An intelligent and dependable voting mechanism for use in real-time control applications is presented. Strategies proposed by current safety standards advocate N-version software to minimise the effects from undetecte...
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An intelligent and dependable voting mechanism for use in real-time control applications is presented. Strategies proposed by current safety standards advocate N-version software to minimise the effects from undetected software design faults (bugs). This requires diversity in design but presents a problem that truly diverse code produces diverse results, that is, differences in output values, timeliness and reliability. To reach a consensus requires an intelligent voter, especially when non stop operation is demanded, e.g. aerospace applications. This paper, therefore, firstly considers the applicable safety standards and the requirements for an intelligent voter service. The use of replicated voters to improve reliability is examined and a mechanism to ensure non stop operation is presented. The formal mathematical analysis used to verify the crucial behavioural properties of the voting service design is detailed. Finally the creation of N-version redundant voters are considered using Neural nets and Genetic Algorithms.
An intelligent and robust voting service for real-time distributed control systems is proposed. Three novel features of the voter are described. Firstly, the voter is distributed using a primary site algorithm. This a...
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A simple algorithm for establishing the presence of points common to some singularity (hyper)surfaces associated to covariance matrices is developed. It allows, on the basis of the new algebraic and geometric properti...
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A simple algorithm for establishing the presence of points common to some singularity (hyper)surfaces associated to covariance matrices is developed. It allows, on the basis of the new algebraic and geometric properties recently given by Guidorzi (1994), the computation of the maximal number of linear relations that can be associated to a given set of data.
A hybrid system is a system containing both of time-evolving components and event-driven components. A formal approach is explored in this paper, based on Extended Duration Calculus (EDC), for the development of hybri...
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This paper introduces a framework of tools which allow the design of distributed, potentially fault-tolerant, real-time control software. This framework takes a system specified in the control engineering domain and t...
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This paper introduces a framework of tools which allow the design of distributed, potentially fault-tolerant, real-time control software. This framework takes a system specified in the control engineering domain and translates this application-oriented representation into a software engineering representation. From this new representation, automatic code generation tools have been developed to create a complete, executable control system implementation.< >
Al planning systems must be able to update their internal model of the domain in order to determine the effects of a possible action. The most widely used update method is the STRIPS operator. STRIPS operators are ext...
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In this paper, a combined method of change detection and failure decision is proposed for the system under the adaptive control based on the self-tuning regulator. The controlled system is assumed encounter unexpected...
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In this paper, a combined method of change detection and failure decision is proposed for the system under the adaptive control based on the self-tuning regulator. The controlled system is assumed encounter unexpected parameter changes, which may be caused by a failure or a normal operation. Such a system change can effectively be detected by using Fullback Discrimination Information (KDI) as an index for model discrimination. In order to decide whether the detected system change is caused by a failure or not, a neural network approach to failure decision is introduced. Based on the knowledge about failure modes and system operations, the regulator parameter variations after the change detection are used as training data for the network learning. In this way an on-line monitoring scheme of adaptively controlled systems can be established. Simulation studies of a second-order damped oscillator have been earned out to demonstrate the effectiveness of the method.
Design and implementation of an autopilot for ships using multiple control strategies are discussed in this paper. Both course-keeping and track-keeping problems are involved, the course-keeping controller is the esse...
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Design and implementation of an autopilot for ships using multiple control strategies are discussed in this paper. Both course-keeping and track-keeping problems are involved, the course-keeping controller is the essential part of the track-keeping project, and the track-keeping controller is in fact a heading error calculator and transmitter. A self tuning regulator (STR) of the generalized minimum variance (GMV) type is taken as the principal controller, to which an integral controller (I) and a linear quadratic gaussian controller (LQG) are superposed to improve the performance of ship motion control and to enhance the energy saving outcomes. When the heading error exceeds a certain threshold a PlO controller or a knowledge-based multi-mode controller (MC), depending on the control is in course-keeping or track-keeping mode, will take over the heading control to overcome the severe environment disturbances or to speed up the track-following processes. Laboratory simulations and full scale sea trials have been performed, the main results are briefly reported.
The problem of correctness and timing of reactions of an agent in interaction with a physical environment is addressed. To this end, a method based on composition of separate models of the software and the environment...
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A robust discrete-time PI controller can be designed for stable systems based on a simple model. The controller has three tuning parameters, one of them being the sampling period, which can be chosen from the step res...
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A robust discrete-time PI controller can be designed for stable systems based on a simple model. The controller has three tuning parameters, one of them being the sampling period, which can be chosen from the step response of the plant. The relationships between the parameters assuring the stability of the system are derived. The structure of the controller is a particular case of Internal Model control (IMC) (Morari and Zafiriou, 1989), and can also be used to control processes with large dead times. The paper establishes the model and derives the discrete controller. The conditions for asymptotic stability of the closed-loop system for an unknown stable plant are derived. The paper applies the proposed scheme to plant with large dead times and its relationship with the predictive PI controller of (Hagglund, 1992) is shown.< >
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