Research On Actuation Mechanism And Kinematic Characteristics Of A Large Attitude Flexible Parallel Mechanism

The flexible parallel mechanism has sufficient flexibility and force sensitivity.It can achieves multi-degree-of-freedom movement,which is lightweight and easy to expand.These features make it useful in micromanipulation、endoscopic surgery and human-machine interaction fields.etc.In this paper,based on the Stewart configuration of the parallel mechanism,the distal and proximal connections of the mechanism are expanded,and a large-angle motion spherical joint is creatively designed,which greatly increases the expandability of the mechanism.An optimal control model for analyzing the elastic stability of a flexible parallel mechanism can evaluate the stability in real-time simulation from the energy point of view,and has guiding significance for the motion planning and design optimization of the mechanism.In this paper,the generalized kinematics model of the flexible parallel mechanism is established first,and the solution method is given.The legs of the flexible parallel mechanism are composed of slender elastic beams.We use the Cosserat equation to describe the actuation of the legs.On this basis,the legs are discussed according to the different constraints of the posture,force,and moment of the legs.The distal and proximal boundary conditions are discussed,which are under different connection modes such as fixed connection with mechanism,free axial rotation connection,and spherical hinge connection.Then,according to the type of input parameters and output parameters of the kinematics model,the kinematics problems are divided into six categories,and the shooting method is selected to solve the ordinary differential equations of the outriggers,and then the kinematics problems are solved.Based on the establishment of a generalized kinematics model,we analyzed the statics characteristics of the mechanism.Firstly,the work space under several different distal connection modes is solved,and a comparative analysis is made.Due to the complexity of the static analysis of flexible mechanisms,we linearized the kinematics model and derived four static characteristic matrices.After solving the kinematics problem,the different positions were obtained using the finite difference method.Correspondence matrix in the posture,using the ellipsoid analysis method to visualize the statics characteristics.Then,the non-dimensional analysis method is used to provide a way of analyzing the influence of different physical parameters of the mechanism on the statics characteristics.We have established an optimal control model to evaluate the elastic stability of the organization.Inspired by the energy stored in the elastic beam when deformed,we use the deformation energy as the performance index of the optimal control,establish the optimal control model,solve the first-order necessary conditions and second-order sufficient conditions of the extreme points,and complete the transformation from the plane beam The establishment of the elastic stability model for coupling to multiple plane beams and the coupling of space beams to multiple space beams and the solution of stability conditions have proved the operability and real-time nature of the solution.Finally,we designed a large-angle motion spherical joint with a working space of ±150°,which is based on the characteristics of the large-angle motion of the mechanism,from the perspective of the working space,using the passive redundancy mechanism.Then the large-angle working characteristics were verified.This lays a foundation for further expansion of the flexible parallel mechanism.