| In this doctoral dissertation, study of parallel robot is reviewed from viewpoint of theory of mechanism and there are six central dissertations in the review: structure theory, kinematics analysis, workspace analysis, singularity analysis, dynamic analysis and dimensional synthesis. The significance for the investigations of each dissertation, essential connections among these different dissertations and the open problems in theory of mechanism for parallel robotics are expounded.From the literature search, no dynamic analysis of six DOF (degree of freedom) 6-3-3 parallel mechanism have yet been a reported. At the same time, 6-3-3 parallel mechanism, which is characterized by high accuracy, excellent rigidity, high strength-to-moving-weight ratio, relatively simple controller and parts, have the unique solution of inverse displacement in comparison with the other parallel mechanism. The unique solution of inverse displacement correspondingly make dynamic analysis based on inverse kinematics of the mechanism and its application simple, so the inherent ability of application with the mechanism is enormous. In addition, the academic researches of the 6-3-3 parallel mechanism are combined with system simulation technology, as system modeling and simulation is a basic theory method and important technical means. The paper investigates theory of mechanism about 6-3-3 parallel mechanism, such as kinematics analysis, links interference and singularity analysis, workspace analysis, inverse dynamic analysis and dimensional synthesis. Supplying basic theory and technology support for application of 6-3-3 parallel mechanism to practice is the chief purpose of the paper.Here, after inverse kinematics analysis and simulation of the parallel mechanism are investigated, according to this, links interference, singularity analysis and workspace analysis of the mechanism are researched into, respectively. Finally, inverse dynamic analysis and dimensional synthesis of the mechanism are achieved. The major idea, important method and conclusion in this doctoral dissertation are as follows:1. Kinematics analysis of 6-3-3 parallel mechanism: making use of MATLAB symbolic math toolbox, nonlinear equations, which are based on theory of mechanism and basic geometrical relation of six DOF (degree of freedom) 6-3-3 parallel mechanism, of solving its direct displacement are educed. Then, problem of solving the above-mentioned equations is transformed into nonlinear least-squares problem and the latter is solved using trust region method. Direct displacement solution having clear engineering significance is given, the investigation supplies basic for kinematics calibration of the mechanism.As for inverse kinematics analysis of 6-3-3 parallel mechanism, inverse kinematics equations of six DOF 6-3-3 parallel mechanism, which are based on multi-body kinematics, are educed and condition of unique solution about inverse displacement is presented and proved. Inverse kinematics simulations are programmed by MATLAB software, viz. the displacement, velocity and acceleration simulation of the sliders; the displacement, the velocity and acceleration simulation of the links at center of mass; the angular velocity and angular acceleration simulation of the links; the displacement, the velocity and acceleration simulation of the motive platform at center of mass; the angular velocity and angular acceleration simulation of the motive platform; the angular displacement simulation between the slider and link and the angular displacement simulation between the motive platform and link. It is indicated that force-of-inertia and moment-of-inertia of the mechanism are all function about pose of the mechanism, because acceleration vector and angular acceleration vector with any member are not invariable by simulation and analysis.2. Study on links interference and singularity for 6-3-3 parallel mechanism: a animation simulation method for links interference test of mechanism is presented, and for programming of the animation, motion equations of thirteen members with the mechanism are educed. Then, animation simulation is programmed by MATLAB software. The methodology not only make test of links interference visual, but also limitations of routine test criterion are avoided. It is validated that ball-join collocation of dividing and forming into layers with motive platform of the mechanism decreases possibility of links interference by animation simulation.With regard to singularity analysis of 6-3-3 parallel mechanism, it is proved that influence coefficients matrix and Jacobi matrix about singularity of parallel mechanism are coessential and a new discriminating matrix about parallel mechanism is given. The range of singularity test about 6-3-3 parallel mechanism is extended from a point to general space by method of computer simulation, in other words, the singularity test is realized on condition that orientation and trajectory of center of gravity about motive platform of the mechanism are given. At the same time, this singularity simulation is programmed by MATLAB language. By simulation of example, it is indicated that incomprehensive variation of orientation of motive platform or motive platform and base platform in a parallel relationship is feasible during movement, but fargoing variation of orientation of motive platform possibly results in singularity of the mechanism, and the singularity test should aim at task trajectory of the mechanism when 6-3-3 parallel mechanism is applied to practice.3. Workspace analysis of 6-3-3 parallel mechanism: a computer simulation method for workspace analysis of 6-3-3 parallel mechanism on given orientation condition is presented, the major idea of the method is that it removes impossible pose points from an given three-dimensional-space according to inverse displacement solution of the parallel mechanism and by relating moving range of sliders, limit of ball-joint angle and condition of singularity with animation test of links interference, and displays set of possible pose points in the given three-dimensional-space, namely dimensional graph of its workspace boundary. Above-mentioned work only need to use three-dimensional search method for traversal of the given three-dimensional-space but need not to dismantle links for workspace analysis of the mechanism, in addition, an inferential method for testing of interior cavity about the workspace is proposed by means of section of the workspace. The investigation provides basis for design and trajectory planning of the mechanism.4. Inverse dynamic analysis of 6-3-3 parallel mechanism: the dynamic equations of this parallel mechanism are derived from Newton-Euler approach of rigid-body dynamics. The matrix QR decomposition method is presented to solve the equations, because there are the coefficient matrix of 42 rows and 36 columns in the equations. Then, the inverse dynamic behavior of the parallel mechanism is simulated by MATLAB software, and validity of this dynamic model is verified by means of simulation and comparison in condition of idle load and imposed load. The investigation makes anticipating dynamic behavior of the parallel mechanism practicable, at the same time, expedites its design process, and reduces the development cost before a physical machine is built 5. Application of 6-3-3 parallel mechanism: after the shortcoming of assembly dolly, which is hoister of modular assembly on assembly line of automobile, is analyzed, it is indicated that substituting 6-3-3 parallel mechanism for assembly dolly can realize orientation function in course of automobile assembly. Then, a optimization method of dimensional synthesis based on function matching rule is presented, relating request for hoisting function in assembly line of automobile and 6-3-3 parallel mechanism. Optimization of dimensional synthesis is modeled mathematically, ensuring existence of workspace that covers upon task trajectory. According to result from this optimization model, case of workspace that covers upon task trajectory, case of ball-joint angle that correspond with the task trajectory, case of links interference that correspond with the task trajectory and case of singularity that correspond with the task trajectory are tested by simulation program from chapter two to chapter five, and the conclusion that 6-3-3 parallel mechanism matches absolutely request for hoisting function in assembly line of automobile is arrived at.
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