Machinery - Repository of the Faculty of Mechanical Engineering, University of Belgrade
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CFD-Driven Ship Trim Optimization: Simplifying Complexity of ANN with User-Friendly Software
No full textThis paper presents a ship trim optimization strategy, employing user-friendly software tool integrating Computational Fluid Dynamics (CFD) and Artificial Neural Networks (ANNs). It evaluates parameters like brake power, shaft speed, and fuel consumption. The tool streamlines complex models into an accessible interface, providing optimized recommendations swiftly. CFD-informed ANN models ensure precise predictions. This advancement minimizes fuel usage, cuts operational costs, and promotes maritime sustainability. By bridging advanced computation and practicality, the tool enhances operational efficiency. The interdisciplinary integration of CFD, ANN, and user interface software underscores technology's role in advancing greener, cost-effective ship trim optimization for the maritime industry's future
Analiza napona puzanja funkcionalnog kompozitnog transverzalno izotropnog pijezoelektričnog rotirajućeg diska promenljive debljine
No full textMaterials exhibiting different piezoelectric properties throughout their volume are referred to as functionally graded piezoelectric materials (FGPM). Due to their graded composition, the characteristics of these materials can be customized to fit particular needs in a variety of applications. Functionally graded piezoelectric materials are beneficial in many technical applications because of their versatility that enables increased performance, efficiency, and adaptability in a variety of disciplines. The objective of the current study is to analyse creep stresses in an annular disc composed of transversely isotropic, functionally graded piezoelectric material with varying thickness parameters. Creep stresses are evaluated analytically using the approach of Seth's transition theory. By using the stress-strain relations, the equations for mechanical stresses and electrical displacement are determined. Substituting these relations into the equilibrium equation a nonlinear differential equation is obtained. The findings are presented both numerically and graphically, demonstrating how the thickness parameter affects the circumferential stresses in the intermediate surface of the rotating disc. The disc made of transversely isotropic piezoelectric material PZT-4 exhibits higher creep stresses than other materials under consideration according to all of the numerical discussions and calculations. This work may provide an effective methodology for the analysis of functionally graded piezoelectric rotating discs and contribute to theoretical research and engineering applications.Materijali koji pokazuju različite pijezoelektrične osobine u svojoj zapremini tretiraju se kao funkcionalni kompozitni pijezoelektrični materijali (FGPM). Usled njihovog kompozitnog sastava, karakteristike ovih materijala se mogu menjati prema specifičnim potrebama u raznim primenama. Funkcionalni kompozitni pijezoelektrični materijali imaju prednosti u mnogim primenama u tehnici zbog njihove svestranosti koja omogućava poboljšanje performansi, efikasnost i adaptabilnost u raznim disciplinama. Cilj rada je analiza napona puzanja u prstenastom disku sačinjenog od transverzalno izotropnog, funkcionalnog kompozitnog pijezoelektričnog materijala sa parametrima promenljive debljine. Naponi puzanja se određuju analitički, primenom pristupa teorije prelaznih napona Seta. Korišćenjem izraza napona-deformacija određuju se jednačine mehaničkih napona i električnih pomeranja. Smenom ovih izraza u jednačinu ravnoteže dobija se nelinearna diferencijalna jednačina. Rezultati su predstavljeni numerički i grafički kako bi se uočio uticaj parametar debljine na obimske napone u međuslojevima rotirajućeg diska. Disk sačinjen od transverzalnog izotropnog pijezoelektričnog materijala PZT-4 pokazuje veće napone puzanja u odnosu na ostale razmatrane materijale, shodno svim diskusijama numerike i proračuna. Ovaj rad pruža delotvornu metodologiju u analizi funkcionalnog kompozitnog pijezoelektričnog rotirajućeg diska i doprinosi teorijskom istraživanju i inženjerskim primenama.Naveden je glavni i odgovorni urednik časopisa
CARNOT BATTERY BASED ON PUMPED THERMAL ENERGY STORAGE WITH REGENERATIVE PEBBLE BED AND STEAM ACCUMULATOR
No full textA novel design of the Carnot battery is proposed based on the thermodynamic cycle consisting of water heating and boiling by heat pumps, steam superheating by compression, high-temperature thermal energy storage in the pebble-bed regenerative porous structure, steam accumulation in the pressurized steam accumulator vessel and steam turbine expansion. The heat pumps and steam compressors are powered by the electricity surplus production from intermittent renewable power sources – solar power plants and wind turbines. The heat pumps are based on the CO2 supercritical cycle, which provides fresh steam generation with a sufficiently high temperature to serve as the input for subsequent compression to a superheated state. The heat is stored in two types of storage devices: steam generators and pebble beds. Steam accumulators enable efficient, cheap and high-capacity thermal energy storage due to the water latent heat of condensation and evaporation, which inherently provides high capacity of thermal energy storage per unit mass and volume of accumulator. The steam accumulator charging and discharging is performed under the sliding pressure and thermal non-equilibrium between the liquid and steam phases in the accumulator vessel. The consequences of such transient behaviour on the Carnot battery operational conditions are evaluated. The porous pebble beds store and release heat at elevated temperature, which provides a superheated steam at the steam turbine inlet. Namely, the pebble beds are alternately heated by the superheated fresh steam and cooled by the saturated steam from the steam accumulator, which is superheated in the pebble bed before entering the steam turbine. The design of the storage facility is based mainly on the equipment confirmed as mature technology in engineering practice. Evaluated are the cycle operational parameters, equipment dimensions and capacities, as well as the roundtrip thermodynamic efficiency of the charging and discharging cycle
CASCADED ILC-MPC CONTROLLER FOR ROBOT MANIPULATORS
No full textTrajectory tracking is one of the key aspects of robot control system design. High-precision
trajectory under disturbances, unmodeled dynamics, and parametric uncertainties of robotic
systems is a highly challenging task for multiple DoFs. Many different control approaches,
from simple PID controllers to advanced controllers such as Sliding Mode Control, Adaptive
Control, Robust Control, Fuzzy Control, and Model Predictive Control (MPC), are used within
trajectory tracking problems for robotic systems [1]. One of the control strategies suitable for
trajectory tracking problems for systems executing repetitive tasks is Iterative Learning Control
(ILC) [2]. The ILC is an intelligent, memory-based control method aimed at improving the
transient response performance of the system that operates repetitively over a fixed time
interval [3]. Several papers tackle improving the MPC with iterative learning controllers [4],
[5]. This research presents the integration of MPC and ILC using a simple structure consisting
of a cascaded ILC and MPC controller (Fig. 1.a) for position control of the robot manipulator.
The motivation for the cascaded structure is that the ILC controller does not interfere with the
MPC controller’s nonlinear optimization solver since the parallel structure of the ILC and MPC
would make MPC’s objective function more complex.
The proposed control system is verified via numerical simulation on a two-degree-offreedom
planar manipulator (Fig. 1.b). The constant disturbance (time and iteration-wise) is
considered in the simulation model. The reference trajectory in joint space is set to be a cubic
polynomial. The performance of the proposed control system is evaluated using Maximal
Absolute Error (MAE).
For each iteration, MAE is calculated and plotted as shown in Fig. 2.a, from which it can be
concluded that the ILC controller reduces the tracking error for both joints in approximately
four iterations. Fig. 2.b shows that the first joint tracks the reference trajectory almost perfectly
while the second joint has a larger tracking error, although still significantly reduced in
comparison to the sole MPC controller.The proposed Cascaded ILC-MPC control solution for robotic systems shows promising results. Further investigation should encompass the reduced dynamics model in the MPC and the fractional derivative in the ILC
METHODS OF MONITORING AND APPLYING ENERGY BALANCE PARAMETERS IN THE EXPLOITATION OF MODERN MACHINE TOOLS
No full textThe digitization procedures of machine tools, which are the basis of modern industry development
strategies, are to the greatest extent based on the application of information collected during the operation of the machines. In this way, it is possible to monitor and manage production processes by applying different criteria. The paper describes the procedure for monitoring and applying energy balance parameters in drive motors of machine tools in real time and the possibility of their application in production conditions.Editor: Dr Boris Dumnić, full professor, dean
Technical treatment and design: Dr Đorđe Vukelić, full professor
Dr Milana Ilić Mićunović, assistant professor
MSc Aleksandar Milošević, assistan
Kinematics and dynamics
No full textKinematics and dynamics relevant for manipulation, locomotion, postural balance and propulsion in fluids are addressed in this chapter 2. Standard terminology is introduced and several conventional computational and problem-solving techniques are reviewed. The rotation transformation matrix, Rodrigues formula, and Euler angles are also introduced and discussed.These theoretical tools and methods are frequently utilized in Biomechatronics research
Specijalni alat za interni transport strukturnih elemenata šinskih vozila - SPECIAL TOOL FOR INTERNAL TRANSPORT OF STRUCTURAL ELEMENTS OF RAIL VEHICLES
Get PDFPronalazak u širem smislu pripada uređajima za rukovanje i transport, a u užem smislu pronalazak se odnosi na uređaje za prihvatanje tereta koji se koriste na uređajima za rukovanje, podizanje i interni transport aluminijumskih elemenata, podsklopova i sklopova nosećih struktura različitih vrsta šinskih vozila, koji se koriste u industriji šinskih vozila
Crack Resistance of AA6156 Welded Stringer Panels
Get PDFExperimental and numerical analysis of crack growth in integral skin-stringer panels, produced by Laser Beam Welding (LBW), was performed in the scope of WELDAIR project and later on. Experiment was performed on full-scale components (four stringers, three welded clips), made of AA 6156 T6. Digital Image Correlation (DIC) was used to measure strains and construct CTOD or J crack resistance curves. It was shown that J vs. Δa can have unusual shape, indicating real component crack resistance instead of critical J value commonly obtained by comparing J-R curves with calculated Crack Driving Forces (CDFs). The applied technique is simple, practical and has no limitation in respect to material and geometr
Analysis of remaining life assessment of three-phase gravity separator for oil rectification with the simultaneous usean RBI matrix
No full textThe paper presents a detailed description of the oil rectification process used in upstream oil and gas plants, including the significant equipment involved. One such equipment highlighted in the study is a pressure vessel utilized as a separator to separate the liquid and gas phases. This pressure vessel has been in operation for over two decades. A thorough examination of the mentioned pressure equipment was conducted during the process evaluation. It was discovered that the internal side of the vessel, particularly its back elliptical head, had suffered extensive damage due to erosion and corrosion, emerging as the most significant cause of the deterioration. The application of RBI-estimation revealed that the vessel falls under the category of highly risk equipment, and there is a significant risk of both environmental and financial consequences associated with its potential failure (leakage). Such failure is anticipated to occur promptly in the area below the wear plate of the vessel's nozzle
