The Theory And Approach Of The Conceptual Design For The Series Mechanical System By Means Of State Space

The approaches of conceptual design of mechanical system, based on state space model, is researched for mechanism and machine creative scheme in the paper, which is supported by National Natural Science Foundation of China (No.50075012 and 50275016).At first, a generalized basic mechanical unit with single-degree of freedom is defined from the point of view of motion transformation. The input and output state vectors are defined, which are a 6×1 column vector including motion types, the magnitude and spatial orientation, respectively. The state matrices (SMs) can be deduced by vectors operation, that is, the output state vectors multiplied by the input state vectors. And then, a state equation is set up by the relationship among the input and output characteristic vectors as well as the state matrices (SMs). The non-zero element in the SMs characteristic is taken according to Taylor series expansion, which is a transfer function of the basic mechanical unit. The properties of the SMs are discussed and 44 basic mechanical units are listed. The storage models of the basic mechanical units are presented to describe the vast sources and types of knowledge at the conceptual design stage. And a database diagram is created to manage the associated data relations. As a result, the concept of state space for conceptual design of mechanical system is presented, which is new to the literature, based on the set of all state vectors. Meanwhile, the properties of state vectors, which are vectors addition, constant multiplying, reversible driving, zero vectors, are discussed in state space.Secondly, the dual-vector is introduced to descript the essential relation among the input and output characteristic vectors as well as SMs. The coordinate transformation rules, the combination characteristic of the transfer function are discussed. The solution procedure of series mechanical system is deduced by applying dual-vector addition and matrix multiplication. And the mathematical models are obtained. The SMs representation scheme allows a given specification to be decomposed into an ordered sequence of sub-SMs, and attempts to match each sub-SMs with one or more stored basic mechanical units. Thus, the possible solutions are generated.The data structures, the decomposing and the synthesis algorithm are presented according to the established mathematical models and the data base system. Thereby, for a given design specification, the possible solutions can be successfully obtained in computer by means of state space method presented in this paper.In additional, the 3-dimension assembly models based on SolidWorks system are explored to aid designers to conceive the schemes by decomposing direction matrices. Evaluation method is also discussed in order to select the optimal one from the possible solutions. The factors ofevaluation involved in the sewing machine industry are discussed. And the fuzzy synthetical decision method is adopted in the paper.At last, a computer program, based on state space method, the algorithm and database techniques, is implemented. The whole design flow is analyzed, the database structure is described and the system function is introduced. Some practical examples are given to show the capabilities of the approach in a series mechanical system.