The modern level of information technology in the field of industrial automation increases the relevance of the development of dispatch control (dispatch) and data collection systems – SCADA / HMI-systems (Supervisory Control And Data Acquisition / Human Machine Interface).
The SCADA / HMI application software is designed to create programs for controlling technological objects. If necessary, the SCADA program allows you to integrate the monitoring mode into a single information network of an enterprise. Its interaction with the operator takes place using a multi-window interface.
When developing SCADA / HMI-based application software for the implementation of a dispatch system, a system integrator can use:
– SCADA / HMI application software based on standard configuration tools, including traditional programming languages;
– ready-made (COTS – Commercial Off The Shelf) SCADA / HMI application software development tools.
The most acceptable for effective development of control programs is the second option, in which the functionality of the applied software (SCADA programs) takes into account all the features of the technological process and provides:
– automated development (makes it possible to use the application software of Scada-systems for process control systems without real programming);
– information exchange with lower-level APCS devices;
– the ability to control the technological process and register signals about the occurrence of emergency modes;
– introduction of additional functions for controlling the parameters of the technological process, including the coefficients characterizing its work;
– regulation of the set parameters of the technological process;
– archiving the database of measured parameters, viewing graphs (trends) of changes in the parameters of the technological process;
– visualization of technological data (graphs, histograms)
– blocking of “false” operator actions;
– restriction of access, depending on the position of the operator.
Many SCADA packages (Trace Mode, Citect, Factorylink, WinCC Scada, Scada Softlogic, Proficy HMI / SCADA – iFIX, Scada Kontur system, MoviconX) are based on typical software components (database of history, input-output, emergency situations, real time) and administrators (management, message access).
Automation systems design technologies using various SCADA / HMI programs are largely similar and include:
– creation of the architecture of the automation system based on a specific SCADA / HMI (definition of the functions of the main nodes in the architecture of the automation system, the possibility of supporting a distributed architecture, the need to introduce nodes of the automation system with hot redundancy)
– creation of an application control program based on SCADA / HMI for each node of the developed architecture of the automation system (development of algorithms, the totality of which describes the operation of the automation system)
– debugging of a control application based on SCADA / HMI in emulation mode, as well as in real mode of operation of a SCADA program.
One of the important aspects is the “openness” of SCADA / HMI programs. The “openness” of SCADA / HMI software systems is an important factor in competition in the industrial automation and dispatching market. The most adequate formulation of the term “open system” is found in the IEEE POSIX 1003.0 committee. An open SCADA system is, if the possible used data formats are defined for it, as well as an interface that allows you to connect to it independently developed, “external” software (hardware) components.
The main reason why an open SCADA / HMI system is predominantly closed is the functional limitation of even a very large, universal software product. There is always an exotic microprocessor controller for which there are no corresponding standard I / O drivers within a given SCADA / HMI (or a unique program that does not support standard generally accepted interfaces, with which it is imperative to establish interaction). The integral functions of SCADA / HMI are data collection with the subsequent transfer of control actions to the object, therefore, the main efforts of developers are aimed at providing their systems with a sufficient number of drivers for seamless connection of many well-known controllers and other intelligent devices.
The concept of openness provides SCADA programs with independence from the automation vendor. This stimulates competition in the ICS market. The importance of the openness of SCADA / HMI systems is explained by the need for their seamless integration with the software systems of the lower and upper levels of the ACS.
In order to unify the operation of their equipment with open systems, hardware manufacturers complete their products with DDE (Dynamic Data Exchange) or OPC (OLE for Process Control) servers. The OPC standard is an open data exchange interface. The goal of OPC is to develop an open interface based on such standardized Windows technologies as OLE (Object Linking and Embedding), COM (Component Object Model), DCOM (Distributed COM). Such an interface should link between custom office and industrial applications. Today, OPC is the de facto standard in the industrial automation systems industry.
For the enterprise management level, SCADA / HMI systems for process control systems can also be used to create MES systems (Manufacturing Executing System). Such capabilities of SCADA / HMI-systems as reflection, data archiving, production logging are successfully implemented for the organization of dispatching centers of enterprises. However, the specifics of dispatch control at the enterprise level led the creators of SCADA / HMI systems to develop special software packages for the enterprise management level. In this case, an important role is played by the function of decision support before the redistribution of material and energy flows of the technological scheme of production by evaluating the results of the proposed decisions by means of modeling. The modeling process in such systems complies with the ISA SP 88.01 standard. (Batch Manufacturing Models).