Dynamics And Stiffness Of A Kind Of Kinematic Redundant Hybrid Mechanism

Compared with the traditional parallel mechanism or serial mechanism,serial-parallel hybrid mechanism combines the advantages of these two kinds of mechanisms,and has a wide application prospect.However,the immature theory of the serial-parallel hybrid mechanism has great limitations on its practical application.Therefore,research on the serial-parallel hybrid mechanism can accelerate its application in industrial production.Among the serial-parallel hybrid mechanisms,we call these mechanisms kinematic redundant hybrid mechanisms(short for KRHMs)when the numbers of independent drives are equal to the degree of freedoms of the mechanism and the degree of freedoms of the mechanism are greater than six.This thesis mainly studies a kind of KRHMs composed of multiple parallel mechanisms with linear active branches(The branch is driven by prismatic pair and two ends are connected to the upper and lower platform by kinematic pair)connected in series.In view of the difficulties of establishing the kinematics,dynamics and stiffness and elastic deformation model considering intertial factors,in-depth theoretical research is carried out on the redundant hybrid mechanisms.The aim of this thesis is to establish the unified theoretical model of kinematics,dynamics and stiffness model of this kind of redundant hybrid mechanism with linear active branches.The main contents of this thesis are as follows:The unified theoretical model for fully forward kinematics of a kind of KRHMs with linear branches is established.The structure of general redundant hybrid mechanisms is introduced,and each specific variable and the naming rules of the symbols are defined.All these can be used to describe the connection and distribution relationships in the mechanism.The unified kinematics model for the single parallel mechanism is established.In order to avoid the problem of velocity iteration in the kinematics of redundant hybrid mechanism,the unified theoretical model of fully forward kinematics for solving generalized output velocity and output acceleration by input velocity and input acceleration is deduced through solving the intermediate velocities.Two new types of 2(3SPR)+3RPS and(4SPS+SPR)+4SPS/SP+3SPR KRHMs are presented,their kinematics models are established according to the unified theoretical model,and their simulation models are constructed.The theoretical models are verified by numerical examples.The unified theoretical model for dynamics of a kind of KRHMs with linear branches is established.Firstly,the velocity and acceleration of the branch centroids are modeled.According to the characteristics of the equation,the generalized velocity models of the branch centroid points are fully expressed by the input velocities using mathematical induction.Then,the inertial force/torque of each component is solved according to the mass characteristics of the component,and the unified statics and dynamics models of the redundant hybrid mechanism with linear branches are established based on the principle of virtual work.Finally,the statics/dynamics model of 2(3SPR)+3RPS KRHM are established according to the unified theoretical models,and the theoretical models are verified by numerical examples.Based on the traditional static stiffness analysis,considering the influence of the constrained force,gravity and inertial force/torque of the moving components,a new method for stiffness and elastic deformation modeling of parallel mechanisms or serialparallel hybrid mechanisms with linear branches is proposed.Firstly,based on the dynamics modeling of general parallel mechanisms or serial-parallel hybrid mechanisms,the driving/constrained force of the branches are solved.Secondly,put the generalized driving force and inertial force/torque apart,analyze the force of the branches respectively,and the elastic deformations of the corresponding branches can be solved.Finally,based on the principle of virtual work and the equation of deformation energy,the total deformation of the end component of parallel or serial-parallel hybrid mechanisms and corresponding stiffness matrix of the general parallel mechanism considering the active/constrained force and the gravity and inertial force/torque of the moving components are solved.The 3SPR parallel mechanism and 3SPR+3RPS serial-parallel hybrid mechanism are used as examples to verify the built theoretical models.Kinematics and dynamics analysis of two new kinds of KRHMs with special applications are carried out.The redundant hybrid mechanisms can be used for emergency rescue and surgery by adding fingers at the end platform.Based on this,a new type of 3SPR+3RPS serial-parallel hybrid mechanism with three fingers is proposed.And its kinematics and dynamics models are established according to the unified theoretical model.At the same time,the models are verified by numerical examples.In addition,based on the advantages of redundant hybrid mechanisms,they can be applied to the design of the humanoid arm,which can increase the rigidity and stability compared with the traditional arm connected in series.Therefore,a novel 3PSS/S+(R+RPR/R)+3PSS/S redundant hybrid humanoid arm manipulator is proposed.Its kinematics model is established and verified by numerical examples.The experimental prototype of the 3SPR hybrid mechanism with three fingers is established,and the movement coordination as well as the grabbing and releasing peformance of this hybrid mechanism are experimentally studied.