Rigid-body Dynamics Simulation Research Articles

Research on non-linear dynamic simulation model of feeding system

Abstract The automatic gun feeding system is an important mechanism for achieving continuous shooting, but due to its complex structure, there is a lot of contact during firing, and its reliability is lower. To improve the reliability of the feeding system and its dynamic characteristics, a multi rigid body dynamic simulation model of the feeding system considering contact nonlinearity was established based on nonlinear dynamics theory. The dynamic characteristics of the feeding system were analyzed for single and continuous firing. The research results indicate that the presence of contact nonlinearity increases the interaction forces between components and also increases the uncertainty of component motion.

Dynamics simulation-based packing of irregular 3D objects

The 3D packing problem has a wide range of applications. However, the complex geometry of irregular objects leads to a sharp increase in the number of placement combinations, making it a challenging problem. In this paper, we propose a packing pipeline based on rigid body dynamics simulation to deal with two types of 3D packing problems. One is the variant bin packing problem, which involves placing more objects into a container of given dimensions to maximize space utilization. The other is the open dimension problem, where the goal is to minimize the container that can accommodate all objects. We first use heuristic placement strategies and a fast collision detection algorithm to efficiently obtain initial packing results. Then, we simulate the shaking of the container according to the dynamic principle. Combined with the vacant space filling operation, shaking the container drives the movement of objects in the container to make the arrangement of objects more compact. For the open dimension packing, the container height is optimized by adjusting the constraints of simulation in the basic pipeline. Experimental results show that our method has advantages over existing methods in both speed and packing density.

Research on Attitude Analysis of Hydraulic Support Based on Column Length

The existing hydraulic support attitude monitoring and control methods integrate multiple sensing technologies, but it is difficult to apply and promote due to unclear monitoring mechanisms, complicated types, and a large number of sensors. Aiming at the problem of attitude monitoring and control of hydraulic support, firstly, the kinematics mathematical model of hydraulic support is established by the key marker point method and the two-dimensional bar system model, and the forward and inverse solution algorithm of hydraulic support attitude based on the double-drive length of front and rear columns is proposed. Secondly, the rigid body dynamics simulation model of hydraulic support is constructed to verify the theoretical analytical model and prove the correctness of the algorithm. The rigid body simulation model can be used as the attitude monitoring system of hydraulic support. Thirdly, considering the influence of material elastic deformation, a rigid-flexible coupling dynamic simulation model of hydraulic support is established to explore the influence of elastic deformation of components on the attitude of hydraulic support and its causes. On this basis, the rigid-flexible coupling dynamic simulation model of the hydraulic support with clearance is established by replacing the revolute pair in the simulation model with the solid axis pin connection unit. The influence of the axis pin connection clearance on the attitude of the hydraulic support and its causes are explored, and the actual attitude and change characteristics of the hydraulic support under simulated real conditions are obtained. Finally, considering the force compression of the hydraulic cylinder of the column, the rigid-flexible and machine-liquid coupling dynamic simulation model of the hydraulic support with clearance is constructed.

Research on intelligent formation operation performance of straddle-type rapid transit vehicles in heterogeneous operating environment

This paper presents an intelligent formation operation mode (IFOM) based on straddle-type rapid transit vehicles. Taking the straddle-type rapid transit vehicles operating in IFOM as the object, the operation mode of the vehicle is defined in the control system architecture of the straddle-type rapid transit system. In addition, considering the heterogeneous operating environ-ment of formation vehicles, an evaluation index system for formation vehicles is proposed. Then, according to the vehicle longitudinal dynamics model and the artificial potential field formation algorithm, we build the formation vehicle operation controller. After that, referring to the vehicle dynamics model, a multi rigid body dynamics simulation model of formation vehicles in a heterogeneous operating environment is established. Finally, the operating performance of formation vehicles in heterogeneous operating environment is analyzed. The analysis results show that the operation performance of the formation vehicle meets the requirements of the evaluation index system, which proves the feasibility of the formation operation of straddle-type rapid transit vehicles operating in IFOM.

3D Virtual reconstruction of asphalt mixture microstructure based on rigid body dynamic simulation

ABSTRACT This paper presents a virtual generation method for the heterogeneous microstructure of asphalt mixtures. The coarse aggregates used in the digital asphalt mixture were derived from real aggregates captured by a three-dimensional (3D) laser scanner. Then, a rigid-body dynamic simulation framework was proposed to generate a stable skeletal structure composed of coarse aggregates similar to those formed by compaction. Furthermore, FAM and air voids were generated based on the generated aggregate skeleton and the assumption of equal thickness of FAM film. To prove the reliability of the model, the air voids of the digital asphalt mixture samples were verified by comparison with real specimens. The generated digital specimens were also applied to finite element method (FEM) simulations to predict the dynamic modulus of the asphalt mixture and the simulated results were in good agreement with the experimental results. The method can be applied to study the spatial distribution of asphalt mixture components, the movement pattern of aggregate particles during compaction and numerical simulations at the microscopic scale.

Leveraging Evolutionary Algorithms for Feasible Hexapod Locomotion Across Uneven Terrain

Optimizing gait stability for legged robots is a difficult problem. Even on level surfaces, effectively traversing across different textures (e.g., carpet) rests on dynamically tuning parameters in multidimensional space. Inspired by biology, evolutionary algorithms (EA) remain an attractive solution for feasibly implementing robotic locomotion with both energetic economy and rapid parameter convergence. Here, we leveraged this class of algorithms to evolve a stable hexapod gait controller capable of traversing uneven terrain and obstacles. Gait parameters were evolved in a rigid body dynamics simulation on an 8 x 3 meter obstacle course comprised of random step field, linear obstacles and inclined surfaces. Using a fitness function that jointly optimized locomotion velocity and stability, we found that multiple successful gait parameter evolutions yielded specialized functionality for each leg. Specific gait parameters were identified as critical to developing a rough terrain gait.

A rigid body dynamics simulation enhanced representative volume element builder for CNT/Al composite

A rigid body dynamics simulation enhanced representative volume element builder for CNT/Al composite

Dynamic balance design and simulation verification of reed system of loom beating up mechanism

In order to reduce the vibration caused by the eccentricity of the reed system in the beating up mechanism of the loom, the centrifugal force generated by the eccentric reed system is decomposed into two parallel base planes, and a dynamic balance design scheme based on the principle of counterweight is established. Based on structural analysis and theoretical calculation, the reasonable balance weight mass, structure and assembly position are determined, and the reed system simulation model based on Adams/view platform is constructed. The correctness of the dynamic balance design scheme is verified by rigid body dynamics simulation and error analysis. The analysis results show that the centrifugal force simulation value F=347.008N, the design value F1=347.222N, and the error is 0.06%, which meets the requirements of mechanical accuracy design. It provides an important technical reference for dynamic balance design, vibration reduction and noise reduction of fixed axis rotation system.

A rigid body dynamics model to predict the combined effects of particle size and shape on pressure filtration

• Developed a novel computational workflow for simulating pressure filtration. • Rigid body dynamics used to simulate cake formation with various particle shapes. • A “local” Ergun equation developed to capture spatial variations in cake structure. • Platelet-shaped particles predicted to generate low porosity and poor filterability. • Large and small particle mixtures predicted to generate spatial heterogeneities. Many theoretical studies have focused on the effects of spherical particle size on pressure filtration, a solid-liquid separation method commonly used in pharmaceutical manufacturing and other industries. While experimental studies have demonstrated the importance of particle shape as well as size on the filterability of non-spherical particles commonly produced from pharmaceutical crystallization, process models that mechanistically capture how particle morphology affects the microscopic properties of the particle cake are lacking. The objective of this study was to investigate the combined effects of particle shape and size on pressure filtration performance using rigid body dynamics simulation, a powerful method for predicting porous cake structure based on the properties of the constituent particles. Once a detailed cake structure was generated, the Ergun equation was used to predict the macroscopic flow behavior of the filtration process. This workflow was validated by comparing model predictions with filtrate flow measurements from a series of dead-end filtration experiments using spherical particles with heterogeneous size. By simulating cylindrical particles over a wide range of aspect ratios, we showed that particle shape can have a dramatic effect on cake porosity and filtrate flow with disk-shaped particles predicted to be particularly difficult to filter. Rigid body simulation allowed the prediction of local as well as average cake properties. We predicted that heterogeneously sized particles with small or large aspect ratios such as disks or needles could produce highly asymmetric cake structures characterized by densely packed and low porosities near the filter medium. A modified Ergun equation based on local particle size and porosity was developed and shown to predict substantially different filtrate flows than the standard Ergun equation based on spatially-averaged properties, especially for cylindrical particles with high aspect ratio.

High-fidelity prediction of flight trajectories of plate-type debris in boundary layer winds

From reconnaissance surveys, plate-type objects, such as roof shingles and tiles, are known to be among the most common types of debris objects. Therefore, a reliable prediction of their flight trajectories is instrumental for evaluating the vulnerability of building envelopes, especially in the regions with severe windstorms. Despite the development of several quasi-steady models for this purpose, the current literature lacks high-fidelity models to predict the flight pattern and impact velocity of the windborne debris objects separated from the ground and/or buildings. To address this gap, a coupled computational fluid dynamics and rigid body dynamics simulation framework was developed in the current study to capture the flight trajectories of plate-type debris objects in atmospheric boundary layer winds. Upon establishing a fundamental understanding of main flight characteristics, this study was extended to investigate the effects of initial pitch and yaw angles, plate characteristics, mean wind velocity, and release height on the flight of plate-type debris. In addition, a set of models were developed to predict debris travel distance, as well as linear and angular velocities associated with it. This can be directly employed to assess the impact-induced loading demand that building envelopes are expected to resist due to windborne plate-type debris.

Modeling and Prediction of Rigid Body Motion With Planar Non-Convex Contact

Abstract We present a principled method for motion prediction via dynamic simulation for rigid bodies in intermittent contact with each other where the contact region is a planar non-convex contact patch. Such methods are useful in planning and controlling for robotic manipulation. The planar non-convex contact patch can either be a topologically connected set or a disconnected set. Most works in rigid body dynamic simulation assume that the contact between objects is a point contact, which may not be valid in many applications. In this paper, using the convex hull of the contact patch, we build on our recent work on simulating rigid bodies with convex contact patches for simulating motion of objects with planar non-convex contact patches. We formulate a discrete-time mixed complementarity problem to solve the contact detection and integration of the equations of motion simultaneously. We solve for the equivalent contact point (ECP) and contact impulse of each contact patch simultaneously along with the state, i.e., configuration and velocity of the objects. We prove that although we are representing a patch contact by an equivalent point, our model for enforcing non-penetration constraints ensures that there is no artificial penetration between the contacting rigid bodies. We provide empirical evidence to show that our method can seamlessly capture transition among different contact modes like patch contact, multiple or single point contact.

Prediction of patellofemoral joint kinematics and contact through co-simulation of rigid body dynamics and nonlinear finite element analysis

Joint-level rigid body dynamics simulations, when coupled with tissue-level finite element analyses, can simultaneously provide movement and tissue deformation metrics to understand mechanical interactions within the joint on a multi-scale level. In this study, a co-simulation workflow of a joint-level rigid body model that predicts the relative motion as a function of the non-linear cartilage response predicted by a non-linear implicit finite element solver is presented. Predictions are compared to in-vitro measurements (The Open Knee(s) project) in terms of the mean error and level-of-agreement: pressureerror = 0.46 MPa (level-of-agreement, −0.23 – 1.1 MPa); areaerror = −89 mm2 (level-of-agreement, −280 – 98 mm2) and contact forceerror = 93 N (level-of-agreement, 7.8 – 180 N). The automated co-simulation control algorithm enables multiscale coupling between joint and tissue-level models with real-time two-way communication as opposed to the traditional feed-forward approach of multi-scale models.

Comparison of a closed-loop control by means of high-fidelity and low-fidelity coupled CFD/RBD computations

This work compares the principle of a basic fin-controlled sounding rocket with coupled computational fluid dynamic and rigid body dynamic simulations of two coupling environments: (1) a low-fidelity approach using Missile DATCOM as semi-empirical aerodynamic solver, and (2) a high-fidelity approach using DLR TAU as URANS CFD code. The flight mechanics solver REENT is used in both cases. A closed-loop flight path control is developed and adjusted via low-fi simulations and then verified via high-fi simulations. For simple roll and pitching maneuvers the environments match well, whereas differences can be seen in complex maneuvers, e.g. body–body interactions of separation procedures.

Effects of Hydrodynamic Interactions on the Near-Surface Diffusion of Spheroidal Molecules.

We investigated diffusion of spheroidal molecules near a planar surface, accounting for spatially dependent translational and rotational mobilities of molecules resulting from their hydrodynamic interactions with the plane. Rigid-body Brownian dynamics simulations of prolate ellipsoids of revolution of an axial ratio in the range of 1.5 to 3.0, suspended in a viscous fluid, with a no-slip flat boundary confining the suspension were employed. Mobility tensor matrices of molecules were evaluated as functions of spheroids’ distance and orientation with respect to the plane. Hydrodynamic interactions with the surface lead to substantial changes of spheroids’ translational diffusion coefficients both in the direction perpendicular and parallel to the plane when compared with the values characterizing the bulk diffusion. Moreover, the short-time translational diffusion of molecules, measured in the laboratory frame, both in an unbounded fluid and under the confinement, is non-Gaussian, with much larger deviations from Gaussianity observed in the latter case. In an unbounded fluid, distributions of translational displacements of molecules deviate from those expected for a simple Brownian motion as a result of shape anisotropy. In the presence of the plane, spheroids experience an additional anisotropic drag, and consequently, their mobilities depend on their positions and orientations. Therefore, anomalies in the short-time dynamics observed under confinement can be explained in terms of the so-called diffusing-diffusivity mechanism. Our findings have implications for understanding of a wide range of biological and technological processes that involve diffusion of anisotropic molecules near surfaces of natural and model cell membranes, biosensors and nanosensors, and electrodes.

Analysis of vibration isolation performance of parallel air spring system for precision equipment transportation

Precision equipment is usually accompanied with vibrations during road or railway transportation. Sometimes the vibration exceeds the given limit, leading to the damage of the equipment. It is necessary to control the vibration during the transportation. However, it is still difficult to adjust the parameters of a designed vibration isolation system for the transportation of different precision equipment under various road conditions. Aiming at satisfying the vibration isolation requirements of different precision equipment, this paper proposes a parallel air spring vibration isolation system based on the principle of limiting lateral deflection. According to the measured parameters, a rigid-body dynamics simulation model of parallel air spring vibration isolation system is established. Then its feasibility is verified, and the optimal parameters of the vibration isolation system are obtained by a simulation. Finally, the vibration isolation system is built and installed in the equipment to carry out the real vehicle transportation test. The test results show that the transportation vibration isolation system based on the parallel air spring structure has not only excellent vibration isolation efficiency but also acceptable lateral stability. The research results in this paper can provide a reference for the design of the vibration isolation system for the large precision equipment transportation.

Role of Conformational Flexibility in Monte Carlo Simulations of Many-Protein Systems.

Efficient computational modeling of biological systems characterized by high concentrations of macromolecules often relies on rigid-body Brownian Dynamics or Monte Carlo (MC) simulations. However, the accuracy of rigid-body models is limited by the fixed conformation of the simulated biomolecules. Multi-conformation Monte Carlo (mcMC) simulations of protein solutions incorporate conformational flexibility via a conformational swap trial move within a predetermined library of discrete protein structures, thereby alleviating artifacts arising from the use of a single protein conformation. Here, we investigate the impact of the number of distinct protein structures in the conformational library and the extent of conformational sampling used in its generation on structural observables computed from simulations of hen egg white lysozyme (HEWL), human γD-Crystallin, and bovine γB-Crystallin solutions. We find that the importance of specific protocols for the construction of the protein structure library is strongly dependent on the nature of the simulated system.

Regulation of Protein Structural Changes by Incorporation of a Small-Molecule Linker.

Proteins have the potential to serve as nanomachines with well-controlled structural movements, and artificial control of their conformational changes is highly desirable for successful applications exploiting their dynamic structural characteristics. Here, we demonstrate an experimental approach for regulating the degree of conformational change in proteins by incorporating a small-molecule linker into a well-known photosensitive protein, photoactive yellow protein (PYP), which is sensitized by blue light and undergoes a photo-induced N-terminal protrusion coupled with chromophore-isomerization-triggered conformational changes. Specifically, we introduced thiol groups into specific sites of PYP through site-directed mutagenesis and then covalently conjugated a small-molecule linker into these sites, with the expectation that the linker is likely to constrain the structural changes associated with the attached positions. To investigate the structural dynamics of PYP incorporated with the small-molecule linker (SML-PYP), we employed the combination of small-angle X-ray scattering (SAXS), transient absorption (TA) spectroscopy and experiment-restrained rigid-body molecular dynamics (MD) simulation. Our results show that SML-PYP exhibits much reduced structural changes during photo-induced signaling as compared to wild-type PYP. This demonstrates that incorporating an external molecular linker can limit photo-induced structural dynamics of the protein and may be used as a strategy for fine control of protein structural dynamics in nanomachines.

Macromolecular crowding effects in flexible polymer solutions

Biological environments are often “crowded” due to high concentrations (300–400[Formula: see text]g/L) of macromolecules. Computational modeling approaches like Molecular Dynamics (MD), rigid-body Brownian Dynamics and Monte Carlo simulations have recently emerged, which allow to study the effects macromolecular crowding at a microscopic level and to provide complementary information to experiments. Here, we use a recently introduced multiple-conformation Monte Carlo (mcMC) approach in order to study the influence of intermolecular interactions on the structural equilibrium of flexible polyethylene glycol (PEG) polymers under self-crowding conditions. The large conformational space accessible to PEG polymers allows us to evaluate the general applicability of the mcMC approach, which describes the intramolecular degrees of freedom by a finite-size ensemble of discrete conformations. Despite the simplicity of the approach, we show that influences of intermolecular interactions on the intramolecular free energy surface can be described qualitatively using mcMC. By varying the magnitude of distinct terms in the intermolecular potential, we can further study the compensating effects of repulsive and nonspecific attractive intermolecular interactions, which favor compact and extended polymer states, respectively. We use our simulation results to derive an analytical model that describes the effects of intermolecular interactions on the stability of PEG polymer conformations as a function of the radius of gyration and the corresponding solvent accessible surface. We use this model to confirm the role of molecular surfaces for attractive interactions that can counteract excluded volume effects. Extrapolation of the model further allows for the analysis of scenarios that are not easily accessible to direct simulations as described here.

Chromophore-Removal-Induced Conformational Change in Photoactive Yellow Protein Determined through Spectroscopic and X-ray Solution Scattering Studies.

Photoactive yellow protein (PYP) induces negative phototaxis in Halorhodospira halophila via photoactivation triggered by light-mediated chromophore isomerization. Chromophore isomerization proceeds via a volume-conserving isomerization mechanism due to the hydrogen-bond network and steric constraints inside the protein, and causes significant conformational changes accompanied by N-terminal protrusion. However, it is unclear how the structural change of the chromophore affects the remote N-terminal domain. To understand photocycle-related structural changes, we investigated the structural aspect of chromophore removal in PYP because it possesses a disrupted hydrogen-bond network similar to that in photocycle intermediates. A comparison of the structural aspects with those observed in the photocycle would give a clue related to the structural change mechanism in the photocycle. Chromophore removal effects were assessed via UV-vis spectroscopy, circular dichroism, and X-ray solution scattering. Molecular shape reconstruction and an experiment-restrained rigid-body molecular dynamics simulation based on the scattering data were performed to determine protein shape, size, and conformational changes upon PYP bleaching. Data show that chromophore removal disrupted the holo-PYP structure, resulting in a small N-terminal protrusion, but the extent of conformational changes was markedly less than those in the photocycle. This indicates that disruption of the hydrogen-bond network alone in bleached PYP does not induce the large conformational change observed in the photocycle, which thus must result from the organized structural transition around the chromophore triggered by chromophore photoisomerization along with disruption of the hydrogen-bond network between the chromophore and the PYP core.

Hydrodynamic Steering in Protein Association Revisited: Surprisingly Minuscule Effects of Considerable Torques.

We investigate the previously postulated hydrodynamic steering phenomenon, resulting from complication of molecular shapes, its magnitude and possible relevance for protein-ligand and protein-protein diffusional encounters, and the kinetics of diffusion-controlled association. We consider effects of hydrodynamic interactions in a prototypical model system consisting of a cleft enzyme and an elongated substrate, and real protein-protein complexes, that of barnase and barstar, and human growth hormone and its binding protein. The kinetics of diffusional encounters is evaluated on the basis of rigid-body Brownian dynamics simulations in which hydrodynamic interactions between molecules are modeled using the bead-shell method for detailed description of molecular surfaces, and the first-passage-time approach. We show that magnitudes of steering torques resulting from the hydrodynamic coupling of associating molecules, evaluated for the studied systems on the basis of the Stokes-Einstein type relations for arbitrarily shaped rigid bodies, are comparable with magnitudes of torques resulting from electrostatic interactions of binding partners. Surprisingly, however, unlike in the case of electrostatic torques that strongly affect the diffusional encounter, overall effects of hydrodynamic steering torques on the association kinetics, while clearly discernible in Brownian dynamics simulations, are rather minute. We explain this result as a consequence of the thermal agitation of the binding partners. Our finding is relevant for the general understanding of a wide spectrum of molecular processes in solution but there is also a more practical aspect to it if one considers the low level of shape detail of models that are usually employed to evaluate hydrodynamic interactions in particle-based Stokesian and Brownian dynamics simulations of multicomponent biomolecular systems. Results described in the current work justify, in part at least, such a low-resolution description.