programmable logic controllers (PLC) manufacturers continue to make their products smaller, smarter, and more open, while others introduce alternative control products and systems. Microprocessors facilitate the unbun...
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programmable logic controllers (PLC) manufacturers continue to make their products smaller, smarter, and more open, while others introduce alternative control products and systems. Microprocessors facilitate the unbundling of the PLC which helps to reduce the footprint size. Thus, today's PLC is often just a central processing unit (CPU) card and power supply. Soft-logic versions of PLC based on Windows NT was introduced. This is a Personal Computer based controls that replaced PLC CPU. An alternative control that reduce the number of controllers needed in many applications is emerging because of these developments.
A microcontroller-based programmable temperature controller developed using an RTD sensor is described. A resistance-to-time converter is employed to obtain a time-interval linearly varying with the sensor resistance....
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A microcontroller-based programmable temperature controller developed using an RTD sensor is described. A resistance-to-time converter is employed to obtain a time-interval linearly varying with the sensor resistance. Using a counter of the microcontroller and suitable software, temperature under control is determined and compared with a target temperature. The resulting error, through a DDC implementation of PID algorithm, is used to control the firing angle of an SCR for controlling the power applied to heater. Experimental results are given in support of the scheme proposed.
programmablelogic arrays (PLAs) are widely used in VLSI systems because of their compactness, ease of automatic design, and regularity in their structure. This paper presents an innovative method for on-chip testing ...
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programmablelogic arrays (PLAs) are widely used in VLSI systems because of their compactness, ease of automatic design, and regularity in their structure. This paper presents an innovative method for on-chip testing of embedded PLAs which makes use of the input/output registers as test aids. Experimental results on the implementation of a real self-testing PLA are given in order to show the effectiveness of our approach.
The demand and current trends for open systems and information continue to grow. Users are tired of restrictions imposed on them with priority protocols, hardware and software. Manufacturers hear the call to develop l...
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The demand and current trends for open systems and information continue to grow. Users are tired of restrictions imposed on them with priority protocols, hardware and software. Manufacturers hear the call to develop low-cost products based on commercially available technologies. The need for more open communication among systems, at all levels, has been user driven and is a prerequisite for protecting existing capital investments and reducing project costs. The innovative use and immediate utilization of current programmable logic controllers (PLCs)/distributed control systems (DCSs) technology is key in maintaining a competitive edge in a global economy.
The technological process of plasma spraying is complicated and there are many switches to be controlled. The present existing plasma spraying system is not reliable and liable to troubles. The paper introduces a prog...
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The technological process of plasma spraying is complicated and there are many switches to be controlled. The present existing plasma spraying system is not reliable and liable to troubles. The paper introduces a programmable controller of Model C60P to control the technological process of plasma spraying. It also introduces the control system of the detection circuit, the protection system. The authors designed the logic diagram of the technological process, the hardware of resisting high frequency interference, the interface distributing system and the programming software. It is proved that the improved equipment has overcome the defects of the original.
Verification method has been developed for determining the safety and operability of programmablelogic controller (PLC) based systems. The method automatically checks sequential logic embedded in PLCs and provides co...
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Verification method has been developed for determining the safety and operability of programmablelogic controller (PLC) based systems. The method automatically checks sequential logic embedded in PLCs and provides counterexamples if it finds errors. The method consists of a system model, assertions, and a model checker. The model is a Boolean-based representation of a PLC's behavior. Assertions are questions about the behavior of the system, expressed in temporal logic. The model checker generates a state space based on the above two inputs, searches the space efficiently, determines the consistency of the model and assertions, and supplies counterexamples. A modeling technique has been developed to verify relay ladder logic (RLL), a PLC programming language. The performance of the model checker is studied in a series of alarm designs
The paper after a briefly discussion on the effects of some voltage disturbances, as sags, interruptions, and swells, both on programmablelogic ControIJers (PLCs) and on the entire industrial process under the contro...
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As automated manufacturing systems become more complex, the need for an effective design tool to produce both high level Discrete Event Control System (DECS) and low level implementation, becomes increasingly more imp...
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As automated manufacturing systems become more complex, the need for an effective design tool to produce both high level Discrete Event Control System (DECS) and low level implementation, becomes increasingly more important. Petri nets represent the most effective method for both the design and implementation of DECSs. The conversion of such Petri nets into real-time applications has recently been greatly simplified through the advent of the Token Passing logic (TPL) methodology. The technique has been developed for normal Petri nets, P-timed Petri nets, T-timed Petri nets and Coloured Petri nets. In this paper the Petri net concepts are extended to deal with Petri net controllers, by including actuators and sensors as formal structures within the Petri net controller. The conversion of such a Petri net controller into ladder logic diagrams is also demonstrated by considering the control of a component sorting manufacturing system.
Reports on power-line carrier (PLC) communication through alternating current (ac) power lines. Serious impediments to its growth and their solutions; Chief application and example of spread-spectrum PLC communication...
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Reports on power-line carrier (PLC) communication through alternating current (ac) power lines. Serious impediments to its growth and their solutions; Chief application and example of spread-spectrum PLC communications; Basic techniques used for signalling on power lines. INSET: To probe further..
The plastic flow behaviour of a beta-titanium alloy (Ti-15% Mo) was investigated over a wide range of temperatures and strain rates covering those conditions where the omega-phase forms dynamically. Portevin-Le Chatel...
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The plastic flow behaviour of a beta-titanium alloy (Ti-15% Mo) was investigated over a wide range of temperatures and strain rates covering those conditions where the omega-phase forms dynamically. Portevin-Le Chatelier (PLC) effect was observed in this alloy at temperatures between 575 and 775 K at a strain rate of 1.31 x 10(-4) s(-1). The serrated flow behaviour of this alloy could be suppressed by rendering the matrix beta-phase more stable against the beta to omega transformation. PLC bands formed in this alloy, studied at different levels of magnification using light, scanning electron and transmission electron microscopy, showed a high density of deformation bands within the macroscopic PLC band. The following mechanism of serrated flow is proposed: the load drop is ascribed to the sudden flow associated with the formation of deformation bands within which omega-particles were destroyed while the subsequent load rise results from pinning of dislocations by omega-particles forming dynamically. Copyright (C) 1996 Acta Metallurgica Inc.
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