Analysis And Experiments Of A Novel Parallel Wrist And Its Hybrid Mechanism With Delta

The huge demand of the national electronics manufacturing and light industrial production is closely considered in this dissertation.A novel 3 degree-of-freedom(DOF)parallel wrist for surface grinding of smartphones and non-planar assembly of printed circuit board(PCB)is proposed.The wrist is connected in series with 4-DOF Delta parallel mechanism to form a new hybrid mechanism.The research focuses on the type synthesis,DOF analysis,kinematics and dynamics performances of the new parallel wrist.Finally,the whole kinematics,trajectory planning,prototype development and experimental testing of the hybrid robot are studied systematically.The main work is as follows:(1)A new 3-RSR(R denotes rotational joint,S denotes spherical joint)parallel wrist mechanism is proposed via the configuration evolution method.This mechanism has 3-DOF which contains 2 rotations and 1 translation,and during the movement,there always exsists a symmetry plane.The moving platform and the base(also called the fixed platform)are symmetrical about this plane.The moving platform can rotate a certain range around any straight line in the symmetry plane,or translate along the center of the two platforms.The modified G-K formula and the atlas method are combined to analyze the DOF of the wrist.To verify correctness of the configuration design,the symmetry of the mechanism is demonstrated by geometrical method.(2)An equivalent kinematics model is established by using the special geometric properties of the new parallel wrist mechanism.The singularity of the end of the wrist mechanism(i.e.the moving platform)under the constraint of the spherical joint limit swing angle is discussed.The three-dimensional slicing method was used to analyze the rotational performance and translational performance of the wrist end under the same height and fixed deflection angle in the actual working space.By defining the local performance index of the parallel wrist force transmission,the performance map of parallel wrists in different sections along the z-axis in the reachable working space is drawed.(3)An instantaneous velocity solving method based on Riemann symmetric space is proposed.The dynamics of parallel wrist mechanism is modeled based on the Lagrange equation method,the correctness and effectiveness of dynamic model is verified by Mathematica calculation and ADAMS.The generalized inertial ellipsoid method is used to determine the workspace with better dynamic performance of the wrist mechanism.(4)Kinematics analysis is carried out for a hybrid robot with two stage RUPUR transmission chains.By constraining the length of one RUPUR transmission chain,the unique solution of the position analytical equation of the hybrid robot is obtained.The reachable workspace of the hybrid robot is drawn by Monte Carlo method.The trajectory planning and motion simulation of the joint space and Cartesian space are performed on the hybrid robot by the fifth-order polynomial interpolation method based on kinematics.(5)A hybrid robot prototype with two stage RUPUR transmission chains was developed and successfully applied to non-planar assembly of PCB with fixed pose and motion simulation of surface grinding.The correctness of kinematics theory and feasibility of trajectory planning for hybrid robot are verified by experiments.