the component parameter value and the error caused by the non-ideal characteristic parameters of the op amp (eg, A. ^,%, ,,, noise, etc.). The reverse amplifier resistor network causes the magnification The relative error is inverted, the magnification IA, .I = Ma, its relative error h = false one | y., Where * = △ ruler 1 / Rl, bamboo = △ pull horse resistance R, and horse relative Error "J. If the month And 5: the relative difference of ± 5%, the magnification of the relative error of ± 10%. And the precision of the digitized control of lanthanum is only related to the quantization error of the transformation of the module and the finite word length of the system. If the signal of the O-lOV change is transformed by 10-bit mode, The quantization error is IeI ≤ sheep = ÷ x rock = o. 004 Harrier 2 812 5. As a result, digital control can achieve very high accuracy.

Finally, the digital welding machine has good interface compatibility. As the bulk of the welder used a large number of single-chip, DsP (digital signal processor) and other digital chips, digital welding machine and other equipment can be very convenient to achieve a lot of information exchange. With the modern welding production network management development and popularization, digital welding machine interface compatibility is bound to play a more important role. Digital welding machine with the traditional analog control welding machine has an undisputed advantage. However, the realization of the welding machine digital system is extremely challenging. Poor processing speed and poor anti-jamming capability are the main drawbacks of digital control. Therefore, in the realization of digital welding machine must be through a reasonable control chip selection and overall design to meet the arc welding process on the digital system processing speed requirements. At the same time, must take effective anti-jamming measures, so that digital control circuit to adapt to high radiation, strong electromagnetic interference arc welding process environment.


2 digital welding machine to achieve

Welding machine to the digital direction of development, Baoji two aspects of the content. One is the main circuit of the digital. The other is the digitization of the control circuit.

2.1 the number of the main circuit 

In the welding power supply, the role of the transformer is very critical, on the one hand to meet the current and voltage matching requirements, on the other hand, the power supply circuit and the welding circuit to play the role of electrical isolation. At the same time, the position of the transformer in the energy transfer circuit determines the volume and quality of the welding power supply. Figure 1 shows the main circuit diagram of the analog welding machine. This power supply consists of a power frequency transformer, three-phase rectifier bridge and a transistor group, the transistor group in the role of the loop is equivalent to the load series resistance. The transistor bank operates in the amplification zone. Unwanted voltage consumption in the weld between the transistor group c, E pole, so the power consumption is great, the transistor group needs water cooling. The output waveform of the analog welding machine is shown in Fig. The advantage of this welder is the fast response, the disadvantage is that the transistor group of energy consumption, and therefore has basically been replaced by other types of power.