Abstract
The development of biochemical engineering towards integrated bioprocesses has influenced the demands of the applied control environment. In particular, in research applications, where the automation structure often has to be flexibly adapted to different plant conditions, new communication techniques like fieldbus networks are required to handle the huge flow of information. In the pilot plant of GBF we use a CAN (Controller Area Network)-based fieldbus network to interconnect the decentralized process control computers under real-time conditions. In this contribution, the implementation and the performance of the CAN fieldbus in a hierarchical automation concept is outlined. While some bioreactors and downstream devices are connected to the network directly via AD/DA converter by a so-called mini-module, additional reactors are automated with decentralized process computers which act as bus nodes with full functionality. The CAN application layer (CAL) enables an open communication from CAN-modules of different manufacturers. The CAN-message specifications (CMS) allows for the description of the data transfer between the individual user programs via a client/server model. In addition, a database is available, where all objects in the network - representing measured, controlled, or on-line calculated variables — are specified. The experience gained with the presented application has shown that the use of a CAN fieldbus in connection with higher protocol layers offers a flexible and transparent functionality for integrating bioprocesses into a plant-wide information network while good real time characteristics are maintained. The installation of the fieldbus and the database has led to a minimum cable expenditure, a better user acceptance of control facilities, and an increased service effective in the pilot plant.
Published Version
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