IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS, VOL. 3, NO. 1, FEBRUARY 2007 21 A New Model for Autonomous, Networked Control Systems Gerhard Pratl, Member, IEEE, Dietmar Dietrich, Gerhard P. Hancke, and Walter T. Penzhorn, Senior Member, IEEE Abstract—Existing communication utilities, such as the ISO/OSI model and the associated automation pyramid, have limitations re- garding the increased complexity of modern automation systems. The introduction of profiles for fieldbus systems, or field-area networks (FANs), was an important innovation. However, in the foreseeable future the number of FAN nodes in building automa- tion systems is expected to increase drastically. And here the authors see an opportunity to revolutionize the operation of intel- ligent, autonomous systems based on FANs. The paper introduces a system based on bionic principles to process the information obtained from a large number of diverse sensors. By means of multilevel symbolization, the amount of information to be pro- cessed is substantially reduced. A symbolic processing model is introduced that enables the processing of real world information, creates a world representation, and evaluates scenarios that occur in this representation. Two applications involving human actions in a building automation environment are briefly discussed. It is argued that the use of internal symbolization leads to greater flexibility in the case of a large number of sensors, providing the ability to adapt to changing sensor inputs in an intelligent way. I. INTRODUCTION AND MOTIVATION N ATIONAL and international standardization organizations such as ISO, IEC, SAE, CEN, CLC, and others [1] have developed standards for automation protocols for the transmis- sion of information from several signal sources through a single communication system. These field-area networks (FAN) ef- ficiently link sensors, actuators, and controllers by means of single communication medium. One of the first organizations to define such a protocol was the Society of Automotive Engineers (SAE) (a technical body of military and industrial members in the U.S.) in 1968 [2]. This protocol was the fieldbus MIL 1553, which was first integrated in the Air Force F-16 and the Apache AH-64A attack helicopter. It is still a communication base in avionic systems. Such simple two-wired transmission principle played an in- significant role in industry at that time, and was of very little interest to the research community. Only in the late 1980s did industry realize that these bus systems are a very efficient and economical way to collect process data, and to control sensors and actuators. CAN and PROFIBUS were among the first FANs, Manuscript received May 23, 2005; revised December 7, 2005, May 14, 2006, and December 14, 2006; accepted December 23, 2006. Paper no. TII-05-12- 0069.R2. G. Pratl and D. Dietrich are with Vienna University of Technology, Vienna, Austria (e-mail: pratl@ict.tuwien.ac.at). G. P. Hancke and W. T. Penzhorn are with the University of Pretoria, Pretoria, South Africa. Color versions of Figs. 2 and 4–12 are available online at http://ieeexplore. ieee.org. Digital Object Identifier 10.1109/TII.2007.891308 and are still very successful to this day [3]. These principles were subsequently adopted in the OSI model defined by ISO. Initially, only two or three protocol layers were defined, because at the time no need was seen to define layers three to seven, due to the nature and constraints of the applications. However, industry soon realized the huge possibility of FANs and defined various other types, with characteristics dependent on the specific application. And in the specific case of building automation it was necessary to define protocols consisting of all seven layers, because the number of sensor nodes is typically very large. At present, buildings with 50 000 or more networked nodes are not uncommon. Obviously, this has lead to a dramatic increase in the complexity of such systems, with the associated difficulty of handling the data in such enormous systems. Initially, the biggest challenge was to bring together the var- ious industry segments that had previously never really commu- nicated with each other. For example, the industry of heating, ventilation, and air conditioning (HVAC) had previously seen no need to communicate with the industry of sunshade systems, or with plumbers, etc. Additionally, interoperability between de- vices from different vendors was a major issue, which is dis- cussed in depth in [4]. In response, the user groups of the var- ious FANs defined profiles, often referred to as the eighth level of the ISO/OSI model. The number of applications where fieldbus systems form an integral part is constantly increasing. New technologies, re- quiring the networking of electronic components, are emerging. Nanotechnology is aiding the development of new types of sensors and actuators with totally new characteristics, at a minimal cost. Technologies such as smart dust, wearable electronics, elec- tronic grains, ubiquitous computing, grid-computing, ambient computing, smart personal objects technology, and body area networks are all new scientific directions based on, or utilizing, fieldbus systems. In the foreseeable future, the number of FAN nodes in building automation systems is expected to increase drastically. It is precisely in this area that the authors see an op- portunity to revolutionize the operation of intelligent systems based on FANs. A compelling question is how to integrate, operate, and main- tain such future fieldbus systems consisting of a very large num- bers of network nodes. Hence, there is a growing need to model huge fieldbus networks. Fig. 1 depicts symbolically the evolu- tionary steps from simple RS232 communication, through low- power bus systems such as the I C-bus, to fieldbus systems whose communication protocols follow ISO/OSI model, and the subsequent addition of profiles to the ISO/OSI stack. Initial models focused only on the networking aspects of the units. More recently, models have emerged that integrate parts 1551-3203/$25.00 © 2007 IEEE