Gábor Péceli

A common structure for recursive discrete transforms

This paper presents a common framework for the recursive implementation of arbitrary discrete transformations. The transform coefficients to be applied are periodically time-varying and can be derived from the discrete basis functions of the transforms. The method is based on Hostetters dead-beat observer approach to signal processing [1], [2], but instead of the ongoing calculation of the transform coefficients, explicit expressions are derived. The proposed structure can be efficiently used even for FIR and IIR filtering operations.

Resonator-based digital filters

A digital filter structure that is structurally passive and can suppress all zero-input limit cycles, and if rounding is applied provides minimum roundoff noise is presented. These properties are due to the fact that this structure generates its output as a linear combination of orthogonal signal components, thus internally implementing an orthogonal realization of a lossless transfer function. >

Iterative fuzzy model inversion

Nowadays model based techniques play very important role in solving measurement and control problems. Recently for representing nonlinear systems fuzzy models became very popular. For evaluating measurement data and for controller design also the inverse models are of considerable interest. In this paper a technique to perform fuzzy model inversion is introduced. The method is based on solving a nonlinear equation derived from the multiple-input single-output (MISO) forward fuzzy model simple by interchanging the role of the output and one of the inputs. The utilization of the inverse model can be either a direct compensation of some measurement nonlinearities or a controller mechanism for nonlinear plants. For discrete-time inputs the proposed technique provides good performance if the iterative inversion is fast enough compared to system variations, i.e. the iteration is convergent within the sampling period applied. The proposed method can be considered also as a simple nonlinear state observer, which reconstructs the selected input of the forward fuzzy model from its output using an appropriate strategy and a copy of the fuzzy model itself. It is also shown that using this observer concept completely inverted models can also be derived.

Transients in reconfigurable control loops

In this paper transient management techniques are investigated in a scenario where the reconfiguration or replacement of a forward-loop controller is required due to changes in the environment or in the plant. Such a change in the closed control loop may have undesirable transient effects, which may degrade the performance of the controlled system. Since the transient cancellation and reduction schemes used in open-loop systems can not be used here, new solutions are proposed for run-time transient handling.

Convergence properties of an adaptive Fourier analyzer

A PLL-like adaptive Fourier analyzer (AFA) was proposed which has shown excellent performance in practical applications. The convergence analysis of this AFA is extremely difficult, and until now theoretical results have not been available. In this paper a modified version of the original AFA is proposed. The new version preserves the effectiveness of the original AFA, and its convergence properties can be exactly analyzed. Sufficient conditions are presented for the exponential stability, and the absolutely monotone convergence, as a function of the harmonic content of the input signal. The speed of the convergence is also estimated, and the effect of the noise and of unmodeled periodic components are analyzed.

Digital filters based on recursive Walsh-Hadamard transformation

The applicability of the recursive Walsh-Hadamard transformation to FIR and IIR (finite- and infinite-impulse-response) filtering is investigated. It is shown that using a common structure for recursive transforms recently introduced by G. Peceli (1986), the usual frequency-domain FIR filtering problem can be easily converted into a Walsh sequency-domain filtering problem. It is also shown that a simple modification of this structure results in a possible alternative for IIR filter implementations. >

Intelligent medical instruments

The authors introduce system design methods that can contribute to the resolution of the rather complex requirements in the field of medical instrumentation, drawing on their own experiences in the development of intelligence EEG recorders and analyzers. They focus on the integration of the knowledge base with the numerical database and the algorithms within the unified real-time control structure of the measuring system. Possible alternatives are presented for the implementation of both conventional data processing and knowledge-based data processing. The authors discuss the problem-oriented user interface and conclude with a short presentation of an intelligent EEG recorder development.<<ETX>>

Transient reduction in control loops in case of joint plant-controller reconfiguration

In control systems undesirable transients may occur when either the controller or the plant is reconfigured during the operation. This paper gives a new solution for the transient reduction problem in simple feedback control loops to maintain the smooth steady-state behavior even if both the plant and the controller are changed simultaneously. The transients are reduced in least-squares sense by using an anti-transient signal.

Transients in reconfigurable digital signal processing systems

To solve measurement and control problems, the processing of input data is performed typically by model-based digital signal processing (DSP) systems, which contain a representation of our knowledge about the nature and the actual circumstances of the problem at hand. If the nature or the actual circumstances change, the corresponding model should also be changed. Similarly, if the amount of knowledge about the problem increases due to measurements, an improved model can be suggested which provides better performance. As a consequence, the real-time adaptation or reconfiguration of the DSP system to be applied can hardly be avoided. The transients caused by these adaptations/reconfigurations is investigated. It is shown that for feedback systems, i.e., for infinite impulse response (IIR) filters, these transients are strongly structure-dependent and that the so-called orthogonal filter structures also provide good performance in this respect.

Model-based fault-adaptive control of complex dynamic systems

Complex control applications require capabilities for accommodating faults in the controlled plant. Fault accommoda- tion involves the detection and isolation of faults, and then taking appropriate control actions to mitigate the fault effects and main- tain control. This requires the integration of fault diagnostics with control in a feedback loop. This paper discusses a generic frame- work for building fault-adaptive control systems using a model- based approach, with special emphasis on the modeling schemes that describe different aspects of the system at different levels of abstraction and granularity. The concepts are illustrated by a fault adaptive notional fuel system control example.