1997 (Volume 6)
A numerically simplified fuzzy logic controller
|Bogdan Kasztenny, Andrzej Wiszniewski|
(Wrocław University of Technology, Poland )
This paper is concerned with the numerical optimization of a Fuzzy Logic Controller (FLC) for both its efficient simulation and easy real-time implementation. The basic concept of the FLC based on generalized T-operators approach has been presented. Several assumptions regarding the mathematical formalization of the FLC have been made leading to its numerical simplification. They include: Goguen formulas for T-operators, "Center of Gravity" method for defuzzification, and the overlapping between not more than two membership functions for fuzzy output from the controller. Under these assumptions, the paper presents the non-fuzzy output from the FLC as the ratio of two weighted sums of certain functions of the inputs, reducing significantly the computational burden of the FLC algorithm comparing with the definition-based implementation. The analysis has been performed for a two-input FLC, but extended to a multi-input FLC. The Fuzzy Logic Power System Stabilizer (PSS) has been chosen as an application example. Results of simulation studies demonstrate the efficiency of both the presented optimization method in terms of numerical simplicity and the designed PSS in terms of improving the power system stability.
keywords: Fuzzy Logic Control, T-operators, Numerical Optimization, Power System Stabilizer.
Adaptive stabilization of a class of semilinear parabolic distributed parameter systems in the case of collocated actuators and sensors
|Toshihiro Kobayashi, Jiachun Fan|
(Kyushu Institute of Technology, Japan )
In this paper we consider adaptive stabilization of a class of semilinear parabolic distributed parameter systems in the case of the input and output operators being unbounded and collocated. So boundary stabilization problems can be treated. Adaptive stabilization is realized by the concept of high-gain output feedback. In the controlled system, the convergence of the system state to zero will be guaranteed.
keywords: adaptive stabilization, semilinear distributed parameter systems, collocated input and output, boundary input and output.
Optimal control of distributed stochastic systems with delays in the control
(Faculté des Sciences Ben M'sik, Morocco )
(Ecole Mohammadia d'Ingénieurs, Morocco )
In this paper we consider the quadratic control problem for stochastic infinite-dimensional systems with delays in the control. It is well known that, using the separation principle theorem, the problem can be reduced to two independant problems of control and filtering. The objective of this paper is to present a new approach for solving this problem when the state of system is completely observed. It is based on the introduction of an adequate Hilbertian topology. To illustrate this work, an example of controlled noisy equation is given.
keywords: Delayed control, Distributed stochastic systems, Hilbert uniqueness method, Optimal control, Separation principle theorem.
On the dynamics of a closed-loop system with hysteresis
(Institute of Fundamental Technological Research PAN, Poland )
A closed-loop hysteretic system of stabilization of a multidimensional stationary linear object is considered. The stability analysis of the system is performed by means of the second method of Lyapunov. Sufficient conditions of stability are provided and optimal estimate of the asymptotical region is obtained. Dynamical properties of the system in the region of hysteresis are described. The existence of a stable limit cycle in the region is proved.
keywords: Lyapunov function, feedback stabilization, bang-bang control, hysteresis.
Overshoots in 2-nd class of linear control systems
(University of Mining and Metallurgy, Poland )
The relation between overshoots and the coefficients of the differential equations describing the system is one of the central problem of control systems. Analytical formulae for the determination of overshoots are known only for the second order systems. In the paper  there are presented such formulae for the 1-st class of the system it means for the systems with only one pair conjugate roots. In this paper the overshoots for the 2-nd class of the systems containing 2-pairs of the conjugate roots are determined.
keywords: control system analysis, 2-nd class of linear control systems, overshoots in linear systems.
Floating-point roundoff errors in first-order filters of digital controllers
(Technical University of Rzeszów, Poland )
Roundoff errors of floating-point arithmetic for first order unity-gain digital filters realized by means of z- and 'delta'-operators are evaluated. 'delta'-realization corresponds to classical analog scheme involving adder, multiplier, and integrator. It allows for much smaller sampling period than z-realization. White noise, sinusoid and a constant with small additive noise are considered as filter inputs. The third case may represent process variable in feedback control loop. It turns out that the 'delta'-realization provides twice smaller roundoff error than z-realization. An upper bound on filter time constant is given in case of process variable input.
The quest for small benchmarks for the chromatic sum problem
|W. Głazek, M. Kubale, K. Manuszewski|
(Technical University of Gdańsk, Poland )
The chromatic sum of a graph is the minimum total of the colors on the vertices taken over all possible proper colorings using natural numbers. Because of practical applications and the fact that computing the chromatic sum is NP-hard, we are interested in the performance of heuristic algorithms. For a given approximate coloring algorithm a graph is said to be slightly HCT (resp. HCT) if some (resp. every) implementation of the algorithm gives a bigger total than the chromatic sum. In this paper we give the smallest HCT and slightly HCT graphs for the most popular vertex coloring algorithms when adapted to the chromatic sum problem. Some of them have been obtained by exhaustive computational search. Our results confirm that algorithms based on the independent sets principle are much better than those realizing a sequential coloring approach.
Circular built-in self-test for controllers with many internal clocks
(University of Silesia in Cieszyn, Poland )
The paper proposes a new extension to Circular Built-In Self-Test (named Multi-Clock Circular-BIST - MCC-BIST) suitable for testing controllers composed of many sequential blocks controlled by different clock signals generated in one block. Testing can be performed in one session and the need of clock line switches between normal and BIST mode is minimised. As a result both logic overhead is reduced and no additional faults in the switching circuitry are inserted. The properties are examined and simulation results of a sample controller are provided. They verify that this technique guarantees high test quality provided that the test time is increased. MCC-BIST is feasible for incorporating into IEEE1149.1 standard.
keywords: Built-In Self-Test, Pseudorandom Test, Sequential Circuit Testing
Robustness of fuzzy control with respect to plant parameters modifications - simulation results
(Rzeszow University of Technology, Poland)
A comparative study on robustness and performance of different controllers is presented. Simulation results on dependence between four basic performance indices and the plant parameters are given. The linear second order plant with time delay and the following controllers: PID, three-dimensional multilevel relay, Mamdani's fuzzy controller, fuzzy controller with G?del's implication, and the "modified" fuzzy controller, which is described in work , are investigated.