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Spot welding assembly
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This paper presents the design, fabrication of a microcontroller based resistance welding system which is used for performing a welding process. The paper is divided into 4 sections. First, a brief introduction to what is a welding, method of welding control such as resistance and spot welding is given. Secondly, the critical factors in the design...
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Citations
... Electrical system is the executive structure of the RSW machine, however, fewer previous works focused on the electrical structure of the RSW machine, compared to the other aspects of works in the RSW relative area. Currently, micro-controller was employed widely in RSW system design and actual production [18,19]. The electrical structure, which conducted the external energy delivery into the RSW system, should be considered seriously in the work, because it related to the stability, safety and energy efficiency of the production, then to facilitate the microcontroller system. ...
Resistance spot welding (RSW) is frequently employed in current industrial occasions. This paper reviewed recent advances of the electrical structure of the RSW system. Two types of electrical structures are used in RSW machines. Single-phase AC power source has a simple structure but low control frequency and power factor, and the measurement and control for the machine have some special operations. While three-phase medium frequency DC power source has a complex structure and high control frequency but high cost, and frequently switching the direction of the output welding current may induce many negative phenomena in the welding transformer. The characteristics of the two structures are presented in detail in this paper. Corresponding measures have been taken to deal with the phenomena during the process, respectively for the two types of electrical structures, according to the previous works. Though many significant achievements have been gained in previous works, it is expected to be more improvements required in the future. This paper can provide references and enlightens for academic researches or actual production in RSW operations.
... During the welding process, the calculation of the RMS value of the welding current should be conducted during each control cycle. The traditional method is successive integration from point to point [12] for all of the collected data of the welding current based on the original definition of the RMS value [13]: ...
... ∑ This means that if a large range of current values is needed, the neural network must be employed. Additionally, although the neural network is used in the proposed algorithm, the neural network is based on the fixed mathematical relation as shown in equation (12) instead of individual experiments. As a result, the training process can be conducted offline, which can save more CPU time when compared to directly solving the nonlinear equations. ...
In this paper, an algorithm based on a model analysis of the online calculation of the root-mean-square (RMS) value of welding current for single-phase AC resistance spot welding (RSW) was developed. The current is highly nonlinear and typically non-sinusoidal, which makes the measuring and controlling actions difficult. Though some previous methods focused on this issue, they were so complex that they could not be effectively used in general cases. The electrical model of a single-phase AC RSW was analyzed, and then an algorithm for online calculation of the RMS value of the welding current was presented. The description includes two parts, a model-dependent part and a model-independent part. Using a previous work about online measurement of the power factor angle, the first part can be solved. For the second part, although the solution of the governing equation can be directly obtained, a lot of CPU time must be consumed due to the fact that it involves a lot of complex calculations. Therefore, a neural network was employed to simplify the calculations. Finally, experimental results and a corresponding analysis showed that the proposed algorithm can obtain the RMS values with a high precision while consuming less time when compared to directly solving the equations.
... General welding effective current measuring method involves the point-by-point integration method [5] [6] [7], the conduction-angle coefficient method [8], and the peak-value coefficient method [9] [10]. The point-by-point integration method, which is popularly adopted in practical applications nowadays, has a high precision but a poor real-time performance. ...
Real-time measurement of effective current is essential for fine control of welding process. However, conventional methods cannot simultaneously satisfy the accuracy and the real-time requirements. On the basis of the welding transformer circuit model, a new measuring method is proposed. This method measures the peak value of the welding current and then multiplies a coefficient K to obtain the root-mean-square value, which enables the processor to calculate the half-wave effective current at the moment of peak current. A Cerebellar Model Articulation Controller(CMAC) model is off-line trained and used online to compute K, which is a nonlinear function against the firing angle and the peak current angle. A DSP-based resistance spot welding monitoring system is developed to perform CMAC computation. Experimental results suggest that this measuring method is feasible.
... Welding in the simplest terms is the process of fusing or joining two or more metal pieces with the application of heat and pressure. The heat energy generated in the process is large enough to weld two work-pieces together [1]. Arc welding is the process based on melting a material to join two work-pieces together. ...
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