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Number of results: 365
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Abstract

The study presented here offers an analysis of the heat flow through the wall of the Yankee cylinder when regarded as a thin-walled vessel. The effect of the selected design and process parameters (i.e. cylinder diameter and steam pressure) on density of the heating stream has been analyzed and discussed for both cast iron and steel cylinders. Based on the work presented here, the optimal ranges for steam pressure have been derived and proposed for cylinders mounted at various locations within the drying section.
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Abstract

The box wing system is an unconventional way to connect the lifting surfaces that the designers willingly to use in prototypes of new aircrafts. The article present a way to quickly optimize the wing structure of box wing airplane that can be useful during conceptual design. At the beginning, there is presented theory and methods used to code optimization program. Structure analysis is based on FEM beam model, which is sufficient in conceptual design. Optimization is performed using hybrid method, connection of simple iteration and gradient descent methods. Finally, the program is validated by case study.
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Abstract

Two fundamental challenges in investigation of nonlinear behavior of cantilever beam are the reliability of developed theory in facing with the reality and selecting the proper assumptions for solving the theory-provided equation. In this study, one of the most applicable theory and assumption for analyzing the nonlinear behavior of the cantilever beam is examined analytically and experimentally. The theory is concerned with the slender inextensible cantilever beam with large deformation nonlinearity, and the assumption is using the first-mode discretization in dealing with the partial differential equation provided by the theory. In the analytical study, firstly the equation of motion is derived based on the theory of large deformable inextensible beam. Then, the partial differential equation of motion is discretized using the Galerkin method via the assumption of the first mode. An exact solution to the obtained nonlinear ordinary differential equation is developed, because the available semi analytical and approximated methods, due to their limitations, are not always sufficiently reliable. Finally, an experiment set-up is developed to measure the nonlinear frequency of oscillations of an aluminum beam within a domain of initial displacement. The results show that the proposed analytical method has excellent convergence with experimental data.
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Abstract

The paper reports on investigation and development of a flywheel device intended for an energy storage prototype. The goal was to design and experimentally verify the concept of self-integrated flywheel with smart control of energy flow and accumulation. The Flywheel Energy Storage System (FESS) must has high energy efficiency and structural robustness. Investigation on structural dynamics of the composite flywheel connected with outer type rotor was carried out using Finite Element Method. The FESS is designed to run in vacuum and is supported on low-energy, controlled, active magnetic bearings (AMBs). The flywheel device of 10 MJ energy density and a weight of 150 kg with two integrated rotors/generators of 50 kW power density each is intended to operate up to 40 000 rpm.
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Abstract

The aim of this paper is to present an in-pipe modular robotic system that can navigate inaccessible industrial pipes in order to check their condition, locate leakages, and clean the ventilation systems. The aspects concerning the development of a lightweight and energy efficient modular robotic system are presented. The paper starts with a short introduction about modular inspection systems in the first chapter, followed by design aspects and finalizing with the test of the developed robotic system.
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Abstract

A complete system of a Laser Radar is described in this paper. One explains the principles of the laser and all additional devices used in this system in order to obtain a compact and eye-safe system. The principle and realization of algorithms for controlling the cruise and speed of the vehicle are described. By applying modal control, and choosing the optimal mode for reducing the speed, one derives the system equation and determines its coefficients. Finally, the paper presents simulations of the laser scanning system, the modal control system and the behavior of the system affected by different errors and disturbances. The effects of instrumental errors are defined and simulation is performed illustrating how such a control system is influenced by internal and external disturbances.
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Abstract

The paper presents a model of a rapping system of an electrostatic precipitator. The rapping system consists of a set of collecting electrodes hanging on a suspension bar and braced together in a brushing bar. The suspension and brushing bars are modeled using the rigid finite element method, while the collecting plates are modeled using the hybrid method. The method combines the rigid finite element method with the classical finite element method. As a result, the mass matrix is diagonal. Some results of numerical simulations concerning free vibrations of the collecting plates and the influence of the number of elements, into which the plate is divided, on the vibrations of the rapping system are presented.
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Abstract

The paper presents a research program carried out to improve understanding of the fluid dynamics mechanisms that lead to rotating stall in the axial flow low speed compressor stage. The stalling behavior of this compressor stage was studied by measuring unsteady casing pressure by means of a circumferentially and axially spaced array of high frequency pressure transducers. Another probe used was a disc static pressure probe, with the pressure transducer, for in-flow and out-flow measurements along the blade span. It was expected that understanding of the fluid dynamics will facilitate at least two important tasks. The first was to accurately predict of when and how a particular compressor would stall. The second was to control, delay, or eventually suppress the rotating stall and surge. In consequence, one could extend the useful operating range of the axial compressor. Another motivation for the research was to compare the results from the three applied analysis techniques by using a single stall inception event. The first one was a simple visual inspection of the traces, which brought about a very satisfactory effect. The second one was application of spatial Fourier decomposition to the analysis of stall inception data, and the third method of analysis consisted in application of wavelet filtering in order to better understand the physical mechanisms which lead to rotating stall. It was shown that each of these techniques would provide different information about compressor stall behavior, and each method had unique advantages and limitations.
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Abstract

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.
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Abstract

The paper presents a prototype of a rehabilitation robot for lower extremities. It is created on the basis of cylindrical kinematic model, equipped with two rigid arms, special handles and fixtures. It has five active degrees of freedom and is designed to repeat the trajectories generated by physiotherapist during the learning phase. Presented prototype of rehabilitation robot has the ability to replay different types of trained exercises such as: hip and knee flexion/extension, leg abduction/adduction. The protection system (including overload detection) implemented in the robot ensures safe working with patients.
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Abstract

The aim of the study is to identify the relevant aspects of numerical analysis of impact of projectiles with soft cores into a package composed of thin flexible plies located on the plastic backing. In order to illustrate the problem, normal impact of 7.62 mm TT projectile into an unclamped package comprising 36 plies of Dyneema SB71 supported on the plastic backing was selected. The problem was solved with the use of the finite element method (FEM) with the explicit integration scheme (central difference method) of motion equations in the matrix form. Based on the conducted numerical computations, it was revealed that obtaining the extreme deformations of a projectile soft core and the backing material in Lagrangian description requires employment of adaptive methods. The proposed R-adaptive method performs its role but must be used carefully due to the mass loss which may appear during calculations.
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Abstract

The paper presents design and experimental verification of platform mechanism with cost-effective wire-based sensors for measuring of spatial displacement or pose of some moving object. This task, also known as spatial tracking, has a very wide application. The proposed mechanism, guided by the moving object, has a parallel structure with two platforms and at least six wire-based sensors for measuring distances between the platform points. Changes of the platform pose cause corresponding changes of the sensors' wire lengths. Forward position problem of an equivalent mechanism model with 6 degrees of freedom is described together with analyses of work space limitations and error propagation in a measurement system. A specific application is illustrated for tracking of a wheel knuckle of 5-link suspension mechanism used in passenger cars. The developed device has the following advantages: it can be installed in a wheel cavity; enables dynamic measurements on the road; is cost-effective. Performance of the latest prototype of the wire-based tracker was verified on the basis of measurements on a test rig, where two other measuring devices were used for comparison purposes.
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Abstract

The paper presents the control concept for an experimental rig with closed-loop controlled pneumatic axis. The objective is the convenient execution of diverse control technologic experiments using free implementable control structures. Since two actuators can be mechanically linked to one another, one is force controlled to generate defined disturbances. Furthermore, a particular simulation model, which can be integrated in the controllers' user program, is pointed out including non-linear effects. Finally, selected experiments are discussed.
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Abstract

The rigid finite element method (RFEM) has been used mainly for modelling systems with beam-like links. This paper deals with modelling of a single set of electrodes consisting of an upper beam with electrodes, which are shells with complicated shapes, and an anvil beam. Discretisation of the whole system, both the beams and the electrodes, is carried out by means of the rigid finite element method. The results of calculations concerned with free vibrations of the plates are compared with those obtained from a commercial package of the finite element method (FEM), while forced vibrations of the set of electrodes are compared with those obtained by means of the hybrid finite element method (HFEM) and experimental measurements obtained on a special test stand.
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Abstract

Today, a cascaded system of position loop, velocity loop and current loop is standard in industrial motion controllers. The exact knowledge of significant parameters in the loops is the basis for the tuning of the servo controllers. A new method to support the commissioning has been developed. It enables the user to identify the moment of inertia as well as the time constant of the closed current loop simultaneously. The method is based on the auto relay feedback experiment by Aström and Hägglund. The model parameters are automatically adjusted according to the time behaviour of the controlled system. For this purpose, the auto relay feedback experiment is combined with the technique of gradual pole compensation. In comparison to other existing methods, this approach has the advantage that a parametric model for the open velocity loop is derived directly.
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Abstract

The paper presents a solution of the control system for fatigue test stand MZGS-100 PL, comprising the integrated Real-Time controller based on FPGA (Field-Programmable Gate Array) technology with LabVIEW software. The described control system performs functions such as continuous regulation of speed induction motor, measuring strain of the lever machine and the test specimen, displacement of the polyharmonic vibrator, as well as the elimination of interferences, overload protection and emergency stop of the machine. The fatigue test stand also allows to set the pseudo-random history of energy parameter W(t).
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Abstract

The paper presents an adapted least squares identification method for reduced-order parametric models. On the example of the open velocity loop, different model approaches were implemented in a motion control system. Furthermore, it is demonstrated how the accuracy of the method can be improved. Finally, experimental results are shown.
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Abstract

The paper focuses on the influence of the longitudinal and lateral suspension damping in correlation with the velocity upon the vibration behaviour of the railway vehicles while moving on a tangent track. The numerical simulations are developed based on a linear model of a 17-degree of freedom vehicle that allows the evaluation of the dynamic behaviour of the vehicle in a sub-critical velocity. Based on the response frequency functions of the vehicle in a harmonic and in a random behaviour, a series of basic properties of the stable behaviour of the forced lateral vibrations has been made evident, as well as the opportunities to lower the level of the carbody vibrations by changing the suspension damping.
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Abstract

The possibility of distinguishing and assessing the influences of defects in particular pump elements by registering vibration signals at characteristic points of the pump body would be a valuable way for obtaining diagnostic information. An effective tool facilitating this task could be a well designed and identified dynamic model of the pump. When applied for a specific type of the pump, such model could additionally help to improve its construction. This paper presents model of axial piston positive displacement pump worked out by the authors. After taking the simplifying assumptions and dividing the pump into three sets of elements, it was possible to build a discrete dynamic model with 13 degrees of freedom. According to the authors' intention, the developed dynamic model of the multi-piston pump should be used for damage simulation in its individual elements. By gradual change in values of selected construction parameters of the object (for example: stiffness coefficients, damping coefficients), it is possible to perform simulation of wear in the pump. Initial verification of performance of the created model was done to examine the effect of abrasive wear on the swash plate surface. The phase trajectory runs estimated at characteristics points of the pump body were used as a useful tool to determine wear of pump elements.
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Abstract

This article presents the results of investigating the influence of tooth contact ratio in helical cylindrical gears on vibroactivity of the gearbox. Based on the measurements carried out on a laboratory test stand, time-domain and frequency-domain start-up characteristics of vibrations and acoustic pressure were determined, and vibroactivity was assessed for a gearbox in which 4 pairs of gears were successively mounted with different face contact ratios equal to, respectively, epsilon beta=1,001; 1,318; 1,574; 2,636.
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Abstract

In this paper, the author presents the possibility of using phase trajectory for detecting damage in an axial piston pump. The wear on main part of pump elements, such as the rotor and the valve plate, was investigated, and phase trajectories were determined based on vibration signal measured in three directions on the pump's body. In order to obtain a quantitative measure of the analyzed trajectory, the At_{p,i} parameter was introduced, and the relation between this parameter and the wear on the pump's parts was determined.
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Abstract

The functionality of a prosthesis is determined by clinical procedures, the manufacturing technology applied, the material used and its strength parameters. The aim of the paper is to evaluate the static strength and fatigue strength of acrylic construction materials directly after the process of polymerisation and for aged materials. It has been confirmed that the deformation speed of the tested materials has an evident impact on their mechanical characteristics. With greater deformation speed, a consistent increase in the material elasticity was observed in static compression tests, which was accompanied by a reduction in engineering stresses at the final stage of deformation. The greatest fatigue strength was observed for Vertex. It was by about 33% greater than the strength of Villacryl – the material that has the lowest fatigue properties. The resistance of acrylic polymers to cyclic loading applied with the frequency of 1 Hz may become an indication for the selection of the material to be used in the clinical procedures in which a patient is provided with full dentures.
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Abstract

In this paper, the author compares the of characteristics of subsystems obtained by the approximate and exact method in order to answer to the question - if the approximate method can be used to nominate the characteristics of mechatronic systems. Frequency - modal analysis has been presented for a mechanical system, i.e. transverse-vibrating clamped-free beam. Consequently, the model of the beam was presented in a five-vertex hypergraph. This model, in the case of approximate frequency-modal analysis, can be imitated in a three-vertex hypergraph. Such formulation could be the introduction to synthesis of transverse-vibrating complex beam systems with constant cross-section.
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Abstract

The Variable Frequency Drive (VFD) is used to control the speed of the pumpmotor to attain the desired flow rate and fluid level in a fluid system. An AC drive provides efficient flow control by varying the pump-motor speed. The comparison of energy requirements and costs in a system where a throttling device is used for flow control on a centrifugal pump with the power used when an variable frequency drive (VFD) is used to control the same flow, evidently shows potential savings. In this system, AC Motor Frequency drive and static pressure transmitter, turbine type flowmeter and Analog/Digital cards, micro-control unit and computer connection are designed specially to control flow rate, fluid flow type (turbulence or laminar) and water level at the different conditions with different PID parameters.
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Abstract

The development of industry is determined by the use of modern materials in the production of parts and equipment. In recent years, there has been a significant increase in the use of nickel-based superalloys in the aerospace, energy and space industries. Due to their properties, these alloys belong to the group of materials hard-to-machine with conventional methods. One of the non-conventional manufacturing technologies that allow the machining of geometrically complex parts from nickel-based superalloys is electrical discharge machining. The article presents the results of experimental investigations of the impact of EDM parameters on the surfaces roughness and the material removal rate. Based on the results of empirical research, mathematical models of the EDM process were developed, which allow for the selection of the most favourable processing parameters for the expected values of the surface roughness Sa and the material removal rate.
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