Riadiace systémy - Automatizácia technológií
Implementation of control systems for technological processes requires knowledge and experience in this field and knowledge of the respective technology. Requirements for the control system are not always well defined in detail by a customer or technology vendor. Thus the first step in process automation is to develop a document in our company called "System Analysis".
System Analysis document includes:
- description of subject of automation - description of the technological process from the point of view of control,
- tables of inputs/outputs from/to the technological process,
- control system architecture design,
- control system hardware and software specification,
- description of the functions of the control system.
System Analysis is a proposal on how to implement a control system for particular technological process. This proposal is a document that can be (and usually is) modified during the development of the control system. After the deployment System Analysis describes the actual state of the system and is the basis for its maintenance and service.
Plant floor level of control system
Plant floor level of control system performs the functions of collection and primary processing of the input variables (inputs from the plant), their filtration, scaling to engineering units, logic and sequence control, open and closed-loop control, and on the other hand, performs the controlling of the actuators (outputs to the plant) and communicates to higher level of the system - the operator level.
Programmable Logic Controllers (PLCs) perform the functions of plant floor level of control system.
Modular structure of PLC
PLCs have mostly a modular structure. The powerful CPU module (Central Processing Unit) is the ‘brain’ of each PLC.
Other modules (examples):
- input modules: sensing analog, binary, counter..., input variables,
- output modules: controlling actuators via analog or binary variables,
- communication modules: communication with other intelligent devices,
- intelligent modules: modules designed to perform special functions with their own processor.
Local operator panels may also be used at the plant floor level of control system:
- local visualization (text or graphic) and monitoring the state of technology,
- local operator/maintenance staff controlling of the technology,
- local input of setpoint values and various parameters of the technology.
Operator level of control system
Operator level of control system performs the functions of in-detail graphic monitoring of technology and control room operator level control.
SCADA system is used to perform the functions on the operator level.
