Research On Type Synthesis Method And Novel Mechanism Of Uncoupled Rotational Parallel Manipulators With Two Degrees Of Freedom

Rotational parallel manipulator with two degrees of freedom is one of the important types of parallel manipulators.It is suit to be used in medical devices,satellite antenna servo devices,bionic joints and other fields requiring spatial attitude adjustment.In order to solve the strong kinematics coupling problem of the general parallel manipulators,the uncoupled rotational parallel manipulator(URPM)with two degrees of freedom(2-DOF)is studied with the support of National Natural Science Foundation of China(5090505).The type synthesis method of 2-DOF URPM are discussed in depth,and kinematics,dynamics,and kinematics performances of the navel RR-RURU mechanism are also deeply studied.A new systematic method for type synthesis of 2-DOF URPMs is presented.Based on the actuation wrench screw theory,the mathematic model mapping the input and the output motions of the URPMs is set up.The relationship between the output motion characteristic of the rotational parallel mechanism and the actuation wrench screws exerted on the moving platform by the actuated joints is also analyzed.The forms of the actuation wrench screws and the corresponding actuated twist screws of the kinematic chains are determined in terms of the condition that the Jacobian matrix is diagonal.Then all possible forms of the non-actuated twist screws are confirmed according to the principle that the actuation wrench screw is reciprocal to all twist screws within a chain except for the actuated one.The steps of structural synthesis for the kinematic chains are put forward and the type synthesis of the parallel mechanisms with the expected mobility is realized successfully.Kinematics and dynamics problems of a novel RR-RURU parallel manipulator are analyzed.The kinematic output characteristics and the mobility of the mechanism are analyzed by using screw theory.Based on the geometric characteristics and attitude transformation matrix of the mechanism,the equations of attitude and angular velocity of the moving platform are derived.And the structural conditions that the mechanism satisfies the complete isotropy of kinematics are discussed.The dynamic model of the mechanism is established based on Lagrange equation.The validity of theoretical analysis is verified by the virtual prototype and the numerical simulation results.Analysis of kinematic Performances of the novel RR-RURU parallel manipulator is carried out as well.According to the screw theory,the limb singularity,actuation singularity and constraint singularity of the mechanism are studied.Then,based on the condition number of Jacobian matrix,the dexterity of the mechanism is discussed.The orientation workspace of the mechanism is studied,and the three-dimensional graphics of its reachable orientation workspace and actual orientation workspace are obtained.Aiming at maximizing the orientation workspace,the dimension parameters of the mechanism are optimized.In addition,a parallel ankle rehabilitation robot for ankle rehabilitation training is designed.The research results in this dissertation provide a useful supplement for type synthesis theory of parallel robotic manipulators.It also contributes to the key theoretical basis and technology for the creative design and physical prototype development of the URPMs.