(A) layered model for performance evaluation of PROFIBUS networks

Abstract

We develop a layered model for performance evaluation of PROFIBUS networks. The performance of a PROFIBUS network for a manufacturing system is determined by the protocol stack, the network configuration, the application program, and the dynamics of the job flow. We thus propose a three-layer model that consists of a job flow model, a message model, and a network model. The job flow model generates commands that request data transmission between the network nodes to achieve manufacturing tasks. Each time when an event occurs in the job flow simulation model, appropriate commands are generated. The message model translates each command into a sequence of PROFIBUS messages. The sequence depends on how the command is implemented in the application program using the PROFIBUS communication services. The message model also initiates or aborts transmission of cyclic PROFIBUS messages as needed in the application program. The network model maps the messages into the lower-layer messages according to the PROFIBUS protocol specifications. We develop these models using an object-oriented modeling framework. We discuss modeling issues and strategies for each layer model. We also present experimental results for an application to a PROFIBUS network for a flexible manufacturing system.