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Control Theory and Applications, IEE Proceedings -

Issue 6 • Date Nov 1996

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Displaying Results 1 - 12 of 12
  • Output tracking for linear uncertain time-delay systems

    Publication Year: 1996 , Page(s): 481 - 488
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    The paper considers the problem of robust output tracking of an uncertain system with multiple delays in both the state and control vectors. The disturbances are assumed constant, unknown but bounded. A robust output tracking scheme is proposed. The scheme guarantees asymptotic tracking of the command reference output, when the mismatched portion of the uncertainties satisfies a certain bound condition. In addition, the paper presents robust output tracking schemes for a class of matched uncertain time-delay systems and matched and mismatched uncertain nondelay systems. A numerical example is given to illustrate the results View full abstract»

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  • Parametric uncertainty bounds for performance robustness of linear systems with output feedback

    Publication Year: 1996 , Page(s): 509 - 513
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (428 KB)  

    The paper is devoted to performance robustness analysis of uncertain state-space models with linear parametric uncertainties and output feedback. The purpose is to find bounds on uncertain parameters within which the system H2 norm performance index is kept below a prespecified value. Through matrix nonsingularity analysis, it is shown that the bounds can be computed from structured singular values of certain composite matrices. To fully utilise the structural information of uncertainties, the authors also develop a method for reducing matrix sizes involved in the computation of structured singular value View full abstract»

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  • Digital redesign of cascaded analogue controllers for sampled-data interval systems

    Publication Year: 1996 , Page(s): 489 - 498
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (924 KB)  

    The paper presents a new method for the digital redesign of cascaded analogue controllers for continuous-time parametric interval systems. The bilinear and inverse-bilinear approximation method is developed to carry out discretisation of the predesigned cascaded analogue controller, taking into account intersample behaviour and implementation errors. A dual concept of the proposed digital redesign method is utilised to construct a new pseudodigital observer such that the estimated states of the digitally redesigned digital observer closely match those of the original continuous-time observer at the sampling instants. Using the newly digitally redesigned observer based controllers, the resulting dynamic states of the digitally controlled cascaded sampled-data interval systems are able to closely match those of the original analogously controlled cascaded continuous-time parametric interval systems View full abstract»

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  • Decentralised control design of uncertain nominally linear symmetric composite systems

    Publication Year: 1996 , Page(s): 530 - 536
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (584 KB)  

    Riccati-type control for a class of uncertain nominally linear large-scale systems composed of identical subsystems and symmetric interconnections is presented. Symmetric composite systems with bounded uncertainties in parameters both in subsystems and interconnections system matrices are considered for decentralised output control design using a controller-observer scheme. The controller-observer is designed for an auxiliary artificial uncertain system whose dimension is equal to the dimension of a subsystem in the original system. Conditions for the validity of this procedure are proved and illustrated on a numerical example. Matching conditions are not needed View full abstract»

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  • Analysis of linear discrete SISO control systems via a set of delta functions

    Publication Year: 1996 , Page(s): 514 - 518
    Cited by:  Papers (17)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    The paper presents a computational technique through operational matrices using a set of mutually disjoint delta functions (DF) for the analysis of linear discrete control systems. Following a brief review of the well known block pulse functions (BPF), new set of delta functions is viewed in the same light. This set is used to develop operational transfer functions in the delta function domain (DOTF) and employed for discrete system analysis which results in the same accuracy as the conventional z-transform method. The presented technique uses simple matrix manipulations and is able to do away with laborious and involved algebraic steps, including inverse transformation, associated with the z-transform analysis without losing accuracy. Also, the accuracy of sample values of the output does not depend upon the number of component functions in a semi-open interval (or the sampling interval). A few linear discrete SISO control systems, open loop as well as closed loop, having different typical plant transfer functions, are analysed as illustrative examples View full abstract»

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  • Model predictive control algorithms for systems with slow sampled outputs

    Publication Year: 1996 , Page(s): 551 - 556
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    Many practical systems involve sensors that provide signals at slow sample rates. Guaranteeing the intersample performance is a fundamental problem in controlling such systems. Two multirate model predictive control schemes are presented as solutions to this problem. In the first control scheme, intersample responses are estimated and used as compensation for the missing measurements of the controlled output. This scheme can therefore operate at the desired fast rate. The second scheme updates the control action at the slow rate that the output is sampled, but it is different from conventional techniques. This scheme finds intersample responses using a modified Z transform, and produces the control variable by optimising a performance index that accounts for both sample and intersample behaviour. Numerical simulations demonstrate that the two multirate algorithms exhibit improved time responses compared to the conventional approach View full abstract»

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  • Expert robust decentralised controller for uncertain large-scale systems

    Publication Year: 1996 , Page(s): 519 - 529
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (836 KB)  

    An expert decentralised robust control algorithm is developed for continuous large-scale systems with dynamic interconnections and external disturbances, taking into consideration the possible structured variation in the system and input matrices. The proposed scheme has three parallel processes: the decentralised robust controller and observer, the overlapped observers for fault detection and, finally, the expert system. The expert system uses the differences between the same states as estimated by different overlapped observers to specify the failure position. Furthermore, it selects the appropriate control and observer gains that guarantee the overall system stability while responding in a satisfactory manner View full abstract»

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  • Author Index

    Publication Year: 1996 , Page(s): 565 - 568
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    First Page of the Article
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  • Optimal strictly positive real approximations for stable transfer functions

    Publication Year: 1996 , Page(s): 537 - 542
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    The problem of finding the optimal strictly positive real (SPR) approximation to a given stable transfer function is considered. The transfer function is further assumed to be strictly proper and the SPR approximation is constrained to have the same pole structure. The optimisation is carried out using the (weighted) H2-norm and the problem is reduced to a strictly convex quadratic programming problem with linear inequality constraints. At the heart of the method is a parametrisation for all SPR compensators which possess a given denominator polynomial. Motivation for the problem stems from the robust stability provided by SPR compensation for passive plants such as flexible structures with collocated sensing and actuation. Numerical examples are provided, as well as the experimental implementation of an optimal approximation to the control of a single-flexible-link manipulator View full abstract»

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  • Two-degree-of-freedom design method of LQI servo systems: use of frequency-dependent weighting matrices for sensitivity reduction

    Publication Year: 1996 , Page(s): 557 - 563
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    The authors previously (1996) proposed a new method to design two-degree-of-freedom robust servo systems for step references and step disturbances. In this method, the tracking characteristics for step references are determined optimally with respect to a quadratic-integral performance index, while the feedback characteristics for step disturbances are determined also optimally with respect to another quadratic-integral performance index. The paper extends these results by introducing frequency-dependent weighting matrices into the latter performance index. By employing appropriate frequency-dependent weighting matrices, some sort of loop-shaping can be achieved for the sensitivity characteristics, and thus more design freedom is obtained. In particular, loop-shaping ability and tuning ability can be separated in some sense. A numerical example is also studied to illustrate the results View full abstract»

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  • Telerobot control and real-time simulation environment using parallel processing

    Publication Year: 1996 , Page(s): 543 - 550
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (800 KB)  

    Simulation can reduce some of the hardware demands of telerobot systems but, to date, a heavy commitment to computer hardware has been required to produce a real-time response. Parallel processing of a balanced division of the Newton-Euler formulation on transputers is used to perform real-time dynamic simulation for a 7 d.o.f. robot. Comparative times for the transputer and other parallel processors are also given. Practical interfaces are derived for robot hardware, other features of the practical system which are developed include data storage and transferral strategies and also a graphical interface to the user on a PC displaying real-time force and position information. Approaches to the practical difficulties of identification and real-time simulation of complex friction effects are also examined View full abstract»

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  • Error specification, monitoring and recovery in computer-integrated manufacturing: an analytic approach

    Publication Year: 1996 , Page(s): 499 - 508
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1044 KB)  

    State transitions in computer-integrated manufacturing (CIM) systems result either from the execution of the planned actions or from the occurrence of unpredictable events. One key requirement for task planning designed for CIM systems is the ability to monitor events and respond to them appropriately. Related issues include the specification and classification of possible system faults, errors and failures. The paper proposes an error-specification language, an error-monitoring mechanism and an error-recovery mechanism. Founded on a mathematical framework, the error-recovery mechanism uses the concept of severity to alter system characteristics. The paper presents some examples from an integrated multirobot system View full abstract»

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