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1
Content available Selected research issues of prototype floating systems
Derewońko Agnieszka, Krasoń Wiesław
Acta Mechanica et Automatica
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2024
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Vol. 18, no. 2
204--211
EN
The paper presents a solution that can be used as a temporary supplement to the existing infrastructure in cases of natural disasters, during structure or bridge repair, in military applications and in areas where it is necessary to provide a floating system crossing. The genesis of the proposed structure and its development, as well as examples of applications of the basic module, referred to as the river module – the floating cassette with the pneumatic pontoon – are presented. The original solutions, such as the bow–stern modules, designed using modern, light and durable materials acting as deflectors, are also described. Examples of the use of floating structures composed of identical/repeatable modules–cassettes are shown. The results of experimental tests of two prototype river modules sets are presented as a validation for numerical studies. Selected aspects of static, kinematic and dynamic analyses using finite element and multibody simulations are presented. The numerical simulation of the prototype floating bridge with an assessment of the impact of clearances and an estimation of the kinematic parameters of the floating ribbon with various configurations are described.
2
Content available Investigation of driving stability of a vehicle–trailer combination depending on the load’s position within the trailer
Dižo Ján, Blatnický Miroslav, Droździel Paweł, Melnik Rafał, Caban Jacek, Kafrik Adam
Acta Mechanica et Automatica
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2023
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Vol. 17, no. 1
60--67
EN
Passenger cars are a means of transportation used widely for various purposes. The category that a vehicle belongs to is largely responsible for determining its size and storage capacity. There are situations when the capacity of a passenger vehicle is not sufficient. On the one hand, this insufficient capacity is related to a paucity in the space needed for stowing luggage. It is possible to mount a rooftop cargo carrier or a roof basket on the roof of a vehicle. If a vehicle is equipped with a towbar, a towbar cargo carrier can be used for improving its space capacity. These accessories, however, offer limited additional space, and the maximal load is determined by the maximal payload of the concerned vehicle. If, on the other hand, there is a requirement for transporting a load with a mass or dimensions that are greater than what could be supported using these accessories, then, provided the vehicle is equipped with a towbar, a trailer represents an elegant solution for such demanding requirements. A standard flat trailer allows the transportation of goods of various characters, such as goods on pallets, bulk material, etc. However, the towing of a trailer changes the distribution of the loads, together with changes of loads of individual axes of the vehicle–trailer axles. The distribution of the loads is one of the key factors affecting the driving properties of a vehicle–trailer combination in terms of driving stability, which is mainly a function of the distribution of the load on the trailer. This research introduces a study into how the distribution of the load on a trailer influences the driving stability of a vehicle–trailer combination. The research activities are based on simulation computations performed in a commercial multibody software. While the results presented in the article are reached for a particular vehicle–trailer combination as well as for a particular set of driving conditions, the applicability of the findings can also be extended more generally to the impact that the load distributions corresponding to various vehicle–trailer combinations have on the related parameters and other driving properties.
3
Content available Analysis of the backlash in the single stage cycloidal gearbox
Król Roman
Archive of Mechanical Engineering
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2022
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LXIX, nr 4
693--711
EN
In this paper the analysis of backlash influence on the spectrum of torque at the output shaft of a cycloidal gearbox has been performed. The model of the single stage cycloidal gearbox was designed in the MSC Adams. The analysis for the excitation with the torque and the analysis with constant angular velocity of the input shaft were performed. For these analyses, the amplitude spectrums of the output torque for different backlashes was solved using FFT algorithm. The amplitude spectrums of the combined sine functions composed of the impact to impact times between the cycloidal wheel and the external sleeves were computed for verification. The performed studies show, that the backlash has significant influence on the output torque amplitude spectrum. Unfortunately the dependencies between the components of the spectrum and the backlash could not be expressed by linear equations, when vibrations of the output torque in the range of (350 Hz – 600 Hz) are considered. The gradual dependence can be found in the spectrum determined for the combined sine functions with half-periods equal impact-to-impact times. The spectrum is narrower for high values of backlash.
4
Content available Resonance phenomenon in the single stage cycloidal gearbox. Analysis of vibrations at the output shaft as a function of the external sleeves stiffness
Król Roman
Archive of Mechanical Engineering
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2021
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LXVIII, nr 3
303--320
EN
In this paper a versatile analysis of the cycloidal gearbox vibrations and the resonance phenomenon was performed. The objective of this work was to show resonance phenomenon and vibrations study in the multibody dynamics model and in the finite element model of the cycloidal gearbox. The output torque was analyzed as a function of the external sleeves stiffness. The results from the multibody dynamics model were verified in the finite element model using natural frequency with load stiffening, direct frequency response and direct transient response analyses. It was shown that natural frequencies of the cycloidal gearbox undergo changes during motion of the mechanism. The gearbox passes through the thresholds of the increased vibration amplitudes, which lead to excessive wear of the external sleeves. The analysis in the multibody dynamics model showed, that the increase in the external sleeves stiffness increases frequency of the second-order fluctuation at the output shaft. Small stiffness of the external sleeves guarantees lower frequency of the second order vibrations and higher peak-to-peak values of the output torque. The performed research plays important role in the cycloidal gearbox design. This work shows gearbox dynamics problems which are associated with wear of the external sleeves.
5
Content available remote Self-Eexcited Full-Vehicle Oscillations
Engel D., Meywerk M.
Machine Dynamics Research
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2018
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Vol. 42, No. 2
5--16
EN
In this paper, self-excited full-vehicle oscillations - in this context referred to as "Power-Hop" - and two appropriate remedies to reduce or prevent these oscillations are described. The results of full-vehicle measurements, as well as the development of a specially designed test rig, examinations and predictions of the MBS full-vehicle model are presented. By using the simulation model, the effectiveness of a specifically modified advanced driver assistance system, which should reduce the oscillations, is discussed. Furthermore, to avoid energy input into this vibratory system, the use and effectiveness of magnetorheological drivetrain mounts are presented.
6
Content available Influence of the front part of the vehicle and cyclist’s sitting position on the severity of head injury in side collision
Fanta O., Boucek J., Hadraba D., Jelen K.
Acta of Bioengineering and Biomechanics
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2013
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Vol. 15, no. 1
105--112
EN
An injury of cyclists during a collision with a car is currently a neglected topic. Most research projects evaluate in detail the injury of pedestrians, but with an increasing number of cyclists it will be necessary to devote more attention to their safety. This study is focused on the most common type of collision and offers insights into the biomechanics of cyclist’s head injury without the use of bicycle helmet. Initial mechanical and kinematic conditions that affect Head Injury Criterion (HIC) after a car hits a cyclist were determined using simulation software MADYMO. In relation to HIC, three different shapes of the front part of the car and three basic cyclist’s positions were compared.
7
Content available Undesidered drift of multibody models excited by measured accelerations or forces
Speckert M., Ruf N., Dressler K.
Journal of Theoretical and Applied Mechanics
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2010
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Vol. 48 nr 3
813-837
EN
In the ground vehicle industry, it is important to simulate multibody models of the full vehicle based on wheel forces and moments in order to derive section forces at certain components for durability assessment. This is difficult due to noise in the input data and the unavoidable deviation between the model and real vehicle. Both lead to an undesired drift of the vehicle model in the simulation. This paper shortly describes the sources of these effects and shows that, due to missing knowledge about the true trajectory of the vehicle, this problem cannot be solved by an improved numerical treatment of the underlying equations. Several ways to deal with the problem are briefly reported. Finally, a simple vehicle model is used to show all the effects.
PL
W przemyśle samochodowym bardzo istotną rolę pełnią symulacje numeryczne wielobryłowych modeli kompletnych pojazdów, wykonywane na podstawie pomiarów sił i momentów działających na koła, w celu późniejszego obliczania sił wewnętrznych w przekrojach różnych elementów dla oceny ich wytrzymałości. Zadanie to jest dość trudne ze względu na szum danych wejściowych uzyskanych w drodze pomiarów oraz nieuniknione rozbieżności w sformułowaniu modelu w stosunku do obiektu rzeczywistego. Obydwa te czynniki powodują niestabilność numeryczną modelu. Prezentowana praca opisuje pokrótce źródła tych efektów i pokazuje, że wskutek braku wiedzy na temat rzeczywistej trajektorii pojazdu, problem ten nie może być rozwiązany jedynie w drodze zastosowania bardziej wydajnych narzędzi całkowania numerycznego równań ruchu. Przedstawiono jednak kilka koncepcji wyjścia naprzeciw temu problemowi. Na koniec, opisano prosty model pojazdu odzwierciedlający wszystkie te zagadnienia.
8
Content available Simulation and numerical parameter identification of a biologically inspired bipedal robot with passive elements
Förg D., Ulbrich H.
Archive of Mechanical Engineering
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2010
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Vol. LVII, nr 2
149-163
EN
The goal of the project is to investigate the influence of elastic mechanisms on technical, bipedal locomotion. In particular, the paper presents the parameter identification for a biologically inspired two-legged robot model. The simulation model consists of a rigid body model equipped with rubber straps. The arrangement of the rubber straps is based on the arrangement of certain muscle groups in a human being. The parameters of the elastic elements are identified applying numerical optimisation. Thus two optimisation algorithms are investigated and compared with respect to robustness and computing time. Moreover, different objective functions are defined and discussed. The behaviour of the resulting configuration of the system is explored in terms of biomechanics.
PL
Celem projektu jest badanie wpływu elementów sprężystych na realizację techniczną dwunożnej lokomocji robota. W szczególności, w artykule przedstawiono identyfikację parametrów inspirowanego biologicznie modelu robota dwunożnego. W modelu uwzględniono człony sztywne oraz gumowe taśmy. Rozmieszczenie taśm jest wzorowane na rozmieszczeniu odpowiednich grup mięśniowych u człowieka. Parametry elementów sprężystych są identyfikowane na drodze optymalizacji numerycznej. Zbadano dwa algorytmy optymalizacyjne, porównując je pod kątem uzyskiwanych wyników i czasu obliczeń. Ponadto, zdefiniowano i przedyskutowano różne funkcje celu. Zachowanie się zoptymalizowanego układu zbadano w kategoriach biomechaniki.
9
Content available remote An object-oriented approach to simulating human gait motion based on motion tracking
Tändl M., Stark T., Erol N. E., Löer F., Kecskeméthy A.
International Journal of Applied Mathematics and Computer Science
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2009
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Vol. 19, no 3
469-483
EN
Accurate bone motion reconstruction from marker tracking is still an open and challenging issue in biomechanics. Presented in this paper is a novel approach to gait motion reconstruction based on kinematical loops and functional skeleton features extracted from segmented Magnetic Resonance Imaging (MRI) data. The method uses an alternative path for concatenating relative motion starting at the feet and closing at the hip joints. From the evaluation of discrepancies between predicted and geometrically identified functional data, such as hip joint centers, a cost function is generated with which the prediction model can be optimized. The method is based on the object-oriented multibody library [...], which has already been successfully applied to the development of industrial virtual design environments. The approach has been implemented in a general gait visualization environment termed Mobile Body.
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