In this paper an extended Petri net, the programmable logic controller net (PLCNet) is defined. A rule-based PLCNet simulator has been designed based on the semantics of PLCNets, with facilities provided to set up and...
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In this paper an extended Petri net, the programmable logic controller net (PLCNet) is defined. A rule-based PLCNet simulator has been designed based on the semantics of PLCNets, with facilities provided to set up and control simulation. Both step and time responses are provided for the presentation of simulation results. A graphical environment is provided for the construction of the PLCNet, simulation and the presentation of simulation results.
In this paper an extended Petri net, the programmable logic controller net (PLCNet) is defined. A rule-based PLCNet simulator has been designed based on the semantics of PLCNets, with facilities provided to set up and...
详细信息
In this paper an extended Petri net, the programmable logic controller net (PLCNet) is defined. A rule-based PLCNet simulator has been designed based on the semantics of PLCNets, with facilities provided to set up and control simulation. Both step and time responses are provided for the presentation of simulation results. A graphical environment is provided for the construction of the PLCNet, simulation and the presentation of simulation results.
A water and wastewater treatment plant, each at a different geographical location, experienced serious damage to instrumentation and control (I&C) equipment in 1994 because of lightning-induced surges. The damage ...
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A water and wastewater treatment plant, each at a different geographical location, experienced serious damage to instrumentation and control (I&C) equipment in 1994 because of lightning-induced surges. The damage may have been caused by the following problems in installation: Incorrect surge suppressor installation and grounding. Improper grounding of shields. Lack of programmable logic controller (PLC) data highway protection. Lack of conduit bonding. Lack of protection on control valves. Violation of principle of single point grounding within control panels. Changes in installation were recommended to eliminate these problems. Following implementation of the recommendations, neither plant has experienced any lightning-related damage. (C) 1996 Elsevier Science Ltd.
Due to recent requirements by the U.S.E.P.A. towards the standards on chlorine residuals for chlorination and dechlorination processes, together with the commitment to optimize the process operating conditions for che...
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Due to recent requirements by the U.S.E.P.A. towards the standards on chlorine residuals for chlorination and dechlorination processes, together with the commitment to optimize the process operating conditions for chemical cost savings and to let the plant operator have more time working on other important projects, the City of Houston has been utilizing automatic control systems (programmable logic controllers) at over twenty WWTPs to meet the above tasks. This paper will present one of the City's WWTPs which implemented the auto-control system. It also discusses how to solve the problems of noises in instrumentation signals and dead time which are common in auto-control systems. Finally, it will show how much success the system has complied with the U.S.E.P.A.'s requirements and effectively reduced the chemical costs.
This paper describes the application of programmable logic controllers (PLCs) to control and protection of bulk power and regional supply substations. PLC requirements are discussed and the concept of ''zones ...
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This paper describes the application of programmable logic controllers (PLCs) to control and protection of bulk power and regional supply substations. PLC requirements are discussed and the concept of ''zones of control'' is explained as applied to standard PP&L substation arrangements. The use of a peer-to-peer communication network between logiccontrollers and other substation equipment is also discussed. Details of an installation completed in spring, 1992, are presented, including experience acquired from power system faults.
Communications is the Keyword in the modern industrial automation environment and effecttive interfaces are required around a programmable logic controller (PLC). In this paper a low-cost solution for communicating wi...
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Communications is the Keyword in the modern industrial automation environment and effecttive interfaces are required around a programmable logic controller (PLC). In this paper a low-cost solution for communicating with a PLC is proposed. A simple printed circuit board, a small part of controller's memory and some digital outputs are the only requirements in order to achieve a low-level communication with a PLC. The method has been implemented and tested in a real environment of PLCs
Recent literature on Petri net applications to model controls of automated manufacturing systems is discussed. Modeling controls is essential to prevent the incidence of system deadlock which could possibly occur due ...
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Recent literature on Petri net applications to model controls of automated manufacturing systems is discussed. Modeling controls is essential to prevent the incidence of system deadlock which could possibly occur due to the concurrent and asynchronous nature of activities. It is difficult to implement an efficient programmable logic controller program for a manufacturing plan without solving this problem. Research findings on control model generation and analysis are discussed in the light of the deadlock problem and performance evaluation. Past and present research in these areas is critically examined in an attempt to focus on the guidelines for on-going research in control modeling.
The use of programmable logic controllers (PLC's) in food industries provides various benfits concern-ing the improvement of quality and productivity. In this paper, special considerations in the application of PL...
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The use of programmable logic controllers (PLC's) in food industries provides various benfits concern-ing the improvement of quality and productivity. In this paper, special considerations in the application of PLC's in industrial processes are discussed. PLC-based distributed control system for a food packing plant is introduced as case study. The experience gained during different stages of the development cycle of this automation system is also presented
A project involving the modernization of a kraft mill in Canada required all discrete logic control to be in the programmable logic controller (PLC) and all analog control to be in the distributed control system (DCS)...
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ISBN:
(纸本)1556173806
A project involving the modernization of a kraft mill in Canada required all discrete logic control to be in the programmable logic controller (PLC) and all analog control to be in the distributed control system (DCS). Because control was split, system maintenance was divided between the instrument and electrical departments, each with different documentation requirements. Using a relational database, the authors pioneered a new way of documenting the interface between the DCS and PLC systems that became an integral part of troubleshooting during start-up as well as for ongoing maintenance. The documentation technique was so successful that the mill expanded its use to all projects.
Flow-type organisation of production lines is often encountered in small and medium sized companies. In order to improve the through put, to ensure a high quality of the products and to reduce the manufacturing time, ...
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Flow-type organisation of production lines is often encountered in small and medium sized companies. In order to improve the through put, to ensure a high quality of the products and to reduce the manufacturing time, flexible automation is necessary, which naturally leads to the CIM approach. The paper describes a flow-type production line for can filling, which can be utilized both in the petrochemical and in the food industries. Considering the typical production line as a numerically controlled workcell, a parallel production structure with multitask workstations is proposed, leading thus to an efficient extension of the company’s shop floor. In such a parallel production line (PL) there are a number of identical multitask workcells (KTWC) which include a fixed number of workstations, seτeral Industrial Robots (IR) with interchangeable grippers and tools and diverting devices. The workstations perform all the necessary operations in order to obtain the final products. Thus the productivity of a PL is given by the sum of the productivities of its parallel branches. For such a process structure, the paper proposes a hierarchical control configuration. At the level of local automation, a number of programmable logic controllers (PLC) are used. Product transfer and handling requires the connection of the PLCs with the controller of two IR, in order to ensure the proper material flow between the production branches. Manufacturing in the PL is integrated by a high-level computer, which analyses order entries, performs job scheduling for the branches which execute identical products, diverts products of different type, downloads programs and reference data to the local controllers, receives information concerning the current state of the production and modifies the job flow according to temporary stops or failures in the individual branches.
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