ساختاربندی دینامیکی از سیستم های تولید توزیع شده

The paper addresses the problem of dynamic structuring of manufacturing systems. The approach presented in this paper is based on the decomposition of manufacturing objectives and the allocation of tasks to autonomous building blocks, i.e. work systems, in a dynamic environment. The allocation is based on a market mechanism that enables the self-structuring and optimization of a manufacturing system by evaluation and selection among competing work systems. The mechanism presented is based on logic relations and constraints. It enables the building of task-oriented manufacturing structures of work systems acting in series and/or in parallel. The approach is discussed in an example in the part fabrication domain.

The rising complexity of products, production structures and processing procedures on one side and turbulent market excitations resulting in growing product variety, individualization and shortening time frames on the other are setting new frontiers for the manufacturing business. Despite research efforts and investments in the context of computer integrated manufacturing the existing manufacturing systems are still predominantly based on the obsolete Taylorian philosophy. Therefore they cannot adequately conform to these requirements because of their structural rigidity, deterministic approach to decision making in a stochastic environment, hierarchical allocation of competencies, and insufficient communication and exploitation of expertise. In order to face these challenges in manufacturing a shift of the existent manufacturing paradigm from deterministic into a new manufacturing prospect considering natural understanding and concern is needed. Several influencing approaches are emerging. Fractal factory [1], bionic manufacturing systems [2], Holonic manufacturing systems [3] and distributed manufacturing systems [4] are some concepts that are making an appearance. Based on these concepts several advances to modeling a manufacturing system in terms of viable structures for more effective mastering of complex and dynamic behavior of the system and its environment are being developed. Various contributions in this direction have been presented and intensively exercised recently [5], [6], [7], [8] and [9]. In the paper an approach to dynamic structuring of manufacturing systems is presented. It is based on the market mechanism which induces a self-organizing principle and is implemented in the system entitled the adaptive distributed manufacturing system (ADMS). Section 2 briefly describes the context of distributed manufacturing systems and related works. Section 3 presents the concept of ADMS and the underlying principles. The case study in Section 4 illustrates the abilities of the system in the part fabrication domain. Particularities of ADMS and distinctions to related works are discussed in Section 5.

In the paper an approach to dynamic structuring of manufacturing systems is presented. It is based on the work system as the building block. The market mechanism governs the dynamic structuring process. The approach is discussed in the part fabrication domain. In ADMS the virtual work system complements an elementary work system. It is an agent which represents the work system in a network. The structuring is task-driven and is based on bilateral, peer to peer communication and coordination between agents with particular reference to time harmonization. The presented structuring process clearly indicates its self-organizing nature driven by self-interest and competition of autonomous EWSs. This concept combines some good properties of hierarchical and heterarchical systems in terms of robustness and stability against disturbances and dynamic flexibility with respect to changes in the environment. The efficiency of control of a complex manufacturing system largely depends on the level of its decomposition. In ADMS it is assumed that the complexity is minimized because the basic building block is the EWS. It consists of a process, a process implementation device and a human subject that is characterized by its competence in relation to the process. It is obvious that human competence cannot be decomposed such that its elements would be divided. That is why the complexity increases if the manufacturing system is decomposed to a greater extent, e.g. very basic elements, such as part description, tool elements, etc. In a traditional manufacturing system allocation of manufacturing tasks to resources is a typical scheduling problem. Scheduling is defined as the planning of n tasks over m resources to be processed at or during a particular time. The issue of planning and control in ADMS is not limited only to classical scheduling but first of all it focuses on the appropriate structuring of the system. Although tasks and time frames are defined, potential resources for task execution are not known in advance. So the point is to build dynamic structures for each order based on a self-organization principle. The resultant structure emerges from the actual state of the system and its environment expressed in constraints. However, there are two issues of particular interest: first, how to balance the autonomy of an individual work system and the potential synergy rising from cooperation, and second, how to control the structuring process if the entire manufacturing system domain is taken into account. Nevertheless the presented approach indicates a viable frame for further investigation in structuring, optimization and control of distributed manufacturing systems.