Dynamics of the Rolling Stock and the Choice of Parameters of Vibration Dampers

Modern railway rolling stock should meet requirements regarding comfort (maximum travel speed with minimum vibrations of wagons, noiselessness of movement, etc.).To eliminate the influence of dynamic loads, rolling stock is equipped with vibration dampers. The objective of the work is to select the parameters of the vibration dampers of rolling stock, depending on its characteristics, to ensure the due indicators of comfort and safety of transportation of passengers and goods by rail. To achieve this objective, applied methods of mathematical modelling were based on numerical programming of operation of dynamic systems. The indicators of vibration dampers are evaluated according to the results of studies of the dynamics of the rolling stock (in particular, of vibration protection rates).Assessment of dynamic state of the rolling stock implies application of methods of mathematical and physical modelling, which include the development of a physical and mathematical model, a calculation algorithm, and computer programming. The study of the mathematical model by numerical methods makes it possible to carry out a multifactorial experiment using a large number of input parameters (factors) and to select the characteristics of vibration dampers that are optimal for the conditions under consideration.To solve dynamic problems, the harmonic perturbation model, which is the most widespread, was specified in the form of a sinusoid with a period corresponding to the rail length.A quantitative assessment of the vibration process (frequency, amplitude) makes it possible to identify the main processes occurring in the system under consideration under various types of external load. The introduced assumptions related to rigidity, mobility and geometric immutability of the system allow determining the methods for obtaining a mathematical model and considering the vibrations as flat ones.The equations were solved in MathCad Prime 4.0 package using the Runge–Kutta method with automatic step selection. The subsequent study of the properties of the dynamic system was carried out by changing the resistance parameter of dampers of the first stage of spring suspension, while recording the values of the amplitude of the vibrations of the system and the period.The analysis of the results has shown that the vibration period of the body and bogies under any changes in the resistance parameter of the damper remains unchanged, while rational parameters of resistance of axle box dampers have been revealed for specified indicators. Hydraulic vibration dampers with the revealed parameters used on rolling stock help to reduce wear and damageability of running gears, improve ride comfort and traffic safety, as well as to reduce repair and maintenance costs.

Fuzzy MRAS rotor resistance identification of bearingless induction motor based on reactive power

As for the inverse decoupling control system of a bearingless induction motor (BL-IM), in order to eliminate the influence of rotor resistance variation on its control performance, on the basis of the reactive power calculation of torque system, a novel fuzzy model reference adaptive (MRAS) identification method of rotor resistance is proposed. The reference model and adjustable model of instantaneous reactive power are derived in detail. In order to improve the identification performance of rotor resistance, a fuzzy PI adaptive law based on popov super stability theory is constructed. On this basis, a rotor resistance identifier is constructed, and it is used to on-line correct the rotor resistance parameter in the inverse system mathematical model of a BL-IM system. Based on the inverse decoupling control system of a BL-IM, the simulation experimental analysis and verification are carried out. The simulation experimental results have shown that when the proposed identification method of rotor resistance is used, not only the identification- and tracking-speed of rotor resistance can be effectively improved, but also the identification accuracy of rotor resistance can be improved; as for the BL-IM system, after the rotor resistance parameter is on-line corrected, not only the inverse dynamic decoupling control performance can be effectively improved, but also the robustness of BL-IM system to the variation of rotor resistance parameters can be improved.

Diagnostics of frost resistance of grape varieties in the conditions of stress modeling

Диагностика степени устойчивости сортов винограда к морозу играет важную роль в селекции, поскольку лишь имея полную точную информацию о присущей конкретному генотипу степени выраженности признака возможно использование его в качестве источника ценного признака в процессе гибридизации. Задачей наших исследований являлось определение степени морозоустойчивости сортов винограда при моделировании стресса в лабораторных условиях с целью отбора наиболее перспективных сортов для включения в селекционный процесс. В исследования включены 53 сорта винограда различного происхождения, в том числе сорта-индикаторы с ранее установленной градацией признака морозоустойчивости. Наибольшую степень устойчивости к стрессу (минус 27 С - 9 баллов по шкале МОВВ) показали сорта Кинг Руби, Молдова, Саперави северный и Берландиери х Рипариа Кобер 5ББ (контроль), обеспечив при этом 100 %-ную сохранность центральных почек. В группу сортов, показавших устойчивость к морозу до минус 24С (7 баллов), определены сорта Альминский, Альминский белый, Атлант, Красностоп золотовский, Мускат ранний, Сибирьковый, Фогельтраубен и контрольный сорт Цитронный Магарача, которые обеспечивают 100 %-ное прорастание центральных почек после промораживания при температуре минус 24С. В ходе анализа данных использованы пять параметров оценки устойчивости к стрессу: % проросших глазков, среднее значение длины проросших побегов, а также количество и длина образовавшихся корней, развитие соцветий. Использование кластерного анализа позволило определить сходство и различия сортов между собой по заданным параметрам. Исследуемые сорта разделились на два различных между собой кластера. Наибольший интерес для селекционной работы представляет кластер, включающий в себя 21 сорт винограда. Эти сорта среди изученных обладают максимальной устойчивостью к стрессу по комплексу параметров. Среди устойчивых к воздействию морозов сортов винограда максимально близкий к контрольному сорту Берландиери х Рипариа Кобер 5ББ является сорт Саперави северный (Ed =0,21). Diagnostics of the resistance degree of grape varieties plays an important role in breeding, since the use of frost resistance parameter as a valuable feature in the process of hybridization is possible only having complete and accurate information about the degree of its expression peculiar for a particular genotype. The objective of our research was to determine the degree of frost resistance of grape varieties when modeling stress in laboratory conditions in order to select the most promising varieties for breeding process. The study covered 53 grape varieties of different origin, including varieties-indicators with previously established gradation of frost resistance parameter. The highest degree of resistance to stress (minus 27°C - 9 points by the OIV scale) showed the varieties ‘King Ruby’, ‘Moldova’, ‘Saperavi Severnyi’ and ‘Berlandieri x Riparia Kobera 5BB’ (control), providing 100% preservation of the central buds. Another group of varieties (7 points): ‘Alminski’, ‘Alminski Belyi’, ‘Atlant’, ‘Krasnostop Zolotovskiy’, ‘Muscat Ranniy’, ‘Sibirkovyi’, ‘Vogeltrauben’ and the control variety ‘Tsitronnyi Magaracha’ provided 100% germination of central buds after freezing at minus 24 ° C . In the process of data analysis, five parameters of stress resistance assessment were used: % of sprouted eyes, average value of length of sprouted shoots, number and length of formed roots, the development of inflorescences. Using of the cluster analysis allowed us to determine the similarity and difference of varieties from each other by given parameters. The studied varieties were divided into two different clusters. The biggest interest for breeding work by the complex of parameters gained the cluster of 21 grape varieties with maximum resistance to stress. Among frost-resistant grape varieties the nearest to the control ‘Berlandieri x Riparia Kober 5BB’ was ‘Saperavi Severnyi’ variety (Ed = 0.21).

Dynamics of Swimmers in Fluids with Resistance

Micro-swimmers such as spermatozoa are able to efficiently navigate through viscous fluids that contain a sparse network of fibers or other macromolecules. We utilize the Brinkman equation to capture the fluid dynamics of sparse and stationary obstacles that are represented via a single resistance parameter. The method of regularized Brinkmanlets is utilized to solve for the fluid flow and motion of the swimmer in 2-dimensions when assuming the flagellum (tail) propagates a curvature wave. Extending previous studies, we investigate the dynamics of swimming when varying the resistance parameter, head or cell body radius, and preferred beat form parameters. For a single swimmer, we determine that increased swimming speed occurs for a smaller cell body radius and smaller fluid resistance. Progression of swimmers exhibits complex dynamics when considering hydrodynamic interactions; attraction of two swimmers is a robust phenomenon for smaller beat amplitude of the tail and smaller fluid resistance. Wall attraction is also observed, with a longer time scale of wall attraction with a larger resistance parameter.

A three-dimensional model of flagellar swimming in a Brinkman fluid

We investigate three-dimensional flagellar swimming in a fluid with a sparse network of stationary obstacles or fibres. The Brinkman equation is used to model the average fluid flow where a flow-dependent term, including a resistance parameter that is inversely proportional to the permeability, captures the effects of the fibres on the fluid. To solve for the local linear and angular velocities that are coupled to the flagellar motion, we extend the method of regularized Brinkmanlets to incorporate a Kirchhoff rod, discretized as point forces and torques along a centreline. Representing a flagellum as a Kirchhoff rod, we investigate emergent waveforms for different preferred strain and twist functions. Since the Kirchhoff rod formulation allows for out-of-plane motion, in addition to studying a preferred planar sine wave configuration, we also study a preferred helical configuration. Our numerical method is validated by comparing results to asymptotic swimming speeds derived for an infinite-length cylinder propagating planar or helical waves. Similar to the asymptotic analysis for both planar and helical bending, we observe that with small amplitude bending, swimming speed is always enhanced relative to the case with no fibres in the fluid (Stokes) as the resistance parameter is increased. For regimes not accounted for with asymptotic analysis, i.e. large amplitude planar and helical bending, our model results show a non-monotonic change in swimming speed with respect to the resistance parameter; a maximum swimming speed is observed when the resistance parameter is near one. The non-monotonic behaviour is due to the emergent waveforms; as the resistance parameter increases, the swimmer becomes incapable of achieving the amplitude of its preferred configuration. We also show how simulation results of slower swimming speeds for larger resistance parameters are actually consistent with the asymptotic swimming speeds if work in the system is fixed.