Research On Laser Flying Welding Process And Control Algorithm For Hair-pin Windings

With the development of automobile driving motor towards high performance,high efficiency and high power density,Hair-pin motor has gradually become the first choice of driving motor for new energy vehicles because of its high slot full rate,high heat dissipation efficiency and good NVH characteristics.In the production process of Hair-pin motor,welding the end of Hair-pin winding is an essential process step,so it is of great significance to study the appropriate welding process and welding strategy to improve the qualified rate and production efficiency of Hair-pin motor.In this paper,the welding quality and production efficiency of Hair-pin winding are improved by studying the laser welding process parameters and laser flying welding control strategy,which provides certain reference value for the welding of Hair-pin winding.The main research contents of this paper are as follows:Firstly,the experimental platform of laser flying welding is built,and the components of the platform,such as laser,vibrating mirror system,robot system,water cooler and inert shielding gas,are introduced in detail.Since the winding of Hair-pin motor is mainly made of copper flat wire,the experimental object chosen in this paper is the copper flat wire with the specification of "4mm×2mm×55mm".The samples to be tested are obtained by pretreatment such as removing thermoplastic insulating materials.Secondly,the laser welding technology of Hair-pin winding is studied.The selected welding trajectory is a circle with a diameter of 2mm.Based on the laser power and welding speed as independent variables,the key process parameter of energy density is defined.Combined with this parameter,the weld morphology,penetration depth,penetration width,cross-sectional area,mechanical strength,surface hardness,weld resistance and other indicators are analyzed.Aiming at the height difference between hair and pin caused by improper clamping at the end of Hair-pin winding,the above process is improved,that is,semi-circular tracks with different sizes on the left and right sides are added on the basis of the original track.According to the above method,the energy simulation and experimental verification are carried out.The experimental results show that the appearance of the weld after process optimization is greatly improved compared with that of the control group(without process optimization),the mechanical properties are improved by 109.52%,and the resistance value is reduced by 13.11%,which shows that the process optimization scheme is a good solution to the dislocation defect of Hair-pin winding.Then,the control algorithm of motion tracking and compensation in laser flying welding process is studied theoretically,and the maximum flying performance of the robot is analyzed.By analyzing the whole process of laser flying welding,the physical model of laser flying welding is established and simplified.On this basis,the mathematical model of motion tracking and compensation algorithm is obtained,and the motion trajectory of the algorithm is simulated by MATLAB.After that,the control flow is obtained under the condition that the communication period between the vibrating mirror system and the robot system is different.According to the constraint characteristics of scanning format and the actual flight strategy requirements,the calculation formula of maximum flight performance is obtained.Finally,in order to verify the feasibility of laser flying welding for Hair-pin winding welding,the control system software is developed,the relevant experimental flow is designed and the process experiment is carried out,and then the welding quality and welding processing time are analyzed respectively.The results show that under the same process parameters,the welding quality of Hair-pin end will not be greatly affected by laser flying welding,and its resistance value is increased by 1.9%compared with the traditional method,and the maximum tensile load is reduced by 1.4%compared with the traditional method.Using laser flying welding can significantly improve the machining efficiency,and the machining time will be reduced by nearly 20%on the original basis.