A knowledge intensive multi-agent framework for cooperative/collaborative design modeling and decision support of assemblies

Abstract

Multi-agent modeling has emerged as a promising discipline for dealing with decision making process in distributed information system applications. One of such applications is the modeling of distributed design or manufacturing processes which can link up various designs or manufacturing processes to form a virtual consortium on a global basis. This paper proposes a novel knowledge intensive multi-agent cooperative/collaborative framework for concurrent intelligent design and assembly planning, which integrates product design, design for assembly, assembly planning, assembly system design, and assembly simulation subjected to econo-technical evaluations. An AI protocol based method is proposed to facilitate the integration of intelligent agents for assembly design, planning, evaluation and simulation process. A unified class of knowledge intensive Petri nets is defined using the O-O knowledge-based Petri net approach and used as an AI protocol for handling both the integration and the negotiation problems among multi-agents. The detailed cooperative/collaborative mechanism and algorithms are given based on the knowledge objects cooperation formalisms. As such, the assembly-oriented design system can easily be implemented under the multi-agent-based knowledge-intensive Petri net framework with concurrent integration of multiple cooperative knowledge sources and software. Thus, product design and assembly planning can be carried out simultaneously and intelligently in an entirely computer-aided concurrent design and assembly planning system.

Introduction

In conventional mechanical systems and assemblies design approaches, designers make the decisions at an early stages in the development cycle. The individual parts are then designed independently with little interaction, due to the lack of a unified representation, simulation, and synthesis framework. Modern mechanical systems and assemblies require a more flexible design strategy in which heterogeneous system components are designed in parallel using specialized models. The designer makes partitioning decisions after first evaluating alternative structures with respect to function, performance, process plan programmability, recurring development costs, manufacturing/assembling costs, reliability and maintenance, etc. This strategy, called co-design, requires tools that support unified representation, heterogeneous models and simulation and synthesis. The pilot environment for computer-aided assembly oriented design should consider many aspects including assembly design and modeling, assembly process planning, assembly system design and layout planning, assembly evaluation and simulation, and task plan execution application families. Fig. 1 depicts the pilot assembly oriented design environment considered in this paper.

The concurrent integration of design and process planning for rapid development of new product variants is an important area that needs teamwork [15]. Due to its complexity, a knowledge intensive or hybrid intelligent integration would be strongly recommended. In recent years, distributed and heterogeneous systems for product and process design are gaining better acceptance as a result of the development of distributed artificial intelligence (DAI) and hybrid intelligent systems. It is well known that Petri nets are a very powerful graph-based representation, modeling, and analytical tool for systems and they are also easy to use and interpret. Petri nets with their high-level and hierarchical generalizations in nature possess capabilities for modeling all the features of distributed design systems in a concurrent and collaborative environment. These include complex local and global time dependencies, concurrency, asynchrony of activities, restrictions imposed on computing resources, and heterogeneity of these resources. Furthermore, its ease of visualization, execution, and evaluation are most appealing to the design and planning process. Furthermore, they possesses the potentials to be incorporated into AI framework with unified knowledge representation, automated reasoning, and decision making [1]. Therefore, they can be used for knowledge intensive modeling and simulation of concurrent environment.

The aim of this paper is to explore the application of Petri nets in concurrent intelligent design for product-assembly process. A methodology and framework using knowledge intensive Petri nets will be developed for concurrent intelligent integration of design and assembly planning.