Computer-based control systems

Simply, SCADA is a computer-based control system that remotely controls processes previously controlled manually. The philosophy behind SCADA control systems can be summed up by the phrase, If you can measure it, you can control it. SCADA allows an operator using a central computer to supervise (control and monitor) multiple networked computers at remote locations. Each remote computer can control mechanical processes (mixers, pumps, valves, etc.) and collect data from sensors at... 

MS Carey, "Safety Management of Process Faults A Position Paper on Human Factors Approaches for the Design of Operator Interfaces to Computer Based Control Systems", HSE Contract Research Report No 60/1993, HSE Books, 1993... 

In an automated process the computer-based control system continuously communicates with every controlled component and transmitter. The control system monitors and controls the process through signals received and sent covering... 

The first step in selecting a computer based control system is to determine the system requirements in terms of input and output signals. In most cases, this effort will have to start before the final process design is complete. Table 8 lists the common input and output requirements for typical system components. 

The commercial development of computer-based control systems for tractors and other agricultural implements has provided a platform that enables coded mapped information to be effectively transferred from a desktop computer to the tractor cab. Initially developed in conjunction with GPS field location for yieldmapping applications, this type of system is now being incorporated into tractors and specialised application vehicles (see Figure 4.6). These can be used to give access to the treatment map in the field, and hence control signals for the application system. Data transfer is commonly by smart cards with current systems, but it is likely that future developments will use radio/telephone connections to automate the data transfer process (Miller, 1999). 

Figure 4.6 Typical computer-based control system for use with agricultural equipment capable of supporting digital treatment map information and with a GPS interface...

Some variability in the flow curves of the different valves is also noted in Fig. 17.6. A level of discrepancy is expected for the first generation, prototype valve, and the variability would be reduced with changes in the manufacturing process for production valves. For rig testing, the variability can be accommodated with the computer-based control system. 

The process of A SW verification and validation assessment is one of the essential parts of NPP I C expert analysis and licensing. For the broad number of systems, particularly computer-based control systems, the problems of A SW verification and validation assessment is desirable to consider simultaneously. This is a reason for theoretical and technological basis improvement for developing and realization of A SW verification and validation assessment process. 

The proposed methodology of complex A SW verification assessment was approbated during the expertise of a number state-of-the-art Ukrainian NPP I C systems. Particularly the proposed methodology was used during the expertise of computer-based control system ASUT-IOOOM for Zaporozhey NPP. It is system for automatic control of turbine. The developed approach ensures the possibility of unification and standardization of A SW assessment verification process. ASUT-IOOOM A SW verification and validation expert analysis consists of three stages. 

In the horizontal section expert analysis performed on stages of system and A SW development starting from EA of system and A SW specification to functional so are V V on the computer-based control systems of ASUT-IOOOM. In this section V V assessment carried out by use of ... 

Traditionally, analog instrnmentation was nsed, and is still used for process control in some cases. However, the advent of the microprocessor in the early 1970s and the development of digital computers, coupled with significant reduction in their cost, have brought about the evolution of computer-based control systems and controllers capable of providing more than basic control. 

It is imperative that the interface between the computer-based control system and the environment it is controlling is well defined and appropriately constrained. This is one of the attractive features of the time-triggered architecture and is equally important for the event-triggered (ET) approach. An ET interface consists of state data and event ports. State data are written by one side of the interface and read by the other. Concurrent reads and writes are noninterfering. The temporal validity of the data is known (or can be ascertained) by the reading activity. This may require an associated time-stamp but may alternatively be a static property that can be validated prior to execution. An event port allows an event to pass through the interface. It is unidirectional. The occurrence of an event at the system interface will result in a computational process being released for execution. The effect of an output event into the computer system s environment cannot be defined it is application-specific. 

The simplest algorithm for a PID controller is the sum of Equations 8.1, 8.2, and 8.3 as shown in Equation 8.4. This is common in computer-based control systems, and all three control actions are considered to be operating in parallel. However, many industrial analog controllers and microprocessor DCS (distributed control system) controllers use a capacitance lag (filter) of about 0.05 to 0.10 in series with the process variable signal to reduce the effect of derivative action from setpoint changes and from short time constant noise described earlier. When the derivative time constant,... 

Data Thend, Computer-based control system, WABASH MPI... 

With a computer-based control system one can move beyond the classical single-loop described above, and the action of a control valve can be governed by information fed from a number of points in the process. Since an understanding of both the complexities of chemical processes and advanced control theory is required, this area is at the interface between process and control engineering. 

Flammini, F., Marrone, S., Mazzocca, N., Nardone, R., Vittorini, V. Model-driven V V processes for computer based control systems A unifying perspective. In Margaria, T., Steffen, B. (eds.) ISoLA 2012, Part II. LNCS, vol. 7610, pp. 190-204. Springer, Heidelberg (2012)... 

A schematic diagram summarizing failures that led to the gasoline pipeline rupture and fire in Whatcom Faiis Park. This accident was due to a combination of pipeline damage (caused by poorly supervised excavation work around the pipeline several years earlier), inadequate non-destructive inspections of the pipeline, a wrongly specified pressure relief valve, inadequate investigation of valve control problems, and uncontrolled software upgrades ( SCADA" was the computer-based control system). 

Douglas et al. presented a computer-based control system of particulate dryers, including the required sensors, a centralized computer system, and the software [34]. The work included the development of a capacitance-type moisture meter. A continuous horizontal conveyor-belt dryer for drying pet food had been used as an illustration. 

Substantial improvements have been done in Narora C I systems over the earlier projects. One area is increased computerization, where computer based control systems have been used for on-power fuel handling controls, reactor controls, plant data acquisition system and other critical areas of the plant. Some of these are described in detail below ... 

Process control and sensing. The use of advanced processes requires improvements in the level of control over day-to-day production operations, such as enhanced computer-based control systems. 

The term fuzzy logic in its true sense means imprecise logic. The concept behind it was developed in the 1960s by Lotfi A. Zadeh, University of Berkeley, California, USA (Zadeh, 1965). Fuzzy logic uses terms similar to human language to describe values of parameters and relations. These linguistic rules thus allow an easy transfer of human expert knowledge into a computer-based control system. 

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