摘要:

Closed-loop stability conditions are given for systems with both structured and unstructured uncertainties. In particular, it is shown that the guaranteed cost regulator taking into account the structured uncertainties, can tolerate unstructured uncertainties as well, If the systems dynamics matrix only is uncertain, this controller provides the same stability margins as the standard LQ optimal regulator, for all admissible parameter variations. If, in addition, uncertainties enter into the input matrix, stability margins depend on the uncertainties on B. Furthermore, these results are extended to the a-stability case.

ISSN:0020-7179    

DOI:10.1080/00207179408921449

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

By considering a previous study (Nie and Linkens 1992) as a first step towards integrating a rule-based fuzzy controller with neural networks from a viewpoint of functional equivalence, this paper continues the process by making a crucial assumption that neither control experts nor teacher signals are available for the multivariable control problem. In response to this challenge, we present a novel and systematic approach capable of learning and extracting required control rules automatically from the controlled environment for use by back-propagation neural networks (BNN)-based fuzzy controllers. Three possible controller structures are suggested with some comparative studies. Some pertinent points relating the present method to other traditional ones are discussed. Simulation results of blood pressure control demonstrate the utility and feasibility of the proposed approach in solving relatively complex control problems, in particular, those problems where neither control experts nor mathematical models of the controlled process are available.

ISSN:0020-7179    

DOI:10.1080/00207179408921450

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A closed-form solution is presented to the H ∞ sub-optimal control problem via state or output feedback. The problem formulation is general and does not impose any restrictions on feedthrough terms between the control input and the controlled output or between the disturbance input and the measurement output variables. It is, however, required that both the transfer function from the disturbance input to the measurement output and the transfer function from the control input to the controlled output have no invariant zeros on the jwaxis and that they satisfy certain geometric conditions. For the same class of systems, the conditions under which the H ∞ optimal control problem, via state feedback, has a solution are given. Moreover, explicit expressions for the optimal solutions are provided. Finally, the pole/zero cancellations in the closed-loop system resulting from the H ∞ optimal or sub-optimal state or output feedback are examined.

ISSN:0020-7179    

DOI:10.1080/00207179408921451

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The individual channel design (ICD) pole-zero structure of systems defined by linear state-space models is investigated. The existence of ‘fictitious’ cancelling poles and zeros and highly structured plant transfer-function matrices leads to a requirement, within ICD, that these systems be handled differently from systems given directly (Leithead and O'Reilly 1992 b) in transfer-function matrix form. Both the pole-zero structures of multiple-channels and of multiple-channels with infinite gain are presented, and it is noted that multiple-channel zeros which coincide with the plant poles are fictitious. A similar statement of pole-zero structure is made for each of the m open-loop Individual Channels Cj. Further, the number Z of RHPZs of Channel Cjis given by Z = N + P − Q where N is the net number of clockwise encirclements of the point (1,0) by the Nyquist plot of the multivariable structure function γj(s), P is the number of RHPPs of γj(s), and Q is the number of RHPPs of the plant. Finally, it is established that weak feedback around an individual plant transfer function element can be used to stabilize the plant, render specific individual plant transfer function elements minimum phase, and render specific plant sub-matrices minimum phase.

ISSN:0020-7179    

DOI:10.1080/00207179408921452

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Narendra and Parthasarathy (1990) demonstrated that neural networks can be used effectively for the identification and control of non-linear dynamical systems. The structure of the controller used was dependent on the structure of the non-linear system under consideration, of which some partial knowledge was assumed. This work is extended by considering a unified approach for the control of higher order systems where full state information is not available, and where no specific information about the structure of the system is assumed. In this case the controller merely emulates the implicit function of some appropriate error criterion. This unified approach includes, as special cases, those systems with special structure previously considered in Narendra and Parthasarathy (1990). Specialization of the method to linear systems allows swift convergence by virtue of a certain convexity property. Extensive simulations confirm the feasibility and effectiveness of the proposed method.

ISSN:0020-7179    

DOI:10.1080/00207179408921453

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

An efficient yet simple automatic tuning algorithm is developed for dead-time compensators (DTC) common to industrial process controllers. The auto-tuner is capable of setting eight tuning parameters: two for the primary controller, three for the process model and another three for an additional modification aimed at improving the disturbance rejection properties. The process model used in the algorithm is a first order + dead time which captures the essential dynamics of the majority of loops in the chemical and process industries. The methodology and methods used, however, can be readily extended to higher order and more complicated models. The auto-tuner utilizes two points on the process Nyquist curve acquired through automatically generated controlled limit cycles in closed loop fashion. Least squares is then used to estimate the process model. It is shown that an appropriate selection of the two points as well as the weighting matrix in the least squares leads to a robust estimation. A simple rule based on robustness considerations is employed by the auto-tuner for tuning the primary controller. The complete auto-tuners fit easily into existing micro-processor-based industrial controllers. Simulations demonstrate the effectiveness and robustness of the auto-tuner as well as the improved performance gained by the automatically-tuned DTC for high-order processes and even for dead-time free processes though it contains a simple model.

ISSN:0020-7179    

DOI:10.1080/00207179408921454

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Explicit design formulae are derived for proportional (P), and proportional and integral (PI), controllers for unstable first-order plus time delay processes. A stability condition for the design of a PI controller is derived. The values ofKmaxand τIfrom the proposed approximate analytical solutions are compared with the exact numerical solutions. The response of the controlled system with the proposed design settings is compared with that of the settings given by De Paor and O'Malley (1989).

ISSN:0020-7179    

DOI:10.1080/00207179408921455

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The pole-zero map, invariably introduced on an ad hoc basis, gives a very good frequency domain approximation in the range 0 ≤ ωT < 1, where T is sampling period, to the unrealizable digital controller transfer functionC(z) which would result from mapping the corresponding analogue transfer functionGc(s) underz = esT,i.e., s = (1/T) Inz. A variation of the well known Tustin transformation emerges as a simple alternative.

ISSN:0020-7179    

DOI:10.1080/00207179408921456

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

It is shown that, by a suitable embedding in the standard H∞ control problem, the generalized H∞-optimal control problem may be recast as a one-block Nehari problem. Since an explicit solution exists for the latter, there seems little need for the iterative polynomial-based solution procedures recently presented in the literature.

ISSN:0020-7179    

DOI:10.1080/00207179408921457

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0020-7179    

DOI:10.1080/00207179408921458

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor