A multi-physics hybrid numerical model,which couples electric,magnetic,thermal and flow fields,was used to investigate electromagnetic stirring behavior in a resistance spot weld nugget.The differences of two kinds of different excitation inputs,i.e.,a sinusoidal current and its root-mean-square(RMS) value,were studied to examine if they could produce equivalent electromagnetic stirring effects in the weld nugget.Research showed that the two types of current inputs could produce almost identical fluid flow and heat transfer patterns and consistent evolution of flow and thermal fields in the nugget.At the end of the welding cycles,the maximum flow velocity and temperature between the two inputs differed by 11.6% and 0.3%,respectively.Therefore,the RMS current can be assumed to produce an approximately equivalent electromagnetic stirring effect with the sinusoidal current,and can be used in the future research to greatly improve the solution efficiency of the electromagnetic stirring behavior in the resistance spot weld nugget.
LI YongBing1,LIN ZhongQin1,2,LAI XinMin1,2,CHEN GuanLong1,2 & ZHANG Ke3 1 Shanghai Key Laboratory of Digital Autobody Engineering,Shanghai Jiao Tong University,Shanghai 200240,China
Based on the Newton-Euler method, the dynamic behaviors of the left and right driving wheels and the robot body for the welding mobile robot were derived. In order to realize the combination control of body turning and slider adjustment, the dynamic behaviors of sliders were also investigated. As a result, a systematic and complete dynamic model for the welding mobile robot was constructed. In order to verify the effectiveness of the above model, a sliding mode tracking control method was proposed and simulated, the lateral error stabilizes between -0.2 mm and ＋0.2 mm, and the total distance of travel for the slider is consistently within 4-2 ram. The simulation results verify the effectiveness of the established dynamic model and also show that the seam tracking controller based on the dynamic model has excellent performance in terms of stability and robustness. Furthermore, the model is found to be very suitable for practical applications of the welding mobile robot.
