Nikola Danković

Design of generalised orthogonal filters: application to the modelling of dynamical systems

In this article, we define a new class of orthogonal filters with complex poles and zeroes inside their transfer function. This further improvement of classical orthogonal filters allows the possibility to model a wider range of real systems, that is, the systems whose mathematical models have complex zeroes besides real ones. These filters can be applied in the following areas: circuit theory, telecommunications, signal processing, bond graphs, theory approximations and control system theory. First, we describe the rational functions with complex poles and zeroes, and prove their orthogonality. Based on these functions, we designed the block diagram of orthogonal Legendre-type filter with complex poles and zeroes. After that an appropriate analogue scheme of this filter for practical realisation is derived. To validate theoretical results, we performed an experiment with a cascade-connected system designed and practically realised in our laboratories. The experiments proved the quality of the designed orthogonal model in terms of accuracy and simplicity.

Probability estimation of certain properties of the imperfect systems

This paper presents one method for probability estimation of some property of imperfect systems (stability, reliability, oscillations appearance, controllability, sensitivity, etc.). The region of certain system property is approximated in parameter space and relations for probability of defined properties are obtained. Application systems with one nonlinearity: of this approximate method in the real technical system is given for the case of determining the probability of oscillations appearance.

CONTROL SYSTEM OF STEEL BATTERY CHARGER

A practical realization of control of a diode–thyristor bridge is provided in this paper. The proposed control logic is applied to an NiCd accumulator charger. These accumulators are used for power supply of electrical devices and equipment in CFR locomotives. The control system provides a regular mode of NiCd accumulators charging and discharging, and, in this way, their long lifespan. A hardware configuration and a control algorithm for efficient NiCd accumulator charging and preventing overcharging and overheating are provided.

The Probability of Stability Estimation of an Arbitrary Order DPCM Prediction Filter: Comparison Between the Classical Approach and the Monte Carlo Method

This paper presents the stability analysis of the linear recursive (prediction) filters with higher order predictors in a DPCM (differential pulse-code modulation) system, where traditional methods become too difficult and complex. Stability conditions for the third- and fourth-order predictor are given by using the Schur–Cohn stability criterion. The probability of stability estimation is performed by using the Monte Carlo method. Verification of the proposed method is performed for lower order predictors (the first- and second-order). We calculated numerical values of the probability of stability for higher order predictors and previously experimentally obtained parameters. With large enough number of trials (samples) in Monte Carlo simulation, we reach the desired accuracy. DOI: http://dx.doi.org/10.5755/j01.itc.46.2.14038

Upravljanje termodimnom komorom

The paper discusses the automatic control of thermo-smoke chamber, which is designed for thermal processing (drying, cooking, roasting, baking) and smoking meat, meat products, fish, cheese, etc. The chamber has electric heating elements for drying and generating the steam, the fan with a frequency control for the air circulation, integrated systems for the generation of smoke and elimination of waste smoke, solenoid valves for washing and valves for regulation of the opening of the smoke channel. Control logic is based on PLC. Display and adjustment of characteristic values and parameters, such as temperature, air humidity in the chamber, the current value of the humidity in one or two point of products to be treated in the chamber and the flow of air is performed in the operators panel. Programs are assigned on the panel and you can see the device status, enabling functionality thermo-smoke chamber. Control procedure of chamber takes place by activating the corresponding recipes, which are created based on the experiences and demands of technology and the result is a good quality of products.

ORTHOGONAL HYBRID-FUZZY CONTROLLERS

The main idea of this paper is to present a possibility of application of hybrid-fuzzy controllers in control systems theory. In this paper, we have described a new method оf using orthogonal functions in control of dynamical systems. These functions generate genarilzed quasi-orthogonal filter, which are used in the concluding phase of the fuzzy controllers. Proposed hybrid-fuzzy controllers of Takagi-Sugeno type has been applied to a DC servo drive system and performed experiments have verified efficiency and improvements of a new control method.