| In this paper,a 5-DOF parallel mechanism is designed as the main actuator of FSW robot to meet the welding requirements of automobile sheet metal and complex curved parts.Firstly,the forward and inverse kinematics solutions are established,the Jacobian matrix is established based on the screw theory,the degree of freedom is derived,and the singular pose is solved;the size of the parallel robot is optimized by using the motion / force transfer performance index;the three-dimensional prototype model is constructed to carry out the kinematics and dynamics of the robot On the basis of the above work,the structural design and static simulation of this new type of FSW robot mechanism are completed,and the prototype is built.The main contents of this paper include:(1)Based on the analysis of the characteristics,welding requirements and functional requirements of FSW for automobile sheet metal and complex curved parts,a parallel robot is proposed as the main actuator of FSW.According to the structural characteristics and welding requirements of automobile hub,a 5-degree of freedom 4-sprr-spr is adopted Parallel mechanism as the main actuator of parallel friction stir welding robot prototype design.(2)The establishment of kinematic model and singularity analysis of mechanism.The structure of the parallel mechanism is determined and described.The degree of freedom of the parallel mechanism is solved by using the screw theory.The forward and inverse kinematics solutions of the mechanism are analyzed.The velocity Jacobian matrix of the parallel mechanism is established.By solving its determinant,five kinds of singular positions of the parallel mechanism are obtained.(3)According to the specific requirements of FSW,the evaluation index of the parallel mechanism's motion performance-motion / force transfer performance is determined.Through the screw theory,the instantaneous power and the maximum power of the parallel mechanism are analyzed,and the solution of the maximum power of the mechanism is described in detail.Taking the welding of aluminum alloy wheel hub as an example,the optimization goal is set,and the optimal size of parallel mechanism is obtained by genetic algorithm,and its performance map is drawn.(4)The three-dimensional prototype model is established,kinematics and dynamics simulation are carried out,and the working space is solved.The three-dimensional modeling and kinematics simulation of the prototype of FSW robot are carried out to verify the correctness of the inverse kinematics equation of the parallel mechanism,and the dynamics simulation of the parallel mechanism is carried out to obtain the force condition of the driving rod when the mechanism is working.The workspace constraints of the mechanism are analyzed in detail,the reachable workspace map of the mechanism is obtained,and the influence of different motion pairs on the workspace size is analyzed.(5)Structural design,prototype construction and finite element static simulation.First,the original parameters of the structure are set according to the work requirements,and the main parts of the robot,such as the ball pair and the moving platform,are described and designed in detail,and the static simulation verification is carried out according to the actual working conditions,the main parts,such as the spindle motor and the electric cylinder,are selected,and the prototype is finally built. |
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