Body Dynamics Research Articles

Simulation of generally shaped 3D elastic body dynamics with large motion using transfer matrix method incorporating model order reduction

Simulation of generally shaped 3D elastic body dynamics with large motion using transfer matrix method incorporating model order reduction

Research on Rigid–Elastic Coupling Flight Dynamics of Hybrid Wing Body Based on a Multidiscipline Co-Simulation

Due to the special aerodynamic layout and mass distribution, the natural frequency differences between the hybrid wing body (HWB)’s rigid-body motion modes and the fuselage structure elastic modes are smaller compared to conventional aircraft, resulting in the disappearance of the decoupling relationship between the HWB’s rigid-body motion and the elastic motion of the airframe structure. For the above reason, the traditional analysis approach based on the rigid-body assumption is no longer applicable when analyzing the flight dynamics of an HWB aircraft, and a shift must be made to an analysis method that takes into account aeroelastic effects. Therefore, in this paper, a time-domain co-simulation program combining the computational fluid dynamics (CFD) method with computational structure dynamics (CSD) and rigid-body dynamics (RBD) is developed to investigate the effect of a rigid–elastic coupling effect on the flight dynamics of the HWB and this co-simulation method is more advantageous in the calculation of unsteady aerodynamics compared to existing methods of rigid–elastic coupling dynamics analysis. By means of the co-simulation technology, this paper completed a series of simulations, based on which the influence of rigid–elastic coupling effect on the short-period dynamic characteristics of aircraft was studied.

Bifurcations of the limit directions in extended Filippov systems

This paper explores special bifurcations that appear in dynamical systems possessing codimension-2 discontinuity sets in the state space. In these systems, the vector field has continuously many directional limits at the discontinuity set. It is shown that the trajectories can reach the discontinuity set along specific limit directions. The number and type of these organising objects characterise the behaviour of the dynamics in the vicinity of the discontinuity set. Thus, bifurcations of limit directions have a remarkable effect on the system. In the paper, two special bifurcations are explored; the tangency bifurcation and the saddle–node bifurcation of limit direction are followed through different formulations of the dynamical system. It is demonstrated that these bifurcations appear in rigid body dynamics in the presence of dry friction.

A new suppression strategy of pitching vibration based on the magnetic-electric-mechanical coupling dynamic model for superconducting EDS transport system

The superconducting electrodynamic suspension (EDS) train is suitable for high-speed maglev rail transit because of its low drag force, strong levitation force, large suspension gap, and so on. However, the electromagnetic forces of four pairs of superconducting coils on one bogie are dynamically unequal in practical operation. This causes the bogie to vibrate in the pitching axis, which affects the train system's safety, stability, and comfort. Therefore, proposing an appropriate strategy to suppress the bogie pitching vibration is significant. First, based on the dynamic circuit theory, energy method and rigid body dynamics, the magnetic-electric-mechanical coupling dynamic model of eight superconducting high-field coils in the bogie and ground null-flux coils was established to explore the characteristics of fluctuating and unequal electromagnetic forces. The synchronous current and motion responses were further calculated using the Runge-Kutta algorithm. Second, the bogie's vibration characteristics were analyzed and the reasons for the vertical and pitching vibration were discussed. And the accuracy of the model was verified by comparing the levitation force with the experiment data. Third, a non-uniform exciting currents supply strategy for the superconducting coils was proposed under the comprehensive evaluation of the suppressing effect on the pitching vibrations. Finally, several cases were given to prove the effectiveness of the strategy. The results show that the total electromotive force increased by 0.005% after adopting the proposed non-uniform exciting currents supply strategy. But the minimum and maximum amplitude of pitching vibration and the growth rate of pitching vibration decreased by 97.00%, 95.76%, and 81.45%, respectively. This new strategy can effectively suppress the pitching vibration of the bogie without changing the already-designed mechanical structure. This established magnetic-electric-mechanical coupling dynamic model and the suppression strategy provide reference and a new idea for the superconducting EDS system's safety, stability, and comfort.

Modifications to head-trunk coordination dynamics during running and sidestepping

ABSTRACT The purpose of this study was to determine how the intrinsic head-trunk coordination dynamics that exist during forward running are modified during a dynamic sidestepping task. Fourteen athletes performed both forward running and sidestepping tasks. Head-trunk coordination and range of motion were assessed during the flight and stance phases in the transverse and sagittal planes. The sidestepping task resulted in greater in-phase head-trunk coordination during stance in the transverse plane (p < .001, ES = −1.71) and in reduced anti-phase coordination between head and trunk in the sagittal plane (p < .001, ES = 1.52). Statistical non-parametric mapping revealed that during sidestepping the sagittal plane coupling angle shifted away from anti-phase earlier during midstance. The sidestepping task resulted in greater transverse and sagittal plane head and trunk range of motion and greater vertical trunk centre of mass displacement. Sidestepping modified the intrinsic coordination dynamics that are present during forward running, with greater transverse plane head contributions and reductions in compensatory sagittal plane head motion, which may occur during the transition from weight acceptance to propulsion during the stance phase. These changes in the intrinsic coordination dynamics of the upper body during sidestepping tasks may impact visual perception and readiness compared to forward running during complex sports tasks.

Brachistochrone of off-centered cylinders

We consider the problem of finding paths of shortest transit time between two points (popularly known as brachistochrone) for cylinders with off-centered center of mass, rolling down without slip, subject solely to the force of gravity. This problem is set up using principles of classical rigid body dynamics and the desired path function is solved for numerically using the method of discrete calculus of variations. We discover a distinct array of brachistochrone trajectories for off-centered cylinders, demonstrate a critical dependence of such paths on the initial location and orientation of cylinders’ centers of mass and bring new insights into the family of brachistochrone problems and solutions.

Non-inertial torques and the Euler equation

The key equation describing the rotational dynamics of a rigid body is \({\vec \tau } = \text{d}{\vec L} / dt\) which can be understood based on the Newton’s second and third laws of motion together with the assumption of mutual centrality of the internal forces and is valid in an inertial coordinate system. While this equation is written down by an inertial observer, for practical purposes, it is efficiently worked out within a non-inertial rotating ancillary coordinate system along the principle axes of the rigid body. This results in the famous Euler equation for rotation of the rigid bodies. We show that it is also possible to describe the rotational dynamics of a rigid body from the point of view of a non-inertial observer (rotating with the ancillary coordinate system), provided that the non-inertial torques are taken into account. We explicitly calculate the non-inertial torques and express them in terms of physical characteristics of the rigid body. We show that the resulting dynamical equations exactly recover the Euler equation.

Non-integrability of a system from the rigid body dynamics

We study the complete integrability of a system describing the motion of a rigid body with a fixed point and a particle oscillating in it in the absence of external forces. Using the Ziglin-Morales-Ramis theory, we prove rigorously that the considered system is integrable only in the case of dynamical symmetry.

Challenges in Implementing Low-Latency Holographic-Type Communication Systems.

Holographic-type communication (HTC) permits new levels of engagement between remote users. It is anticipated that it will give a very immersive experience while enhancing the sense of spatial co-presence. In addition to the newly revealed advantages, however, stringent system requirements are imposed, such as multi-sensory and multi-dimensional data capture and reproduction, ultra-lightweight processing, ultra-low-latency transmission, realistic avatar embodiment conveying gestures and facial expressions, support for an arbitrary number of participants, etc. In this paper, we review the current limitations to the HTC system implementation and systemize the main challenges into a few major groups. Furthermore, we propose a conceptual framework for the realization of an HTC system that will guarantee the desired low-latency transmission, lightweight processing, and ease of scalability, all accompanied with a higher level of realism in human body appearance and dynamics.

Comparative dynamic analysis of SCR and LWR in the coupled platform–mooring–riser system under internal solitary wave conditions

As a frequently occurring and widely distributed environmental load, an internal solitary wave (ISW) always appears with a large amplitude and may result in the instability of deepwater structures and offshore accidents. In this study, a self-developed program was established to describe the dynamic behavior of a coupled platform–mooring–riser system. The response of the platform is based on the rigid body dynamics theory, that of the risers/mooring lines is obtained by the lump mass method, and the coupled effect between them is achieved by a semi-coupled analysis. Two types of riser configurations, steel catenary risers (SCRs) and lazy-wave steel catenary risers (LWRs), in the coupled system were compared under only ISWs and combined excitation of ISWs and random waves. The numerical results were proven to be reliable through validation against previous literature. The results show that different riser configurations have little influence on the platform response or mooring top tension. Both riser configurations exhibit a second-order deformation mode along the riser length and a half-wave shape with time. Additionally, a mutation in the horizontal tension, shear force, and bending moment occurs near the ISW interface. Compared with SCRs, LWRs always produce larger motion characteristics and responses with time differences owing to their complex configuration.

VTOL UAV digital twin for take-off, hovering and landing in different wind conditions

With UAVs becoming increasingly popular in the industry, vertical take-off and landing (VTOL) convertiplanes are emerging as a compromise between the advantages of planes and multicopters. Due to their large wing surface area, VTOL convertiplanes are subject to a strong wind dependence on critical phases such as take-off, landing, and hovering. Developing a new and improved unmanned aerial vehicle (UAV) is often expensive and associated with failures and accidents. This paper proposes the dynamic characterization of a commercial VTOL convertiplane UAV in copter mode and provides a novel method to estimate the aerodynamic forces and moments for any possible wind speed and direction. Starting from Euler’s equations of rigid body dynamics, we have derived the mathematical formulation to precisely consider aerodynamic forces and moments caused by any wind speed and direction. This unique approach will allow for VTOL convertiplane UAVs to be trained and tested digitally in take-off, hovering, and landing maneuvers without the cost and hassle of physical testing, and the dependence on existing wind conditions. A digital twin of a VTOL convertiplane UAV in copter mode has been modeled and tested in the Gazebo robotics simulator. Take-off, hovering and landing maneuvers have been compared with and without the wind physics model. Finally, the simulator has been tested against real flight conditions (reproducing the mean wind speed and direction only), showing a natural and realistic behavior.

Powertrain Modal Analysis for Defining the Requirements for a Vehicle Drivability Study

The powertrain of a car plays a major role in establishing the vehicle’s offered comfort due to vibrations because it is the heaviest single component installed on the chassis; therefore, when oscillating, it transmits considerable forces to the chassis, inducing unwanted vibrations. For this reason, it is important to identify some associated properties with the powertrain suspension system that describe the performance of its rigid body dynamics. In this way, we could place constraints and requirements on these quantities in order to exclude all the configurations that cause intolerable levels of vibrations, and include all the others in the analysis for further evaluation. The definition of these requirements is critical: a poor setting of requirements excludes potentially good powertrain suspension setups and includes those ones with a drivability index that is too poor. In this paper, we identify a set of quantities that show correlation with the vibration performance of the powertrain setup. A method for testing the specificity of the requirements is also shown in order to evaluate which requirements perform best when it comes to filtering engine suspension setups that provide an acceptable level of vibrations.

Energy-Based Footstep Planning of Biped on Uneven Deformable Terrain Using Nonlinear Inverted Pendulum

Abstract In this work, the motion of a nonlinear inverted pendulum (NIP) on deformable terrain due to foot contact forces is used for energy analysis and footstep placement. In order to include the linear and rotational motions of the NIP, the mass moment of inertia of the body is also considered in the center of mass (CoM) model. The terrain deformation is modeled using a spring-damper contact model, and based on the rigid body dynamics of the NIP, its motion is generated. The energy analysis of the system provides the regions of possible foot placement. Based on the loss of potential energy due to ground deformation, the limits of terrain stiffness are also obtained for walking on uneven deformable terrain.

Optimized Wiper Design using Computational Fluid Dynamics

This paper presents the robust use of Computational Fluid Dynamics (CFD) techniques as complement to wind tunnel testing for the performance assessment of rain water and wiper wash behavior on windscreen surfaces. The objective of this paper is to predict windscreen wiper design performance and its effectiveness with the help of CFD. Clear visibility to the occupants is the key for stress free and safer driving experience, therefore it is important to study the windscreen wiper system performance under different work load conditions. A multi-phase CFD code is used to simulate rain drops and its impingent on the vehicle is modeled with the help of thin liquid film. The wiper blade motion is defined with inputs from multi body dynamics (MBD) considering the driver and passenger side wiper blade speed and extent. Time-dependent results for the wiper blade location, water fluid film spread, and its height on the windscreen, A-pillar, leaf-screen rain gutters were obtained. The CFD results then equated with the physical test data. The calculated water film pattern found to be associated with the observed patterns of the waterways on the test vehicle. Multiple design studies were performed on the CFD model which are also reliable with similar test configurations. From the results, it is concluded that numerical simulation of water behavior on vehicle surfaces is possible, and CFD method is effective tool to assist engineers in envisaging, analyzing, and designing water management systems. A Computational Fluid Dynamics code had been introduced in order to simulate the cleaning performance of the automobile wash. Multi-phase thin film with rigid body motion models were used for this purpose. The objectives of the project were to quantify the water flow, enhance visualization, and develop a CAE methodology which will assist in the product development process.

Optimal Feedback Control for Modeling Human–Computer Interaction

Optimal feedback control (OFC) is a theory from the motor control literature that explains how humans move their body to achieve a certain goal, e.g., pointing with the finger. OFC is based on the assumption that humans aim at controlling their body optimally, within the constraints imposed by body, environment, and task. In this article, we explain how this theory can be applied to understanding Human-Computer Interaction (HCI) in the case of pointing. We propose that the human body and computer dynamics can be interpreted as a single dynamical system. The system state is controlled by the user via muscle control signals, and estimated from observations. Between-trial variability arises from signal-dependent control noise and observation noise. We compare four different models from optimal control theory and evaluate to what degree these models can replicate movements in the case of mouse pointing. We introduce a procedure to identify parameters that best explain observed user behavior. To support HCI researchers in simulating, analyzing, and optimizing interaction movements, we provide the Python toolboxOFC4HCI. We conclude that OFC presents a powerful framework for HCI to understand and simulate motion of the human body and of the interface on a moment-by-moment basis.

Disc golf trajectory modelling combining computational fluid dynamics and rigid body dynamics

In the sport of disc golf, athletes utilize discs with various shapes to achieve their desired throws. Computational methods have the potential to give further insight into how the disc shape and throw parameters influence the disc trajectory. A methodology is presented that combines computational fluid dynamics to obtain the aerodynamic coefficients for a given disc shape, with rigid body dynamics to simulate the disc golf flight. The computational fluid dynamics simulations were performed in OpenFOAM, and compared against wind tunnel experiments from the literature. The trajectory model was implemented in an open-source software, and compared against simulated trajectories against measured trajectories of actual disc golf throws. The methodology was applied to three different discs, comparing their aerodynamic coefficients and flight trajectories. How the disc shape impacts lift, drag and moment coefficients and corresponding flight trajectories is discussed. The methodology has the potential to consistently characterize the flight of a disc and lead to greater understanding of disc flight, and thereby contribute to both training, disc development and regulation.

Estimation of torsional and global loads for a wave-piercing high-speed catamaran at full-scale in irregular bow quartering seas using CFD simulation

Catamarans experience more types of global load than monohulls, these include pitch connecting moment, transverse bending moment, and split force. High-speed catamarans are widely used for passenger transportation but as the speed and size increase the severity of loads rises due to slam induced effects. In this study, full-scale CFD simulations are undertaken to investigate the loads acting on a 98m Incat wave-piercer catamaran (Hull 061) HSV2 Swift. Simulations are performed for conditions of a selected sea trial run in bow quartering seas at 20 knots forward speed undertaken by the Naval Surface Warfare Center, Carderock Division (NSWCCD), enabling comparisons and validation. In order to estimate internal global loads at different sections of the vessel, rigid body dynamics is applied based on the hydrodynamic and inertia forces. Those internal loads include longitudinal bending moment (LBM), pitch connecting moment (PCM), torsional moment (TorM), transverse bending moment (TBM), split force and prying moment. The estimated and measured global loads are also compared with design loads limits provided by DNV GL rules, and peak values of pitch and roll accelerations corresponding to each slam load are determined at the same wave height and wave period as the sea trial. The application of CFD to simulate sea trials runs in oblique seas is shown to provide a reliable estimation of slam induced loads for application in early design stages.

Simulating dual-arm robot motions to avoid collision by rigid body dynamics for laboratory bench work

Simulating dual-arm robot motions to avoid collision by rigid body dynamics for laboratory bench work

Global weak attractors in the dynamics of bodies with vector-type microstructure

We investigate the dynamics of bodies with vector-type microstructure. We consider linear constitutive relations and a nonlinear coupling between macroscopic and microscopic motions, determined by gyroscopic-type inertia. Based on an existence result obtained in the presence of viscous-type stress components, we determine the existence of a global attractor; its weak nature derives from the lack of uniqueness determined by the nonlinear coupling.

Physical processes leading to surface erosion and dust particles dynamics of airless bodies

The article is a review of the state of research on physical processes occurring near the surface of airless bodies, in particular, the Moon, asteroids, comets, which lead to their erosion, that is, to the modification of superficial and sometimes even deeper layers. External influences on the bodies are considered—micrometeor streams, solar wind and geomagnetic tail plasma flows, solar electromagnetic radiation, and cosmic rays, which are the main causes of erosion. The main features of airless bodies belonging to different classes are given. The main physical mechanisms that can lead to the release and removal of dust particles from the surface of regolith are analyzed, in particular, the energy aspects of high-speed micrometeor impacts, electrostatic processes of particle release from the surface, and thermodynamic processes occurring in the near-surface layers of cometary nuclei. The conditions for the removal of dust particles from the surface of a rotating body and the conditions under which the body can collapse are considered. Depending on the characteristics of these bodies, the processes of erosion, as well as the causes of its occurrence, can vary significantly. The main unresolved problems associated with the processes of erosion of bodies, which require further research, are considered.