| Friction stir welding is an advanced,green and reliable welding technology,which is widely used in automobile manufacturing at home and abroad.Most of the existing friction stir welding equipment can only adapt to regular welding,lack of process flexibility,it is difficult to adapt to complex 3D space inner surface welding.In this paper,the problems and difficulties encountered in the development of 3CD/3UPS-UP rigid flexible cooperative hybrid robot for automobile parts welding are studied.In addition to the characteristics of high rigidity and precision of parallel robot,the redundant flexible cable driving part also increases the load-carrying capacity of the whole machine,which can achieve the purpose of friction stir welding of curved surface.The main contents of this paper are as follows:(1)In order to solve the problems of incomplete penetration and complex fixture in single shoulder welding,a kind of floating double static shoulder stir friction welding head was invented and designed.The mechanical analysis of the two shoulder stir head was carried out,the mechanical model and heat production model of the stir head were established,and the numerical simulation results of the model were studied.The relationship between the parameters of FSW and the heat production is obtained by comparing the data of numerical simulation and the data of actual measurement.With the increase of the rotating speed of the mixing head,the heat input increases first and then decreases,and the shaft shoulder is the main heat production part of the welding,which provides a theoretical basis for the development of FSW equipment.(2)According to the welding requirements of aluminum alloy parts of automobile,a hybrid robot of 3CD/3UPS-UP is proposed and the inverse kinematics solution is solved.According to this configuration,the hybrid robot system of FSW is designed.By using Solid Works,the structure design and engineering drawing drawing of the key parts of the FSW robot,such as the fixed platform,the moving platform,the ball hinge,the flexible cable connection device and the traction device,are carried out,which lays the foundation for the processing and construction of the prototype.(3)The static models of 3CD and 3UPS-UP hybrid mechanism are established by disassembly method.The example model of automobile hub is established by ADAMS simulation software.The correctness of the model is verified by comparing the simulation results with the static model results calculated by MATLAB.According to the analysis results,with the decrease of the working position,the load of these key parts increases,and the change range of the force in the X,Y plane is larger.It can be used as a reference for judging the failure position of key parts and selecting the standard parts of physical prototype.(4)Through the workbench software to analyze the stress and deformation of the initial position of the main feed mechanism,optimize the structure according to the cloud chart results,and compare the results before and after the optimization,we can see that the mechanical performance of the main feed mechanism has been improved.At the same time,the stress and deformation of the optimized main feed mechanism at any limit position are analyzed,and the analysis cloud chart shows that the main feed mechanism meets the design requirements.Through the modal analysis of the main feed mechanism,the first six modal shapes and resonant frequencies of the main feed mechanism are obtained.(5)In order to test and analyze the hybrid FSW robot in the later stage,the main feed mechanism is processed and assembled.According to the design requirements of the whole machine,the drive and some parts are selected,and the prototype of parallel mechanism which can be used for welding is obtained.And the control system of the rigid flexible cooperative robot is designed,which lays the foundation for the research and experiment of the force/position hybrid control of the rigid flexible cooperative hybrid friction stir welding robot. |
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