Materiały konferencyjne, referaty (WM)

Stały URI dla kolekcji

http://hdl.handle.net/11652/163

Przeglądaj

Teraz wyświetlane 1 - 20 z 36

1D, 2D and 3D dosimetry – a brief overview of the DosLab group’s research work
(Wydawnictwo Politechniki Łódzkiej, 2022) Sąsiadek-Andrzejczak, Elżbieta; Jaszczak, Malwina; Maras, Piotr; Dudek, Mariusz; Piotrowski, Michał; Kozicki, Marek
DosLab is a research group from the Lodz University of Technology, Poland. The research topics carried out by the DosLab group are innovative and interdisciplinary, covering the area of textile engineering, materials engineering, radiation chemistry and medical physics. This study is intended to present an overview of the group's work related to 1D, 2D and 3D dosimetry of UV and ionizing radiation.
Anisotropic friction sliding rule influence on the mechanical systems dynamics
(Wydawnictwo Politechniki Łódzkiej, 2021) Wijata, Adam; Stańczyk, Bartosz; Awrejcewicz, Jan
Anisotropic friction can produce friction force which is not collinear with a sliding direction. How much friction deviates from a sliding direction is described with a so-called sliding potential or equivalently a sliding rule. A sliding potential is often described with an ellipse or a superellipse. In this paper we propose an oval curve which provides piecewise continuous mathematical description for a sliding rule and fits better to the experimental results than a typical superepllipse. For an exemplary mechanical system it is shown, that an anisotropic sliding potential can lead to an unstable equilibrium position in the system. Furthermore, for what parameters the unstable equilibrium occurs differs between sliding potential models. We have tested four different geometrical models of sliding potential in this regard.
Antykorozyjne warstwy nanokrystalicznego diamentu na implantach medycznych
(Politechnika Łódzka, 2000) Bąkowicz, K.; Grabarczyk, J.; Niedzielski, P.; Mitura, S.
Bionic hand control using EMG signals
(Wydawnictwo Politechniki Łódzkiej, 2021) Sencerek, Jędrzej; Zagrodny, Bartłomiej
Abstract. 3D printed prototype a human hand which is controled by sEMG signal was created to simulate two types of fingers motions. The first one includes fingers flexion/extension and the second one is focused on opposing the thumb. These two types of motions are executed by one pair of biological muscles, by the meaning of sEMG signals. The recruting electrodes are attached to both biceps brachii. One of them is responsible for fingers flexion/thumb abduction, and the other is for fingers extension/thumb adduction. The simultaneous contraction of both muscles couses a change in the mode of movement ( fingers - thumb). Control is based on the Arduino microcontroller extended by two EMG Olimex shields and two servos. The main idea behind this project was to create an easy and cheap alternative to commercial prosthetic solutions.
Conditions Regulating Tumor Cell Behaviour in Biological Systems with Memory of States
(Wydawnictwo Politechniki Łódzkiej, 2021) Dzyubak, Larysa; Dzyubak, Oleksandr; Awrejcewicz, Jan
For biological systems with memory of states there were found conditions which regulate tumor cell behaviour. These conditions depend on parameters of the multi-parametric space. Based on the Masing–Bouc-Wen’s framework, the state memory in the biological system was simulated by means of supplemental state variables (internal variables). The additional state variables were introduced into the generalized non-linear multi-scale diffusion cancer invasion model and the chaotic cancer attractors were found. To quantify chaotic cancer attractors, the technique based on the wandering trajectories analysis was applied.
Construction and 3D model of stand for investigating a non-ideal forcing in a nonlinear chain dynamics of self-excited oscillators with friction
(Wydawnictwo Politechniki Łódzkiej, 2021) Rogala, Patryk; Olejnik, Paweł; Awrejcewicz, Jan
The research involves application and research on a non-ideal forcing to modelling and identification of vibrating systems with friction. It is still an innovative approach in the numerical analysis of vibrations of mechatronic machines and devices. This will allow to make a much real numerical modelling and more efficient identification of nonlinear dynamic phenomena observed in vibrating systems with friction, and thus, a better modelling of such phenomena in computer programs. To obtain the goal, initial 3D model of the mechanical stand was made in the CAD software. Based on the 3D model, real stand will be built, and experiments will be held to obtain data that will be necessary to ensure correctness of the mathematical model, which also will be studied and developed.
Design and simulation of a lower limb exoskeleton with linear electric actuators
(Wydawnictwo Politechniki Łódzkiej, 2021) Grzelczyk, Dariusz; Jarzyna, Olga; Awrejcewicz, Jan
In the present study, we proposed and investigated a relatively simple and inexpensive construction of a lower limb exoskeleton driven by linear electric actuators and controlled by an Arduino microcontroller board. Moreover, to study crucial kinematic and dynamic parameters of the proposed device, we developed a general, three-dimensional simulation model of the exoskeleton in Mathematica software. To control individual joints of the investigated exoskeleton, we employed time histories of human joint angles in normal gait, recorded with the use of a motion capture system. As a result, we developed a novel human gait generator, which can be used to produce rhythmic movements in hip, knee and ankle joints of both limbs. Finally, the developed control approach was verified with the use of the constructed prototype of the exoskeleton.
Determination of global damping and stiffness coefficients of journal foil bearing
(Wydawnictwo Politechniki Łódzkiej, 2021) Łagodziński, Jakub; Tkacz, Eliza; Kozanecki, Zbigniew
For the few last years, in modern low-power generation systems, a demand for oilfree compressors has appeared. The development of reliable bearing technology for this relatively high-speed small turbomachinery could be crucial. In order to implement this technology more widely, a selection of the optimal design from the viewpoint of machine reliability must be conducted. A high speed turbomachinery with nominal speed of tens of thousands rpm strongly depends on the proper rotordynamic design. This is especially important when the foil bearings are taken to consideration. These compliant surface gas bearings are a class of hydrodynamic bearings that use the ambient gas as their working fluid and, thus, require no dedicated lubrication system. On the other hand, due to their relatively low damping, a designer should analyze thoroughly the dynamics of the rotor-bearing-casing system in the whole operating rpm range. A correctly operating rotor supported in foil bearings is a design solution that have wide possibilities of applications, unavailable for conventionally supported one. In the turbomachinery, a dynamic behaviour of the machine is related mostly to the stiffness and damping coefficients of system components like rotor, bearings and casing. The foil bearings, although simple in design, indicate complex behaviour resulting from Coulomb friction between their elements. This Coulomb friction affects the damping and stiffness of a given bearing support. Gas film, as a bearing part with relatively high stiffness, plays less role in the rotordynamics than the elastic structure of corrugated foils. So far, many more or less reliable numerical models of this phenomenon have been built and their experimental verification results have been described in literature. The research approach presented in this paper is different. The authors suggested obtaining the data experimentally from the bearing isolated on a test bench, where, the shaft is stationary (fixed), and the gas film is not present. The shaker excites the bearing sleeve while the damping and stiffness are provided to the system by the foil structure. The test bench can be described mathematically as system with single degree of freedom with damping and external forcing. The information collected about the bearing’s global coefficients can be implemented afterwards to the rotordynamic software as a tabular data. This will allow to prepare reliable models that will shorten the design process of newly developed compressors with these oilfree supports.
Drive-by-wire of a converted into electric car Syrena 105 enabling Hardware-In-Loop tests of driving
(Wydawnictwo Politechniki Łódzkiej, 2021) Adamski, Paweł; Olejnik, Paweł
In this work, replacing an electronic throttle pedal and a driver in an electric car converted into electric by a hardware-in-loop workbench is described, highlighting the advantage of drive-by-wire feature that appeared after conversion. Drive-by-wire facilitates replacing a driver by Hardware-In-Loop (HIL) workbench, as instead of simulating a mechanical pedal depression by a servomechanism, electric signals can be transmitted directly from the workbench. Thanks to one-pedal-driving feature of the motor controller used in the car, there is a possibility of performing a variety of road tests replacing only the electronic throttle pedal. Hardware interventions in the car are described and sample HIL test results are presented.
Dynamic analysis of functionally graded sandwich shells resting on elastic foundations
(Wydawnictwo Politechniki Łódzkiej, 2021) Tetyana, Shmatko; Lidiya, Kurpa; Awrejcewicz, Jan
Free vibrations of sandwich shallow shells resting on elastic foundations are investigated. It is assumed that shell consists of three layers of the different thickness. Different schemes of arrangement of layers are considered. Namely, the core is made of ceramics or metals , and the upper and lower layers are made of FGM. The volume fractions of metal and ceramic are described by the power law. Shear deformation shell theory of the first (FSDT) that includes interaction with elastic foundations is applied. To study shells with an arbitrary plan form the R-functions theory combined with the variational Ritz method are used. Validation of the proposed method and developed software has been examined on test problems for FG shell with rectangular plan form. New results for shallow shells with complex plan form were obtained. Effects of the power law index, boundary conditions, thickness of core and face sheet layers, elastic foundations on fundamental frequencies are studied in this work.
Dynamics of Energy Harvesting Mechanical System in the Vicinity of 1:1 Resonance
(Wydawnictwo Politechniki Łódzkiej, 2021) Puzyrov, Volodymyr; Awrejcewicz, Jan; Losyeva, Nataliya
Energy harvesting provides a useful way to power electronic devices without using batteries or electrical wiring. Energy harvesting can be defined as the conversion of environmental energy, such as mechanical, thermal, light energies into usable electrical energy. Conventional mechanical energy harvesting devices use a line harvester to generate electricity through vibrations or other mechanical motion. However, linear generators generate significant power in a narrow band around resonance, and the power is limited by the internal damping factor and the driving force at the resonant frequency. Such devices implementing a linear (resonant) generator cannot generate sufficient specific power. In present paper the mechanical system is considered which consists of two coupled oscillators (nonlinear absorber connected with primary mass) and a piezoelectric element attached. Two goals are pursued: the mitigation of the responses of the main mass and maximizing the amount of energy extracted from vibrations. The influence of nonlinear stiffness's component is discussed. It is shown that the piezoelectric element allows the effective energy harvesting and at the same has very limited influence on reducing the amplitude of oscillations of the main mass.
Efekty degradacji folii opakowaniowych przez mikroflorę termofilną
(Wydawnictwo SIGMA-NOT, 2006) Szumigaj, Joanna; Żakowska, Zofia; Klimek, Leszek; Bartkowiak, Artur
Badano podatność folii opakowaniowych otrzymanych z celulozy, polikaprolaktonu i polikwasu mlekowego na działalność glebowej mikroflory termofilnej. Po 2 miesiącach kompostowania w temperaturze 48°C przeprowadzono analizę mikrobiologiczną powierzchni folii i wyniki porównano z analizą ilościową mikroflory mezofilnej kolonizującej folie. Liczba mikroflory termofilnej była o rząd lub dwa rzędy wielkości większa niż ilość mikroflory mezofilnej. Dominującą mikroflorą termofilną były szczepy bakterii Bacillus oraz pleśni Aspergillus fumigatus. Na podstawie obserwacji mikroskopowych stwierdzono, że proces biodegradacji folii przez mikroflorę termofilną przebiegał efektywniej i szybciej.
Energy flow control in a system of coupled pendulums using magnetic field
(Wydawnictwo Politechniki Łódzkiej, 2021) Pilipchuk, Valery; Polczyński, Krystian; Bednarek, Maksymilian; Awrejcewicz, Jan
In the presented work, we proposed a methodology of controlling the resonance energy exchange in mechanical systems by creating appropriate electromagnetic fields around the system’s structural subcomponents. It has been shown theoretically and confirmed experimentally that properly guided magnetic fields can effectively change mechanical potentials in such a way that the energy flow between the oscillators takes the desired direction. In particular, a model of two weakly coupled pendulums subjected to an electromagnetic load using a specific set of descriptive functions was considered. The developed control strategies are based on the observation that, in the case of antiphase oscillation, the energy is moving from the pendulum, which is in the repelling magnetic field, to the oscillator not subjected to magnetic field. The advantage of the suggested control strategy is that the temporal rate of inputs is dictated by the speed of beating, which is relatively slow compared to the carrying oscillations.
Estimation the Domain of Attraction for a System of Two Coupled Oscillators with Weak Damping
(Wydawnictwo Politechniki Łódzkiej, 2021) Awrejcewicz, Jan; Puzyrov, Volodymyr; Losyeva, Nataliya; Savchenko, Nina; Nikolaieva, Oksana
When solving a wide class of problems of nonlinear dynamics, the stability property of a given system regime is a prerequisite for design. An important role is played by the concept of the domain of attraction (DoA) of the equilibrium point (or limit cycle). However, as a rule, this domain is difficult to find and describe in explicit form. Therefore, the search for DoA estimate has been a fundamental problem in the control theory since the middle of the last century. Currently, methods based on Lyapunov functions predominate in the literature. We have studied the problem of obtaining the estimates of the DoA for equilibrium of the mechanical systems. The method for using Lyapunov function of special kind for a system with polynomial right-hand side to find the estimates for DoA is proposed. This procedure is illustrated by the example of a mechanical system which consists of two coupled nonlinear oscillators with weak damping.
Fundusze strukturalne UE dla zrównoważonego rozwoju w regionie łódzkim
([Wydawnictwo Politechniki Łódzkiej], 2010) Jóźwik, Krzysztof
Geometrically nonlinear vibrations of double-layered nanoplates
(Wydawnictwo Politechniki Łódzkiej, 2021) Awrejcewicz, Jan; Mazur, Olga
The geometrically nonlinear vibrations of simply supported double-layered graphene sheet systems are considered in the presented manuscript. The interaction between layers is taken into account due to van der Waals forces. The investigation is based on the nonlocal elasticity theory, Kirchhoff plate theory and von Kármán theory. The governing equations are used in mixed form by introducing the stress Airy function. The analytical presentation of the nonlinear frequency ratio for in-phase vibration and anti-phase vibration modes is presented. It is shown that the nonlocal parameter included in the compatibility equation can significantly change the vibrating characteristics.
Higher order asymptotic homogenization for dynamical problems
(Wydawnictwo Politechniki Łódzkiej, 2021) Awrejcewicz, J.; Andrianov, I.I.; Diskovsky, A.A.
In general, asymptotic homogenization methods are based on the hypothesis of perfect scale separation. In practice, this is not always the case. The problem arises of improving the solution in such a way that it becomes applicable if inhomogeneity parameter is not small. Our study focuses on the higher order asymptotic homogenization for dynamical problems. Systems with continuous and piecewise continuous parameters, discrete systems, and also continuous systems with discrete elements are considered. Both low-frequency and highfrequency vibrations are analyzed. For low-frequency vibrations, several approximations of the asymptotic homogenization method are constructed. The influence of the boundary conditions, the system parameters is investigated.
Identification of the model parameters based on the ambiguous branches of resonance response curves
(Wydawnictwo Politechniki Łódzkiej, 2021) Sypniewska-Kamińska, Grażyna; Awrejcewicz, Jan
A concept of the method of determining the parameters describing the damping and the nonlinearity, which can be of physical or geometrical nature, is presented in the paper. The main idea is explained regarding mechanical systems with one degree of freedom, however, the method can be also employed to identification for systems with two DoF provided that the couplings are weak and the resonances do not occur simultaneously. The analysis of stationary resonance states can be reduced only then to the third-degree equation, which is a necessary condition for the applicability of this method. Numerical simulations, which are carried out, confirm the usefulness and accuracy of the method.
Influence of a relatively high frequency structure vibrations on the dynamics of real stick-slip motion
(Wydawnictwo Politechniki Łódzkiej, 2021) Olejnik, Paweł; Górniak vel Górski, Adrian; Cebulak, Maciej; Awrejcewicz, Jan
The work concerns the research on the impact of structure vibrations on the dynamics of frictional contact of bodies moving in relation to each other and remaining in frictional contact, causing a stick-slip motion. A literature review was carried out, describing mainly the phenomena concerning friction, but also the dynamics of vibrations and non-ideal energy sources that induce system oscillations. In the next step an experimental station for investigation of friction equipped with a new subsystem inducing high-frequency vibrations is presented to propose a modified physical model of the investigated frictional system. After analysing the most important factors influencing the behavior of the tested system, a mathematical description was prepared, which in theory showed the potential influence of the attached subsystem on the dynamics of the movement of the tested object - the frictional connection. Various methods of implementing the unbalance of rotors, being the source of highfrequency excitation, have been considered. At the final stage, a series of measurements of the displacement of the vibrating block on the moving belt was performed with the highfrequency excitation turned on and off. The prepared graphs were used to analyse the dynamics of frictional contact and the impact of non-autonomous vibrations on the occurrence of the stick-slip phenomenon.
Influence of fractional order parameter on the dynamics of different vibrating systems
(Lodz University of Technology Press, 2021) Zafar, Azhar Ali; Awrejcewicz, Jan
In this work, we will investigate the fractional differential equations associated to different vibration phenomena. More specifically, we will discuss Bagley-Torvik equation, composite fractional relaxation differential equation and the motion of a linear oscillator using fractional derivative operator in the sense of Atangana-Baleanu. In order to be consistent with the physical systems the value of the fractional parameter that characterizes the existence of fractional structures in the system, lies within unit interval. The solutions of the non-integer order differential equation are obtained and expressed in terms of generalized functions depending upon the fractional parameter. The classical cases could be recovered by making the limit of fractional parameter approaches to unity. Moreover, we will analyze and compare the control of the fractional order parameter on the dynamics of the models and useful conclusions are recorded.

Przeglądaj

Przeglądaj Materiały konferencyjne, referaty (WM) wg Tytuł

Wyników na stronę

Opcje sortowania