Design And Analysis Of A Novel Hybrid Processing Mechanism With Large Workspace

In order to solve the problems of large size,severe deformation,and complicated convex structure for the coating process of oversized cylindrical boxes' spherical crown surface in the aerospace field,the research on box processing method and serial-parallel hybrid mechanism is carried out.A novel hybrid processing mechanism based on 5-PUS/(2UR)PU parallel mechanism as a machining head is proposed,and its theoretical analysis and size optimization are carried out.The virtual prototype model of the hybrid processing mechanism is constructed,and the simulation analysis of the hybrid processing mechanism is carried out.The research will eventually provide technical support for the actual processing method of the large-scale box spherical crown surface and the structural configuration of the processing equipment.It has important research significance.Therefore,the following research and analysis are carried out.(1)The overall design of the equal-thickness processing for the spherical crown coating of the oversized box is carried out.According to the processing requirements,structural characteristics and processing technology,and combined with the actual engineering needs,the overall scheme of different box spherical crown coating processing is proposed.By comparing and analyzing the advantages and disadvantages of different schemes,the optimal processing scheme that meets the actual engineering needs is determined.(2)The configuration of the hybrid processing mechanism is designed.According to the requirements of the spherical coating of the box in the processing,the mechanism should meet the processing requirements of large workspace and high flexibility.Therefore,the processing mechanism adopts a structure configuration form in which the lifting adjustment device and the parallel mechanism are mixed.The mechanism can realize three-stage superposition of displacement in the vertical direction,which meets the design requirements of large workspace.At the same time,the real-time detection and processing method of the local parallel processing head is adopted,which improves the processing flexibility.The degree of freedom of the mechanism is calculated as 5,which meets the machining requirements.(3)The kinematics and dynamics of the novel hybrid processing mechanism are analyzed.Kinematics analysis includes the derivation of positive and negative solutions and the establishment of velocity Jacobian matrix.For the analysis of dynamics,the motion of each branch centroid is analyzed first.Secondly,the external force suffered by the moving platform is analyzed.Finally,given the force and motion of the moving platform,the driving force of the driving pair is solved.(4)The workspace,dexterity and static stiffness of the novel hybrid processing mechanism are analyzed.The workspace of the hybrid mechanism is solved and compared with the single parallel mechanism.Based on the speed Jacobian matrix,the local condition number index is solved,and the dexterity performance of the mechanism is analyzed.The minimum eigenvalue of the static stiffness matrix is calculated,and the stiffness performance of the hybrid processing mechanism is analyzed.(5)The size of the novel hybrid processing mechanism is optimized.Firstly,the genetic algorithm is selected as the optimization algorithm of the mechanism.Secondly,the objective function to be optimized is established,and the constraints and optimization parameters of the mechanism are given.Finally,based on the MATLAB software programming calculation,a set of optimal design size parameters of the hybrid processing mechanism is obtained.(6)The virtual prototype simulation of the novel hybrid processing mechanism is carried out.According to the optimized size parameters,a virtual prototype model is established in the ADAMS software.The kinematics simulation is carried out by taking circular arc trajectory as an example.Based on MATLAB software,the dynamic simulation of the hybrid machining mechanism is carried out.Numerical simulation of dynamics is carried out in three aspects: circular motion in two planes,rotation around xaxis and rotation around y-axis.The research results show that the novel hybrid processing mechanism has a large workspace and can meet the needs of box processing.At the same time,the simulation results verify the correctness of the theoretical analysis.