Research On Kinematics Behaviors Of 2-DOF Decoupled Spherical Parallel Mechanisms

Decoupled spherical parallel mechanisms are a type of useful and applicable parallel mechanisms in engineering. In-depth investigation and comprehensive analysis to this type of mechanisms is the foundational key work for innovation and utilization of mechanical sysytems.Aimed at analysing and developing 2-DOF decoupled spherical parallel mechanisms, this dissertation systematically deals with key issues of the mechanisms design, such as mechanism configuration, kinematics analysis, relations between linkage length and mechanism performances, and movement error analysis, etc., by employing mechanism theory and computer simulation techniques. The creative contributions may be summarized as follows.1. The general configurations of two types of 2-DOF decoupled spherical parallel mechanisms, termed respectively as RR &ΠLRand , are given. For the mechanism, in order to meet the workspace requirements, two types of improved mechanism are presented by combining structure design and kinematics design.2. Aimed at the mechanisms of RR &ΠLRand , kinematics analyses are conducted and the kinematics equations are also established, thus deriving and formulating the direct and reverse solutions of position, velocity and acceleration.3. The workspace and singular configuration of those two mechanisms are analyzed, and their practical workspaces are also given.4. The spatial models of the mechanisms are established by employing the non-dimensional method to design mechanisms. The methods of describing the performance indexes of velocity, load-carrying capacity and stiffness are given. Also, a novel method to describe the mechanism's performances by using the mean value of performance indexes and its fluctuation is proposed. And the performance spectrum diagrams are drawn in the form of contour series. In addition, the effect of linkage length on mechanism performance is also studied, and the relations between linkage length parameters and the mechanism performance are therefore quantitatively given. And the effective ranges of the non-dimensionally designed linkage length are determined under different requirements for performance indexes.5. The closed-loop equations of the mechanisms are given by employing closed-loop increment method. After establishing the constraints relations among the original linkage parameters errors, the relations between the movement error of the moving platform and the linkage length are analyzed by using the position and pose error models, velocity error models and acceleration error models.The work in this dissertation will lay a solid foundation for developing the configuration design theory of parallel mechanism and for boosting application of spherical parallel mechanism in engineering.