Aprroach To Intelligent Assembly Planning And Its Related Key Technologies

Assembly planning is an important componet of the advanced manufacturing technologies such as agile manufacturing, virtual manufacturing. It attracts concerns from both academic and industrial circles, because it meets the manufacturing's need of responding to market changing fast. Assembly planning aims to identify and evaluate the different ways to construct a mechanical object from its components. The problem can be formulated as follows: given a geometrical and technological description of a product, find an assembly sequence that satisfies the precedence relations between operations and meets certain optimization criteria. With the help of assembly planning, the designers can evaluate the assembly schema conveniently during the product research and design process, to find the assembly defects and revise them as early as possible. In assembly planning, the designers analyse a product without actually making a physical prototype of the product, that means the design is not yet created in its final form but that only a geometric representation of the object is presented to the user for observation, analysis and manipulation. This virtual prototype does not necessarily have all the features of the final product but has enough of the key features to allow testing of the product design against the product requirements. Assembly planning has profound significance in meeting rapid product development (RPD) requirements, increasing global competition for industries, especially when it is a part of the concurrent engineering and computer integrated manufacturing practice.This work is supported by the Special Funds for Major State Basic Research Program (973) of China under grant 2002CB312106. Our research focuses on automatic generation of assembly sequences from assembly model and assembly task allocation according to assembly conditions.On the basis of analyzing the background and history of assembly planning, Chapter 1 reviews the state of the art in assembly planning, then points out the objective of the thesis and presents the research frame.Chapter 2 presents the architecture of KBAPS (Knowledge-based Assembly Planning System). Then it discusses the foundational theory of assembly model and how to establish it. The role of assembly model taking in planning is presented. After analyzing the typical assembly models and the process of top-down design, it presentsan approach to build the product model at multiple LOD (Levels of Detail) model and CSBARM (Connection Semantics Based Assembly Relational Model) that integrates both geometric and non-geometric assembly data.Chapter 3 is the key of this thesis. It focuses on the automatic generation of assembly sequences, there are three ways to construct plans for a CSBAT: (1) by retrieving the typical base, (2) by retrieving the standard base, and (3) by geometric reasoning. A novel approach for assembly sequence planning using directed-connector and a case-based approach to generating sequences are proposed. After analyzing the characteristics of directed-connectors, directed-connector knowledge is exploited for assembly sequence planning.In Chapter 4, a novel approach to find the feasible disassembly direction set is presented by applying discrete spherical algorithm to analyzing assembly constraints. Hie global disassembly direction is finally determined by verifying the disassembled part being free from interference on its removal path.Chapter 5 presents an approach for cooperative assembly task planning for a multiple manipulators environment to improve the flexibility and reliability of the automated assembly system. The outline of the agent-based and cooperative assembly task planning system is presented. For the sake of mmirnizing the makespan, the algorithm of task planning takes into account not only the assembly processing time but also the time needed for the manipulators to change tools.In chapter 6, Some applications of assembly planning are described to verify the validity of the algorithm.In chapter 7, all achievements of the thesis are summarized and the future research work is sketched out.