Principles of building an automated facility control system.
An automated facility control system (hereinafter referred to as ACS) is a modern industrial system for integrated automation and control of life support and security subsystems for facilities of varying complexity and having different levels of security and privacy requirements.
A modern system must be multi-level, scalable, dynamically changeable and expandable.
The main functions of the automated control system are to ensure monitoring and interaction in automatic mode of the life support and security subsystems installed at the facility, such as security and fire alarms, video surveillance, access control, notification, fire extinguishing, power supply, lighting, ventilation and air conditioning, etc.
Another important requirement is the ability to integrate equipment from many manufacturers into the system: with the appropriate drivers, a modern automated control system should work with any systems.
The complex usually includes three levels:
- The lower level consists of end devices (sensors and actuators) and control controllers.
- The integration level can be built on the basis of single-board industrial controllers (SBCs).
- The upper level should combine a server cluster and automated user workstations (AWS).
Lower level.
The lower-level control controllers provide operation both under the control of the upper-level system and in a completely autonomous mode, while all the necessary parameters, the user database and the event log are stored in the non-volatile memory of the controller.
This guarantees the absence of data loss in the event of abnormal situations at the upper and/or integration level.
Communication with the OPK is unified for all subsystems and is implemented on the basis of the standard serial interface EIA-232/485.
Other interfaces for connecting equipment are also supported — USB, Ethernet.
Integration level.
Single-board industrial controllers (SBC) are today an integral part of any modern industrial automation system, providing high reliability, the best weight and size parameters and requirements for mean time between failures.
It is better if mechanical elements such as fans and hard disk drives are replaced by solid-state ROM with a file structure and an IDE interface.
The OPCs have two serial EIA-232/485, which provides connection of up to two subsystems to one OPC.
These OPCs are connected via an Ethernet interface into a local area network (LAN) and provide communication with the upper level.
The OPC software includes a set of drivers for working with lower-level equipment and a main program that provides communication between subsystems at the facility.
The main program is a virtual machine that processes a set of input events (including sequences) – events from subsystems – and generates a set of output reactions (including sequences) – control commands for subsystems.
Thus, this level implements the main control link for the entire system, while abnormal situations in the upper-level system do not affect the operability of the system as a whole: automatic scenarios are executed, event logs are generated.
The obviously higher reliability of the OPK, offered for the class of industrial equipment systems, the absence of the possibility of direct operator intervention in the operation of this level and professionally developed software running under the control of the UNIX family operating system, guarantee a high degree of failure-free operation of the complex.
Top level.
The upper level implements the «client-server» technology and can be built on the basis of a server (a server cluster is possible for large systems) and a set of non-operating terminals — diskless PCs, including a network adapter with a bootloader from the network.
Automated workstations are organized on the terminals, and each of the workstations can have its own access rights to the system resources.
The absence of an operating system on the terminals eliminates the possibility of system desynchronization and allows the influence of the human factor to be minimized.
Additionally, electronic USB keys can be used for authorization, which are defined for workstations and the server, which ensures a high degree of protection against unauthorized access directly from the automated workplace.
The upper-level software must provide the user with a modern graphical interface and its own language for describing interaction scenarios between subsystems.
The number of existing subsystems is increased by increasing the number of industrial control systems and associated equipment.
Adding new subsystems requires developing a driver for industrial computers.
The graphical user interface provides the ability to define multi-level plans of the facility, on which «objects» can be placed in accordance with the physical location of the equipment.
An «object», the configuration of which is determined during system administration and can be dynamically changed during operation, provides a method for controlling a particular subsystem directly from the terminal.