African cities’ fast rate of population increase from 4 to 6% per year and the decline of organized public transport systems are the origin of the rapid development of non-conventional means of transport [2]. The city of Lomé, since its creation in 1897, has experienced growing demography and spatial extension apart from its socio-collective and mobility infrastructure [5]. Faced with the inability of public transport services to meet the demand, we are witnessing the emergence of informal transport solutions such as taxi-motorbikes and taxi-tricycles in response, not only to the demand but also to youth unemployment and the economic crisis. This article focuses on actors in the taxi-tricycle sector. It analyzes the spatial economic and socio-professional dynamics of taxi-tricycle drivers in Lomé. The scientific interest of this article is dual. Firstly, it makes it possible to map the spatial dynamics of taxi-tricycles in Lomé and, secondly, it identifies the problems related to the propagation of the phenomenon of urban taxi-tricycle transport which, until now, has not been apprehended by Togolese researchers. The methodology focuses on the analyses of data (primary and secondary) collected through a literature search, observations, and a survey. A sample of 47 individuals was selected, made up of 40 taxi-tricycle drivers and seven association leaders. The results show that the diffusion of taxi-tricycles is supported by the logic of marginality and informality. The sector contributes somewhat to solving the problems of mobility and unemployment as well as the increase in municipal revenues. Given the difficulties raised by this study, it is imperative that the sector be regulated by the State.
This study focuses on utilizing computer modeling and simulation techniques, specifically the ANSYS software, to analyze the dynamics of bridge structures. The primary objective was to study the vibrations of a riverbed metal bridge structure and determine their characteristics. The research involved theoretical dynamic calculations considering the design features of the bridge components and the materials used in their construction. The obtained results enabled the determination of resonance frequencies for the vibration modes. By utilizing the ANSYS software, a three-dimensional virtual model of the bridge structure was created, allowing for a detailed analysis of its dynamic behavior. The first three vibration modes of the riverbed metal bridge structure were calculated, and numerical results were obtained for six modes. The findings of this research have practical significance as they provide informed decision-making support during the construction, maintenance, and modernization of bridge structures. The study of bridge dynamics using advanced technologies contributes to enhancing the safety, reliability, and longevity of these vital infrastructure assets.
PL
Niniejsze badanie koncentruje się na wykorzystaniu technik modelowania komputerowego i symulacji, w szczególności oprogramowania ANSYS, do analizy dynamiki konstrukcji mostowych. Głównym celem było zbadanie drgań metalowej konstrukcji mostu w korycie rzeki i określenie ich charakterystyki. Badania obejmowały teoretyczne obliczenia dynamiczne uwzględniające cechy konstrukcyjne elementów mostu oraz materiały użyte do ich budowy. Uzyskane wyniki umożliwiły wyznaczenie częstotliwości rezonansowych dla postaci drgań. Wykorzystując oprogramowanie ANSYS stworzono trójwymiarowy wirtualny model konstrukcji mostu, pozwalający na szczegółową analizę jego dynamicznego zachowania. Obliczono trzy pierwsze postacie drgań metalowej konstrukcji mostu koryta rzeki i uzyskano wyniki numeryczne dla sześciu postaci. Wyniki tych badań mają znaczenie praktyczne, ponieważ zapewniają świadome wsparcie w podejmowaniu decyzji podczas budowy, utrzymania i modernizacji obiektów mostowych. Badanie dynamiki mostów przy użyciu zaawansowanych technologii przyczynia się do poprawy bezpieczeństwa, niezawodności i trwałości tych kluczowych elementów infrastruktury.
Variation in cutting forces with cutting parameter selection, tool geometry, and wear status plays an important role for milling process evaluation and modeling. While piezoelectric force measurement is commercially available, it is often considered a precise but expensive method. This paper presents a novel solution for vector-valued cutting force measurement. The table-mounted, flexure-based kinematics provide three degrees of freedom that are used to measure the in-process milling force vector components in the working plane by low-cost optical sensors. Based on analytical models and FEM analysis, an appropriate design was derived. The assembly and testing of the developed dynamometer are presented. A test setup based on a machining center was used for the system evaluation and the data are compared to the forces measured by a commercially available, piezoelectric cutting force dynamometer.
The aim of the work is to develop a method of landscape dynamics under anthropogenic impact. The developed methodology is tested on the territory of Kostanay region, which is one of the main regions of mining industry development, with a focus on iron ore mining and crop production. Space images and field survey results are used as input materials. In general, the work consists of the following six stages: the first stage includes the selection and processing of space images, the second stage includes the calculation of indices based on data from different channels of space images, the third stage includes field work aimed at collecting information for verification of the obtained results on the basis of RS data, the fourth stage includes the calculation of range values, the fifth stage comprises verification of the obtained indices, and the final sixth stage deals with calculation of the integral index of landscape degradation degree and analysis of landscape dynamics under anthropogenic impacts. The calculation of the integral indicator of the degree of degradation of the natural environment of the Kostanay region, based on the degradation of each indicator in the conditions of anthropogenic impact, allowed for identification of landscapes with different degrees of degradation (from weak to very strong). The research confirmed that landscapes with a high degree of degradation under anthropogenic impact are confined to semi-desert landscapes in the south of the study region. The degradation of these landscapes is associated not only with anthropogenic impacts but also with natural and climatic features that influence the development of landscape pollution processes. On the contrary, landscapes with a weak degree of degradation correspond to the forest-steppe and steppe zones, characterized by a high level of economic development and resistance to anthropogenic impacts. The verification of the obtained indicators by the values of the remaining 25% of field points determines the reliability of the obtained results, ranging from 87% to 92%, confirming the correct choice of methods and techniques for obtaining the results, especially the choice of field methods and vegetation and non-vegetation indices for assessing the selected indicators. Subsequently, based on the verified map of degradation of the natural environment, created through space monitoring for a certain period, it is possible to forecast the functioning of the natural environment in the conditions of anthropogenic impact.
Footbridges, like all building structures, must be designed in a way that ensures their safe and comfortable use. Steel footbridges characterised by low vibration damping often turn out to be a structure susceptible to the dynamic influence of users during various forms of their activity. For these structures, the impact of running users may be a key type of dynamic load for the verification of the serviceability limit state due to vibrations. In the literature, there are several proposals for models of dynamic load generated by runners (models of ground reaction forces - GRF). The paper presents the characteristics, analyses and comparisons of selected GRF load models. The analyses were performed using the GRF recorded during the laboratory tests of runners (tests planned and carried out by the author) and the GRF determined using various load models. In order to illustrate the accuracy of the estimation of the dynamic response of the structure, depending on the GRF model used, dynamic field tests and dynamic numerical analyses of the selected steel footbridge were carried out. The obtained results were analysed and compared.
PL
W artykule przedstawiono charakterystyki i analizy porównawcze wybranych modeli GRF. Analizy przeprowadzono z wykorzystaniem GRF zarejestrowanych podczas badań laboratoryjnych osób biegnących (badania własne autora) oraz GRF wyznaczonych z wykorzystaniem różnych modeli. W celu zobrazowania dokładności oszacowania odpowiedzi dynamicznej konstrukcji, w zależności od zastosowanego modelu GRF, przeprowadzono dynamiczne badania terenowe oraz dynamiczne analizy numeryczne stalowej kładki dla pieszych podatnej na oddziaływanie osób biegnących. Przeprowadzone analizy pozwoliły ustalić poprawność odwzorowania przebiegów GRF oraz dokładność wyznaczania odpowiedzi dynamicznej konstrukcji narażonych na dynamiczne oddziaływanie osób biegnących. W artykule przedstawiono własne zalecenia dotyczące modelowania oddziaływania osób biegnących na kładki dla pieszych oraz własne zalecenia dotyczące doboru parametrów wybranych modeli GRF opracowane na podstawie własnych badań sił reakcji podłoża generowanych podczas biegu. Zalecenia te pozwalają zwiększyć dokładność odwzorowania przebiegów GRF oraz dokładność oszacowania odpowiedzi dynamicznej konstrukcji narażonych na dynamiczne oddziaływanie osób biegnących. W szczególności: zaproponowano rozróżnianie technik biegu w celu dokładniejszego odwzorowania oddziaływań dynamicznych osób biegnących na konstrukcje, przedstawiono wartości współczynników Fouriera i przesunięć fazowych dla różnych technik biegu na potrzeby modelu bazującego na szeregu Fouriera, przedstawiono zalecenia dotyczące doboru wartości czasu kontaktu stopy z podłożem tcr dla różnych technik biegu na potrzeby modelu półsinusoidalnego (ang.: half-sine model), przedstawiono zalecenia dotyczące maksymalnych amplitud GRF dla różnych technik biegu oraz scharakteryzowano własną propozycję odwzorowania przebiegów GRF za pomocą funkcji Gaussa.
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Accurate dynamical models are imperative to the development of accurate monitoring and control systems, which are foundational to safety in construction and infrastructure projects. However, the highly coupled non-linear dynamics of crane systems requires the application of many simplifying assumptions to the dynamical crane model. To achieve accurate control, simplifications should yield minimal error in modelled behaviour for maximal reduction in model complexity. However, limited information is available on the situational suitability of different combinations of simplifications to construction tower crane models. This paper informs designers of the optimal dynamical models to represent boom tower cranes, with respect to the crane characteristics and selection criteria. The optimal models are determined though the comparison of ten 2D and 3D dynamical models in representation of three variations of boom tower crane that are commonly deployed on construction sites. The comparison includes analysis of over 100 simulations and experimentation. The value of the presented optimal model selection framework is in facilitating systems designers to develop accurate crane monitoring and control systems.
This article presents research carried out using physical data from the experimental construction of an overhead crane. This article aims to determine the dynamic behaviour of the cart-pendulum system when the hoisting mechanism hits the new bumper design at the end of the girder support structure with selected speed and bumper material to the length of the wire rope. This research shows the influence of the horizontal speed of the hoisting mechanism on the bumper force during a collision with a standard buffer and its modifications. The presented model can be the basis for modelling more complex cases, and its assumed role (i.e. the ability to determine the angle of deflection of the rope during an impact) has been confirmed and is possible to use in a specific case of an overhead crane on an industrial scale. Preliminary analysis of the construction of the bumper considered reveals its positive features, aiming, among other goals, to reduce the acceleration and force acting on the crane cart in emergency situations.
Referat podejmuje próbę zaadaptowania wariacyjnych metod rejestracji obrazów do kalibracji kinematyki robotów manipulacyjnych. Rozpatrzono możliwość wykorzystania dyfeomorficznego dopasowania punktów charakterystycznych (ang. Diffeomorphic Landmark Matching) jako narzędzia do obliczania przekształceń dla szczególnej metody kalibracji, mianowicie kalibracji przez dyfeomorfizmy. Sformułowano problem rejestracji obrazów oraz przedstawiono idee związane z kalibracją prze dyfeomorfizmy. Efektywność takiego podejścia została zweryfikowana badaniami symulacyjnymi dla modelu kinematyki podwójnego wahadła.
EN
The paper addresses an attempt to adapt variational methods of the image registration to the calibration of manipulator kinematics. In particular, it considers an application of Diffeomorphic Landmark Matching as a tool for computing transformations for a specific calibration method, namely the calibration by diffeomorphisms. Image registration formalism as well as the ideas underlying the calibration method has been presented. The results of bonding these two theories have been evaluated by means of simulations.
W referacie przedstawiono zasady konstrukcji odpornych algorytmów kinematyki odwrotnej w konfiguracjach osobliwych i ich otoczeniu, uzasadniające także klasyczny algorytm odpornej odwrotności. Zaproponowano sposób addytywny i multiplikatywny wprowadzania poprawki do macierzy źle uwarunkowanej, by przywrócić jej dobre uwarunkowanie.
EN
In this paper additive and multiplicative methods of making inverse kinematics robust at (or around) singular configurations were presented. The methods are provable good and as special case cover also the literature robust inverse kinematics method. A clear advantage of robust methods is their independence on the cornak of singularities and simplicity in implementation.
W pracy rozważa się problem identyfikacji parametrów modelu dynamiki dwukołowego robota mobilnego z napędem różnicowym. Model dynamiki robota sformułowany został przy założeniu, że prędkości kół robota są mierzalnymi sygnałami wyjściowymi, natomiast prądy silników napędzających robota są sygnałami wejściowymi. W celu identyfikacji nieznanych parametrów robota wykorzystano zaproponowany niedawno adaptacyjny obserwator stanu rozszerzonego (PIESO) sformułowany poprzez połączenie klasycznego obserwatora stanu rozszerzonego (ESO) z gradientowym prawem adaptacji. Skuteczność proponowanego podejścia potwierdzono badaniami symulacyjnymi i eksperymentalnymi.
EN
In this paper a problem of identification of parameters of a two-wheeled mobile robot equipped with differential drive is considered. Model of the robot dynamics is formulated under an assumption that velocities of wheels are measurable outputs of the system, while the motor currents are input signals. In order to identify unknown parameters, a recent adaptive parameter identifying extended state observer (PIESO) algorithm is employed, which combines a classic ESO observer with a gradient adaptation law. The effectiveness of the proposed approach is validated by numerical and experimental trials.
W artykule przedstawiono koncepcję metody pozwalającej na ocenę działania silnika pracującego na charakterystyce regulatorowej w nagłej zmiany obciążenia i związanej z tym akceleracji/deceleracji. Do analizy przebiegu zmian podstawowych własności użytkowych silnika w tym czasie wykorzystane zostało wartościujące (ilościowe) ujęcie działania interpretowanego jako pewna wielkość fizyczna. Podejście takie umożliwia jednoczesne uwzględnienie wykonywania określonej pracy (podejście energetyczne) oraz czasu, w którym ta praca jest wykonana.
The dynamic processes of the system of stabilization of the speed of the conveyor belt with a built-in hydraulic drive on the basis of an improved mathematical model, which takes into account the physical phenomena occurring in the hydraulic system during the action of alternating load. The influence of the main parameters of the hydraulic system and the magnitude of the load on the course of dynamic processes is analyzed and recommendations for their selection are formulated. The proposed scheme of the built-in hydraulic drive of a conveyor belt with system of stabilization of speed of movement automatically provides its uninterrupted work. The use of an additional hydraulic pump allowed to stabilize the speed of the conveyor belt to 7.8%, provided that the load on the working link is 2.3 times.
PL
Rozważono procesy dynamiczne układu stabilizacji prędkości taśmy przenośnika z wbudowanym napędem hydraulicznym w oparciu o udoskonalony model matematyczny uwzględniający zjawiska fizyczne zachodzące w układzie hydraulicznym podczas działania obciążenia zmiennego. Przeanalizowano wpływ głównych parametrów układu hydraulicznego i wielkości obciążenia na przebieg procesów dynamicznych oraz sformułowano zalecenia dotyczące ich doboru. Zaproponowany schemat wbudowanego napędu hydraulicznego przenośnika taśmowego z systemem stabilizacji prędkości ruchu automatycznie zapewnia jego nieprzerwaną pracę. Zastosowanie dodatkowej pompy hydraulicznej pozwoliło ustabilizować prędkość taśmy przenośnika na poziomie 7,8% przy założeniu, że obciążenie ogniwa roboczego jest 2,3 razy większe.
Nowadays, the constant striving to reduce the emission and increase the overall efficiency over a wide range of speeds and loads of the internal combustion engine (CE) is observed. The different methods for improving the charge exchange in the engine, particularly ones based on the variable valve timing are sought. This variability can be achieved, among others by using the electrohydraulic valve drive. The goal of the present study is to compare the dynamic parameters of the engine valvetrain utilizing the unilateral electrohydraulic valve drive and various types of valve springs. The model of such a drive being developed by authors and experimentally verified was used for the analysis. Using the Finite Element Method, the models of springs made through the machining from single sleeves were developed. The effect of various geometrical parameters of the modernized springs on their stiffness and on the resulted valvetrain dynamics was examined.
The aim of this article was to perform a practical measurement of the braking properties of a selected Škoda Yeti vehicle on a wet and dry asphalt road and then evaluate and compare the measured data using a decelerograph and a mobile application mSTK. It is a new application for measuring driving dynamics, which was developed for the needs of technical inspection stations in Slovakia. The subject was the intensive braking of a Škoda Yeti passenger car with a fully compressed service brake from different velocities and on different surfaces. A total of 18 measurements were performed, of which 9 on the dry and 9 on the wet surface. This is a new alternative method for recording vehicle driving dynamics. The developed application in conjunction with modern smartphones can thus compete with the current decelographer, both in terms of technical parameters, measurement accuracy (total average deviation 2.11%) and ease of use. The results and data processed in this way are presented in the final part of the paper.
Although gear teeth give lots of advantages, there is a high possibility of failure in gear teeth in each gear stage in the drive train system. In this research, the authors developed proper gear teeth using the basic theorem of gear failure and reliability-based design optimization. A design variable characterized by a probability distribution was applied to the static stress analysis model and the dynamics analysis model to determine an objective function and constraint equations and to solve the reliability-based design optimization. For the optimization, the authors simulated the torsional drive train system which includes rotational coordinates. First, the authors established a static stress analysis model which gives information about endurance limit and bending strength. By expressing gear mesh stiffness in terms of the Fourier series, the equations of motion including the gear mesh models and kinematical relations in the drive train system were acquired in the form of the Lagrange equations and constraint equations. For the numerical analysis, the Newmark Beta method was used to get dynamic responses including gear mesh contact forces. From the results such as the gear mesh contact force, the authors calculated the probability of failure, arranged each probability and gear teeth, and proposed a reasonable and economic design of gear teeth.
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.
In this article, the authors mentioned the function of short-recoil-operated weapons with a vertical sliding-wedge breechblock. The dynamic simulation was conducted and then the results were compared with the corresponding experimental data to verify reliability of the model. The model is calculated and tested out on the 37 mm twin anti-aircraft gun. Besides, the article presents the effect of some structural parameters on functionality of the automatic weapon. The reported results are an important theoretical basis to determine the rate of fire and the forces acting on the guns. The movement of the breechblock also affects stability of the weapon and can therefore be used to a math model or to simulate the movement of the weapon. Calculated and verified data could be used for the design of an automatic firing system as well as for solving vibration on automatic guns when burst firing.
The homogeneity of an immiscible liquid–liquid system was investigated in a baffled vessel agitated by a Rushton turbine. The dispersion homogeneity was analyzed by comparing Sauter mean diameters and drop size distribution (DSD) determined in different measured regions for various impeller speeds. The sizes of droplets were obtained by the in-situ measurement technique and by the Image Analysis (IA) method. Dispersion kinetics was successfully fitted with Hong and Lee (1983) model. The effect of intermittency turbulence on drop size reported by Bałdyga and Podgórska (1998) was analyzed and the multifractal exponent 𝛼𝐹𝑇 was evaluated.
In order for the ultimate state methods to be applied in dimensioning of the load-bearing elements in a conveyance, it is required that their design loads during their normal duty cycle and under the emergency braking conditions should be first established. Recently, efforts have been made to determine the interaction forces between the shaft steelwork and the conveyance under the normal operating condition [1,2]. Thus far, this aspect has been mostly neglected in design engineering. Measurement results summarised in this paper and confronted with the theoretical data [3] indicate that the major determinant of fatigue endurance of conveyances is the force acting horizontally and associated with the conveyance being hoisted in relation to the vertical force due to the weight of the conveyance and payload.
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.
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