5Other Control Systems

SoftPLC systems are usually SW implemented at industrial computers that use usually programming according to the standard IEC/EN 61131-3 (described above). The main advantages include the operating system and a simple way to activate standard software products, handling of standard peripherals of the computer, use of archive and communication functions, Ethernet interface, Internet communication and a significant computational power.

The risk of instability of the operating system is usually solved by the use of a robust, real‑time operating system, or an extension module is attached to the standard computer which implements the functions of the programmable automaton (PLC module). There is a variety of methods to implement the SoftPLC systems. There are still other devices that may be programmed in the style of PLC, such as frequency converters programmable according to the standard IEC/EN 61161-3. Similar features are typical for some intelligent terminal modules.

The name industrial computers usually contain a wide class of computer products. The most common category is represented by embedded systems – these are systems that are "embedded" into a switchboard, control system or other device. Industrial computers are sometimes called by the abbreviation IPC (Industrial PC). It is sometimes used in the same meaning as embedded systems, in some cases it distinguishes a special class of PCs, which are specially constructed for extreme durability and unfriendly condition of the industrial environment.

Often used devices are presented by embedded computers with operator panels, usually with a touchscreen. Their main function is to implement the operator interface (HMI). Standard computer equipment, memory, communication and quality colour graphics enable comfortable visualization, monitoring and documentation of the state of the controlled object; at the same time, they provide a user-friendly interface. Similar function may be implemented by a compact embedded computer without a screen. - used mainly for its computational functions in many cases, for data archiving, communication functions, standard operating system; it may be used as a tool to access standard peripherals or software products. It may be used for archiving of large files of data, as a communication adapter (for Ethernet), Internet access point, or to perform numerically extensive computational algorithms.

Modular embedded computers are used for demanding applications. Similarly, to programmable automat (PLC), they are very versatile and their configuration may be modified according to the requirement of the controlled object.

Industrial computers are approached by programmable automata. Standard equipment for PLCs of majority of the main PLC manufacturers includes computer modules (i.e. embedded industrial computers), or the central units of the PLCs are implemented as a computer (somewhere between PLC and SoftPLC).

It is difficult to tell on the first sight, whether the control system is implemented as a modular industrial computer, programmable automat (PLC) or a SoftPLC system. The main classification criteria include the programming method and available programming languages (for PLCs, they comply with the norm IEC/EN 61131-3).