| Multilayer spot welding is widely used in actual production, but the quality control for multilayer spot welding is rarely reported at home and abroad. Comparing to two-layer spot welding, multilayer spot welding is more complicated, and there is no effective quality control measures applying to multilayer spot welding. Therefore, different specifications are often used in two-layer spot and multilayer welding technology at present. However, the quality of nugget also can not be guaranteed. To solve this problem, a suitable fusion-control algorithm is worked out for multilayer spot welding in the paper on the basis of IDRC monitoring methods.Any theory is based on practice. In this paper, a new control algorithm is explored by IDRC intelligent spot welding controller. Comparing to the three methods, such as simple regular method, constant current control method and double-feature fusion IDRC control method, the constant current method can take the same time to complete multilayer spot welding without shunt, two or three-layer spot welding can reach a level of excellent nugget, but the nugget quality of the four-layer spot welding is unsatisfactory. Though the high quality nugget can be achieved in IDRC method for weld multilayer spot welding, consistency of welding time is not good. Deficiency of the two methods is the more prominent under the impact of shunt.In the case of severe shunt, the quality control of multilayer spot welding is not good. In response to this phenomenon, the two decision-making in fusion-control algorithm will be applied in this paper. Welding current deviation information is replaced by the information of nugget quality in double-feature fusion algorithm, such as the cumulative incremental deviation of current lag angle(Σen), it reflects the nugget growth status at a period of time, it is able to ensure that the quality and the time of multi-layer spot welding is consistent. Meanwhile, based on some quality control strategy, the control algorithm's control rules, discourse domain, membership function and the software program were carefully designed in the paper. Any theory must stand up to practice. In this paper, information fusion control algorithm must be accepted the testing of practical welding results in multi-layer spot welding process. The new fusion-control algorithm is still imperfect in experiments. Therefore, in the course of this trial are also constantly improving the control algorithms, including fuzzy-control rules, the data of DRC, description ofΣen and real-time correction ofδψ*. In addition, other multi-layer spot welding process should be properly modified.Using the complete control algorithm, two or three-layer spot welding quality control is good without shunt. It reaches the spot welding quality and consistency. In the four-layer spot welding, due to changes of the structure of nugget solder joints splashing easily happen. Therefore, four-layer joint does not exist in the actual production.This article focuses on that lap joints of the three-plate spot welding were tested. Through the study found, in shunting current situation, the new fusion algorithm in the three-plate welding process play a good role, In ensuring the quality of the nugget,time consistency can be better guaranteed. In the situation of 15% heat fluctuates, the new fusion algorithm has played a very good control effort.In summary, there is the phenomenon for severe shunt, poor nugget quality and welding time inconsistency in this article, through the IDRC Dual features fusion Control algorithm, that is, in the second decision-making, original use of the dynamic current message replaces for quality information of reflecting nugget state,that is current lag angel cumulative incremental deviationΣen.. Furthermore, with the output of a decision-makingΔMn+1 together to complete a second fuzzy reasoning, and thus improve the quality of multilayer welding process control to solve the difficult problem of multilayer welding. At the same time, on base of the experimental verification, the new control algorithm has been continuously improved, and summed up a spot welding process parameters for multilayer sheets. In summary, this conclusion follows:(1) In the new fusion-control algorithm, the increment deviation of current lag angle at each cycle and the cumulative incremental deviation of current lag angle before the present cycle take a decision step by step, to reduce the difficulty of fuzzy reasoning and extend control algorithm adaptability. It also increases the sensitivity of a given DRC, so a more accurate model of given DRC must be designed.(2) The new fusion-control algorithm is still designed based on IDRC method. In multilayer spot welding, because the constant current control was used in period of the non-nugget, and therefore in situation of serious shunting current, the control efforts of multilayer spot welding is still insufficient, the problem of valley point lag become inevitable on current lag angle curve, which requires to correctδψn* and the initial value ofΣen to improve efficiency and quality of the control algorithm. The testing results proved that there is a good applicability using the improved control algorithm to the process of multilayer spot welding quality control.(3) Three sheets spot welding test showed that the new fusion-control algorithm has the characteristic of fast response and parameters have a good dynamic quality,so that the consistency of nugget quality and weld time is ensured in the case of heat fluctuations at±15% and shunting current.
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