The Characteristic State Space Theory And The Automated Conceptual Design Methodology For The Mechanical System

A new methodology for the conceptual design of hybrid combined mechanical system based on the characteristic state space approach is developed. The goal is to conceive the appropriate hybrid system given only the kinematic function posed in the problem specifications. This research supported by the National Natural Science Foundation of China under Grant No. 50475154.The key enabler of the conceptual synthesis is the method of capturing kinematic behavior. A new characteristic state analyzing method for Multi-DOF basic mechanism units (BMUs) is proposed. Firstly, the input and output characteristic state vectors are established through the generalized kinematic functions according to the motion transformation process of the specific mechanisms. Based on Taylor series expansion, the phase step function converts kinematic transformation units into characteristic transformation units and disengages the influence of detailed dimension. Then the characteristic state equations are established by motion relationship between the multiple inputs and the outputs,which including characteristic transformation matrices and the characteristic state vectors. Meanwhile, transfer relationships of the characteristic state equations are studied, from which the properties and variations of the function characteristic are obtained. Thus the Multi -DOF BMUs are identified, classified and represented qualitatively from various perspectives.Characteristic state analysis method is used to describe the behavior of the multi-loop mechanism. For mathematical modeling of the compound mechanism units, the transformation of the kinematic characteristic state from the relative motion to the absolute motion for the moving links is investigated and the corresponding characteristic properties are intensively addressed. Using the relationship of the jointed links, the characteristic vectors compounded formula deduced serves as to achieve the characteristic state functions for the absolute motion transformation of the additional mechanism. The gear-linkage case studies are included to illustrate the methods and the corresponding generalized procedures concluded.In sharp contrast to the related research in conceptual design, the combination patterns are investigated and related this to the behavior of mechanisms composed of BMUs. The generalized characteristic state model sets are established according to the classified basic combination units(BCUs). And then, the generalized characteristic state equations are derived and the mathematic models of variety combination patterns are set up. Meanwhile, the algorithm of transferring the combination system into the operation of the generalized characteristic state vectors is analyzed corresponding to the varied combination patterns. Thus, the reference regulation and the decomposition method provide the hybrid system synthesis procedure further.The mathematical model of the hybrid combination system facilitates the characterization of the BMUs and BCUs, transformation of problem specifications, decomposition into sub-problems, and the ability to search for alternate solutions. The new mechanical system can be automatically generated, in particularly, to generate alternate mechanism concepts by combining BMUs with the aid of the BCUs. The characteristic state space is estabilshed by transversing the design space elements to the state space, and the properties as well as the space relationship of the transfered elements are analyzed. Additionally, the operation rule and the metric form are studied elaborately. The characteristic state space graph theory and the routing model between the random dual points in the space are established. Furthermore, with the manipulation of the dual vectors, the mathematic synthesis model is presented and the groundwork is laid for the conceptual design in the characteristic state space.To fine tune the automated decomposition and the synthesis algorithm, the design knowledge transformation technique is established through the analysis of the mathematical model of the BMUs and the BCUs. The rational information storage organization and associated knowledge base management, which including the relationships of the dataflow and the manipulation strategies for the combined pattern are essentially investigated. The effectiveness of the methodology depends on the quality of the available decomposition formulation, which directs the creation of solvable sub-problems based on the mapping between the state space and the function space.A number of design scheme alternatives can be generated from a given specification, which employs the characteristic search in an applicable library of BMUs and BCUs. It can be shown that the suggested design examples are compact and compatible with the general design principles.