| This thesis proposes a new 2R1 T three-degree-of-freedom parallel robot as the posture adjustment mechanism of the whole automated hole-making system,and carries out relevant theoretical calculations and structural optimisation.The theoretical calculations and structural optimisation are carried out.The theoretical calculations and structural optimisation are carried out.The specific research content is as follows:(1)A new parallel mechanism configuration is proposed to meet the actual processing requirements of the entire automated holemaking system.Based on the actual working conditions and requirements,three different automated holemaking solutions are compared in terms of load capacity,space occupation and holemaking accuracy to determine the optimal solution.The calculation and selection of key connecting hinges and active and passive moving subsets are completed,and finally the assembly of the 3D structure of the parallel robot is realised.(2)The analysis of the degrees of freedom of the mechanism is completed by integrating the spiral theory with the degree of freedom correction formula.The closed-loop vector method is then used to solve the positive and negative solutions for the position of the mechanism,on this basis,the velocity and acceleration of the mechanism are analyzed.Finally,the working space of the parallel robot is obtained based on the grid search method,and the dexterity of the mechanism is judged by the Jacobi condition number.The kinetic equations are established using the virtual work principle method.(3)The effect of drive element stiffness,hinge clearance and linkage deformation on the overall static stiffness are investigated.A vibration model of the global end platform dynamic stiffness is also developed.The key components of the parallel mechanism are calibrated for static strength,and the kinematics and dynamics,including position inversion,workspace,dexterity and drive forces,are simulated and analysed by means of given numerical examples.(4)Optimisation of the redundant material removal from the dynamic and static platforms to reduce the overall mechanism weight while ensuring the machining performance of the parallel mechanism.The ultimate length of the connecting rod and the ultimate angle of the hinge are optimised based on the maximum working space volume.The simulation and optimisation results show that the structural arrangement of the parallel mechanism is reasonable and the theoretical calculation is correct,which verifies the feasibility of the holemaking scheme. |
