Zeljko Juric

Parametric identification of plants with multiple delays and internal feedbacks using genetic algorithm

This paper proposes a procedure for parametric identification of plants having multiple sources of the pure time delays and internal feedbacks, which are extremely complicated for the identification. The procedure is based on a genetic algorithm applied to the samples of the frequency response on the plant.

Protection of computer equipment from power surges

This paper presents some solutions for high-quality, safe and inexpensive overvoltage protection of computer electronic equipment within both the industry and households. The presented solution is partly present in our networks. However, the complete solution is used only in some European countries. This paper describes the advantages and the reasons that suggest the application of such solutions in low voltage networks in Croatia and Bosnia & Herzegovina.

A Simple Extension of Ziegler-Nichols’ Method Based on Damped Oscillations

This paper proposes a simple extension of the well-known Ziegler-Nichols’ (ZN) method. As in the standard ZN method, the experiment may be performed using the controller only, without any extra equipment. But, in opposite to the ZN method, the experiment may be performed using damped oscillations. Also, the proposed method allows more complex models of the plant, so a better tuning may be obtained.

New concept of surge arresters in low voltage networks

The problem of high resistance of the earth is common for all kinds of surge protections used in networks. Therefore, it is not easy to prefer any of them, This paper proposes a new concept of surge arresters based on zinc oxide, which do not use spark gaps. It also explains various reasons that suggest the application of such arresters in low voltage networks in Croatia and Bosnia & Herzegovina.

Identification of an Ethane-ethylene distillation column system — A procedure for MIMO system identification using the IDENT toolbox

This paper deals with the identification process of an ethane-ethylene distillation column system and introduces a procedure for MIMO system identification using Matlabs IDENT toolbox. An existing, five inputs and three outputs, ninety samples dataset has been analyzed. Four separate datasets are analysed, each having a different level of noise. As a part of the proposed procedure, both nonparametric and parametric identification methods have been implemented and results have been discussed. A comparative analysis of the results for all of the tested model structures has been carried out and the best performing model has been chosen. A Simulink model of the identified system has been implemented based on the best performing parametric model. It has been stimulated with the existing input datasets and the resulting output signals have been compared to the existing output datasets. The obtained results confirm the quality of the obtained model and affirm the correctness of the proposed and implemented procedure.

A frequency-based method for complete identification of some types of wiener-type plants based on relay feedback

This paper proposes a new closed loop frequency based method for a parametric identification of some types of Wiener-type nonlinear plants. It provides a parametric model of the linear part of the plant, and a point by point relationship between input and output of the nonlinear part of the plant. Two approaches are proposed for the identification of the nonlinear part. The first approach is slower, but it does not require any additional equipment expect the relay. The second approach is much faster, but it requires some additional equipment.

Novel matrix-based improvement of nodal analysis for circuits with singularities

This paper presents an alternative to existing techniques based on Nodal Analysis designed specifically to suit implementation in matrix-oriented programming languages, keeping the simplicity of original Nodal Analysis and bringing improvements to make virtually all circuit topologies solvable through it, dealing with potential singularities, hence the name Singular Nodal Analysis (SNA). Two variants of this novel algorithm are described. Their validity is proven and their applicability is shown through two practical examples.

A simple method for estimation the time delay based on damped oscillations

This paper describes a simple closed loop procedure for estimating the value of the time delay in an all-pole system. The procedure may be used to track slow changes in the time delay. It uses the damped oscillatory response of the closed-loop system. Two slightly different methods are presented to obtain unknown value of τ. Additionally, this paper also illustrates how the Pronys method may be used to obtain necessary initial data.

Adaptive procedure for adjusting settings of PI controller for plants with slowly varying parameters

This paper proposes a new method for retuning the parameters of a PI controller to compensate changes in the plant parameters. The presented closed-loop procedure requires only three simple experiments that introduce a small disturbance in the system to obtain an oscillatory response. New values of the parameters of the PI controller may be obtained using simple arithmetic operations on the dominant poles of the responses.