摘要:

A problem which arises in the convergence of LQG explicit self-tuning controllers is considered, concerning the possibility of unstable pole-zero cancellation in the estimated system model. Since the underlying plant cannot contain such a term the problem is to stabilize this estimated system model knowing that the cancellation does not arise from the plant description itself. The assumption is therefore made that the cancellation arises due to unstable terms in the external stochastic signal inputs to the system. The problem is then to derive the LQG controller for such a system and to show that it stabilizes the assumed system model. The LQG stochastic optimal controller is obtained for systems which can include unstable disturbance, reference or measurement noise models. Although an infinite-time solution is required, this must be obtained by considering the limiting case of a finite-time problem. The necessary and sufficient conditions for optimality are therefore derived in the time-domain for a finite-time situation. The required solution is then obtained using a polynomial systems approach. Finally the resulting self-tuning algorithm, and the convergence and stability proof which avoids the unstable pole-zero cancellation problem, are discussed.

ISSN:0020-7721    

DOI:10.1080/00207729008910465

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The stabilization of large structural systems (LSS) under (i) mode truncation and linear parametric perturbations, or (ii) mode truncation and actuator saturations is considered. A new robust stability condition for the perturbed LSS controlled by observer-based compensators is derived. A stability criterion is also given for the stabilization of LSS by observer-based constrained controls. Finally, a simply supported beam problem is provided for illustration.

ISSN:0020-7721    

DOI:10.1080/00207729008910466

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Developmental systems are constructed that have multi-level development, i.e. development occurs in several successive stages. Some parts of the system remain ‘dormant’ until other parts have reached a certain level of development.

ISSN:0020-7721    

DOI:10.1080/00207729008910467

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

This paper deals with the profit analysis of a single-server two-unit (one priority and the other ordinary) cold standby system with two modes of each unit normal and total failure. A switch is used to operate the standby unit (ordinary unit) and it works successfully at the time of need with known probability p (= 1 − q). The priority unit gets preference both for operation and repair. After working for a random length of time, the ordinary unit needs rest for a random length of time. System failure occurs when both the units fail totally. Identifying the system at suitable regenerative epochs, integral equations are set up for the probabilities of the system being in the ‘up’, ‘down’ or ‘failed’ state; to solve these equations the Laplace transform technique is adopted. Various reliability characteristics are obtained to carry out the cost-benefit analysis, and numerical results pertaining to a particular case are also presented.

ISSN:0020-7721    

DOI:10.1080/00207729008910468

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

General conditions for the strong consistency of estimates made by the method of orthogonal projections are discussed, referring to the problems of identification of regression equations with errors in the independent variables. Computational aspects of the application of different numerical algorithms and their regularization problems are studied in order to find estimates by the method of orthogonal projections.

ISSN:0020-7721    

DOI:10.1080/00207729008910469

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

We examine the variational stability of infinite dimensional optimal control problems governed by non-linear evolution equations. Our tools are the Kuratowski-Mosco convergence of sets and the corresponding τ-convergence of functions. We prove the τ-convergence of cost functionals, the convergence of the values of the problems and we examine the variational stability of the solution and reachable sets. These results are then applied to a sequence of non-linear parabolic distributed parameter optimal control problems.

ISSN:0020-7721    

DOI:10.1080/00207729008910470

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A new method for the testing of combinational digital circuits is presented. The method is based on the concept of the ‘index vector’ of a switching function (Gupta 1987), and represents an extension of syndrome testing. A large percentage of syndrome untestable faults are found to be index vector testable. An approach to testing index vector untestable circuits that relies only on the function realized by the circuit and is independent of the circuit topology is presented. The method can be used for the detection of both single and multiple stuck-at faults in a combinational circuit.

ISSN:0020-7721    

DOI:10.1080/00207729008910471

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

TheP-model approach of modeling a combinational digital network using Petri nets is introduced. In this model a given logic circuit its represented by a graph With only two types of nodes, places and transitions. A logic 1 value in any line of the circuit corresponds to the presence of a so-called token, and a logic 0 corresponds to the absence of tokens, in the corresponding place of theP-model. The operation of the circuit is reflected in the execution of theP-model resulting from the firing of transitions. Several minimizing transformations in theP-model domain are discussed, which reduces the number of places and transitions by an order of magnitude. Based on thisP-model representation of a logic circuit, a logic simulation algorithm is outlined. The method is faster and also simpler to implement than conventional simulation techniques.

ISSN:0020-7721    

DOI:10.1080/00207729008910472

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

This paper deals with the ‘on-line strategic control’ of flights viewed in the framework of a multilevel model of the air traffic control functions. In particular, this problem is'solved by a decomposition in two sequential sub-problems called ‘altitude control’ and ‘speed control’. For each of these, the mathematical optimization model and the corresponding solution algorithm are developed. Finally, computational tests and results are reported and discussed.

ISSN:0020-7721    

DOI:10.1080/00207729008910473

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Most firms rely mainly on the PERT method (with or without CPM/PERT COST) for project planning. Some use a structured PERT via the work break-down structure approach. This paper examines how this classical procedure could be improved. In the MPSP model, the project structure identified during the functional decomposition phase is used as a support for a piloting system meant to assist the project manager during all the project's lifetime. The model views a project as a hierarchy of functional states (f-states) communicating with each other via the functional links: in it, the functional structure gets a new dynamic, real-time use. Eachf-state's evolution along the project lifetime is modelled as that of a finite state automaton: its input alphabet is made up of the signals indicating the presence of input documents and/or products necessary to thef-state's operations and its output alphabet comprises all the intermediate output it produces. The model associates one PERT graph with each terminalf-state but it does not enforce precedence rules across terminalf-states as does WBS. The necessary intercommunication is made possible by the use of control signals circulating through the functional network and communicating the presence of specific events. The project manager using MPSP can follow-up eachf-state's evolution and control an effective and smooth production of all intermediate outputs.

ISSN:0020-7721    

DOI:10.1080/00207729008910474

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor