New Trends in SCADA systems.

Introduction

In this article, we present and discuss the state of the art of new trends in SCADA systems.

In recent years, the panorama of the automation market has been based in constant technological change and search of productivity by companies. These factors act as driving forces for a market that must invest in research and development to continue to grow.

On the other hand, there is a continuous pressure to reduce costs, both in products and in services. This pressure leads to finding the best cost-benefit ratio; studying which technologies to invest in; researching which of them have consolidated and which are still just promises; and deciding what products a service provider will offer to remain competitive in its segment performance.

In the specific case of supervisory systems, one has to consider these facts:

• The continued use of older tools based on Windows platform; despite having less advanced concepts, these are best known in the market.
• The creation of new tools, also for the Windows platform, with better concepts of productivity and flexibility.
• The search for new forms of supervision, such as the use of PLC-based web servers on Linux or Java.
• Windows CE-based HMIs as an alternative to HMIs with proprietary hardware.
• Using Linux and Unix systems for larger systems; this usually happens in environments where this is part of users’ culture. These group is willing to pay higher values due to the fewer copies available in the market (such as systems of SNMP network management, traffic systems ).
• Consolidation of OPC (OLE for Process Control).
• The addition of new features to SCADA systems, as part of its expansion strategy; features such as analysis of production systems and processes, batch control, and others.
• Full integration with the web.

Operating System

The first conclusion from the analysis of these facts is the consolidation of the Windows operating system to SCADA systems. This is because this platform offers an adequate level of training and professional training; additionally, it is reliable, and software and hardware are easier to maintain, with additional alternatives for “shelf products” available. These and other factors aggregate a competitive cost for most applications and users. Keep in mind that the goal is always to maintain the productivity and effectiveness of solutions, both for buyers and for sellers.

Additionally, Linux is an interesting alternative when you can eliminate or suppress its negative factors, especially when it comes to professional training and maintenance. One example is using Linux or Java as a web server within a PLC; then, you can restrict it to a certain platform. However, several points should always be studied, such as connectivity, flexibility, and productivity.

Architecture

Once we define the market strategy, we ponder issues on new possibilities of use of SCADA systems. We can see that the architecture becomes important when we incorporate these new uses with greater or lesser degree of flexibility, without sacrificing performance or the time spent for configuration.

Effective use of wireless networks, for example, assumes that the user interface via a PocketPC with your SCADA server must be rich enough to provide management information on the process and at the same time, take enough to occupy the minimum possible bandwidth of the network, and security aspects that cannot – or should – be neglected.

Protocols

The use of open protocols is not only a requirement from the market, but has also become a strategic issue to reduce integration costs, to obtain more reliable data, and also to reduce setup time applications. This is because we must consider not only the compatibility with a given protocol, but their optimal use within the SCADA system. Thus, we should consider issues such as self-configuration and synchronization of databases between devices and software in order to obtain more benefits from an open architecture.

Web

The next question on architecture is how to provide data for access via web. Several different products use many different technologies, especially Java- and ActiveX-based objects. The latest possibility is the use of Microsoft’s .NET technology.

As a rule, the web page that will be viewed by users on the Internet browser must contain a plug-in; its goal is to make the processes of animation and other background tasks occur spontaneously, without prompting the user. Notice that hypertext formats of web pages (HTML, ASP, PHP) do not allow this behavior without the use of such components.

Thus, a few SCADA software programs have decided to carry out conversions between screen formats and its objects to another standard, which could be understood by the ActiveX or Java component in the browser, since it is not always possible that the same format is used in both cases. But there are other problems; like the fact that based scripts in VBA (Visual Basic for Applications) cannot be run in the available browsers, which makes the screens converted to web do not always work in its original form.

Other solutions, such as Elipse E3, assume that the same aspect ratio can be used on both the SCADA client, in Windows, and on the browser – which avoids the format conversions -, as well as using VBScript-based scripts that can run in both environments.

Restrictions

However, Java and ActiveX have some restrictions. Java requires a runtime, able to interpret the code running, installed on the client machine. This factor causes performance drops, as some customers have reported, just because it is interpreted and not compiled. ActiveX, on the other hand, will only work in the Windows environment, with Internet Explorer, which can be a problem for customers who use other browsers.

Regarding communication, both Java and ActiveX exchange messages via models such as CORBA or DCOM over TCP/IP to obtain the screens from their servers and receive notifications of values’ changes. ActiveX, however, has an aggravating factor: it is based on COM (Component Object Model) technology, as well as its distributed variant (Microsoft’s DCOM); therefore it has several problems of traffic via firewalls, since DCOM uses random ports for data exchange. One solution would be to adopt a specific protocol for data exchange network based on pure TCP/IP, which is quite complex.

.NET

The (dot)NET platform proposes two kinds of solutions for these issues. The first is by creating a single development environment for both Windows and the Web, through the Windows Forms and Web Forms. The second is by exchanging data via an XML-based web, which is a structured text format that can pass through any firewall. Besides these two factors, (dot)NET provides a new world of possibilities through the integration of dynamic web services, reusing components, and creating corporate portals such as SharePoint Server, allowing it to reach a level of evolution and integration never seen before, always keeping the focus on the issue of productivity and total cost of ownership solutions.

In addition, (dot)NET allows several different programming languages to be used in the same program (e.g., C++, VB, C#, FORTRAN …), which until now had not been possible with other technologies.

Figure 1 – Structure of .NET’s Framework

However, some users are a little resistant to using (dot)NET. This is because, like Java, you must install an interpreter ((dot)NET Framework) on the client machine, so that (dot)NET code is executed. Nonetheless, in the long run, when all new installations of Windows already have (dot)NET Framework default, this will be a minor factor.

Data Integration and OPC Unified Architecture

The range of options for data integration between SCADA and enterprise systems (ERP, Supply Chain, others) has become increasingly important. In addition to keeping older methods, the search for new ways of modeling and data exchange is the main part of the evolution of these systems. The native access to databases via SQL, data exchange over TCP/IP, I/O drivers implementing Master/Slave protocols, COM objects and ActiveX, among many other forms, have already led to major developments.

Notice, however, that none of these methodologies is as important or as widely used as OPC. This pattern emerged in an attempt to standardize the layers of I/O drivers; later, it was consolidated as a great modeling standard, with specifications for Data Access (DA), Alarms and Events (AE), Historics (HDA), Complex Data, among others. Nonetheless, since the OPC specification depends on the standard COM/DCOM, a new OPC Foundation’s work culminated in the unification of the previous standards; the new model is called UA (Unified Architecture or Unified Architecture), more open and based in dynamic services (Web Services) and XML.

This initiative, focused on interoperability, shows that the OPC being a standard accepted universally allows you to permanently abandon the model of proprietary solutions in search of added value that each solution offers. The approach adopted in this search uses (dot)NET platform as the most logical way to achieve this by providing a means to adapting the existing OPC servers and clients, by using standards that can be used on any operating system and, finally, by creating a data model that goes far beyond the SCADA system, expanding it to the corporate level.

Final Remarks

After this analysis, the conclusion is that a particular technology can hardly ever be considered “the winner”, because there will always be segments where each solution has benefits that can be decisive when compared with competing technologies. We believe, however, that the (dot)NET, a natural extension of the standards most commonly found today, appears as a promising alternative, especially when taken into account all aspects involved in the solutions.