International Journal of Electrical Engineering and Computing

Editorial

Nataša Popović — 2024-06-26

Impresum

Budimir Kovačević — 2024-06-26

A new electrode structure of IrOx/Bi-doped SrRuO3 for highly reliable La-doped Pb (Zr, Ti)O3-based ferroelectric memories

WENSHENG WANG — 2024-06-26

We successfully developed a lanthanum (La)-doped Pb (Zr,Ti)O₃ (PLZT) based ferroelectric capacitor (FC) using a new electrode material of bismuth (Bi) doped SrRuO₃ (B-SRO) aiming at reduction of energy consumption of ferroelectric random access memory (FeRAM) by suppressing the leakage current of its FC. Our employed B-SRO layer is effective for suppressing the leakage current due to reducing atomic interdiffusions of Iridium and lead between IrO_x top electrode (TE) and PLZT. Space charge limited conduction (SCLC) is dominant in the leakage current of the FC with B-SRO, while defect assisted conduction possibly includes in the leakage current of FC without B-SRO in addition with the SCLC. Switchable polarization, depending on the B-SRO thickness, has largest value for 1.0-1.5 nm thick B-SRO. Excellent imprint and switching (fatigue) endurances is proven on the FC with 1 nm thick B-SRO.

A New Design Approach to Discrete-Time Sliding Mode Controllers With Disturbance Compensation

Cedomir Milosavljević — 2024-06-26

Abstract— A new design approach to discrete time sliding-mode-based controllers with disturbance compensation is proposed in this paper. The approach is applicable for linear time invariant plants with matched disturbances. Starting from the known methods for disturbance estimation (i) using discrete time nominal plant model and (ii) using original sliding mode control design method, full integration of those two algorithms into single one is proposed. Besides, the proposed algorithm can be additionally simplified for a small sampling time. The simplified algorithm does not directly depend on the equivalent control but only on the present and previous values of the sliding variable and previous value of the control. The obtained results are compared with the corresponding system with disturbance estimator based on sliding variable measurement. It is established that both methods give identical results in the nominal case. The method is illustrated in a positional servo system design. Comparative analysis of different methods is done by computer simulation.

Disturbance Compensation in Discrete-Time Sliding Mode Control – A Comparative Study

Goran Milosavljević — 2024-06-26

This work is intended to compare three methods for disturbances estimation and compensation in discrete-time variable structure systems with sliding modes. All methods detect disturbance, which appear in control channel, with time delay of one sampling perio. The first method is based on nominal discrete-time plant model and can be used in any type of discrete-time control systems. The second and the third methods detect disturbance by measurement of sliding function, and it is applicable in discrete-time sliding mode control systems only. The main task of this work is to check efficiency of the given methods in the presence of unmodeled inertial dynamics in actuators and position and velocity sensors of a positional servo system. It is shown that all three methods give near identical results in the nominal case, while the second and the third methods are superior in the presence of unmodelled dynamics. The third method introduces zig-zag motion in the nominal case. Results of research are illustrated by computer simulation of an example of positional servo system.

An Integrated System for Smart and Efficient Irrigation of Crop Fields

Vuk Pavic — 2024-06-26

The widespread adoption of new technologies has led to the development of various innovative solutions in agriculture. Crop monitoring using drones for early detection of plant diseases, autonomous machinery for soil preparation, and various robotic systems for harvesting and sorting fruits are just some examples of technology application to increase productivity in agricultural production. This paper describes an integrated system solution for irrigating agricultural production plots aimed at increasing production efficiency while efficiently utilizing necessary resources. All system components (hardware and software) are custom designed, taking into account real-world aspects and constraints in the field. The paper provides a detailed description of all functional units of the system, as well as preliminary experiences with the operation of the implemented prototype system. We also provides some initial characterization of the soil moisture probe that is designed in-house by running extensive LTSpice simulations.

Realization of adaptive beamformer on open-source hardware

Marija Ratkovic — 2024-06-26

Realization of an efficient system for extracting useful audio signals in the presence of interferences is an important
engineering problem in the field of acoustics. This paper proposes a method for extracting sound signals from a specific direction of
incidence. A microphone array consisting of eight microphones was used, coupled with space-time signal processing executed in real
time on hardware. The microphone signals are filtered by an adaptive beamformer, whose coefficients are optimized in real time on
open-source hardware using the Least Mean Square algorithm. This paper describes the characteristics and limitations of the used
microphone array. Testing the system through simulation indicates that extracting narrowband and wideband signals using the
presented adaptive beamforming method is theoretically possible. This paper aims to experimentally evaluate the algorithm under
real-world conditions, as well as identify the limitations of extracting wideband signals. Adaptation of the filter coefficients and filtering
the signals from the microphones was implemented on Bela hardware, specialized for processing audio signals. This experiment
highlights the limitations that arise from extracting a wideband signal using this type of hardware in real conditions. By comparing the
useful and filtered signals in both time and frequency domains, the quality of the filtering was analyzed. Our experiments suggest that
the current hardware specifications are a limiting factor for successful wideband signal filtering in real conditions, as they limit the
maximum possible order of the adaptive filter, which proved to be insufficient.