Journal of Computing and Information Technology - CIT 10, 2002, 2, 115–124 115 Future Directions of Internet-based Control Systems M. Coccoli and A. Boccalatte University of Genova — DIST, Department of Communication, Computer, and Systems Science Recent advances in object-oriented, clientserver tech- software system with full network capabilities nologies, and the Internet are supplying the technology specifically designed for embedded real-time enablers needed to provide a uniform information archi- tecture that can be used to build software architecture control systems Open Control System . Such allowing the inter-operation and integration of a wide set a system will exploit the most advanced and of diverse applications. Moreover the emerging standards promising concepts and technologies, aiming start playing a significant role in the shaping of automa- to provide a real-time process control engine tion architectures in enterprises. The inclusion within a classical control system of Internet-related technologies running on standard platforms both hardware and open distributed application concepts would give and software commercial off-the-shelf, COTS the present system compliance with current and future thus avoiding the disadvantageous use of pro- technological trends. At the present time, in the field of the industrial automation, real-time embedded control prietary ones. The entire system will strongly systems more and more need Internet connectivity for leverage on Web related technology, field-bus operations of remote plant administration, training, and device networks , control networks, and stan- supervisory activities. In this paper the state of the art in dard communicationinterfacing methods, thus embedded control systems is presented within the field of industrial automation applications, and the technological enabling the system to be used within Com- scenario is discussed, followed by the trend for the ponent Based Solution Assembly CBSA ar- evolution in process control systems. Guidelines for the design of innovative, thus competitive control systems are suggested. A case study is presented, outcome of an EC project in which one of the authors is involved, where a remote maintenance system is realized. Keywords: networking, real-time, control systems, embedded systems. 1. Introduction In this paper, the state of the art and future di- rections of novel Internet-based control systems will be presented together with some guide- lines, which should drive software and hard- ware architecture design for the next genera- tion of process control systems. The proposed target will be achieved by describing a set of components which, joined together, can enable the development of a really open and flexible Fig. 1. Control systems’ layers. This work has been supported by the European Commission Directorate-General Information Society, contract No. IST-2000-28318 NEOXITE. 116 Future Directions of Internet-based Control Systems Fig. 2. The evolution of process control systems. chitectures or together with Laboratory Infor- tion of truly advanced Flexible Manufacturing mation Management Systems LIMS . Indeed, Systems FMS . Moreover, the inclusion of In- adoption of field-bus technology will provide ternet technology will ensure full compliance a flexible and open communication layer for of the system with current trends of informa- the link between the control level and the de- tion technology IT within process industry vices’ one as it is sketched in Fig. 1. Such towards future control systems architectures, a system, devoted to an effective plant con- where devices will more likely become smart trol, will also embed and demonstrate opti- and autonomous, also embedding web servers misation by means of advanced mathematical as well as connection services. tools, thus providing a modular, flexible, cus- tomisable, and self-sufficient control system for The proposed technical and conceptual scenario even complex processes and applications, out- can be graphically summarised as it is repre- lining the main features for the future genera- sented in Fig. 2, in which an interesting trend is Fig. 3. The area of process control. Future Directions of Internet-based Control Systems 117 presented, within process control systems, that, integration between these layers cannot be so at first glance, could be considered quite “vi- smooth. A variety of communication protocols, sionary”, but, on the other hand, IT researchers proprietary technologies, and non-standard in- believe it is more likely achievable within five terfaces exist and are widely used. For exam- to six years. In Fig. 3, the project context is ple, current systems use very different networks highlighted, that is the automation level which typology for the interconnection of their three will be the main target for the proposed con- main layers. Such networks, usually propri- cepts. Process industry community is increas- etary, may show very different characteristics, ingly looking for easier and seamless integration from both functional protocols and physical between these layers, but minimising, even if electric signals points of view, therefore im- not trying to completely skip, the development peding the desired smooth integration and in- of custom code. On the other hand, end users are formation flow throughout the above layers. also wishing and expecting modern integrated Today, only the network systems in the upper plant systems embedding complementary, and level can be considered close to the standard, usually customerprocess customisable, tools because of the increasing use of Ethernet and for optimisation such as statistical process con- the success of TCPIP. The other two networks, trol and advanced control algorithms e.g., sim- specifically the device network and the control ulation tools, on-line parameter tuning.At network, are still based on more or less propri- present, in most cases, such tasks must be per- etary protocols, even though during the past few years several different field-busses have been formed by external systems e.g., mathemati- cal models and observers running on dedicated adopted, some of them internationally standard- ised, some other being “de facto” standards. PCs as it is not possible for them to be executed on PLCs or even on some DCSs. Currently available technology provides great A control system designed and developed ac- potentiality, which is confirmed by the increas- cording to the guidelines outlined within this ing importance of IT within modern and com- paper will be able to perform standard as well petitive enterprise systems. As regards plant as advanced control mechanisms by means of systems, over the past years the focus has moved a main control engine, including both local from the hardware to the software, mainly due to the achievable system flexibility. Migration of and remote human-machine interfaces HMIs , standard networking capabilities, and web ser- control capabilities from dedicated devices and vices. The resulting system will definitely rep- systems e.g., PLCs and DCSs towards stan- dard architectures is fully in line with the men- resent a step ahead towards next generation of tioned technological trend. Moreover, increas- process control systems. After this short intro- ing reliability and performance offered by stan- duction, the state of the art for real-time control dard PC platforms are gaining ground. There- systems will be outlined in Sec. 2. Needed fore, what could be considered visionary some innovation will be enumerated in Sec. 3 while years ago, will be more likely the state of the the migration from PLC to standard PC archi- art within three to four years. Convergence of tecture will be described in Sec. 4. Some tech- different functionality towards a single piece nical highlights will be discussed in Sec. 5, and of hardware is, as a concept, increasingly ac- conclusions will follow thereafter. cepted, even if, from a very practical point of view, the era where PLCs and DCSs, or any process control-dedicated architectures, will be 2. State of the Art in Process Control completely replaced with the new ones, is still Systems far to come. In fact, the industrial community is somehow reluctant with respect to discontin- A traditional control system can be split into uous innovation. three main layers: the field, related to the in- Here, an influential theory is worth mentioning. putoutput devices, the controller itself, which Well known within evolutionary biology com- is in charge of executing the control logic, and munity, it states that evolution does not gradu- a monitoring, programming, and supervision ally occur as small steps over long periods of level as sketched in Fig. 1. As already men- time, but rather as long periods of stability in- tioned, at present, due to many reasons, the terspersed with rapid changes. These periods of 118 Future Directions of Internet-based Control Systems rapid changes are often the result of severe envi- cost reduction, time-to-market, enterprise-wide ronmental changes. This theory is called punc- integration. Up to now, the problem has been tuated equilibrium Harrold, 2000 . Analysing the lack of technology infrastructure needed to the story of process control systems, there is ev- build a uniform and consistent information ar- idence of the punctuated equilibrium behaviour chitecture that could work for both low-level is this area and over the last few years, Internet- process control systems and high level plant au- related technology