| As one of the most important branches of modern mechanics,hybrid mechanisms have been widely used in aerospace,medical rehabilitation,industrial robots and other engineering applications.The type synthesis of parallel and hybrid mechanism is the key link of product innovation,and many kinds of type synthesis theory and method system have been formed.In the process of type synthesis,the query of the mechanism structure conditions is complex,and the degree of visualization is not enough.Four degree of freedom hybrid mechanism has been applied in real life,but its configuration is not rich enough.In this paper,based on GF set theory,a visual synthesis method for four degree of freedom hybrid mechanisms is proposed.Firstly,the basic theory of GF set and the visualization method of database are analyzed.Various types of comprehensive theory are compared,GF set theory is chosen for type synthesis.The basic definition,expression and classification of GF set are expounded;the intersection and summation rules of GF sets with pure rotation,pure movement,simultaneous rotation and moving features are illustrated.The analysis of the database software tools are analyzed,the Access is selected as software tool for visual type synthesis of hybrid mechanisms.Secondly,the synthesis steps of the parallel unit,which is the important components of four degrees of freedom hybrid mechanism,are described.Each configuration and its corresponding geometric conditions are listed based on primitive branched chain.Based on GF set theory,the configuration and its geometric conditions are expressed in the form of database strings,and the visual interface is generated.By means of the rotation axis migration theorem,kinematic pair substitution and structural transformation,the branched chain of the parallel unit is transformed in configuration,so as to generate different kinds of branched chains.The methods are provided for the diversity of parallel unit,and the foundation is laid for the type synthesis and visualization of the hybrid mechanisms.Then,the steps of four degree of freedom hybrid mechanism synthesis are presented.The expression of GF sets of parallel unit and series unit in hybrid mechanisms with the type of 2T2 R,1T3R,3T1 R are obtained by the summation operation rule.Based on the type synthesis of parallel unit,branched chain transform and series unit motion transform,parts of the hybrid mechanism configuration are enumerated;the models are built by SolidWorks.Finally,visualization of the four degree of freedom parallel mechanism is achieved.Taking the types of 2T2 R hybrid mechanism as example,the configuration and geometric conditions are searched through the visual interface,and the detailed design of the configuration is explained in detail,and the three-dimensional model is established.The accuracy of the model is verified by the method of GF set inverse operation of each type. |
