Faculty of Mechanical Engineering

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    Fault Diagnosis of Rotating Machinery Using Supervised Machine Learning Algorithms with Integrated Data-Driven and Physics-Informed Feature Sets
    (MDPI AG, 2026-03-17)
    Ignjatovska, Anastasija Angjusheva
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    Shishkovski, Dejan
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    Domazetovska Markovska, Simona
    This study proposes a supervised machine learning framework for vibration-based fault diagnosis of rotating machinery using integrated data-driven and physics-informed fea-ture sets. A dataset acquired under variable load and multiple operating conditions was used for model training. Parallel signal processing techniques were applied to capture fault-related information across multiple frequency bands including time-domain analy-sis, frequency-domain analysis, baseband analysis, and envelope analysis. From the cor-responding signal representations, statistical, spectral, and physics-based features associ-ated with characteristic fault frequencies were extracted and combined into integrated feature sets. The diagnostic performance of models trained using purely data-driven fea-tures was systematically compared with models incorporating integrated data-driven and physics-informed features. Support Vector Machine, Random Forests, Gradient Boosting, and an ensemble classifier were evaluated using accuracy, precision, recall, and F1-score metrics. The proposed framework employs a two-layer classification strategy, where the first layer performs multiclass fault identification, while the second layer evaluates the presence of imbalance as a coexisting fault. In addition, the influence of different feature groups as well as individual measurement axes and their combinations on diagnostic performance were analyzed. Validation using a new dataset measured in laboratory con-ditions confirmed the robustness and generalization capability of the proposed diagnostic framework.
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    A Multimodal Hybrid Piezoelectric–Electromagnetic Vibration Energy Harvester Exploiting the First and Second Resonance Modes for Broadband Low-Frequency Applications
    (MDPI AG, 2026-03-27)
    Shishkovski, Dejan
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    Markovska, Simona Domazetovska
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    Pecioski, Damjan
    The increasing demand for autonomous wireless sensors in Internet of Things (IoT) ap-plications has intensified research on vibration energy harvesting, particularly in the low-frequency range where ambient vibrations are most prevalent. However, most vibra-tion energy harvesters operate efficiently only at a single resonance mode, resulting in a narrow operational bandwidth and pronounced performance degradation under fre-quency detuning. To address this limitation, this paper proposes a multimodal hybrid pi-ezoelectric–electromagnetic vibration energy harvester that exploits both the first and sec-ond resonance modes of a cantilever-based structure to achieve broadband low-frequency operation. The design is guided by the complementary utilization of strain-dominated and velocity-dominated regions associated with different vibration modes. Numerical model-ing and finite element simulations are employed to investigate the influence of mass dis-tribution, deformation characteristics, and relative velocity on energy conversion perfor-mance. A secondary cantilever carrying the electromagnetic coil is introduced to enhance the relative motion between the coil and the magnetic field, thereby extending the effective operational bandwidth. The experimental results demonstrate increased harvested power, improved energy conversion efficiency, and a significantly broadened effective frequency range compared to conventional single-mode piezoelectric and electromagnetic energy harvesters.
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    Energy efficiency of combined compressor-ejector vapor compression systems applied in industrial concentrators
    (National Library of Serbia, 2025)
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    Gjerasimovska, Natasha
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    Sarevski, Vasko
    Investigations of the energy characteristics of thermocompression systems applied in industrial concentrators are presented in this paper. A significant increase of the energy efficiency in comparison with traditional industrial concentrators is achieved with the implementation of turbocompressor and/or ejector thermocom-pression. Single stage centrifugal compressors with water (R718) as a refrigerant are especially suitable for application in concentrators for production of fruit or grape concentrates because of the relatively small temperature difference between condensation and evaporation temperatures (Tc – Te). The heat pump cycle in the ejectors is realized with thermocompression of one part of the waste water vapor in the solution, which together with the primary steam from the boiler, or other heat generator, is used as a motive steam for the process of concentration. Several solutions of highly efficient single stage and multistage concentrator systems with turbocompressor and/or ejector thermocompression are proposed. The process of boiling - evaporation of the water from the treated solution in the concentrator is realized at low temperatures, under deep vacuum conditions, which is a guarantee for a high product quality. Due to the low costs of conventional fuels used in the processes of production of concentrate, the products made with these procedures are relatively low-priced, which makes them competitive on the market. A solution of a polygeneration system for production of electricity and thermal energy (steam and hot water) for the needs of technological processes in industrial concentration plants is presented.
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    SIMULATION OF AN ACTUATOR & DRIVE OF A WIRE DRAWING MACHINE’S MECHATRONIC SYSTEM USING MATLAB/SIMULINK
    (Mechanical Engineering – Scientific Journal, 2014-02)
    Goce Tasevski; Zlatko Petreski; Dejan Shishkovski
    Simulation of a mechatronic system actuator, implemented in a wire drawing machine, developed in Matlab/Simulink environment is presented in this paper. AC induction motor with vector control drive is chosen as an actuator. Mathematical model of the actuator is expressed in d-q reference frame rotating at synchronous speed. Diagrams for calculation of the important parameters for the simulation of the actuator were constructed. Simulation results from the model behaviour were discussed in comparison with the specified parameters by the manufacturer of the existing actuator integrated in such mechatronic system.
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    Experimental Measurements of System Dynamics Between Two Stages of Wire Drawing Machine
    (Walter de Gruyter GmbH, 2015-03-01)
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    Shishkovski, Dejan
    <jats:title>Abstract</jats:title> <jats:p>In multi-stage wire drawing machines productivity growth can be achieved at higher drawing speeds by preventing wire breakage during the process. One disadvantage of high-speed wire drawing is the requirement imposed by machine dynamics in terms of its stability and reliability during operation. Tensile forces in the wire must maintained by fast synchronization of all capstans speed. In this process, the displacement sensors play the main role in providing the control system with feedback information about the wire condition. In this study, the influences between the sensors and actuator driven capstans have been studied, and tuner roll concept of a wire drawing machine was experimentally investigated. To this aim, measurements were carried out on two drawing stages at different drawing speeds and obtained results were presented. These results clearly show the fast changes of the capstans speed and the angular displacements of the rollers that tighten the wire, which only confirms the high dynamics of the wire drawing machine.</jats:p>
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    Development of system for displacement measurement of a cantilever beam with strain gauge sensor
    (Mechanical Engineering – Scientific Journal, 2015)
    Dejan Shishkovski; Zlatko Petreski; Goce Tasevski
    In this paper, strain gauge based experimental system for displacement measurement of a cantilever beam was developed. The system comprises strain gauge sensors, signal conditioning module and data acquisition unit. Two strain gauges installed at the beam surface are connected in Wheatstone half-bridge configuration. Signal conditioning process is described in details along with the procedure for signal processing. Eventually, experimental investigations were conducted to verify the analytical gained results and certain conclusions were drawn.
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    REVERSE ENGINEERING – AN EFFECTIVE TOOL FOR DESIGN AND DEVELOPMENT OF MECHANICAL PARTS
    (A CTA TECHNICA CORVINIENSIS – Bulletin of Engineering, 2018-04)
    The Reverse Engineering has already found an extensive application in industry and other different fields. Reverse engineering (RE) is a process of taking the existing physical model and reproducing its surface geometry in three-dimensional (3D) data file on a computer-aided design (CAD) system. This paper will analyze the real situation in one industrial plant and provide comparative analysis of the application of current measuring methods and possibility of incorporating digital measurement. The Reverse Engineering (RE) is based on a method of reducing the time of dimensioning and modeling of mechanical parts which can be complex by geometry or dimensionally very accurate. In this paper we can give some practical examples of parts that are really produced in one manufacturing factory. Recommendation for digitalization will be of crucial importance for every company in its measurement and quality control activities
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    DESIGN OF AN ENERGY HARVESTING SYSTEM USING PIEZOELECTRIC MATERIALS
    (University Ss. Cyril and Methodius in Skopje, 2023)
    Pecioski, Damjan
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    Ignjatovska, Anastasija
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    Šiškovski, Dejan
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    Domazetovska, Simona
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    Anačkova, Maja
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