Body Dynamics Research Articles

Coupling Dynamics Study on Multi-Body Separation Process of Underwater Vehicles

Based on the Newton-Euler method, a coupling rigid-body dynamics model of a Trans-Medium Vehicle (TMV) separating from an Unmanned Underwater Vehicle (UUV) has been established. The modeling is based on the “holistic method” and “Kane” ideas respectively, so that most of the equations can be derived without considering the internal forces between the two bodies. The separation propulsion force, which is an internal force, only appears in the relative glide dynamics equation of the TMV along the axis of the separation tube that is installed on the UUV. This greatly reduces the workload of modeling and derivation. The UUV works entirely underwater, while the hydrodynamic shape of the TMV changes continuously during the process of the TMV separating from the UUV. Therefore, accurate hydrodynamic calculations for the UUV and TMV are the basis of numerical resolution for the two rigid bodies’ coupling dynamics model in water. A large number of numerical simulations was conducted using CFD methods to investigate the hydrodynamic performance of the UUV and TMV under various conditions. These simulations aim to establish a hydrodynamic database, and accurate hydrodynamic models were developed through fitting methods and online interpolation. In the process of solving the coupling dynamics of two bodies, the hydrodynamic model is used to calculate the hydrodynamic force experienced by the UUV and TMV. This balances the accuracy and efficiency of a numerical simulation. Finally, numerous simulations and comparative analyses were conducted under various operational conditions and separation parameters. The simulation results indicate that the impact of TMV separation on the motion state of the UUV becomes more prominent with smaller UUV to TMV mass ratios or deeper TMV separation depths. This effect can further influence the stability control of the UUV. The coupling rigid body dynamics analysis method established in this paper provides a fast and effective prediction method for use during the scheme design and separation safety evaluation phases of creating UUV-TMV systems.

Алгоритмы группового управления подводными подвижными объектами

The problem of formation control is relevant when searching for objects, surveying a given area, and group monitoring. In the underwater environment, this problem is complicated by restrictions on the frequency of receiving navigation data and the speed of information exchange between underwater robots. The purpose of this article is to develop and study group control algorithms that ensure the given formation and the maintenance of this formation during movement. The article provides an overview of the results in the field of group control of underwater vehicles, provides a mathematical model of the object, navigation system, underwater environment and communication system. The equations of kinematics and dynamics of a solid body in three-dimensional space, supplemented by equations of actuators, are used as a mathematical model. Algorithms for the distribution of moving objects in formation and nonlinear control algorithms for moving in a line are proposed. When constructing the devices, it is assumed that there is a group leader who transmits his coordinates to the rest of the underwater robots. Motion control is synthesized by the method of positional trajectory control in the form of a function of external coordinates. A study was carried out using numerical methods, during which the process of the formation and movement along the trajectory described by straight line segments was studied. The influence of errors in the navigation system and the frequency of data updates on the error of maintaining a given position by a separate underwater robot is investigated.

LITERARY REVIEW ON DHARANIYA VEGA IN ASHTANGA HRIDAYA

Ayurveda is the most ancient system of medicine, not just in India but also in the world. It mentioned the corre-lations of body and mind and how our emotions affect our overall health. Vega Dharana is not just about with-holding or letting go of urges but about respecting the body's dynamics and expressions. When we respect them, we receive respect in return in the form of balanced mind-body health. Ashtanga Hridaya Sutrasthana 4th chapter in which Dharaneeya Vegas are explained is named Rogaan Anutpaadaneeya Adhyaya meaning those which do not allow diseases to manifest. In this chapter there is a description of Adharaniya Vega and Dharaniya Vega. Dharaniya Vega1 suggests that if the Vegas are not suppressed, it will turn into mental disorders; to attain the Mansika Swasthya we must suppress these Dharaniya Vega. It also implies that we can either invite or prevent many diseases by ignoring or addressing the body's small expressions, respectively. When the body wants to expel something to protect itself in the long run, just cooperate and allow the body to express itself naturally. The remote control of our health lies in our own hands. All you need to do is use it skill fully. Simply admire and address the body's expressions at the proper time, and you'll find yourself in the best of health. Some Vegas must be suppressed to keep our mind in ideal state.

Dynamic features and wind-resistant strategy of suspended monorail vehicle-track beam systems subjected to turbulent wind

Suspended monorail vehicles (SMV), hung beneath box beams with open bottoms, exhibit significant transverse wobble when exposed to turbulent winds, markedly impacting passenger comfort. This study presents an effective methodology for comprehensively evaluating the dynamical behavior of suspended monorail vehicle-track beam systems (SMVTBS) under wind action. First, based on the multi-rigid body dynamics theory and finite element method, an integrated vehicle-track beam interaction model is established. Then, by applying the auto-regressive (AR) linear filtering method, a turbulent wind velocity field with inherent correlations is adequately simulated through a stochastic process, which is later converted into wind force acting on both the track beam and vehicles. On this basis, the vibration responses of the SMVTBS with and without wind actions are compared, and the effects of the wind load on the vehicle-track beam dynamical behavior are revealed. Furthermore, to improve the wind-resistant performance of the SMV, several crucial design parameters are reasonably selected and effective wind-resistant strategies are proposed. Finally, the dynamic performance of the SMV is evaluated under wind action, and suitable train running speeds were recommended at different wind velocities to guarantee vehicle riding comfort. The research results can provide useful guidance for the design and operation of SMVTBS against crosswinds.

Jeans mass and Gamow temperature: insights from q-Deformed systems

Abstract In this study, we investigate the potential for star formation within a gas system governed by q-deformed statistics. Our findings show that stars with masses below the conventional Jeans mass threshold can indeed form, with the specific formation depending on the value assigned to the deformation parameter q. In particular, the application of q-statistics allows the emergence of stars with reduced Jeans mass requirements. In addition, within the framework of q-deformed kinetic theory, the ignition temperature of a star may exhibit a decrease relative to the traditionally accepted Gamow temperature. This suggests important implications for the mechanisms driving star formation and the thermal dynamics in stellar bodies under the influence of q-deformation.

Mechanisms Underlying Rail Corrugation on Tracks Equipped with Cologne-Egg Fasteners

Rail corrugation is the most common type of abnormal damage in subway track systems, and there is currently no unified theory that fully explains this specific wear phenomenon. In this research, a coupled rigid–flexible dynamics model and a multi-rigid body dynamics model was established, accounting for the effects of fastener systems, to study severe rail corrugation on tracks equipped with Cologne-egg fastener (CE fastener). The low vertical support stiffness of CE fasteners, combined with heavy train loads, leads to the “soft mud effect.” This effect causes the creep force between the wheel and rail to become saturated more easily, which is the root cause of frequent rail corrugation on both tangent tracks and curved tracks with large radii. Additionally, drawing on the theory of friction-driven self-excitation vibration, a finite element model of a wheelset–rails system with CE fasteners was established to study the unstable vibration caused by wheel–rail sliding. An increased friction coefficient increases the tendency toward unstable vibration in a wheelset–CE fastener–rail system. Three types of composite under-rail vibration absorbers were designed to suppress rail corrugation, with the continuous-type absorber demonstrating the best suppressive effect.

Data-physics hybrid-driven external forces estimation method on excavators

To enhance the accuracy of excavator external forces estimation, a data-physics hybrid-driven excavator external forces estimation method is proposed. MultiLayer Perceptron (MLP) model is applied for nonlinear component modeling and is used to compensate for Rigid Body Dynamics (RBD) models. Gaussian Process Regression (GPR) model is developed to estimate the external forces and uncertainties based on the joint angles, angular velocities, cylinder actuation forces, and actuation end velocities of the excavator. The external forces estimated by the GPR models are used as a new measurement in the Disturbance Kalman Filter (DKF), and the uncertainty is incorporated into the covariance of the process noise. The constructed GPR-DKF estimator is validated on a scaled-down excavator. The results demonstrate the robustness and effectiveness of the proposed method in estimating out-of-distribution samples.

The elliptope and bounds in the rotational dynamics of rigid bodies

The main result of this paper establishes a new polynomial relation among several projections of the angular momentum vector on the spatial and moving frames involved in the rotational dynamics of rigid bodies. This relation is surprisingly simple to derive and provides a geometric insight into the attitude dynamics of bodies with axial symmetry, explaining the bounds for the nutation angle [Formula: see text].

Effect of stratification on the combustion behavior and dynamic response of a bluff-body stabilized ammonia–hydrogen flames with radial staging

The present study deals with the flames of ammonia–hydrogen blends that form a prospective fuel for power generation in practical devices. In particular, the spatial flame dynamics of the bluff body stabilized laminar and stratified ammonia–air/hydrogen–air mixtures with acoustic excitation are considered. For this, we consider a radially staged burner consisting of two concentric tubes namely, the inner and outer tubes with the bluff body housed by the former. Two annulus passages are formed between (i) the inner and outer tube, and (ii) the inner tube and bluff body in which premixed hydrogen–air and ammonia–air mixtures are supplied, respectively. The stratification is controlled by varying the upstream location of the inner tube about the burner exit, termed mixing length taking the values namely, 20 mm (stratified), 60 mm, and 100 mm (unstratified). Time-resolved images of the flames are obtained using OH* (320 ± 10 nm) and NH2* (632 nm ± 10 nm) filters. For the unforced stratified flames, the flames are narrower and the spatial separation between OH* and NH2* region increases towards rich NH3/air mixtures ( ϕNH3–air) compared to the unstratified flames. In addition, the mean spatial OH* is relatively localized for the unforced stratified flames. For any operating condition of the flames, the forced flame response is significant for frequencies < 120 Hz. The rich stratified flame exhibits a higher response at a frequency of ∼ 40 Hz compared to the unstratified flame having a flatter response. The forced flames accompany lobed spatial patterns in OH* and NH2* for richer ϕNH3–air. The flame oscillation registers a non-sinusoidal oscillation for the rich stratified flame compared to flames of any other condition. The main effect of stratification is the alteration of flame shape resulting in a low-frequency response for which regions of significant flame flapping coincide with regions of peak flame OH*.

Low temperature phase transitions in the visible and near-infrared (VNIR) reflectance spectra of (NH4)2HPO4 and (NH4)HSO4 salts

The detection of ammonium bearing crystalline solids in salt-water systems on icy bodies and solar system bodies could provide information about the ascent of these salts from a deep reservoir within the hydrosphere. Due to their chemical-physical properties, NH4+ compounds play a key role both in the internal dynamics of celestial bodies and in the potential habitability of ocean worlds. In this work we analysed the reflectance spectra of two synthetic NH4+ salts: ammonium hydrogen phosphate (NH4)2HPO4 and ammonium hydrogen sulphate (NH4)HSO4 in the 1–4.2 μm spectral range at low temperature, between 110 and 290 K. For (NH4)2HPO4 we also examined the effect of three different grain sizes (150–125 μm; 125–80 μm; 80–32 μm). The collected reflectance spectra show absorption features related to NH4+ group overtone and combination modes in the 1–2.5 μm range. In particular, the bands located at ∼1.09 μm (3ν3), ∼1.30 μm (2ν3 + ν4), ∼1.58 μm (2ν3), ∼2.02 μm (ν2 + v3) and ∼ 2.2 μm (v3 + v4) could be useful to discriminate these salts. The low temperature spectra, compared to those at ambient temperature, reveal finer structures, displaying sharper and narrower absorption bands. The selected NH4+-bearing salts are subjected to reversible low temperature phase transitions, which are revealed in the spectra by a progressive growth and shift of the bands toward shorter wavelengths with a drastic change of their depth. We performed laboratory measurements of ammonium (NH4+) compounds to address the limited data available expanding the existing database. The collected cryogenic spectra can be directly compared with remote sensing data from planetary missions of the upcoming decade such as NASA's Europa Clipper, and ESA's JUICE and the newly launched James Webb Space Telescope expanding the existing database of ammonium compounds at cryogenic temperature.

Language-guided temporal primitive modeling for skeleton-based action recognition

Human actions describe the complex body dynamics, which are defined by an ordered set of sub-action primitives. Existing methods in skeleton-based action recognition primarily focus on designing various networks to learn the entire action representation, in alignment with the action label. However, training the heterogeneous action as a whole increases the burden on the network and is not conducive to learning the temporal structure of the action. In this paper, the traditional action label is extended into the ordered primitive language description by employing a large language model, which not only unveils the temporal structure of the action but also enriches its connotation. Based on this, we propose a language-guided skeleton representation learning network (LGS-Net) that leverages the language description to guide the skeleton feature learning from the ordered primitive and global action levels. Especially, the primitive guidance aligns the features of skeleton clips with those of the ordered primitive descriptions while preserving temporal order, which promotes the network to model the temporal primitive and capture the internal structure within the action from skeletons. To enhance the cross-modal alignment performance, we develop an innovative temporal alignment loss supplemented with diversity and sparsity regularization terms to generate the discriminative multi-modal representation. Evaluated on three benchmark datasets, NTU-60, NTU-120 and N-UCLA, the proposed LGS-Net achieves comparable results to state-of-the-art methods, which proves the effectiveness of the language-guided learning mechanism.

Topology optimization with the redesigned suspension system of the internal combustion vehicle converted to an electrical vehicle

Abstract In this paper, the topology optimization of lower wishbone for a passenger car which is the converted of an internal combustion engine vehicle to an electrical vehicle was presented. On the other hand, the need to study on a suspension system arose for electrical car that was redesigned. In study, topology optimization of the structural design of the lower wishbone to be used in the front suspension was carried out by Finite Element Analysis (FEA) Method. For this purpose, firstly, the suspension spring curves and damper curves that will improve the handling, ride and comfort behaviour of the vehicle were determined, suspension system was modelled with the Multi Body Dynamics (MBD) approach. Hardpoints is necessary for vehicle dynamics and that is also an input for FEA were obtained from new suspension system via MBD analysis. In the second step, The preliminary design of the lower wishbone was created, taking into account together with the positions of the wheel drive shaft, suspension spring and brake system structural elements according to hardpoints. After designing the structure suitable for the joint types, initial design was studied on the remaining region that is for weight reduction region except the joint connection surfaces. Then, topology optimization was applied to the preliminary design for the selected load types that is come from MBD analysis. Thus, the excess volume on the preliminary design was determined for each load type. In the last stage, the results of topology optimization analysis were evaluated to reach out target weight and the producible design of the wishbone was made. Finally, Finite Element Analysis were applied to the final design for validation purposes within topology optimization work was done with the forces coming from Multi Body Dynamics. After statically solved Finite Element Analysis, a modal neutral file(.mnf) was created via FEA solver and was integrated to Adams Car as a flexbody. Flexbody was attahced to the other parts which are rigid bodies like nuckle according to Multi Body Dynamics approach. Dynamics durability cases was carried out via Adams Car. Stress results was compared to FEA results and evaluated depends on yield stress. Study results shows that the new design is lighter and competitive design and also safe in dynamics analysis for redesigned passenger car.

Advances In Celestial Mechanics And Dynamical Astronomy: A Literature Review

This research paper provides a comprehensive examination of recent developments within the realm of celestial mechanics and dynamical astronomy. By conducting an in-depth analysis of existing literature, this study aims to elucidate the pivotal advancements and contributions that have significantly enhanced our understanding of celestial body motion and dynamics. Through a meticulous evaluation of scholarly articles, books, and conference proceedings, this literature review delves into the fundamental concepts and methodologies that underpin celestial mechanics and dynamical astronomy. The paper explores a wide array of topics, encompassing orbital dynamics, dynamical systems, asterodynamics, planetary science, and explanatory systems. By synthesizing the findings of esteemed researchers and scientists, this study reveals the profound impact of novel numerical methods, analytical techniques, and observational discoveries on the field. Furthermore, it identifies areas ripe for future investigation, underscoring the vast potential for continued exploration and innovation within celestial mechanics and dynamical astronomy. Ultimately, this literature review seeks to provide a valuable resource for scholars, researchers, and students seeking insight into the latest advancements and emerging trends in celestial mechanics and dynamical astronomy, while also highlighting the boundless opportunities for future research and discovery.

Modelling of Vehicle Longitudinal Dynamics for Speed Control

Longitudinal dynamics control is one of the essential tasks for an autonomous vehicle, where it deals with speed regulation to ensure smooth and safe operations. To design a good controller, a simple yet reliable mathematical model is needed so that it can be used as a plant and to tune the controller. Although there are many types of mathematical models available in the literature, finding the right one for control application is essential. The model cannot be too complex and can be too simple. Thus, the main objective of this work is to derive a simple yet reliable vehicle longitudinal model so that it can be used as a simulation plant in MATLAB Simulink to test or tune various types of control algorithm's performance. The model consists of three main parts which are the vehicle body dynamics, simplified power train dynamic, and braking dynamic. To validate the reliability of the model, standard urban drive cycles will be used as a reference speed and a hierarchical PID control structure with inverse plant model is used to control the pedal inputs replacing the driver in simulation environment. Results show that the controller managed to track the drive cycle with an acceptable pedal pressing response which is between 40% throttle press and 20% brake press that in line with the normal operation of a vehicle. Although only simulation result is presented, the model can be used as a good starting point for further development and testing of different types of control algorithms for future work.

Surface water dynamics of Lake Chad Basin (Sahelian Africa) based on daily temporal resolution Earth observation time series

ABSTRACT Water availability is vital for the sustenance of livelihoods in the Lake Chad Basin. However, the daily and seasonal dynamics of open water bodies are not well understood. This study aims to (1) analyze the daily and seasonal dynamics of water bodies, (2) estimate changes in surface water area extent including trends and change points, and (3) assess the connection between surface water extent and seasonal rainfall variation. To achieve this, we used the Global WaterPack and ERA5-Land daily aggregated datasets. We employed time series decomposition, trends analysis, and temporal lag correlation in our analysis. The results showed strong seasonal patterns of natural lakes compared to reservoirs/dams. Between 2003 and 2022, Lake Chad averaged 2,475.64 km2. The Northern pool of Lake Chad exhibited significant fluctuations, remaining below 600 km² between 2005 and 2012, from 2016 to 2019), with less than 350 km2 lasting only for a few days annually. The Southern pool averaged between 2,200 and 2,400 km2, except during drought years (2006–2007), specifically between the days of the year to approximately 66, and days 301–365/6. In Lake Fitri, the yearly maximum and minimum water extents were observed between days 1–59 and 305–365/6, and between days 60 and 304, respectively.

A doctor for the crown princess: child mortality and women’s political agency at the Danish court, 1784–1797

ABSTRACT This article examines the entwined dynamics of gender, material bodies, and court politics at the Danish, absolutist court during what has been termed the reform reign, 1784–1797. The reform reign was inaugurated by a 1784 bloodless coup d’état, in which the crown prince took power in the royal Privy Council. During the following years, his leading advisers faced opposition from other factions at court and within the royal family, and the crown prince and his wife faced reproductive challenges, as they lost several children shortly after birth. The article explores the attempts at seeking influence made by two wives of leading advisers to the royal crown prince, Frederik (6.). Producing a male heir was imperative to the crown prince couple’s claim to power in the absolutist reign, and the advisers’ political positions therefore also hinged on the couple’s reproduction. I discuss how the advisers’ wives, the two sisters Sybille Reventlow (1753-1827) and Charlotte Schimmelmann (1757-1816), attempted to solve these issues and advance their group’s position at court. The article identifies several strategies employed by the women to help the crown prince couple’s situation, but primarily aimed at the crown princess; firstly, conversations on childrearing; secondly, the discussion of adoption; while a third strategy included traveling to the spa at Bad Pyrmont, where the advisers’ wives would engage the spa’s famous doctor Heinrich Mathias Marcard as accoucheur to the crown princess. The women’s struggles to gain influence show how those women who were not members of the royal household tried to navigate the political world of a hereditary and personal monarchy, where personal relationships and parenting experiences were also a political matter.

Synergistic Integration of Multiple Wave Energy Converters with Adaptive Resonance and Offshore Floating Wind Turbines through Bayesian Optimization

We developed a synergistic ocean renewable system where an array of Wave Energy Converters (WEC) with adaptive resonance was collocated with a Floating Offshore Wind Turbine (FOWT) such that the WECs, capturing wave energy through the resonance adapting to varying irregular waves, consequently reduced FOWFT loads and turbine motions. Combining Surface-Riding WECs (SR-WEC) individually designed to feasibly relocate their natural frequency at the peak of the wave excitation spectrum for each sea state, and to obtain the highest capture width ratio at one of the frequent sea states for annual average power in a tens of kilowatts scale with a 15 MW FOWT based on a semi-submersible, Bayesian Optimization is implemented to determine the arrangement of WECs that minimize the annual representation of FOWT’s wave excitation spectra. The time-domain simulation of the system in the optimized arrangement is performed, including two sets of interactions: one set is the wind turbine dynamics, mooring lines, and floating body dynamics for FOWT, and the other set is the nonlinear power-take-off dynamics, linear mooring, and individual WECs’ floating body dynamics. Those two sets of interactions are further coupled through the hydrodynamics of diffraction and radiation. For sea states comprising Annual Energy Production, we investigate the capture width ratio of WECs, wave excitation on FOWT, and nacelle acceleration of the turbine compared to their single unit operations. We find that the optimally arranged SR-WECs reduce the wave excitation spectral area of FOWT by up to 60% and lower the turbine’s peak nacelle acceleration by nearly 44% in highly occurring sea states, while multiple WECs often produce more than the single operation, achieving adaptive resonance with a larger wave excitation spectra for those sea states. The synergistic system improves the total Annual Energy Production (AEP) by 1440 MWh, and we address which costs of Levelized Cost Of Energy (LCOE) can be reduced by the collocation.

The analysis for fatigue caused by vibration of railway composite beam considering time-dependent effect

The time-dependent effects in steel-concrete composite beam bridges can intensify track irregularities, subsequently leading to amplified train-bridge coupling vibrations. This phenomenon may increase the stress amplitudes in the bridge steel, thereby impacting the fatigue performance of the composite structures. This paper employs multiple rigid body dynamics to construct a high-speed train model and utilizes the finite element method to develop a steel-concrete composite beam element model that accounts for time-dependent effects, interfacial slip, and shear hysteresis. This approach enables the computational analysis of the train-bridge coupling system, facilitating an investigation into the influence of concrete’s time-dependent effects on the fatigue performance of railway steel-concrete composite bridges. Focusing on a 40-m simply supported composite bridge, the train-bridge coupling dynamic responses were computed for each operational year within a decade of the completion of construction. Applying the P-M linear fatigue damage accumulation theory, statistical analysis of stress history data across various operational periods was conducted to quantify the fatigue damage induced by a single eight-car high-speed train on the lower flange of the mid-span steel beam and the beam-end studs. The findings reveal that the beam-end studs sustain greater damage than the mid-span steel beam. Moreover, the detrimental impact of time-dependent effects diminishes with the increase of operational years. Notably, compared to the initial year, the fatigue damage to the lower flange of the mid-span steel beam by an eight-car train in the tenth year has surged by 39.3%. Conversely, the damage to the beam-end studs has decreased by 47.5%.

Fixed-time prescribed performance consensus formation tracking control of multiple electrically driven nonholonomic mobile robots with complete unknown parameters

This paper delves into the fixed-time consensus formation problem for wheeled mobile robots (WMRs) with completely unknown parameters under prescribed constraints. By integrating the rigid body dynamics of the robot and the high-order dynamics of the drive circuit, and utilising voltage as the control input, we propose a fixed-time prescribed performance control (PPC) protocol. The controller aims to ensure that the formation error of WMRs evolves under prescribed constraints and converges to a small neighbourhood around zero within a fixed time. Furthermore, the designed adaptive laws ensure control accuracy even in scenarios where WMR parameters are unknown. Finally, the feasibility and effectiveness of the proposed controller are validated through simulations under various conditions.

An alternative to the Euler equation of rigid body rotational dynamics

The Euler equation provides a convenient framework for studying the rotational dynamics of rigid bodies in solid mechanics. While this equation is written from the point of view of an inertial observer, it is implemented in a non-inertial ancillary coordinate system attached to the rigid body and the equations of the rotation are consequently expressed in this ancillary system. We examine how the rotational dynamics of rigid bodies can be described by the inertial observer directly in the inertial coordinate system (instead of employing an ancillary non-inertial frame), and derive the differential equations of the rotation in this inertial system. This approach can have advantages in situations where the rigid body has both translational motion in addition to rotational motion.