The Structural Synthesis Method And Application Of Planar Linkage Metamorphic Mechanism

The metamorphic mechanism is a new kind of mechanism with multi-configuration and reconfiguration.Different functions can be realized by changing the number of links,attribute of kinematic pair and degrees of freedom,which can meet the requirements of different working conditions.Compared with the traditional mechanism,the metamorphic mechanism provides a good solution for the contradiction between economy,adaptability and efficiency.As a new field of mechanism studies,metamorphic mechanism has been widely concerned by scholars at home and abroad,and it is the frontier and hotspot in the field of modern mechanism studies.This paper focuses on the basic issues of topology inference structural synthesis theory: configuration description of the metamorphic mechanism,isomorphism determination of planar kinematic chains,the graphic problem of kinematic chain,etc.Meanwhile,size optimization and motion characteristics of planar linkage metamorphic mechanism were analysed.Secondly,a novel holographic matrix method is used to describe the topology and configuration transformation of metamorphic mechanisms.The element of this matrix is the serial number of links,length of links and attributes of kinematic pairs in the kinematic chain.The holographic matrix also implies information such as linkage attribute,joint attribute and loops path.Array code,joint code and link code are proposed to represent the implied information of kinematic chain.And the metamorphic source matrix with evolutionary function is established.Thirdly,two effective isomorphism judgment methods,information comparison method and improved Hamming Number method(IHM),which can realize automatic recognition by computer are designed.A novel joint-joint adjacency matrix description method is used to describe the structure of the kinematic chain with multiple joints.It is unique to describe the structure of the kinematic chain.This method realizes the one-to-one correspondence between the kinematic chain diagram and the joint-joint adjacency matrix.Aiming at the graphic problem of kinematic chain,an automatic sketching method of plane kinematic chain is proposed to display the structure diagram in a matrix.The tree diagram between links and the kinematic pairs is drawn by the Breadth-First Search tree(BFS)algorithm based on the joint-joint adjacency matrix.According to the minimum crossover rule,the row and column Numbers of the matrix are transformed into a graphical adjacency matrix.And a new type synthesis method for kinematic chain with multiple joints is presented.Fourthly,the configuration synthesis method of metamophic mechanism is introduced.The transformation mode of metamophic mechanism is summarized,and several kinds of structures of metamorphic cell with single kinematic pair are designed.The Assur group with 1 degree of freedom contains metamorphic cell structure into metamophic cell group.According to the design requirements of brick-pressing machine,a 7-bar brick-pressing metamophic mechanism was synthesized.Then,the 2-dof five-bar linkage metamorphic mechanism(RRRRP)is taken as the research object.The multiobjective function of metamorphic mechanism is established according to the track optimization function of different configurations.The teaching-learning-based optimization(TLBO)algorithms is used to optimize input parameters of metamorphic mechanism.However,the impact and vibration of configuration transformation is unavoidable.The nonlinear dynamic Lagrange equation of metamorphic mechanism with flexible joint and Hertz collision mode is established.The test platform is made to analyze the vibration problem caused by configuration transformation.Finally,the multidegree of freedom metamorphic hand is taken as an example.According to the design requirements,a multidegree of freedom metamorphic hand is designed by using the innovative design method of metamorphic mechanism.According to the comprehensive design rules of metamorphic mechanism,the appropriate kinematic chain selected from kinematic chain atlas library is turned into the mechanism.The finger mechanisms with the two joints are added to the metamorphic clip to become the metamorphic hand by the mechanism combination method.A prototype was made and the feasibility of the theory was verified.