Failsafe systems, which control potentially hazardous operations to ensure they are shut down if faults occur, have in the past traditionally been hard-wired installations. But there are serious drawbacks to the hard-...
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Failsafe systems, which control potentially hazardous operations to ensure they are shut down if faults occur, have in the past traditionally been hard-wired installations. But there are serious drawbacks to the hard-wiring approach-an inherent inflexibility, and lack of data communications facilities, to name but two. These are prompting a growing move towards using specialised systems based on programmable logic controllers (PLCs) that are tailor-made for failsafe applications.
Two large-resistance realisation schemes are proposed using switched-capacitor circuits. The equivalent resistance of the array realisation increases as the third power of the number of capacitor pairs, and that of th...
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Two large-resistance realisation schemes are proposed using switched-capacitor circuits. The equivalent resistance of the array realisation increases as the third power of the number of capacitor pairs, and that of the ladder realisation increases exponentially. The equivalent resistance for the ladder scheme also grows with the capacitance ratio. Using these schemes, large resistances can be fabricated with standard CMOS process in an affordable chip area. Simulation results show that very low pole frequency (similar to 9 Hz in the example) can be achieved with practical element values, and with a capacitance spread of only 10 in a three-stage ladder.
Since its introduction in 1997, model-free adaptive (MFA) control products have been widely deployed in most major process industries and achieved significant economical benefits for the users. It is the only 'no ...
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Since its introduction in 1997, model-free adaptive (MFA) control products have been widely deployed in most major process industries and achieved significant economical benefits for the users. It is the only 'no model' advanced controller on the market that can control complex systems without the need to use first-principle mathematical models. Once it is installed, no controller parameter tuning is typically required.
A binary decision controller is a programmable logic device whose use falls between that of hard-wired logic and microcomputer controllers. The paper explores the use of this type of controller for a number of simple ...
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A binary decision controller is a programmable logic device whose use falls between that of hard-wired logic and microcomputer controllers. The paper explores the use of this type of controller for a number of simple tasks.
The advantages of combining a crisp algorithmic controller and a soft knowledge-based controller are addressed, in the specific context of controlling a space-based manipulator with flexible deployable and slewing lin...
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The advantages of combining a crisp algorithmic controller and a soft knowledge-based controller are addressed, in the specific context of controlling a space-based manipulator with flexible deployable and slewing links. A hierarchical control structure having a high-speed conventional controller at the bottom layer and an intelligent tuner at an upper layer, is developed. The top-level intelligent tuner uses a valid set of linguistic rules for adjusting proportional-derivative servos, based on fuzzy system concepts. The performance of the hierarchical control system is evaluated on the basis of the space-based simulation results. Based on the analysis it can be concluded that initial tuning of the parameters of a conventional low-level controller together with tuning during operation can improve positioning accuracy of the manipulator. The hierarchical control structure permitted desirable combination of a conventional high-bandwidth and knowledge-based low-bandwidth controllers. (C) 2002 Elsevier Science Ltd. All rights reserved.
The International Electrotechnical Commission is currently standardising four compatible languages for designing and implementing programmable logic controllers (PLCs). The language family includes a diagrammatic nota...
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The International Electrotechnical Commission is currently standardising four compatible languages for designing and implementing programmable logic controllers (PLCs). The language family includes a diagrammatic notation that supports the idea of software ICs to encourage graphical design techniques and systematic software reuse. This paper presents an interactive system with a graphical interface for constructing and validating PLC software. The semantics of a graphical design is defined by a mapping associating each design with an executable formal specification. The specification provides the basis for rigorous proofs and early tests of critical properties of a new design. A realistic example illustrates these features.
In this study, an adaptive second-order sliding mode (SOSM) controller is proposed to control a laboratory helicopter called the twin-rotor multi-input-multi-output system (TRMS). The design objectives of the controll...
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In this study, an adaptive second-order sliding mode (SOSM) controller is proposed to control a laboratory helicopter called the twin-rotor multi-input-multi-output system (TRMS). The design objectives of the controller are to stabilise the TRMS in significant cross couplings, reach a desired position and accurately track a specified trajectory. The TRMS model is divided into a horizontal and a vertical subsystem (VS). The cross coupling existing between the two subsystems is considered as the system uncertainty. A simple adaptive tuning law is developed for the SOSM controller to deal with the bounded system uncertainty. The major advantage offered by this adaptive SOSM controller is that advance knowledge about the upper bound of system uncertainty is not a necessary requirement. The adaptive SOSM controller for the VS uses a proportional plus integral sliding surface to counter the offset present in the pitch angle. System robustness and the stability of the controller are proved by using the Lyapunov criterion. Apart from imparting robustness, the proposed adaptive SOSM controller reduces undesired chattering in the control input and thus is suitable for application in practical motion control applications. The proposed control scheme is validated by simulation results and is compared against the existing proportional-integral- derivative controllers to show that the overall performance of the proposed adaptive SOSM controller is better in the aspects of error and control indices.
Describes the standardization of control systems in the water industry in Great Britain. Development of mechanical and electrical systems; Requirements and specifications for data gathering to enable plant optimizatio...
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Describes the standardization of control systems in the water industry in Great Britain. Development of mechanical and electrical systems; Requirements and specifications for data gathering to enable plant optimization; Use of industrial computer-based processors such as programmable logic controllers; Systems integration.
Equipping processors with programmable hardware to patch design errors lets manufacturers release regular hardware patches, avoiding costly chip recalls and potentially speeding time to market. For each error detected...
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Equipping processors with programmable hardware to patch design errors lets manufacturers release regular hardware patches, avoiding costly chip recalls and potentially speeding time to market. For each error detected, the manufacturer creates a fingerprint, which the customer uses to program the hardware. The hardware watches for error conditions;when they arise, it takes action to avoid the error.
Power line communications uses the existing power line infrastructure for communication purposes. While the majority of recent contributions have discussed PLC for high-data-rate applications like Internet access or m...
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Power line communications uses the existing power line infrastructure for communication purposes. While the majority of recent contributions have discussed PLC for high-data-rate applications like Internet access or multimedia communication serving a relatively small number of users, in this article we are concerned with PLC as an enabler for sensing, control, and automation in large systems comprising tens or even hundreds of components spread over relatively wide areas. Typical examples of such systems are energy management (Smart Grid) and facility automation systems. We provide a discussion of the communication network requirements common to such systems and present transmission concepts for PLC to make use of the existing infrastructure resources (i.e., power lines) to meet these requirements.
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