3.2 Analysis of the assembly characteristics of machine tools
The assembly features of the module make it possible to assemble a large number of standard modules and a small number of expansion modules to meet the requirements of the user. Figure 3 is an analysis of the assembly features of the machine tool. The contact feature refers to the information of the module with the assembly relationship, such as the module name and its topological relationship. The assembly geometry and azimuth features are the core of the assembly. To ensure the consistency of the assembly model and the module model, the specific content is partially extracted from the module model. The reason why the module model information is not fully accepted is because the module model is versatile, so information redundancy is inevitable in its design.
Figure 3 Analysis of the assembly characteristics of the machine tool
4 system model creation and implementation
4.1 Model structure
Establish a system model based on the feature hierarchy tree.
To implement computer support for the model, the model must satisfy:
(1) Describe the readability of the method. Readability requires both a proper understanding of the content and a formal program that can be understood by the computer, which is conducive to the generation of computer applications. Use formalized data and normalized language to describe and eliminate ambiguity.
(2) The integration of the description mode. Defines all product data throughout the product lifecycle to provide a unique representation of the characteristics of the system model.
(3) One-time definition of information. Minimize the redundancy of integrated information, with each information element defined only once. The integrated resources are composed of extracting data from different stages and different applications, sorting and classifying these resources, and eliminating redundancy.
4.2 Expression of the model
From the model structure of the system, the model is encapsulated and inherited. There are three ways to exchange data in the system: dynamic working file format, shared database mode, and shared knowledge base.
In order to realize the integration of information, it is necessary to express the unified data structure of the module model and the machine tool assembly model. It can be seen that the system model is very similar to the tree structure in the computer field, so the expression of the model in the computer is in the form of a multi-fork tree. For the convenience of operation and storage, it is converted into a binary tree form, and its storage uses chain storage. Each information set of the model constitutes a node of the binary tree; the left subtree points to the child information set node of the node with inheritance and affiliation, and the right subtree points to the sibling information set node of the node with the same level relationship; The model is the root of a binary tree. Figure 4 shows the binary tree representation of the model by taking the motion model in the module model as an example.
Figure 4 Binary tree expression of the motion model
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