Last issue
2016 (vol. 26) - Number 4

Andrzej Ruszewski:

Practical and asymptotic stability of fractional discrete-time scalar systems described by a new model

D. Krokavec, A. Filasova, P. Liscinsky:

On fault tolerant control structures incorporating fault estimation

Sundarapandian Vaidyanathan:

Hyperchaos, adaptive control and synchronization of a novel 4-D  hyperchaotic system with two quadratic nonlinearities

H. Górecki, M. Zaczyk:

Analytic solutions of transcendental equations with application to automatics

F. Mnif:

Predictor-based stabilization for chained form systems with input time delay

S. Daniar, R. Aazami, M. Shiroei:

Multivariable predictive control considering time delay for load-frequency control in multi-area power systems

T. Kaczorek:

Analysis and comparison of the stability of discrete-time and continuous-time linear systems

M. Rachik, M. Lhous:

An observer-based control of linear systems with uncertain parameters

L. Malinski:

Identification of stable elementary bilinear time-series model

V.V. Huynh:

New observer-based control design for mismatched uncertain systems with time-delay

ACS Abstract:

2008 (Volume 18)
Number 1
1. Supervised multiple model adaptive control of a heating fan
2. A new stopping criterion for iterative solvers for control optimal problems
3. Realization problem for fractional continuous-time systems
4. Towards robust minimum variance control of nonsquare LTI MIMO systems
5. Robust stability of systems with parametric uncertainty
6. A comparative study on estimation techniques with applications to power signal frequency
7. Robust nonlinear PI for attitude stabilization of a four-rotor mini-aircraft: From theory to experiment
8. Positive fractional discrete-time Lyapunov systems

Supervised multiple model adaptive control of a heating fanDownload full PDF article
J.M. Lemos
(INESC-ID/IST, Lisboa, Portugal)
L. Marreiros
(INESC-ID/IST, Lisboa, Portugal)
B. Costa
(INESC-ID/IST, Lisboa, Portugal)

The paper presents a case study on the application of supervised switched multiple model adaptive control (SMMAC) to drive the temperature in an air heating fan. The plant considered is of distributed parameter type and its linearized dynamics changes with the value of air flow. The compromises in the design of the different elements of SMMAC are discussed, with emphasis on the trade-off involved in selecting the observer poles. Experimental results show the impromevent in performance of SMMAC with respect to the use of a single linear controller.

keywords: adaptive control, switched control, distributed parameter, thermal processes


A new stopping criterion for iterative solvers for control optimal problemsDownload full PDF article
K. Krumbiegel
(University Duisburg-Essen, Duisburg, Germany)
A. Rosch
(University Duisburg-Essen, Duisburg, Germany)

Linear quadratic optimal control problems governed by PDEs with pointwise control constraints are considered. We derive error estimates for feasible and infeasible controls of the problem. Based on this theory an error estimator is constructed for different discretization schemes. Moreo ver, we establish the estimator as a stopping criterion for several optimization methods. Furthermore, additional errors caused by solving the linear systems are discussed. The theory is illustrated by numerical examples.

keywords: linear quadratic optimal control problems, control constraints, error estimates, projected gradient method, primal-dual active set strategy, penalty methods, stopping criteria


Realization problem for fractional continuous-time systemsDownload full PDF article
T. Kaczorek
(Bialystok Technical University, Bialystok, Poland)

The realization problem for positive fractional continuous-time linear systems is addressed. Sufficient conditions for the existence of positive realizations for continuous-time linear systems are established. Procedures for computation of positive fractional realizations for SISO and MIMO continuous-time linear systems are proposed and illustrated by numerical examples.

keywords: fractional, positive, realization, continuous-time linear system


Towards robust minimum variance control of nonsquare LTI MIMO systemsDownload full PDF article
W.P. Hunek
(Opole University of Technology, Opole, Poland)

The paper presents a new contribution of the so-called control zeros to robustification of the minimum variance control strategy for nonsquare LTI MIMO systems. A plethora of new, MVC-related inverses of nonsquare polynomial matrices are analytically presented, which give rise to generation of various control zeros. Possible detrimental effects of unstable control zeros can be eliminated making use of a new, pole-free MVC design methodology, but on the other hand, one can take advantage of stable control zeros in a new, minimum-energy design of robust MVC. Thus, control zeros are shown to essentially complement the transmission zero-based Davison's theory of minimum phase nonsquare LTI MIMO systems.

keywords: robust minimum variance control, nonsquare systems, inverses of polynomial matrices, transmission zeros, control zeros, minimum energy


Robust stability of systems with parametric uncertaintyDownload full PDF article
R. Matusu
(Tomas Bata University in Zlin, Czech Republic)
R. Prokop
(Tomas Bata University in Zlin, Czech Republic)

Systems with parametric uncertainty represent an important class of uncertain objects that are characterized by mathematical model containing parameters which are not precisely known, but the values thereof lie within given intervals. This type of uncertainty can arise during the control of real processes, e.g. as a consequence of imprecise measuring or of the influence of certain external conditions. If individual uncertain coefficients (in polynomial, in transfer function etc.) are mutually independent, the uncertainty has a simple interval structure. This article presents several possibilities of interval uncertainty for systems description as well as the tools for robust stability analysis, emphasizing advantages and limitations connected with the use of this simple structures, even for more complex problems.

keywords: robust control, interval uncertainty, Kharitonov theorem, zero exclusion condition, polynomial toolbox


A comparative study on estimation techniques with applications to power signal frequencyDownload full PDF article
A.M. Panda
(Department of Electrical Engineering, NIT Rourkela-769008, Orissa, India)
S.R. Mohanty
(Department of Electrical Engineering, NIT Rourkela-769008, Orissa, India)
P.K. Ray
(Department of Electrical Engineering, NIT Rourkela-769008, Orissa, India)
B. Subudhi
(Department of Electrical Engineering, NIT Rourkela-769008, Orissa, India)

An extended least square (ELS) technique has been proposed in this paper for power system frequency estimation. The validation of the above technique has been made by comparing its performance with the existing techniques such as Kalman filter (KF) and least mean square (LMS) technique etc. It has been observed through a series of simulation studies on frequency estimation that the ELS technique exhibits better performance in comparison to both the LMS and KF methods of power system frequency estimation. In Kalman filter, the determination of covariance matrix is very crucial leading to delay in convergence. LMS algorithm becomes complicated with the incorporation of correlation matrix, which may affect the convergence. On the contrary extended least square algorithm seems to be very simple and attractive without the implementation of covariance and correlation matrix. The feasibility of the ELS algorithm for frequency estimation has been tested with a signal buried with noise. The above estimation technique can be applied in real-time implementation, which will be immensely helpful for the power system protection. A comparative study on performance of the KF, LMS and ELS techniques for power system estimation has been made and included in the paper.

keywords: extended least square (ELS) technique, Kalman filter, least mean square (LMS) technique, power system parameters


Robust nonlinear PI for attitude stabilization of a four-rotor mini-aircraft: From theory to experimentDownload full PDF article
M. Bouchoucha
(LCC, Ecole Militaire Polytechnique, Algerie)
M. Tadjine
(LCP, Ecole Nationale Polytechnique, Algerie)
A. Tayebi
(ACL, Lakehead University, Thunder Bay, Canada)
P. Mullhaupt
(ACL, Ecole Polytechnique Federale de Lausanne, Switzerland)
S. Bouabdallah
(ASL, Swiss Federal Institute of Technology, Switzerland)

Based on the Euler angles parametrization, a new method for the attitude control of a vertical take-off and landing (VTOL) quadrotor aircraft is proposed. It relies on the combination of the backstepping technique and a nonlinear robust PI controller. The integral action gain is nonlinear and based on a switching function that allows a robust behavior for the overall control law. One of the strengths of the proposed approach is its robustness with respect to plant parameters uncertainties. The proposed approach has been tested in simulation and in real time and shows good performance.

keywords: attitude stabilization, backstepping, Euler angles parametrization, nonlinear robust PI, quadrotor


Positive fractional discrete-time Lyapunov systemsDownload full PDF article
P. Przyborowski
(Warsaw University of Technology, Warsaw, Poland)

The positive linear fractional discrete-time Lyapunov systems are introduced. The necessary and sufficient conditions for the positivity, reachability, controllability to zero and observability of the systems are established. The sufficient conditions for stability are given. The notion of the dual positive fractional Lyapunov system is introduced and the relationship between the reachability and observability is given. The considerations are illustrated on the numerical example.

keywords: fractional, positive, discrete-time, Lyapunov system, stability, controllability to zero, reachability


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