In 2017, Control’s sister publication, Control Design, published an article demonstrating how an Arduino single-board microcontroller for do-it-yourself applications could control a flow loop when integrated with ind...
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In 2017, Control’s sister publication, Control Design, published an article demonstrating how an Arduino single-board microcontroller for do-it-yourself applications could control a flow loop when integrated with industrial-grade instruments and control devices. It compared this inexpensive "maker" approach to using a simple and commercially available industrial programmablelogic controller (PLC) configured to carry out the identical task.
Traditional cyber security mechanisms, such as network-based intrusion detection systems and signature-based antivirus software, have limited effectiveness in industrial control settings, rendering critical infrastruc...
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The paper presents a review of methods of implementing timers in programmable logic controllers, along with a discussion of the timer properties. The authors focus on software implementations, as this approach has dom...
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The paper presents a review of methods of implementing timers in programmable logic controllers, along with a discussion of the timer properties. The authors focus on software implementations, as this approach has dominated practical solutions. An important part of the discussion is analysis of errors in time delay generation, and possible error sources. A typical case of a PLC generating a predefined time delay is analyzed. The discussion is concluded with recommendations on implementing timers, intended for PLC designers.
In this paper a method is proposed to translate control algorithms for manufacturing systems designed in Sequential Functional Charts into the Ladder Diagram language typical of programmable logic controllers. The met...
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In this paper a method is proposed to translate control algorithms for manufacturing systems designed in Sequential Functional Charts into the Ladder Diagram language typical of programmable logic controllers. The method preserves the structure of SFCs : In the resulting program each instruction is directly related to the evaluation of a transition. to the update of the marking or to the execution of an action. The method transparently handles the conversion of macro-actions thus allowing exploitation of hierarchical SFCs in the design phase. A case study is presented to illustrate the technique.
This paper examines the effect of scan time (S/T) of programmable logic controllers (PLCs) on cycle time (C/T). S/T is considered an internal feature of the PLC, and it becomes economically impracticable to examine di...
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This paper examines the effect of scan time (S/T) of programmable logic controllers (PLCs) on cycle time (C/T). S/T is considered an internal feature of the PLC, and it becomes economically impracticable to examine different PLCs to vary scan time and to monitor the effect on cycle time. Although the relationship between the two parameters is expected to differ in linear proportion, an optimum S/T region exists beyond which the rate of C/T change decreases. This region of scan time is particularly important for practitioners because more investment in the processor's speed might not achieve convenient reduction in cycle times. The effect of scan time variation on discrete event processes has been investigated during this research, and factors influencing cycle time have been identified. Also, using intelligent decision analysis tools in engineering has been considered through associated work in which the analytic hierarchy process (AHP) and fuzzy logic have been employed in an intelligent system. In this paper, different criteria that affect the scanning time of a PLC are examined. The methods use a multiple-criteria decision-making tool, called AHP (analytic hierarchy process), that gives a prioritized rank of alternatives that contribute to those criteria.
The main functionalities and characteristics of a new application for the emulation of programmable logic controllers are described in this paper. The objective of this work has been to design and implement an emulato...
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This paper proposes a technique which can be applied in the processing operations of programmable logic controllers. It is called multi-rate scanning and originates from multi-rate digital signal processing. It enable...
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This paper proposes a technique which can be applied in the processing operations of programmable logic controllers. It is called multi-rate scanning and originates from multi-rate digital signal processing. It enables the I/O signals processing by using different scanning rates according to their anticipated switching rates. The paper describes how the multi-rate technique can be applied in any type of PLC in order to increase its I/O capacity and share the control tasks. Finally, the utilization of the technique is illustrated by the use of an application example.
In this paper, an example of the use of programmable logic controllers (PLC), computer programming, and computer interfacing, for teaching purposes and student projects implementation is presented. This is carried out...
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In this paper, an example of the use of programmable logic controllers (PLC), computer programming, and computer interfacing, for teaching purposes and student projects implementation is presented. This is carried out through the design and implementation of a mechanical ventilation system that can be used on respiratory patients and controlled by a PLC. The physical control and operation of the ventilator are accomplished by the PLC via analog input and output modules located within the PLC chassis. Operator adjustment, mode selection, and patient monitoring are accomplished using a personal computer running a visual basic application designed specifically for this project. The operator interface mimics the look of a traditional ventilator control chassis. A serial data connection provides the communication path between the PLC and the personal computer. Using a PLC and a computer interface (HMI) as the respirator control system has distinct advantages over traditional microprocessor control systems. These include: the operation and adjustment of the respirator can be accomplished at a location other than the location of the respirator, alarm conditions can also be determined and evaluated from a remote location, reprogramming of the system can be easily accomplished onsite should newer respiratory modes become available. Through the use of a PLC and a HMI many different applications, similar to the one presented here, can be designed and implemented. This senior capstone design project was designed and implemented by an electrical engineering technology student as part of graduation requirements.
programmablelogic Controller (PLC) programs are programs that control physical devices by continuously reading sensor inputs and writing actuator outputs. A main challenge in designing and comprehending PLC programs ...
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programmablelogic Controller (PLC) programs are programs that control physical devices by continuously reading sensor inputs and writing actuator outputs. A main challenge in designing and comprehending PLC programs is the emergent behavior which arises from the complex interaction between the dynamic behavior of the program and the physical device. In this paper we present an approach for building a formal model characterizing the reactive interaction behavior of a PLC program with the physical device it controls. Based on program recordings, first a model of the transition behavior of the program run is built. Then, using symbolic execution and a formal abstraction process, we generate a specification of the input/output behavior as a state model with transition labelings in terms of conditions on input values. We present the main ideas of the approach, a formal model for representing the reactive behavior, the abstraction process, and two application scenarios.
Hydrogen sulfide is a gas that highly toxic, colorless, and heavier than air that is heavy with the kind of 1,152 kg/m~3. The type of weight resulted in H_2S gas at the bottom make it easy wafted by the human senses. ...
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ISBN:
(纸本)9781467373470
Hydrogen sulfide is a gas that highly toxic, colorless, and heavier than air that is heavy with the kind of 1,152 kg/m~3. The type of weight resulted in H_2S gas at the bottom make it easy wafted by the human senses. The presences of H_2S gas, often encounter in the process of exploration and drilling for natural gas and petroleum refining. Therefore, it's necessary to build a system design of H_2S gas leak solution in the oil and gas industry. Thus, the system can maintain the security of environment and human resources in the industrial area. The system is mixing the concept of individual well with water scrubber method to generate multiple securities. Hence, it should be getting intensive treatment with quick response, so as not to cause damage to the industry, due to its very existence threatened workers. H_2S Safety Instrument System consists of H_2S sensor and programmable logic controllers as a safety function components. PLC is often chosen for safety instrument system as a logic solver. PLC also gives appropriate action for set-point which has been programmed before. There are 4 stages of set-point in the H_2S SIS. First, when the H_2S levels reached 10 ppm, an actuator is a strobe light. Second, when simply applied the actuator reaches 20 ppm, a strobe light and siren. Third, when it reached 25 ppm, the actuator is vacuum compressor that integrated with the system of purification of water scrubber. Fourth, shutdown system for inactive throughout the process at this stage, the plant is used as a safety system double layer when the H_2S safety instrument system is not functioning. The result of this research is decrease of Probability of Failure on Demand value from 7.997 E ~(-01) to 1.17 E~(-03) and increase Safety Integrity Level from 1 to 3.
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