معماری چند عامله برای کنترل سیستم AGV

Agent is an autonomous, computational entity that can be viewed as perceiving its environment and acting upon it. Agents are event-driven objects that can be integrated in automated manufacturing environments to control certain tasks. In this paper a set of agents (a multi-agent system) is introduced to control an automated manufacturing environment. The architecture includes functions at the manufacturing cell level, materials handling and transport level, and factory scheduling level. Communication between these agents is accomplished by using a relational database (blackboard system). The relational database also integrates the requirements of a manufacturing execution system within the multi-agent task structure, which is unique to this architecture. Manufacturing cell and scheduling agents have been previously described in the literature. Here we focus our attention on the functions of the agents of the transport system, which is composed of a set of AGVs.

Generally speaking an agent is a software (or hardware) object that is capable of doing some specific tasks autonomously. Parunak [1] defines an agent as a “proactive object”. That is, a software entity is an agent if it has the data and code encapsulation of a software object, its own thread of control (making it an active object) and the ability to execute autonomously without being invoked externally (thus proactive rather that reactive). Wooldridge [2] has another definition: “An agent is a computer system that is situated in some environment, and that is capable of autonomous action in this environment in order to meet its design objectives.” The definition of agent that has been followed in this paper is that which Weiss introduced [3]: “Agents are autonomous, computational entities that can be viewed as perceiving their environment through sensors and acting upon their environment through effectors.” This definition is related to Wooldridge's. Sensors and effectors can be either physical (field devices) or software (files or data streams). From these definitions the following characteristics can be introduced for agents:

Agents are computational entities that sense their environment, analyze the events and act upon the environment. Independence, interaction, flexibility and intelligence are common characteristics of agents. This work introduced a multi-agent system architecture that controls different aspects of a manufacturing environment. The material manager and the traffic controller are agents that manage the AGVs and their movements. In addition, the Material Manager Agent also manages the database of the manufacturing execution system, providing a permanent record of shop floor activities. The system of agents has been implemented in C++ and an experimental test has been performed in which the agents control the simulation model of a production facility programmed in Arena. Four different routing methods are introduced that could be used by the Traffic Controller Agent to guide the AGV in the network of links. This experiment showed that using a combination of routing criteria regularly outperformed the use of shortest distance path. The experiment suggests that performance of the routing methods depends on the design of the network and current states of AGVs in the system. Further research will incorporate these considerations in a dynamic selection of routing method by the Traffic Controller.