| Parallel manipulator has many advantages,such as high bearing capacity,high positioning accuracy,high structural stiffness and stable motion,and has been widely used in many industrial fields.As one of the performances of parallel mechanisms,stiffness plays a very important role in practical industrial application.It has very important research and application value for real-time variable stiffness under the condition of human-computer interaction and stiffness matching of working environment.In order to ensure that the parallel manipulator has the characteristics of variable stiffness and high precision positioning at the same time,the research can start from two aspects of mechanism reconfiguration variable stiffness and low stiffness coupling.In this paper,the mechanism is a generalized 6-DOF parallel mechanism based on compound single leaf hyperboloid.The kinematic redundancy is introduced into the parallel mechanism to make the mechanism reconfigurable.The mechanism of variable stiffness,stiffness coupling optimization,variable stiffness realization and experimental verification of the kinematic redundancy parallel manipulator is studied.Firstly,based on the kinematics analysis and the statics analysis of kinematic redundancy parallel manipulator,the variable stiffness mechanism and the stiffness model of parallel manipulator have been given.The stiffness decoupling condition of the moving platform is derived based on the stiffness model of the motion redundant structure.Based on the GCI,the layout direction of redundant linear driving joint is designed.The correctness of the stiffness model is verified by the simulation analysis,which lays the foundation for the mechanism reconfiguration of variable stiffness.Based on GCI,the moving datum of the adjustable lower hinge point for the mechanism reconfiguration in Z-direction translational motion of the moving platform is given.Based on this,the variable stiffness algorithm for 6-DOF direction mechanism reconfiguration is given.The algorithm solves the adjustment trajectory of adjustable lower hinge point with 6 degrees of freedom and variable stiffness when the parallel mechanism platform moves in the z direction.At this time,the stiffness of the mechanism in the direction of 6degrees of freedom can be changed according to the set rules.The correctness of the algorithm is verified by simulation.Based on GCI,the stiffness characteristics of the mechanism are optimized.The design range of three orthogonal stiffness of the redundant linear actuator and the optimization of the position of the lower hinge point when the mechanism approaches the stiffness decoupling are given.The influence of the workspace and maneuverability of the moving platform of the kinematic redundant generalized parallel mechanism is analyzed.The maximum force and velocity transfer characteristics of the generalized parallel mechanism in the workspace are given.It is prove that the introduction of kinematic redundancy can greatly improve the performance of the generalized parallel mechanism. |
PDF Full Text Request