Resistance spot welding quality control device and method based on electrode displacement

Abstract

The invention discloses a quality control device and a method for resistance spot welding based on electrode displacement, which belongs to the technical field of welding. 380V alternating current power supply is added to the input end of a primary loop; under the controllable trigger of an anti-parallel thyristor; the alternating current voltage is reduced by a transformer and the welding energy is switched to a secondary loop; the heavy current acquired from the secondary loop welds workpieces; a spot welding part of the workpiece generates heat expansion and the expansion capacity is measured by an electrode displacement sensing device; a spot welding quality controller collects the displacement measured value of the electrode displacement sensing device and processes the numerical value to acquire the estimation of splashing prevention judgment and nugget size, thus acquiring a welding current control voltage signal and transmitting the signal to a trigger driving circuit; the trigger driving circuit sends trigger pulse to the anti-parallel thyristor to control a conduction angle of the thyristor, thus effectively regulating the welding current and controlling the welding quality. Therefore, the device can solve the real-time monitoring and control problem of the quality of the resistance spot welding well.

Description

technical field [0001] The invention relates to a quality control device and method in the field of welding technology, in particular to a resistance spot welding quality control device and method based on electrode displacement. Background technique [0002] Resistance spot welding is widely used in industrial production due to its advantages of high efficiency, low cost and high degree of automation. However, resistance spot welding is a highly nonlinear process with multivariate coupling effects and a large number of random uncertain factors. The quality of its joints is easily affected by many factors, and it is difficult to extract the quality information of solder joints. [0003] After searching the literature of the prior art, it is found that the Chinese patent ZL98102944.2 obtains the power factor angle by looking up the table through the control angle and conduction angle provided by the current sensor, and then calculates the average resistance value of each half...

AI Technical Summary

Problems solved by technology

However, resistance spot welding is a highly nonlinear process with multi-variable coupling effects and a large number of random uncertain factors. The quality of its joints is easily affected by many factors, and it is difficult to extract solder joint quality information.

[0003] After searching the literature of the prior art, it is found that the Chinese patent ZL98102944.2 obtains the power factor angle by looking up the table through the control angle and conduction angle provided by the current sensor, and then calculates the average resistance value of each half cycle, and then uses the dynamic The resistance curve estimates the size of the nugget. The disadvantage of this method is that the obtained information is single, and it cannot effectively prevent the generation of spot welding spatter. It is difficult to establish an accurate hidden Markov model for interference such as shunt and electrode wear. The curve is obtained indirectly by look-up table calculation, and the accuracy is easily affected

During the search, it was also found that Chinese patent 200510047082.6 extracts effective feature information by collecting network voltage synchronization signals, secondary loop current signals, current zero-crossing signals and electrode displacement signals, and estimates the nugget diameter by information fusion processing based on the expert knowledge base. The fuzzy or PID control method is used to adjust the heat and time of the spot welding process. This method collects a lot of characteristic information, which makes the construction of the expert knowledge base more difficult. The invention is based on the relationship between the resistance spot welding current, dynamic resistance and electrode displacement signals and the fusion The linear corresponding relationship between the diameter of the nugget is modeled, but in fact, there is a strong nonlinear relationship between the spot welding monitoring parameters and the diameter of the nugget, which reduces the accuracy of the information fusion model in estimating the diameter of the nugget.

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