Faculty of Mechanical and Civil Engineering, Kraljevo
Permanent URI for this collectionhttps://dspace.unic.kg.ac.rs/handle/123456789/8211
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Item Determination of relative weight coefficients based on thermal characteristics of materials using the F-AHP method(University of Kragujevac, Faculty of Mechanical and Civil Engineering, 2022) Bošković, Goran; Čepić, Zoran; Ubavin, DejanIn this paper, multi-criteria problem solving method - Fuzzy Analytical Hierarchy Process Method (F-AHP) is proposed, the goal of this paper is to implement the F-AHP procedure, which is to obtain weight coefficients based on the thermal characteristics of materials deposited in one warehouse. In subsequent research, the mentioned coefficients will be used in fire simulations inside the warehouse.Item Bending, buckling, and free vibration analysis of multi-span beams(University of Kragujevac, Faculty of Mechanical and Civil Engineering, 2022) Nikolić, AleksandarIn this paper, the modified segmented rod method (MSRM) will be used for bending, buckling, and free vibration analysis of multi-span beams. Since there is MSRM for a one-span beam in literature, slight corrections will enable the application of this method to the case of multi-span beams. The motivation for this research lies in the fact that there are engineering objects that must be modeled as multi-span beams, such as bridges. The proposed MSRM uses the absolute coordinates of the rigid segments, so the introduction of different boundary conditions as well as the loads can be done easily. The effectiveness of the MSRM was tested through numerical examples where the comparison with current results from the available literature was done.Item An analytical approach for free vibration analysis of Euler-Bernoulli stepped beams with axial-bending coupling effect(University of Kragujevac, Faculty of Mechanical and Civil Engineering, 2022) Šalinić, Slaviša; Todorović, Marko; Obradovic, AleksandarFree vibration of eccentrically stepped beams with one step change in cross-section is considered. It is assumed that the longitudinal symmetry axes of the beam segments are translationally shifted along the vertical direction with respect to each other. The effect of that arrangement of the segments on the coupling of axial and bending vibrations of the stepped beam is analyzed. The beam segments are modeled in the frame of the Euler-Bernoulli theory of elastic beams. Two numerical examples are presented.Item A mathematical model of a novel automated medical device for needle insertions(2015) Buzurovic, Ivan; Šalinić, SlavišaIn medical procedures, needle insertion is a challenging task highly dependent on the surgeon's manual skills. Implanted needles are used for drug delivery, biopsy, delivery of radiation sources, etc. In the named clinical procedures, the accuracy of the needle placement is crucial for patient treatment outcomes. Therefore, we have proposed an automated medical device for needle implantation to eliminate uncertainties of the standard procedures and to increase the accuracy of the needle placement. In this article, the mathematical model of such a device has been developed. The mathematical model takes into account the needle deflection; therefore, with the adequate development of the control strategy, the deflection could be minimized using predictive or adaptive controllers.Item A novel approach to an automated needle insertion in brachytherapy procedures(2018) Buzurovic, Ivan; Šalinić, Slaviša; Orio P.; Nguyen P.; Cormack, RobertOne of the most challenging phases in interstitial brachytherapy is the placement of the needles. In these medical procedures, the needles are inserted inside the tissue to guide the positioning of the radioactive sources. The low-dose-rate radioactive sources are placed inside the tissue permanently, whereas a radioactive source in the high-dose-rate brachytherapy is temporarily placed in the desired positions so that the delivery of the prescription dose to the clinical targets can be achieved. Consequently, the precise needle placement directly influences the radiation dose delivery and the treatment outcomes of patients. Any deviation from the desired position of the radioactive sources can cause a suboptimal dose distribution and inadequate tumor coverage. Therefore, it is of significant importance to develop a robust and sophisticated tool that can perform the automatic needle placement with a high level of accuracy for different medical procedures and conditions. In this study, we propose a novel concept for the automatic needle insertion using a new miniature automated robotic system. The mathematical model of this system was presented in detail, allowing the implementation of the model predictive control that can be used to govern the mechanism. The purpose of this approach was to minimize the lateral components of the generalized reactive force which is responsible for the tissue displacement and, consequently, for the needle deflection. The proposed approach was designed to predict and to compensate for the unmeasured disturbances, such as needle deflection or tissue resistance and reactive force, and it was capable of correcting them without waiting until the effect appears at the output of the system causing the needle deviation from the desired positions. The extensive simulation of the system was presented to evaluate the feasibility of the method and the parameters of interest including displacements, system errors and system responses to the change in the environmental conditions.Item A Method for Collision Avoidance in 4π External Beam Radiation Therapy(2020) Buzurovic, Ivan; Šalinić, Slaviša; Simeunovic, Goran; Cormack, RobertIn this study, a method for collision avoidance (CA) in external beam radiation therapy (EBRT) is proposed. The method encompasses the analysis of all positions of the moving components of the beam delivery system, such as the treatment table and gantry, including patient specific information obtained from the computed tomography (CT) images. This method eliminates the need for time-consuming dry runs prior to the actual treatments. This method includes a rigorous computer simulation and CA check prior to each treatment. With this treatment simulation, it is possible to quantify and graphically represent all positions and corresponding trajectories of all points of the moving parts during treatment delivery. The development of the workflow includes several steps: (a) derivation of combined dynamic equation of motion of the EBRT delivery systems, (b) developing the simulation model capable of drawing the motion trajectories of the specific points, (c) developing the interface between the model and the treatment plan parameters, such as couch and gantry parameters for each field. The patient CT images were registered to the treatment couch, so the patient dimensions were included into the simulation. The treatment field parameters were structured in an XML file that was used as an input into the dynamic equations. The trajectories of the moving components were plotted on the same graph using the dynamic equations. If the trajectories intersect, it was the signal that collision exists. This CA method is effective in the simulation of the treatment delivery.Item Robust point-to-point iterative learning control with trial-varying initial conditions(2020) Tao H.; Li J.; Chen, Yiyang; Stojanović, Vladimir; Yang H.Iterative learning control (ILC) is a high-performance technique for repeated control tasks with design postulates on a fixed reference profile and identical initial conditions. However, the tracking performance is only critical at few points in point-topoint tasks, and their initial conditions are usually trial-varying within a certain range in practice, which essentially degrades the performance of conventional ILC algorithms. Therefore, this study reformulates the ILC problem setup for point-to-point tasks and considers the effort of trial-varying initial conditions in algorithm design. To reduce the tracking error, it proposes a worstcase norm-optimal problem and reformulates it into a convex optimisation problem using the Lagrange dual approach. In this sense, a robust ILC algorithm is derived based on iteratively solving this problem. The study also shows that the proposed robust ILC is equivalent to conventional norm-optimal ILC with trial-varying parameters. A numerical simulation case study is conducted to compare the performance of this algorithm with that of other control algorithms while performing a given point-topoint tracking task. The results reveal its efficiency for the specific task and robustness against trial-varying initial conditions.Item Mathematical Model of Patient Support System in Medical Linear Accelerators for External Beam Radiation Therapy(2022) Buzurovic, Ivan; Šalinić, Slaviša; Misic V.In this study, a mathematical model of the patient support system (PSS) in medical linear accelerators was presented. The PSS consists of a treatment table capable of performing vertical, horizontal and rotational movements to position patients to the required location. The mathematical model includes the set of differential equations of motion. The model was developed for two basic designs of the lifting mechanisms: (a) a PSS mounted above the floor, and (b) a PSS mounted in a deep pit. In addition, this model includes dynamic equations of motions for the linear accelerator gantry and treatment head. The proposed model can be utilized for various tasks, such as adaptive or robust control design, tracking and motion compensation or collision avoidance assessments. The use of the proposed mathematical model can potentially improve real-time tracking of target-volumes when delivering a highly conformal radiation dose at full duty cycle while minimizing irradiation to healthy tissues and sparing critical organs during radiation treatments with linear accelerators. Furthermore, the equation of motion can be used to confirm the position of the mechanical isocenter of the linear accelerator. Such results can be compared against the radiation isocenter; thus, possible deviations can be tested more frequently without additional resources.Item IMPROVING DESIGN AND OPERATING PARAMETERS OF THE RECUPERATOR FOR WASTE HEAT RECOVERY FROM ROTARY KILNS(2022) Stojić, Nenad; Karamarkovic, Rade; Karamarković M.; Nikolić, MilošDepending on their applications, heat losses from the shells of rotary kilns account for 3-25% of the total heat input. Over the hottest zone of the kiln shell, an annular duct with a variable diameter is formed. Two air streams entering the annulus at both ends flow to a common extraction point to receive the thermal power equal to the ambient heat loss of the bare kiln. The design does not require airtightness, utilizes the entire heat loss, and by the variation of the air-flow can be used over the kilns with variable operating parameters (±20% heat loss), which show similar surface temperature patterns. The main disadvantage of the design is the approaching of the surfaces of the kiln and the recuperator at the outlet of preheated air. This means that for a given heat loss and a surface temperature pattern, the rotational eccentricity of the kiln shell is the most influencing parameter that defines the air preheating temperature and the efficiency of the recuperator. To solve the problem, four redesigns with: double annuluses, the usage of radiation fins, air addition, and a combination of two basic designs are analyzed by the use of analytical and CFD models. From the listed redesigns: first could be used only to prevent overheating, second has a modest positive effect, third should be applied in combination with fourth.Item Potential for Use of Recycled Cathode Ray Tube Glass in Making Concrete Blocks and Paving Flags(2022) GrdiĆ D.; Despotovic, Iva; Ristic, Natasa; Grdic, Zoran; Topličić-ćurčić G.The potential to use waste glass, including cathode ray tube (CRT) glass, for making new products or as an admixture to existing ones is being intensively investigated. This kind of research intensified particularly in the period after CRT TV sets and computer monitors were replaced in the market by the advanced technology of thin film transistor (TFT) and liquid crystal display (LCD) screens. Cathode ray tube glass represents a considerable part of electronic waste (e-waste). E-waste globally increases at a far higher rate than other solid waste materials. There is a possibility to recycle cathode ray tube glass and use it in the construction industry. This paper shows the test results of physical and mechanical properties of blocks and paving flags. The reference specimen was made with quartz sand, while the other product employed a combination of quartz sand and ground panel cathode ray tube glass. The glass was ground to the fraction 0.25/1.00 mm, which corresponds to quartz sand fineness. The following tests were performed: shape and dimensions, resistance to freeze/thaw and de-icing salts, water absorption, splitting tensile strength and tensile strength by bending. Special attention was paid to the tests of Böhme wear resistance, slip resistance of the top surface of CRT products using a pendulum, radioactivity and leaching. The texture of the experimental concrete products was observed by SEM (scanning electron microscopy) and analyzed. The results obtained by experimental testing unequivocally show that CRT glass can successfully be used for making concrete blocks and paving flags.Item Iterative learning control for repetitive tasks with randomly varying trial lengths using successive projection(2022) Zhuang Z.; Tao H.; Chen, Yiyang; Stojanović, Vladimir; Paszke, WojciechThis article proposes an effective iterative learning control (ILC) approach based on successive projection scheme for repetitive systems with randomly varying trial lengths. A modified ILC problem is formulated to extend the classical ILC task description to incorporate a randomly varying trial length, while its design objective considers the mathematical expectation of its tracking error to evaluate the task performance. To solve this problem, this article employs the successive projection framework to give an iterative input signal update law by defining the corresponding convex sets based on the design requirements. This update law further yields an ILC algorithm, whose convergence properties are proved to be held under mild conditions. In addition, the input signal constraint can be embedded into the design without violating the convergence properties to obtain an alternative algorithm. The performance of the proposed algorithms is verified using a numerical model to show the effectiveness at occasions with and without input constraints.Item A Rational Approach to Determining Environmental Noise Indicators(2022) Mihajlov D.; Prascevic, Momir; Licanin M.; Raos M.; Radičević, BrankoEnvironmental noise indicator values that are completely accurate and precise can only be obtained through continuous noise monitoring, which is a highly complex and multifaceted task. In case heavy road traffic is the dominant noise source, accurate and precise data on annual noise indicator values are also obtainable through semicontinuous monitoring. Such a procedure is a rational approach to the given task, as it requires considerably shorter utilization of resources, whereby the primary issue is how to choose the measurement time interval. To help determine the optimal measurement time interval, this paper uses the results of continuous noise monitoring at a selected measurement location as an attempt to minimize the measurement time interval. The choice of the optimal measuring strategy of the problem defined by multiple criteria has been made using the PROMETHEE method, as the most acceptable method for comparing the different alternatives.Item Note on difference equations with the right-hand side function nonincreasing in each variable(2022) Stević S.; Iricanin, Bratislav; Kosmala W.; Smarda, ZdenekWe present an example of a difference equation of arbitrary order, possessing the right-hand side function that is homogeneous to a certain degree and nonincreasing in each variable, which has a unique positive equilibrium, as well as solutions that do not converge to the equilibrium. The example shows that the main result in the paper: O. Moaaz, Dynamics of difference equation xn+1= f(xn−l, xn−k) (Adv. Differ. Equ. 2018:447, 2018), is incorrect.Item Experimental Study of the Phase Equilibria in the Ternary Ga-Ge-Zn System(2022) Djordjevic A.; Premovic, Milena; Minic D.; Manasijevic D.; Radičević, Branko; Kolarević, Nenad; Ristić V.In the current study the ternary Ga-Ge-Zn system was experimentally and analytically tested. The ternary system is chosen due to the importance of germanium-based alloys in the electronic industry and their special application as memory materials. There are no previous studies related to the Ga-Ge-Zn system up to this paper. Used experimental techniques were differential thermal analysis, scanning electron microscopy with energy dispersive spectrometry, x-ray powder diffraction, electrical conductivity and hardness tests. The experimentally obtained results were compared with the results of thermodynamic calculation of phase equilibria using the calculation of phase diagram (CALPHAD) method and literature data. Calculated phase diagrams were three vertical sections (Ga-GeZn, Ge-GaZn and Zn-GaGe), three isothermal sections (100, 200 and 300 °C) and liquidus projection with invariant reactions. Good agreements between calculated phase diagrams and experimental data have been obtained without introducing ternary thermodynamic parameters.Item DATA-DRIVEN CONTROL OF HYDRAULIC SERVO ACTUATOR BASED ON ADAPTIVE DYNAMIC PROGRAMMING(2022) Đorđević, Vladimir; Stojanović, Vladimir; Tao H.; Song X.; He R.; Gao, WeinanThe hydraulic servo actuators (HSA) are often used in the industry in tasks that request great powers, high accuracy and dynamic motion. It is well known that HSA is a highly complex nonlinear system, and that the system parameters cannot be accurately determined due to various uncertainties, inability to measure some parameters, and disturbances. This paper considers control problem of the HSA with unknown dynamics, based on adaptive dynamic programming via output feedback. Due to increasing practical application of the control algorithm, a linear discrete model of HSA is considered and an online learning data-driven controller is used, which is based on measured input and output data instead of unmeasurable states and unknown system parameters. Hence, the ADP based data-driven controller in this paper requires neither the knowledge of the HSA dynamics nor exosystem dynamics. The convergence of the ADP based control algorithm is also theoretically shown. Simulation results verify the feasibility and effectiveness of the proposed approach in solving the optimal control problem of HSA.Item Event-driven NN adaptive fixed-time control for nonlinear systems with guaranteed performance(2022) Song X.; Sun P.; Song S.; Stojanović, VladimirThis article investigates the adaptive neural network fixed-time tracking control issue for a class of strict-feedback nonlinear systems with prescribed performance demands, in which the radial basis function neural networks (RBFNNs) are utilized to approximate the unknown items. First, an modified fractional-order command filtered backstepping (FOCFB) control technique is incorporated to address the issue of the iterative derivation and remove the impact of filtering errors, where a fractional-order filter is adopted to improve the filter performance. Furthermore, an event-driven-based fixed-time adaptive controller is constructed to reduce the communication burden while excluding the Zeno-behavior. Stability results prove that the designed controller not only guarantees all the signals of the closed-loop system (CLS) are practically fixed-time bounded, but also the tracking error can be regulated to the predefined boundary. Finally, the feasibility and superiority of the proposed control algorithm are verified by two simulation examples.Item Robust point-to-point iterative learning control for constrained systems: A minimum energy approach(2022) Zhou C.; Tao H.; Chen, Yiyang; Stojanović, Vladimir; Paszke, WojciechIterative learning control (ILC) is a high performance control scenario that is widely applied to systems that repeat a given task or operation defined over a finite duration, and has been introduced to point-to-point motion tasks in existing work. However, its design degree of freedom has not been fully utilized to optimize performance beyond tracking accuracy in constrained conditions. The framework of point-to-point ILC in this article is extended within discrete linear time-invariant (LTI) system, so as to take the tracking time instants of desired positions as changing variables. Therefore, it is possible to achieve the objective of minimizing energy while maintaining the required tracking accuracy. The multiobjective optimization problem is divided into two sub-problems, which are solved with an iterative algorithm composed of norm-optimal ILC approach as well as the coordinate descend method. Furthermore, the impact of model uncertainty on algorithm performance is also considered, and the iterative algorithm is further extended to capture constrained systems. The algorithm is robust to the model uncertainty and has a certain robustness to output disturbances. Finally, the validity of the proposed algorithm is verified by a twin rotor aerodynamic system (TRAS) model.Item Waste-to-Energy in Transition Countries: Case Study of Belgrade (Serbia)(2022) Čepić, Zoran; Bošković, Goran; Ubavin D.; Batinic B.This paper gives an overview of the current situation in the field of energy and municipal solid waste management (MSWM) in Serbia with the emphasis on identification of opportunities and challenges related to obtaining energy from municipal solid waste (MSW) on a specific example of the future waste management center in Belgrade (Serbia). This waste management center will be equipped with two plants for energy production, from waste and from landfill gas. These plants will annually produce about 216 GWh of electricity and about 174 GWh of heat. The importance of such a project is manifold because it solves the long-standing problem of waste management in Belgrade based on landfilling at the non-sanitary landfill Vinca, which is a great burden on the environment with potential risk to human health, while introducing a new dimension in energy production in Serbia.Item Hybrid-driven-based fuzzy secure filtering for nonlinear parabolic partial differential equation systems with cyber attacks(2022) Zhang Z.; Song X.; Sun X.; Stojanović, VladimirThe problem of hybrid-driven fuzzy filtering for nonlinear semi-linear parabolic partial differential equation systems with dual cyber attacks is investigated. First, a Takagi-Sugeno (T-S) fuzzy model is employed to reconstruct the original nonlinear systems. Second, a hybrid-driven mechanism is applied for filter design to balance the systems' performance and the limited network resource consumption under dual cyber attacks composed of deception and denial of service attacks. Based on the Lyapunov direct method, sufficient conditions to guarantee the stability of the augmented system are obtained, and the parameters of the designed filter are earned with explicit form. Finally, a simulation example with robust analysis and comparative analysis is provided to illustrate the effectiveness of the proposed method.Item Composite adaptive finite-time fuzzy control for switched nonlinear systems with preassigned performance(2022) Sun P.; Song X.; Song X.; Stojanović, VladimirThis article investigates the composite adaptive fuzzy finite-time prescribed performance control issue of switched nonlinear systems subject to the unknown external disturbance and performance requirement. First, by utilizing the compensation and prediction errors, the piecewise switched composite parameter update law is employed to improve the approximation accuracy of the unknown nonlinearity. Then, the improved fractional-order filter and error compensation signal are introduced to cope with the influences caused by the explosive calculation and filter error, respectively. Meanwhile, the effect of the compound disturbances consisting of the unknown disturbances and approximation errors is reduced appropriately by designing the piecewise switched nonlinear disturbance observer. Moreover, stability analysis results prove that the proposed preassigned performance control scheme not only ensures that all states of the closed-loop system are practical finite-time bounded, but also that the tracking error converges to a preassigned area with a finite time. Ultimately, the simulation examples are given to demonstrate the effectiveness of the proposed control strategy.