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APPLYING RODRIGUES' FORMULA FOR KINEMATIC MODELING OF VIBRATORY CONVEYORS
No full textVibratory technology is involved in various industries, such as food, metallurgical, arms
industry, etc. [1]. Major implementation can be found in material conveyance in the form of
vibratory conveyers. Depending on the continuity of the contact of the conveyed particles and
vibratory trough’s surface, these machines can set material into motion in two ways – hopping
and no-hopping motion. Conventional vibratory conveyers (Fig. 1) have an actuator positioned
at a certain angle to the ground. This angle defines the force vector that sets the material into
forward motion.Main goal of this research is to explore a potential design with two orthogonally positioned
actuators that can change the direction of the resultant vector. Variation of frequencies, phase
differences and amplitude ratios enable different vibratory regimes implemented not only in
conveyance, but at fine dosing, shaking and stirring, sifting etc.
Contrary to conventional technological processes that use hopping motion, where a new
machine is introduced for various operations, this way only the vibratory trough should be
replaced, and the control and actuating system generally remains the same. Additionally, with
dual excitation, the no-hopping motion can be achieved in simpler control algorithms. This form of motion is suitable for industries that demand sensitive handling with material (e.g.
chemical or military industry).
For this purpose, a mathematical model of a standard vibratory conveyer is defined with
segregated upward and sideways displacements of the base. This research explores the
kinematics of such vibratory machines from a robotics aspect (Fig. 1). More precisely, the
conveyer system (vibratory trough with stationary base) is being analyzed and remodeled as an
open serial kinematic chain. The interdependencies of the virtual segments are derived using
Rodrigues’ formula, that’s thoroughly defined in [3].
The analysis starts by defining the relative coordinates of the virtual robotic system. Since
the conveyor depicted in Fig 1. can be approximated to perform exclusively planar motion it
can be visualized as a robotic system with multiple segments interconnected by means of joints
– one for each degree of freedom (DOF). The proposed system will consist of a total of four
joints - two linear and one rotational joint to define the absolute movement of the stationary
base in the vertical plane and an additional linear joint to define displacement of the trough
relative to the base itself.
After the definition of the configuration of the robotic system, absolute radius vectors of
centers of inertia of corresponding segments are defined. Furthermore, expressions for angular
and translational velocities are obtained for each proposed segment which will be served for
setting in an automatic manner of the kinematic model of vibration conveyor
STABILITY OF FRACTIONAL-ORDER TIME-DELAY DYNAMICAL SYSTEMS: NEW RESULTS
No full textTime delay often appears in many engineering systems and it may lead to bifurcation,
chaos and even instability, [1]. Control design and stability issues of time-delay systems
(TDS) were widely studied due to the effect of delay phenomena on system dynamics, which
often leads to poor performance or even instability. In the biomechanics of humans, a well-known
fact is due to the human reaction time, which introduces the effect of a time delay
into a control problem. Particularly, it has been obtained that self-balancing models of
standing man can be presented in the form of neutral time-delay systems of the integer
order, where in solving the stabilization problem, feedback control is introduced that contains
a delay (TDTC) and include into account its position, speed, and acceleration [2]. Recently,
fractional calculus (FC) has attracted the increased attention of scientific society where
fractional operators are often used for complex dynamical systems,[3]. Also, fractional order
dynamical systems have drawn much attention from researchers and engineers over
the past few decades, [4,5], particularly for different kinds of stability. Here, we study the
problem of human postural balance by applying fractional-order TDFC where the
asymptotic stability closed loop of fractional-order neutral time delay systems is studied.
Also, some attention will be devoted to the finite-time stability (FTS)/stabilization problem
of nonlinear fractional-order (uncertain) time-delay systems,[6]. By use of the (generalized)
Gronwall inequality and its new extended form, new sufficient conditions for FTS of such
systems are obtained.
Finally, suitable numerical examples will be given to illustrate the effectiveness and
applicability of the proposed theoretical results
MASS OPTIMIZATION OF TIMOSHENKO BEAMS BY USING THE PONTRYAGIN MAXIMUM PRINCIPLE
No full textThe mass optimization of axially functionally graded (AFG) circular Timoshenko beams is
considered in this paper for a given fundamental natural frequency. The case of coupled
longitudinal, bending and torsional vibrations is considered based on given boundary
conditions. The Pontryagin maximum principle is applied for shape optimization with respect
to the limited diameter under the constraints of structural integrity and Timoshenko beam
theory. Governing equations are transformed into a system of ODEs and the problem is
formulated as the TPBVP. For the self-adjoined systems all coupled variables except one, are
expressed through state variables, thus the numerical solution is more approachable.
Theoretical considerations are illustrated with a numerical example. In the example,
different boundary conditions and mechanical characteristics of materials are implemented.
The mass reduction is compared for beams with constant cross-sectional profiles and beams
with optimized profiles for the given fundamental natural frequency
Model analysis of bucket wheel excavator ultimate strength
No full textThe possibilities of testing real constructions are often limited, especially in case
of large constructions. One of the solutions is to create a sub-scaled model and subject it
to the experimental (and numerical) testing. In most cases, testing on the model instead of
the actual construction results in a great saving of money and time. In previous study,
structure is evaluated in elastic response (the classical approach in structure evaluation).
In that scenario once-in-a-lifetime loadings are neglected, that include overloading
scenarios that lead to structural collapse, i.e., ultimate strength. Hence, in this study, the
same series of testing were performed, but within a domain of plastic deformation. Firstly,
series of numerical calculations were performed in order to anticipate behavior of a model
and a real structure, and to connect those two calculations using mathematical equations.
Existence of welded joints (inevitable parts of large steel structures) made this problem
even more complex. Namely, in previous study, welded joints were not considered,
because all welded zone regions have practically the same modulus of elasticity. However,
within the plastic deformation domain, difference in material properties of welded joint
regions (base metal, weld metal and heat affected zone) have a great influence to structural
behavior. As a finale of this study, it is planned to perform the overloading experiment to
the existing model. Series of small experiments will be performed on simple structures
(containing several plates) in order to indirectly confirm repeatability of the experiment. The
experiment on the complex model should be performed with care, since there is only one
attempt of overloading this complex structur
Influence of Thickness Ratio on the Aerodynamic Characteristics of a Family of Hybrid Semielliptical Dolphin Airfoils
No full textApplication and characterization of a kerosine-fuelled High Velocity Oxy-Fuel (HVOF) Ti2AlC coating on thermally stable P91 steel
Get PDFA class of ternary layered carbides and nitrides, known as MAX
phases, combines some of the best properties of two distinct
classes of materials: metals and ceramics. Specifically, MAX phases
are stable at high temperatures, resist thermal shock, and some
even form stable and protective oxide layers in oxidizing environments.
Thus, they are excellent candidates for protective coatings
in high-temperature applications. In this context, our focus is on
using kerosene-fueled High-Velocity Oxy-Fuel spraying to deposit
MAX phases onto P91 steel substrates for use as thermal barrier
coatings. The chosen MAX phase for this study is Ti2AlC, which
offers an outstanding oxidation resistance. Our results indicate that
during the spraying procedure, a portion of the MAX phase decomposes,
another portion oxidizes, yet more than half maintains the
initial and desired stoichiometry. Nevertheless, the resulting coating
establishes a stable and robust bond with the steel substrate. In this
presentation, we will discuss the detailed analysis concerning the
relationship between the process, structure, and performance of the
Ti2AlC coating on the P91 steel substrate
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
Energy Efficiency in Serbia: Challenges and Opportunities
No full textEnergy efficiency plays a critical role in achieving economic, social, and environmental sustainability. This paper provides an overview of the current state of energy efficiency in Serbia, focusing on the challenges, opportunities, and potential pathways towards a more sustainable energy sector. The country has recognized the importance of energy efficiency in improving energy security, reducing costs, and complying with international environmental standards. However, Serbia faces significant challenges, including a lack of awareness of the benefits of energy efficiency, insufficient financing, and policy support for energy-efficient technologies. Nevertheless, Serbia possesses considerable potential for energy-efficient technologies and practices, particularly in the residential and industrial sectors. By promoting energy efficiency, Serbia can reduce energy costs, improve energy security, and contribute to global climate-change mitigation efforts. The paper also highlights the global challenges faced by the energy sector, such as rising energy demand, climate change, pollution reduction, and energy poverty, emphasizing the need for greening the energy sector and investing in renewable energy sources. The energy consumption trends, energy intensity, energy productivity, and share of renewable energy sources in Serbia were analyzed using EuroStat data. The paper concludes by emphasizing the importance of ambitious goals, public awareness, modernizing infrastructure, and securing adequate financing to drive energy efficiency improvements in Serbia. This overview serves as a valuable resource for policymakers, researchers, and stakeholders interested in promoting sustainable energy practices in Serbia and fostering a transition towards a more energy-efficient and environmentally friendly energy sector
A Step Towards Smart, Ergonomic and Sustainable Mining Machinery Workplaces
No full textAlthough the mining industry is the oldest one, it is still a major source of pollution with more people hurt or injured than in any other industry, while social conflicts around it are worldwide spread. Namely, mining projects still have direct and indirect environmental impacts and seriously affect land, water, air, biota, and people, while mining equipment focused in this paper has the highest footprint. The reason for the lack of progress in mining industry is the most likely the fact that in current research streams technology-centered design dominates. Our novel Smart Miner concept aims to create a step toward smart, ergonomic and sustainable mining machinery workplaces. It proposes a paradigm shift from pure technology to a Human and Data-Centric Engineering, which could be easily transferred to other industries, and develops solutions for raising the level of environmental quality in complex interactions between phys- ical, behavioral and organizational processes field, by matching advanced operator I4.0&5.0 and society S5.0 standards.
An original idea approval route starts with mining machinery operator wellbeing in its microenvironment and its cyclical alignment with stakeholders in the value chain. After development of smart, ergonomic, non-invasive and reliable operator aid systems for regulation of physical environment job stressors - noise, human vibration, lighting, temperature, air quality, workplace layout issues etc., which solve environmental and human health issues and influence overall performance, research passes to operator macroenvironment determined by organizational contextual factors, which also impair sustainable development results. Micro and macro levels are planned to be connected and balanced by real time analytics to fit high sustainability performance indicators in novel, flexible and scalable system, aimed to increasing productivity and production together with reducing emissions and decrease of accidents rate
Variational Approach to 2D and 3D Heat Conduction Modeling
Get PDFThe paper proposes an approximate solution to the classical (parabolic) multidimensional 2D and 3D heat conduction equation for a 5 × 5 cm aluminium plate and a 5 × 5 × 5 cm aluminum cube. An approximate solution of the generalized (hyperbolic) 2D and 3D equation for the considered plate and cube is also proposed. Approximate solutions were obtained by applying calculus of variations and Euler-Lagrange equations. In order to verify the correctness of the proposed approximate solutions, they were compared with the exact solutions of parabolic and hyperbolic equations. The paper also presents the research on the influence of time parameters τ as well as the relaxation times τ∗ to the variation of the profile of the temperature field for the considered aluminum plate and cube