Configuration Synthesis Of Parallel Mechanisms With Metamorphic Joints

Metamorphic parallel mechanism has the advantages of variable topology structures,high stiffness and rapid dynamic response.Currently,the parallel mechanism with specific metamorphic function is obtained by replacing the tranditional joints with metamorphic joints.Less work has been done to investigate the systematic configuration synthesis methods of metamorphic mechanism parallel.Therefore,a configuration synthesis method of metamorphic mechanism is proposed based on analysis of constraint variation features and structure design of metamorphic joints.The main research contents are as follows:(1)The mathematical descriptions of variable structure mechanisms is proposed.Based on the traditional description of topology of mechanisms,a sequential six-tuple is presented to describe information of mechanism,such as functions,properties,interactions and relevance of links.The mathematical expressions are provided to identify the relationship of different variable structure mechanisms including reconfigurable mechanism,variable topology mechanism,metamorphic mechanism.Moreover,the mathematical descriptions of configurations of mechanism,such as stable configuration,variable structure configuration,metamorphic configuration,etc.are obtained to determine the conditions of configuration transformation of mechanism.(2)The design catalogues of metamorphic joints are built.Metamorphic joints are the crucial structures for changing topological characteristics of metamorphic mechanisms.The design of metamorphic joints is a challenge for the configuration synthesis of metamorphic mechanism.Adopting arithmetic operation of constraint functions,the constraint variation features of metamorphic joints in the processes of metamorphosis are described for three metamorphic ways respectively,namely orientation changing,number changing,type changing,etc..Based on summarizing and designing the corresponding metamorphic structures of general joints,the design catalogues of metamorphic joints are built by classifying and compiling the design information,including the ways of topological variations,constraint variation features,and structures of metamorphic joints.(3)The configuration synthesis of metamorphic parallel mechanisms with metamorphic joints is proposed.The GF sets theory of parallel mechanism is used to design the sub-configuration parallel mechanism.The "Similarity" analysis method is applied to select combination schemes of sub-mechanisms.In addition,analyzing the constraint variation features and designing the corresponding structures of metamorphic joints based on the design catalogue of metamorphic joints,the metamorphic mechanism can be synthesised eventually.(4)A new metamorphic parallel manipulator is designed.Mutiple configuration schemes of a new metamorphic parallel manipulator are designed by the above configuration synthesis method of metamorphic parallel mechanisms.The effectiveness of the proposed configuration synthesis method is verified finally.