An Automated Approach On Type Selection And Dimensional Synthesis Of Symmetrical Parallel Manipulator

Symmetrical parallel manipulators have the advantage of isotropic, high load bearing and high stiffness; they are wildly used in the fabrication of aviation thin-wall components. Our laboratory has designed a huge milling equipment based on parallel manipulator, however, the key devices, Exechon and Tricept, are both exclusive to the foreign patents, which are much more expensive for applying in practice. Therefore, a new manipulator owned by ourselves is needed to break the monopoly of foreign patents.The design of new manipulator needs innovation in mechanism, which involves topological analysis, type selection and dimensional synthesis. Due to the spatial complexity of parallel manipulator, the current method mainly rely on experience and manual analysis, which lead to the incomplete traverse of topology, with no automatic method in type selection and synchronous optimization in dimension and structure parameter. And there is not a set of computer aided theory or formula to design and optimize the parallel manipulator from topology to dimension and structure parameter till now. This paper takes the symmetrical parallel manipulator as case studies, and makes an initial trial in the automation of type selection and dimensional synthesis.An automated approach on type selection and dimensional synthesis of symmetrical parallel manipulator is designed. A digital model based on graph theory is set up, and type selection and dimension-structure parameter auto-optimization based on PSO method is realized, which provides a quick and effective approach for parallel mechanism design. The main achievement of this paper is summarized as below:1) A graph model and its digital model on symmetrical parallel mechanism are set up; Map mechanism type to type matrix; DOF analysis and topological traverse based on generalized adjacent matrix; Automatic topological traverse for the 3-DOF and 6-DOF symmetrical parallel mechanism.2) A programming method for the kinematic pair based on kinematic screw is set up; Automatic calculation for arbitrary mechanism speed jacobian matrix is realized using screw theory. Type selection model is built using PSO method; An example is given to illustrate the method mentioned above.3) Considering the load factor, a synchronized synthesis method for dimension-structure parameter of parallel manipulator is designed A general procedure for the synchronized optimization model is built, by using nested PSO method; Based on KED theory, finish the Tricept optimization by using the above model.This paper has introduced a set of automated approach for the type analysis and dimensional synthesis of symmetrical parallel mechanism, which can automate the process from topology to dimension and structure analysis, the results of which can provide valuable reference for the designers or can be utilized in practice directly. This platform can provide solutions for the design and optimization of new parallel manipulator, and improve efficiency for the mechanism type design and analysis.