Faculty of Mechanical and Civil Engineering, Kraljevo

Permanent URI for this collectionhttps://dspace.unic.kg.ac.rs/handle/123456789/8211

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A combination of frequency photoacoustic and photoacoustic spectroscopy techniques for measurement of optical and thermal properties of macromolecular nanostructures
(2016) Todosijević, Slobodan; Šoškić, Zlatan; Galovic, Slobodanka
© 2016, Springer Science+Business Media New York. Macromolecular nanostructures represent a class of materials of considerable interest for application in nanooptics and nanoelectronics. The potential applications require understanding of the transport mechanisms in macromolecular nanostructures, and the recent theoretical studies indicated that the transport mechanisms of heat generated by absorption of IR and visible light are different. In this paper is proposed a combination of experimental techniques that would enable simultaneous measurement of optical and thermal properties of macromolecular structures excited by wide spectrum of light. The results of the experiments would enable credible testing of validity of the predictions of the theoretical studies, and further insight of the transport processes in macromolecular nanostructures.
A global convergent outlier robust adaptive predictor for MIMO Hammerstein models
(2017) Filipovic, Vojislav
Copyright © 2016 John Wiley & Sons, Ltd. The paper considers the outlier-robust recursive stochastic approximation algorithm for adaptive prediction of multiple-input multiple-output (MIMO) Hammerstein model with a static nonlinear block in polynomial form and a linear block is output error (OE) model. It is assumed that there is a priori information about a distribution class to which a real disturbance belongs. Within the framework of these assumptions, the main contributions of this paper are: (i) for MIMO Hammerstein OE model, the stochastic approximation algorithm, based on robust statistics (in the sense of Huber), is derived; (ii) scalar gain of algorithm is exactly determined using the Laplace function; and (iii) a global convergence of robust adaptive predictor is proved. The proof is based on martingale theory and generalized strictly positive real conditions. Practical behavior of algorithm was illustrated by simulations. Copyright © 2016 John Wiley & Sons, Ltd.
A mathematical model of a novel automated medical device for needle insertions
(2015) Buzurovic, Ivan; Šalinić, Slaviša
In 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.
A Method for Collision Avoidance in 4π External Beam Radiation Therapy
(2020) Buzurovic, Ivan; Šalinić, Slaviša; Simeunovic, Goran; Cormack, Robert
In 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.
A nature inspired optimal control of pneumatic-driven parallel robot platform
(2017) Pršić, Dragan; Nedić, Novak; Stojanović, Vladimir
© 2016 Institution of Mechanical Engineers. Woodworking industry is increasingly characterized by processing complex spatial forms with high accuracy and high speeds. The use of parallel robot platforms with six degrees of freedom gains more significance. Due to stricter requirements regarding energy consumption, easy maintenance and environmental safety, parallel platforms with pneumatic drives become more and more interesting. However, the high precision tracking control of such systems represents a serious challenge for designers. The reason is found in complex dynamics of the mechanical system and strong nonlinearity of the pneumatic system. This paper presents an optimal control design for a pneumatically driven parallel robot platform. The Proportional-Integral-Derivative (PID) algorithm with feedback linearization is used for control. The parameter search method is based on a firefly algorithm due to the empirical evidence of its superiority in solving various nonconvex problems. The simulation results show that the proposed optimal tuned cascade control is effective and efficient. These results clearly demonstrate that the proposed control techniques exhibit significant performance improvement over classical and widely used control techniques.
A Nature Inspired Parameter Tuning Approach to Cascade Control for Hydraulically Driven Parallel Robot Platform
(2016) Stojanović, Vladimir; Nedić, Novak
© 2015, Springer Science+Business Media New York. This paper presents the optimal tuning of cascade load force controllers for a parallel robot platform. A parameter search for the proposed cascade controller is difficult because there is no methodology to set the parameters and the search space is broad. The proposed parameter search scheme is based on a bat algorithm, which attracts a lot of attention in the evolutionary computation area due to the empirical evidence of its superiority in solving various nonconvex problems. The control design problem is formulated as an optimization problem under constraints. Typical constraints, such as mechanical limits on positions and maximal velocities of hydraulic actuators as well as on servo-valve positions, are included in the proposed algorithm. The simulation results indicate that the proposed optimal tuned cascade control is effective and efficient. These results clearly demonstrate that applied techniques exhibit a significant performance improvement over classical tuning methods.
A new approach for the determination of the global minimum time for the brachistochrone with preselected interval for the normal reaction force value
(2018) Radulović, Radoslav; Jeremić, Bojan; Šalinić, Slaviša; Obradovic, Aleksandar; Drazic M.
© 2018 Elsevier Ltd We consider the brachistochrone problem of the particle with a preselected interval for the normal reaction force value as well as the terminal position of the particle lying on an arbitrary planar curve. We use optimal control theory to solve the formulated brachistochrone problem. Here we treat the brachistochrone curve as a bilateral ideal constraint. We study the cases of symmetrically and unsymmetrically preselected intervals for the normal reaction force value. We show that in the case of a symmetrically preselected interval for the normal reaction force value, the brachistochrone curve is a two-segment curve, and in the case of an unsymmetrically preselected interval, it is a three-segment curve. We present a numerical procedure for the identification of the global minimum time of motion. Finally, we present several examples to illustrate the approach proposed in the paper.
A new approach for the determination of the global minimum time for the Chaplygin sleigh brachistochrone problem
(2017) Radulović, Radoslav; Šalinić, Slaviša; Obradovic, Aleksandar; Rusov S.
© SAGE Publications. A new approach for the determination of the global minimum time for the case of the brachistochronic motion of the Chaplygin sleigh is presented. The new approach is based on the use of the shooting method in solving the corresponding two-point boundary-value problem and defining either the crossing points of surfaces or the crossing points space of curves in a three-dimensional space of two costate variables and the time of the brachistochronic motion of the sleigh. A number of examples for multiple extremals of the Chaplygin sleigh brachistochrone problem are provided. In these examples, the global minimum is the solution to which the minimum time of motion corresponds.
A new pseudo-rigid-body model approach for modeling the quasi-static response of planar flexure-hinge mechanisms
(2018) Šalinić, Slaviša; Nikolić, Aleksandar
© 2018 Elsevier Ltd In this paper a new pseudo-rigid-body model (PRBM) of flexure hinges used in planar flexure-hinge mechanisms with small deformations is presented. Unlike the 1-DOF freedom PRBM used in the existing literature, the PRBM proposed has 3-DOF (degrees of freedom). Using the 3-DOF PRBM of flexure hinges, planar flexure-hinge mechanisms can be represented as rigid multibody systems whose adjacent rigid bodies are connected by 3-DOF joints. After applying this modeling procedure, the principle of virtual work yields a matrix relation for the determination of the quasi-static responses of a flexure mechanism due to external loads. The validity and accuracy of the approach for quasi-static analysis of planar flexure-hinge mechanisms based on the 3-DOF PRBM are examined using the examples of two types of compliant mechanisms: RRR and 3-RRR compliant micro-motion stages.
A note on fixed point theorems for rational Geraghty contractive mappings in ordered b-metric spaces
(2015) Kadelburg Z.; Radenovič S.; Rajovic M.
© 2010 Mathematics Subject Classification. In this short note we prove the existence of fixed points for nondecreasing mappings in ordered b-metric spaces. Our results improve the recent results, established by F. Zabihi and A. Razani [Fixed point theorems for hybrid rational Geraghty contractive mappings in ordered b-metric spaces, Journal of Applied Mathematics, Volume 2014, Article ID 929821, 9 pages], with much more general conditions and shorter proofs. An example is given to show the superiority of our generalization.
A novel approach to an automated needle insertion in brachytherapy procedures
(2018) Buzurovic, Ivan; Šalinić, Slaviša; Orio P.; Nguyen P.; Cormack, Robert
One 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.
A Rational Approach to Determining Environmental Noise Indicators
(2022) Mihajlov D.; Prascevic, Momir; Licanin M.; Raos M.; Radičević, Branko
Environmental 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.
A rigid multibody method for free vibration analysis of beams with variable axial parameters
(2017) Nikolić, Aleksandar; Šalinić, Slaviša
© SAGE Publications. This paper presents a new approach to the problem of determining the frequencies and mode shapes of Euler-Bernoulli tapered cantilever beams with a tip mass and a spring at the free end. The approach is based on the replacement of the flexible beam by a rigid multibody system. Beams with constant thickness and exponentially and linearly tapered width, as well as double-tapered cantilever beams are considered. The influence of the tip mass, stiffness of the spring, and taper on the frequencies of the free transverse vibrations of tapered cantilever beams are examined. Numerical examples with results confirming the convergence and accuracy of the approach are given.
Adaptive input design for identification of output error model with constrained output
(2014) Stojanović, Vladimir; Filipovic, Vojislav
Optimal input design for system identification is an area of intensive modern research. This paper considers the identification of output error (OE) model, for the case of constrained output variance. The constraint plays a very important role in the process industry, in the reduction of degradation of product quality. In this paper, it is shown, in the form of a theorem, that the optimal input signal, with constrained output, is achieved by a minimum variance controller together with a stochastic reference. The key problem is that the optimal input depends on the system parameters to be identified. In order to overcome this problem, a two-stage adaptive procedure is proposed: obtaining an initial model using PRBS as input signal; application of adaptive minimum variance controller together with the stochastic variable reference, in order to generate input signals for system identification. Theoretical results are illustrated by simulations. © 2013 Springer Science+Business Media New York.
Adaptive optimization algorithm for nonlinear Markov jump systems with partial unknown dynamics
(2021) Fang H.; Zhu G.; Stojanović, Vladimir; Nie R.; He J.; Luan X.; LIU F.
© 2021 John Wiley & Sons, Ltd. An online adaptive optimal control problem for a class of nonlinear Markov jump systems (MJSs) is studied. It is worth noting that the dynamic information of MJSs is partially unknown. Applying the neural network linear differential inclusion techniques, the nonlinear terms in MJSs are approximately converted to linear forms. By using subsystem transformation schemes, we can transfer the nonlinear MJSs to N new coupled linear subsystems. Then a new online policy iteration algorithm is put forward to obtain the adaptive optimal controller. Some theorems are given afterward to ensure the convergence of the new algorithm. At last, a simulation example is provided to verify the applicability of the algorithm.
Advantages and Drawbacks of Additive Manufacturing
(Faculty of Mechanical and Civil Engineering, 2017) Vranić, Aleksandar; Bogojevic, Nebojsa; Ćirić Kostić, Snežana; Croccolo, D.; Olmi, G.
- This paper presents some various imperfections that can occur during Direct Metal Laser Sintering (DMLS) and their effects on part quality. Direct Metal Laser Sintering is one of the Additive Manufacturing (AM) technologies that enables fast production of an accurate, functional, complex shape parts and tools, without additional tooling, directly from 3D CAD model. This process is based on layer by layer manufacturing, where the fusion of the metal powder is performed by selective melting with laser beam. The laser beam moves and scans area that correspond to section of the part for the specific layer. In the DMLS the part is built layer by layer, where the process of the melting and solidification occur in small volume in relatively short time. Thanks to this kind of approach, the DMLS has much less limitations than the subtractive methods of part production. However, the production in the layers has some drawbacks, which can have a significantly influence on the part geometry, structural errors and part imperfections. Some of the advantages as well and drawback of the DMLS of metal parts has been presented in this paper.
Advantages of using new technology in textile and fashion design
(2021) Milinic Bogdanovic M.; Bogojevic, Nebojsa
© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021. New technology has transformed traditional approaches to contemporary art and design and has led to a completely new forms in the creative world. 3D technologies enable the production process to accelerate. Digital arts are increasingly being used by artists to express their ideas. With the application of CAD/CAM technology, today, the design solutions of designers are realized faster. Advantage of using additive manufacturing relies on its ability to produce directly based on the CAD model – 3D model, whose file is the source of information for generating the incremental control file. The specific features of additive manufacturing can be developed with digital design, and software based construction of model, which adapts to the capabilities of this technique. Today the Inovation in the textile and fashion design is in an upward trajectory. Additive production is increasingly available especially with FDM Technology (Fused Deposition Modeling). This is production based on the principle of melting deposit modeling by heating and extruding thermoplastic filaments, proved to be very affordable and efficient. Textile and fashion design is developing not only in the aesthetic sense, but also developing software programs in which products of textile design and fashion are designed. Textile design in the industry is necessary to return to a sustainable production model, which involves more localized production, and also allowing small design and production houses to be competitive in the market production. Exploit the new design technics and involve a new technologies, a sustainable production model in textile design is possible to be achieved.
Air flow resistance of polyamide 12 made by selective laser sintering
(2019) Bogojevic, Nebojsa; Muharemović, Nusret; Radičević, Branko; Vranić, Aleksandar; Ciric-Kostic, Snezana
This paper presents the measurements of the air flow resistance of polyamide 12 samples made by selective laser sintering. The results have shown that, due to the porosity of the microstructure, the samples with thickness smaller than 1.7 mm cannot be considered airtight, while the samples with thickness 2.2 mm are airtight. The airflow resistance of the samples that allow airflow increases with air speed.
An approach to machine tools structure selection for wooden product machining based on evidence networks
(2016) Djapic, Mirko; Lukić, Ljubomir; Pavlović A.
© Faculty of Mechanical Engineering, Belgrade. During the product development phase, especially in the case of innovative products, designers used to face the unpleasant situation to be obliged to take decisions under conditions which are characterized by a relevant degree of uncertainty and even contradiction. This situation is quite frequent in the very early phases of the design process, where a large part of external conditions are not fully defined. It is also the case of a designer of machine tools. As methodological response able to fill this informative gap, the present paper presents a way for using evidential systems as supporting tool for designers. These tools represent a sort of expert systems in which knowledge is represented and processed by the function of the Belief Function Theory (also called Dempster-Shafer Theory). In particular, beyond a deep description of this methodology, the paper is focused on the conceptual design of a machine tool, i.e. determination of the best structure of machining center in the phase of conceptual design for a predefined group of wooden parts that are being machined on them.
An extension to the methodology for characterization of thermal properties of thin solid samples by photoacoustic techniques
(2016) Šoškić, Zlatan; Ciric-Kostic, Snezana; Galovic, Slobodanka
© 2016 Elsevier Masson SAS. The paper presents a study of possibilities to extend the present methodology for thermal characterization of thin solid samples by photoacoustic techniques. The present methodology consists of linear fitting of the experimental data to approximate the expressions derived from the composite piston model of photoacoustic response and it is mainly used for calculation of thermal diffusivity of thin samples. The study has shown that the methodology may be extended to calculation of thermal diffusivity, thermal conductivity and thermal expansion coefficients of thin samples by linear fitting in multiple frequency ranges and by analysis of the intersection frequency, which is the frequency where the magnitudes of two components of photoacoustic response in the composite piston model are equal. The analysis of numeric errors of the methodology has revealed the dominant sources and magnitude of the errors, leading to the conclusion that photoacoustic techniques should be carefully used as a tool for extensive thermal characterization of thin samples in the cases when other techniques are not applicable or have larger errors.

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