The Modular And Reconfigurable Lower-mobility Parallel-serial Structure And Its Basic Theory

The lower-mobility parallel-serial structure draws on the advantages of both parallel and series mechanisms.It not only has a large work space,but also has large stiffness and carrying capacity.However,different configurations of the lower-mobility parallel-serial structure can only complete specific tasks.When the task changes,it is necessary to be replaced by the corresponding type of structure.In order to solve this problem,this paper analyzes the basic characteristics of common lower-mobility parallel-serial structure from the modular point of view,and they are classified and modularized.A new modular reconfigurable lower-mobility parallel-serial structure is proposed,and it is studied from both static and dynamic aspects.First of all,based on the common synthesis and classification methods of parallel mechanism,the common lower-mobility parallel mechanism is divided into four categories.The structure of each class is analyzed in detail and its characteristics are extracted.The motion pairs that make up the parallel mechanism are divided into two categories of basic motion pair and compound motion pair,and five kinds of compound motion pairs which are very useful for modular structure design are analyzed.A series of motion branch types with definite motion characteristics are analyzed,including simple motion branching type,compound motion branch type and2-5 degree of freedoms motion branch with definite motion characteristics,which lays the foundation for the research of modular reconfigurable parallel mechanism.Secondly,based on the analysis of the structural characteristics of the common lower-mobility parallel mechanism,the fixed platform module,the moving platform module,the motion pairs module,the connector module and the connecting rod module are designed.A series of 2-5 degree of freedom motion branches are constructed by the motion pairs module,the connector module and the connecting rod module.Based on the basic theory of parallel mechanism,this paper uses a variety of modules to create a series of modular parallel mechanism.And then,a new modular reconfigurable lower-mobility parallel-serial structure is proposed,and its structural features are analyzed in detail.Based on the spiral theoryand the modified Kutzbach-Grüble formula,the degree of freedom of the structure is calculated and its degree of freedom is 6.Based on the mechanism influence coefficient method,the velocity and acceleration of the structure are deduced,and the mathematical model of velocity and acceleration is obtained.At last,the virtual prototyping model is created by using the 3D drawing software Creo,and the model is imported into the engineering analysis software ANSYS and ADAMS through the data interface.Through the static and kinematic simulation of the virtual prototype model,the static image,the curves of velocity and acceleration of the working platform under different parameter settings and its position change image were given.In this way,the correctness of the mathematical model of velocity and acceleration is verified.All the works included in this thesis will be the foundation work for the application of modular concept in the field of lower-mobility parallel-serial structure.Which has very important and realistic meaning to establish a set of system theory suitable for modular reconfigurable lower-mobility parallel-serial structure.