Theoretical Research On Parallel Robotic Mechanisms Based On Single-Opened-Chain Units

Based on the principle of the composing of sub-chain single-opened-chain and ordered single-opened-chain, this dissertation presents a profound and systematic research on parallel mechanism. By using the single-opened-chain unit to describe the topological structure of the mechanism, the dissertation reveals the essential relationship between topological structure and kinematics and dynamics of parallel mechanisms. The research intends to achieve the systematization of parallel manipulators theory and to provide a solid theoretic foundation for parallel mechanism innovation.Firstly, the definition and calculation formula for constraint degree of sub-chain single-opened-chain are presented to reveal the quantitative relationship between constraint degree and over-constraint of the mechanism, which indicates that a totally symmetrical mechanism with four or five degrees of freedom must be a over-constraint mechanism. And a topological structure synthesis method based on sub-chain single-opened-chain is proposed to demonstrate all possible topological structure types for a parallel mechanism with 3-6 degrees of freedom without over-constraint. These types are classified with topological characteristics such as symmetry, coupling degree, decoupling control of the mechanism. Some new topological structures of parallel mechanism are synthesized, of which includes a sub-chain with serial inputs.Then, a new numerical method named ordered single-opened-chain method for directed kinematics of parallel mechanism is presented based on the principle of composing of ordered single-opened-chain. Mathematical models for mechanism displacement, velocity and acceleration analysis are built on the base of constraint relationships between ordered single-opened-chain units, which are coherent with the mechanism topological structure. This method needs no skill in dimension reduction to obtain kinematics equations with least dimension that equals to the coupling degrees of the mechanism. The method reveals the essential relationship between the topological structure and kinematics of a parallel mechanism. The analysis results...