Translational Oscillations Research Articles

A novel design of compact elastomer shock absorption system to protect sensitive objects from underwater shock for naval application

This research paper proposes a unique way to safeguard delicate systems on submerged platforms from the undesirable effects of underwater explosion shock loads. The underwater detonation of an explosive charge and mines produce devastating underwater shocks against underwater platforms. Shock load developed underwater has been analyzed, and a shock response spectrum (SRS) approach to compute shock peak responses has been adopted. SRS shock absorption frequency satisfies requirements for both shock absorption and delicate systems. The shock load was reduced to 2g by altering the delicate system stiffness and damping properties. The analytical model for a single DOF system was formulated, and simulation was carried out using ANSYS solver. The stiffness has been spread across various points along the length of the delicate system, allowing it to undergo translational oscillations when subjected to shock loads. This research paper presents an innovative design approach for a shock absorption system intended for underwater sensitive objects, emphasizing simplicity, distinctiveness, compactness, reliability, and electromagnetic compatibility. Experimental testing validated the shock absorption design on the prototype. Shock testing determined the absorber’s maximum displacement and sensitive object acceleration.

Adaptive second-order backstepping control for a class of 2DoF underactuated systems with input saturation and uncertain disturbances

An adaptive second-order backstepping control algorithm is proposed for a kind of two degrees of freedom (2DoF) underactuated systems. The system dynamics is transformed into a nonlinear feedback cascade system with an improved global change of coordinates. Fully taking the cascade structure into consideration and in order to simplify the design process, each step in the backstepping process is designed for a second-order subsystem. Two neural networks are applied to approximate system unknown functions and two adaptive laws are designed to estimate the upper bound of the sum of approximation error and external disturbances. To overcome the explosion problem of complexity, a second-order filter is applied to produce the virtual control and its second-order derivative that is needed in the next backstepping step. Two auxiliary dynamic systems are proposed and integrated into the backstepping process to eliminate the effects of filtering error and input saturation. The system stability is analyzed by the Lyapunov stability theory and verified by numerical simulations with two 2DoF benchmark underactuated systems: the translational oscillator with a rotational actuator (TORA) and the inertial wheel pendulum (IWP).

Theory of Collective Excitations in the Quadruple-Q Magnetic Hedgehog Lattices.

Hedgehog and antihedgehog spin textures in magnets behave as emergent monopoles and antimonopoles, which give rise to astonishing transport and electromagnetic phenomena. Using the Kondo-lattice model in three dimensions, we theoretically study collective spin-wave excitation modes of magnetic hedgehog lattices which have recently been discovered in itinerant magnets such as MnSi_{1-x}Ge_{x} and SrFeO_{3}. It is revealed that the spin-wave modes, which appear in the subterahertz regime, have dominant amplitudes localized at Dirac strings connecting hedgehog-antihedgehog pairs and are characterized by their translational oscillations. It is found that their spectral features sensitively depend on the number and configuration of the Dirac strings and, thus, can be exploited for identifying the topological phase transitions associated with the monopole-antimonopole pair annihilations.

Asymptotic Study of Flows Induced by Oscillations of Cylindrical Bodies

Hydrodynamic flows induced by translational oscillations of cylindrical bodies of various cross-sectional shapes are studied. The motion of fluid around oscillating bodies is described using the system of Navier–Stokes equations written in a generalized curvilinear coordinate system. Transition to a given body shape is implemented using a conformal mapping. The problem is solved using the method of successive asymptotic expansions under the assumption that the oscillation amplitudes are small. In each asymptotic approximation, the subproblems are solved numerically using the finite-difference method. Based on the results of the work, estimates of the hydrodynamic effect are obtained, the applicability of the high-frequency asymptotic approximation is estimated, and secondary stationary flows near cylinders are studied, in particular, the occurrence of directed stationary flows near an oscillating asymmetric body is considered with reference to the Joukowski airfoil.

Study on Rotor-Bearing System Vibration of Downhole Turbine Generator under Drill-String Excitation

Downhole turbine generators (DHTG) installed within drill-string are susceptible to internal and external excitation during the drilling process, causing significant dynamic loads on bearings, and thereby reducing the bearing’s service life. In this study, a finite element model of an unbalanced rotor-bearing system (RBS) of DHTG with multi-frequency excitations, based on the Lagrangian motion differential equation, is established. The responses of the RBS under different drill-string excitations in terms of time-domain response, whirl orbit, and spectrum are analyzed. For a constant rotor speed, lateral harmonic translational and lateral oscillation both transform the whirl orbit to quasi-periodic, while axial rotation only changes the response amplitude. Changing the duration of pulse excitation leads to different response forms. Then, the dynamic characteristics of the RBS supported by a squeeze film damper (SFD) are investigated. The results indicate that SFD effectively reduces the displacement response amplitude and bearing force near the critical speed. As the axial rotation angular velocity of the drill-string increases, the first critical speed and displacement response decrease, while the variation of lateral oscillation frequency and amplitude has limited impact on them. The established model provides a means for analyzing the dynamic characteristics of DHTG’s RBS under drill-string excitations during the design stage.

The translational oscillation in oocyte and early embryo development.

Translation is critical for development as transcription in the oocyte and early embryo is silenced. To illustrate the translational changes during meiosis and consecutive two mitoses of the oocyte and early embryo, we performed a genome-wide translatome analysis. Acquired data showed significant and uniform activation of key translational initiation and elongation axes specific to M-phases. Although global protein synthesis decreases in M-phases, translation initiation and elongation activity increases in a uniformly fluctuating manner, leading to qualitative changes in translation regulation via the mTOR1/4F/eEF2 axis. Overall, we have uncovered a highly dynamic and oscillatory pattern of translational reprogramming that contributes to the translational regulation of specific mRNAs with different modes of polysomal occupancy/translation that are important for oocyte and embryo developmental competence. Our results provide new insights into the regulation of gene expression during oocyte meiosis as well as the first two embryonic mitoses and show how temporal translation can be optimized. This study is the first step towards a comprehensive analysis of the molecular mechanisms that not only control translation during early development, but also regulate translation-related networks employed in the oocyte-to-embryo transition and embryonic genome activation.

Decentralized robust adaptive backstepping control for a class of non-minimum phase nonlinear interconnected systems

In this paper, a class of interconnected systems is considered, where the nominal isolated subsystems are fully nonlinear and non-minimum phase. A decentralized Extended Kalman Filter-Extended High Gain Observer (EKF-EHGO) is designed to observe the system states. Then, a systematic backstepping design procedure is employed to develop a novel decentralized robust adaptive output feedback control, in which the adaptive law is designed to counter the effects of the interconnections and uncertainties. The proposed decentralized dynamic output feedback control scheme can guarantee that all the signals in the closed-loop system are uniformly ultimately bounded (UUB). Both interconnections and uncertainties are allowed to be unmatched and bounded by an unknown high-order polynomial, which is a more general form when compared with existing work. Two MATLAB simulation examples are used to demonstrate the effectiveness of the proposed method including a system comprising translational oscillator with rotating actuator (TORA) sub-systems.

Ferrofluid drops-based actuator in a narrow gap

Directional transport of a liquid is an important issue in microfluidic systems and application purpose. Here, through combining the ideas of pressure-driven gas bubble-induced acoustic streaming flow and magnetic field-deformed ferrofluid drop, we study the ambient flow induced by an oscillating ferrofluid drop as an in situ actuator in a millimeter-sized gap environment. A drop squeezed by two parallel glass sheets, under the influence of a magnetic field, is discovered to undergo multimodal oscillations. The particle image velocimetry technique helps us to reveal the vortex-typed flow structure surrounding the oscillating drop. The shape changes of drop are found including the circular, elliptical, triangular, inverse-triangular, and circular shapes. We employ the numerical front-tracking method and analytical mixed-mode model to elucidate a drop-driven flow. We find that the pulsating, translational, and quadrupole mode oscillation of the drop is capable to describe most features of the flow distribution. Furthermore, we demonstrate an in situ pump by applying a spatially non-uniform pulsating magnetic field onto the arranged ferrofluid drops. The ferrofluid drop-based in situ pump shows the ability to produce a flow rate of 108 μl/min, which should be a great help in microfluidic pumping.

Formula omitted] fuzzy observer-based dynamic sliding mode control: Unknown input rejection approach

This article presents an H∞ fuzzy dynamic observer-based dynamic sliding mode control (SMC) for continuous-time Takagi-Sugeno (T-S) fuzzy systems in the presence of external disturbances and uncertainties. Compared with the conventional SMC and the existing approaches, the effects of the unknown input signals whether linear or nonlinear are completely eliminated. Furthermore, the nonlinear systems which are modeled as T-S fuzzy systems are allowed to share different input matrices under the proposed SMC. The matrix gains of the proposed dynamic sliding surface are derived from the solution of the linear matrix inequalities (LMIs). In addition, an H∞ fuzzy dynamic observer is proposed based on a new approach for T-S fuzzy systems affected by uncertainties and external disturbances. To reduce the analytical complexity and avoid the non-convex problem, a new transformation is used to propose both dynamic sliding surface and the dynamic observer. The stability conditions are extracted also in form of an optimization problem. Lastly, a Translational Oscillator with an eccentric Rotational proof mass Actuator (TORA) system is simulated with the proposed methods to show the superiority and effectiveness.

Overall picture and details of diffusion dynamics for liquid benzene by quasielastic neutron scattering and mode distribution analysis

We investigated the diffusion dynamics of liquid benzene as a basic molecular liquid. Quasielastic neutron scattering (QENS) was utilized to elucidate the overall behavior of molecular diffusion in liquid benzene. Mode distribution analysis, which does not require specific model assumptions and can describe molecular dynamics by QENS as a distribution of Lorentz functions, revealed that the diffusion of benzene molecules is represented by three dynamic modes. The Q-dependencies of the scattering intensity and the relaxation time were analyzed using diffusion models constructed to match each dynamic mode. (1) The slowest mode is translational diffusion, described as continuous diffusion rather than jump diffusion. (2) The intermediate-speed mode is rotational diffusion, which is due to the three-dimensional reorientation of benzene molecules with a jump angle of approximately 90°. (3) The fastest mode involves local fluctuations, which may originate from translational oscillations and librations of the benzene crystal. The overall picture of the diffusion dynamics and characteristics of the individual modes were clarified without using a model, which is a new approach in the field of diffusion dynamics of molecular liquids.

Adaptive Backstepping Integral Sliding Mode Control for 5DOF Barge-Type OFWT under Output Constraint

This article presents a new control solution for a dynamical model of a translational oscillator with a rotational actuator (TORA) based on multi-body dynamics for a barge-type offshore floating wind turbine (OFWT). TORA has been employed as an active structural control strategy. The solution of bounding the output movements of platform pitch and tower bending angle to a certain limit, along with mitigating the OFWT vibrations due to environmental disturbances and uncertainties, is presented in this novel control framework. This new control algorithm consists of a high-gain observer (HGO)-based adaptive backstepping integral sliding mode control (ISMC) and a barrier Lyapunov function (BLF). This guarantees satisfying the constraints on the states and effectively resolves the problem of the unavailability of the system states. The proposed control law based on the BLF has been compared with an adaptive backstepping ISMC to show the efficiency of the output-constraint control scheme. Through MATLAB/SIMULINK numerical simulations and their numeric error table, the effectiveness of the proposed control scheme has been examined. The results confirm the validity and efficiency of the proposed control approaches.

A twin wavemaker model for liquid sloshing in a rectangular tank

Sloshing of a liquid in a rectangular container under horizontal excitations is modelled using a wave basin analogue within the framework of a potential flow theory. An initial boundary-value problem is formulated replacing fixed walls of the tank with two orthogonal twin piston-type wavemaker paddle pairs. The proposed equivalent mechanical system may be applied to a class of problems covering irrotational flow of an inviscid and incompressible fluid inside partially-filled rectangular containers exposed to translatory oscillations. An analytical solution to the problem is provided under the assumption of a small-amplitude monochromatic forcing for a classical linear wavemaker in a closed flume and two- and three-dimensional twin wavemaker problems. The model is extended to cover an arbitrary horizontal motion using a semi-analytical approach based on a difference time-marching schemes applied to linearised evolution equations in a spectral domain. This relatively simple conceptual model may be used to design a novel experimental framework for studying water wave mechanics at smaller scales relying on elongated sloshing tanks substituting typical wave flumes.

BEDA PENGARUH PEMBERIAN TRANSLASI OSILASI DAN THERABAND EXERCISE ATAU HOLD RELAX TERHADAP PENURUNAN NYERI DAN PENINGKATAN RANGE OF MOTION PADA PENDERITA OSTEOARHRITIS KNEE DI RUMAH SAKIT ISLAM FAISAL MAKASSAR

Background: Osteoarthritis of the knee is a degenerative joint disease that causes cartilage damage in the knee joint which is characterized by loss and erosion of the knee joint cartilage and the growth of osteophytes on the edges of the knee joint, causing stiffness, pain and impaired movement.Methods: This study was a quasi-experimental study with a pre-test post-test design with two groups aiming to determine the difference in the effect of translation oscillations and theraband exercise with translation oscillations and hold relax on pain reduction and ROM improvement in patients with knee osteoarthritis. This research was conducted at the Faisal Islamic Hospital in Makassar, with a sample of knee osteoarthritis patients who fit the inclusion criteria. The number of samples was 14 people who were randomly divided into 2 groups, namely 1 group that was given translation oscillation and theraband exercise as many as 7 people and group 2 that was given translation oscillation and hold relax as many as 7 people. Measuring instruments used are VAS and Goniometer.Results: Analysis of the paired sample t test in the treatment and control groups obtained a value of p = 0.000 <0.05 for the actuality of pain and ROM, which means that there was a significant effect in the treatment and control groups on reducing pain and increasing ROM. The results of the independent sample t test for actuality of pain obtained a value of p = 0.053 > 0.05 and for ROM obtained a value of p = 0.365 > 0.05 which means that there was no significant difference between the two sample groups.Conclusion: It can be concluded that the administration of translational oscillations and theraband exercise has no more effect than translational oscillations and hold relax on reducing pain and increasing ROM in patients with knee osteoarthritis.Keywords: Translational Oscillation, Theraband Exercise, Hold Relax, Knee Osteoarthritis

Dynamics of a clamped drop under translational vibrations

The free and forced translational oscillations of an ideal liquid drop have been investigated. The drop was placed in a large-sized vessel filled with a liquid of different density. In equilibrium, the drop has the shape of a circular cylinder, and it is sandwiched between the lid and bottom of the vessel. The contact line-speed at the end plates is proportional to the deviation of the contact angle from its equilibrium value (the angle is formed by the corresponding plate and the undeformed cylindrical surface of the drop). The proportionality coefficient (the wetting or Hocking parameter) is different for each surface; it characterizes the force of interaction between the contact line and the solid surface, which leads to energy dissipation during its movement. This makes it possible to use the velocity potential to describe motion in the presence of a deformed interface between inviscid fluids. It is shown that the fundamental frequency of the translational mode of natural oscillations may not vanish in contrast to the case of equal wetting parameters. The energy dissipation is determined by the total contribution of these parameters, which makes it possible to vary the motion of the contact line over a wide range. The oscillation amplitude is proportional to the density difference of the liquids, i.e., at equal densities, the system moves as a whole. It has been found that both integer and non-integer harmonics of shape oscillations are excited due to different wetting parameters. The external vibrational force excites only even harmonics and, with identical surfaces, only they are present in the oscillation spectrum.

Adaptive Neural Network Command Filtered Backstepping Control for the Underactuated TORA System

An adaptive neural network command-filtered backstepping design algorithm is proposed for the underactuated translational oscillator with a rotating actuator (TORA). The system dynamics are transformed into a nonlinear cascade system through a global change of coordinates. Considering the weak sinusoid-type nonlinear interaction and affine-free appearance in the cascade model, the TORA is looked at as a pure feedback system. Two neural networks are used to approximate the unknown functions and a command filter is used to produce the virtual control and its first and second-order derivatives to overcome the explosion of complexity problems in backstepping. A filter error compensation dynamic system is designed to overcome the error influence on control performance. Taking full account of the cascade model structure of the underactuated TORA, each backstepping step is designed for a second-order subsystem to reduce the design steps and simplify the design process. The system stability is proved through the Lyapunov stability theorem and verified by numerical simulations.

КОВЗАННЯ ЧАСТИНКИ ПО РУХОМІЙ ГОРИЗОНТАЛЬНІЙ ПЛОЩИНІ

A lot of engineering problems relate to the interaction of working bodies of machines with particles of technological material and require analytical dependencies of particle movement on a moving rough plane. When a particle hits a moving horizontal rough plane, which remains horizontal during movement, the particle begins to slide along it. The character of the movement of the plane determines the shape of the particle's sliding trajectories. The reciprocating oscillations of the horizontal plane, as well as translational oscillations, when all points of the plane describe circles, are sufficiently researched. However, there is no rotation of the plane in these cases. However, numerous parts of machines and mechanisms carry out just such a movement. If the plane moves translationally, the particle moves along a trajectory, which is similar to the curve described by the plane. During the rotational movement of the plane, the particle moves along a spiral of the correct shape. In the case of a combination of these two movements, at the initial stage the relative motion of the particle is chaotic, but over time it acquires the shape of a spiral regardless of point of particle incidence to the plane. The article deals with the relative motion of a particle on a horizontal rough plane, which carries out complex oscillations, which are the result of moving a point of the plane in a circle with a constant angular velocity relative to its center and simultaneous rotation of the plane around this point with the same angular velocity in the opposite direction. The partial case of oscillations, when the lengths of the crank and slider are equal to zero, is considered. Analytical dependencies of particle motion were found by methods of differential geometry. The obtained regularities make it possible to significantly expand the theory of particle movement on the surface. In addition, they can be applied to the geometric design of mechanisms of the crank-slider type, in which the length of the slider is equal to the length of the crank. Key words: relative motion, horizontal plane, oscillations with rotational motion, particle, differential equations.

Rotational and Translational Oscillations of Small-Aspect-Ratio Cylinders in an Air Flow

Rotational and Translational Oscillations of Small-Aspect-Ratio Cylinders in an Air Flow

Robust Stabilization of Underactuated TORA System Based on Disturbance Observer and Fixed-Time Sliding Mode Control Method

A translational oscillator with a rotational actuator (TORA) is an underactuated nonlinear mechanical system with two degrees of freedom (DOF). This paper concerns the robust stabilization control problem for the system with multiple external disturbances. First, a disturbance observer is constructed based on the internal nonlinear dynamic behavior of the system. Second, a robust stabilization controller is designed by the estimated disturbances and the fixed-time sliding mode control method. The controller realizes the global robust stabilization control objective of the TORA system, and the stability of both disturbance observer and robust closed-loop control system are analyzed using the Lyapunov theorem. Finally, the effectiveness of the theoretical results are verified by numerical experiments.

Общая и локальная устойчивость многоэтажных зданий при динамических и сейсмических воздействиях

The issues of general and local stability of multi-storey buildings and high-rise structures under emergency (explosions, earthquakes) loads are considered. Differential equations describing three-dimensional translational and three-dimensional rotational oscillations are given. Dependences of local and general stability estimation are obtained. A numerical example is given that takes into account local stability in higher forms of oscillation. At the same time, the behavior of a real 16-storey frame building in Leninakan during the earthquake in Spitak on December 7, 1988 is analyzed. The main causes of loss of stability and destruction are carried out.

Dynamics and control of vibratory finishing machine with translational motion of lapping-polishing plates

The lapping and polishing operations are of the most important ones considering the finishing treatment of machine parts. These operations can be performed by numerous methods, among which the vibration-driven ones are of the most widespread. The present paper is focused on studying the dynamic behavior of the vibratory finishing machine providing the single-sided lapping and polishing of flat surfaces of cylindrical and prismatic parts. The major scientific novelty of this research consists in an improved control technique of generating the translational oscillations of the lapping (polishing) plates by means of implementing the double-magnet excitation system. In order to investigate the machine’s double-mass vibratory system dynamics, the corresponding mathematical model is developed using the Lagrange-d’Alembert principle. The numerical modeling is carried out with the help of the Mathematica software and presents the time dependencies of the lapping (polishing) plates kinematic parameters. The simplified experimental prototype of the vibratory lapping machine is developed and tested under different operational conditions. The proposed design ideas and obtained theoretical and experimental results can be effectively used by the designers of lapping and polishing equipment, as well as by the technologists implementing new techniques of finishing treatment.