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1

Analysis of fractional electrical circuit containing two RC ladder elementsof different fractional orders

Piotrowska Ewa, Melnik Rafał

Acta Mechanica et Automatica

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2024

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Vol. 18, no. 1

77--83

EN

The study addresses the topic of different fractional orders in the context of simulation as well as experiments using real electrical elements of fractional-order circuit. In studying the two solutions of the resistance-capacitance (RC) ladder circuit of appropriate parameters, different fractional orders of the electrical circuit are considered. Two fractional-order (non-integer) elements were designed based on the Continued Fraction Expansion (CFE) approximation method. The CFE method itself was modified to allow free choice of centre pulsation. It was also proposed that when making individual ladder circuits, in the absence of elements with the parameters specified by the program, they should be obtained by connecting commercially available elements in series or parallel. Finally, the theoretical analysis of such a circuit is presented using state-space method and verified experimentally.

2

Feasibility study of a rail vehicle damper fault detection by artificial neural networks

Melnik Rafał, Koziak Seweryn, Dižo Ján, Kuźmierowski Tomasz, Piotrowska Ewa

Eksploatacja i Niezawodność

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2023

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Vol. 25, no. 1

art. no. 5

EN

The aim of the study was to investigate rail vehicle dynamics under primary suspension dampers faults and explore possibility of its detection by means of artificial neural networks. For these purposes two types of analysis were carried out: preliminary analysis of 1 DOF rail vehicle model and a second one - a passenger coach benchmark model was tested in multibody simulation software - MSC.Adams with use of VI-Rail package. Acceleration signals obtained from the latter analysis served as an input data into the artificial neural network (ANN). ANNs of different number of hidden layers were capable of detecting faults for the trained suspension fault cases, however, achieved accuracy was below 63% at the best. These results can be considered satisfactory considering the complexity of dynamic phenomena occurring in the vibration system of a rail vehicle.

3

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.

4

Assessment of ride properties of a tricycle by means of simulation computations

Dižo Ján, Blatnický Miroslav, Barta Dalibor, Melnik Rafał

Zeszyty Naukowe Instytutu Pojazdów / Politechnika Warszawska

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2019

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z. 2/120

33--38

EN

This contribution introduces process and results of assessment of the ride properties of a tricycle in terms of driving safety as well as in terms of ride comfort for passengers. The analysed tricycle has been designed at the authors’ workplace. Ride comfort for passenger of road vehicles is one of the most important performances of a vehicle. The research of automotive passenger ride comfort is still very important. Values of vertical wheel forces were evaluated as critical parameters for assessment of driving safety and values of total accelerations were assessed in terms of ride comfort. At the same every vehicle has to meet quite strict criteria for driving safety. All calculation and evaluation of results were carried out by means of multibody software package.

PL

Praca prezentuje proces oceny i wyniki badań właściwości jezdnych pojazdu trójkołowego pod względem bezpieczeństwa jazdy, a także pod względem komfortu jazdy dla pasażerów. Analizowany trójkołowiec został zaprojektowany w miejscu pracy autorów. Komfort jazdy dla pasażerów pojazdów drogowych jest jednym z najważniejszych parametrów pojazdu. Badania komfortu jazdy pasażerów samochodów są nadal bardzo ważne. Wartości sił pionowych kół oceniono jako parametry krytyczne do oceny bezpieczeństwa jazdy, a wartości przyspieszeń całkowitych oceniono jako najważniejsze w kwestii komfortu jazdy. Jednocześnie każdy pojazd musi spełniać dość surowe kryteria bezpieczeństwa jazdy. Wszystkie obliczenia i oceny wyników przeprowadzono za pomocą pakietu oprogramowania wieloobiektowego.

5

Tram track stiffness measurement based on the vision method

Koziak Seweryn, Melnik Rafał, Firlik Bartosz

Prace Naukowe Politechniki Warszawskiej. Transport

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2019

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z. 125

45--52

EN

One of the main parameters characterizing properties of railway track is vertical stiffness. Provision of its appropriate value is crucial from the point of view of dynamic interactions occurring in a wheel-rail contact, what in turn translates into vehicle running behaviour and safety, passenger comfort, as well as further degradation of track condition. Track stiffness measurement is a cumbersome process requiring expensive equipment and can be carried out only if the line is closed. The following research is intended to estimate tram track vertical stiffness by means of vision method which can be performed during regular tram operation. Track deflections of tram line in the city of Poznan were carried out using high-speed camera and further used for vertical stiffness estimation.

PL

Jednym z głównych parametrów określających właściwości toru kolejowego jest jego sztywność pionowa. Zapewnienie właściwej wartości sztywności jest istotne z punktu widzenia zjawisk dynamicznych zachodzących w kontakcie kołoszyna, co z kolei przekłada się na zachowanie pojazdu i bezpieczeństwo biegu, komfort pasażerów a także dalszą degradację toru. Pomiar sztywności toru jest uciążliwy i wymaga kosztownej aparatury, a ponadto sam pomiar można wykonać tylko w torze wyłączonym z ruchu. Przedstawione w pracy badania miały na celu określenie sztywności pionowej toru tramwajowego z wykorzystaniem metody wizyjnej, która może być stosowana bez konieczności zamykania linii na czas pomiaru. Ugięcia toru tramwajowego w Poznaniu zostały przeprowadzone za pomocą szybkiej kamery a następnie wykorzystane do obliczenia sztywności pionowej.

6

Powłoki samosmarowne kół zestawów kołowych w aspekcie właściwości dynamicznych pojazdu szynowego

Chudzikiewicz Andrzej, Melnik Rafał, Góra Ignacy

Prace Naukowe Politechniki Warszawskiej. Transport

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2019

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z. 124

19--30

PL

Eksploatacja pojazdów szynowych, zwłaszcza w prowadzeniu przewozów towarowych, na liniach z łukami o małym promieniu skutkuje przyspieszonym procesem zużycia profili kół oraz szyn na łukach. Powoduje to zwiększone koszty eksploatacji oraz może być przyczyną wykolejeń na takich liniach. Jednym ze sposobów zmniejszenia tych negatywnych skutków oraz poprawy współpracy koła z szyną na łukach o małych promieniach jest pokrywanie powierzchni obrzeży kół zestawów kołowych, pojazdów eksploatowanych w takich warunkach, powłokami z materiałów posiadających właściwości samosmarowe. Pokrycie powierzchni koła w części obrzeża odpowiednią powłoką powoduje zmniejszenie współczynnika tarcia w przypadku współpracy koła z szyną na łuku, kiedy to ta współpraca odbywa się pomiędzy obrzeżem koła i krawędzią główki szyny. Pojawia się jednak pytanie odnośnie wpływu powłoki samosmarownej na bezpieczeństwo biegu pojazdu. W artykule przedstawiono rezultaty symulacyjnych analiz zachowania dynamicznego dwuosiowego wagonu towarowego typu węglarka z zamodelowaną powłoką samosmarowną oraz jej wpływ na zużycie kół.

EN

Exploitation of railway vehicles, especially in the case of goods transport, on lines with small-radius curves, results in accelerated wear of wheel profiles and rails in curves. This results in increased operating costs and can lead to derailments on such the lines. One of the ways to reduce these negative effects and to improve the wheel-rail interaction in sharp curves is to cover the surface of the wheel flange with coatings of materials with self-lubricating properties. Covering the wheel flange surface with a suitable coating reduces friction coefficient in case of flange-rail head interaction. However, there is a question about the effect of the self-lubricating layer on the safety of the vehicle. The paper presents the results of simulation analysis of dynamic behavior of a two-axial coal wagon with a modeled self-lubricating coating and its effect on wheel wear.

7

Application of simulation computations in investigation of vibration properties of a tricycle

Dižo Ján, Blatnický Miroslav, Barta Dalibor, Melnik Rafał

Diagnostyka

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2019

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Vol. 20, No. 3

97--104

EN

Vibration properties of road vehicles can be in principles evaluated using two ways, i. e. by simulation computations using a virtual model of a vehicle and by measuring on a real vehicle prototype, whereby, their dynamical properties are usually assessed in compliance with to two criterions, namely from the ride comfort for passengers point of view and from the driving safety point of view. The topic of this article is focused on evaluation of passenger’s ride comfort of a tricycle. In this regard, vertical movements of a vehicle are most important. In respect of ride comfort for passengers, accelerations in vertical direction are critical. Accelerations are usually detected on a seat. In regard of driving safety, value of the contact force between a wheel and a road are decisive. In our research we present process of investigation of level of ride comfort for passengers and level of driving safety of a tricycle based on simulation computations using the tricycle multibody model.