Advancement of Contact Dynamics Modeling for Human Spaceflight Simulation Applications

2017 ◽  
Author(s):  
Thomas A. Brain ◽  
Erik B. Kovel ◽  
John R. MacLean ◽  
Leslie J. Quiocho
Keyword(s):  
Collision Detection ◽  
Software Tool ◽  
Contact Dynamics ◽  
Dynamics Simulation ◽  
3D Graphics ◽  
Dynamics Modeling ◽  
Geometric Data ◽  
Computational Performance ◽  
Dynamics Response ◽  
Multibody Contact

Pong is a new software tool developed at the NASA Johnson Space Center that advances interference-based geometric contact dynamics based on 3D graphics models. The Pong software consists of three parts: a set of scripts to extract geometric data from 3D graphics models, a contact dynamics engine that provides collision detection and force calculations based on the extracted geometric data, and a set of scripts for visualizing the dynamics response with the 3D graphics models. The contact dynamics engine can be linked with an external multibody dynamics engine to provide an integrated multibody contact dynamics simulation. This paper provides a detailed overview of Pong including the overall approach, modeling capabilities, which encompasses force generation to computational performance, and example applications.

Experimental Validation of Nonlinear Compliant Contact Force Models

2007 ◽  
Author(s):  
Yuning Zhang ◽  
Inna Sharf
Keyword(s):  
Contact Force ◽  
Research Area ◽  
Local Deformation ◽  
Contact Dynamics ◽  
Dynamics Simulation ◽  
Damping Coefficient ◽  
Engineering Practice ◽  
Dynamics Modeling ◽  
Normal Contact ◽  
The Impact

Contact dynamics modeling continues to be an intensive research area with new applications of contact dynamics simulation arising in engineering practice. One approach to normal contact force modeling that has gained significant popularity is the compliant model in which the contact force between two objects is defined explicitly as a function of local deformation and its rate. Probably the most well-known model in this category is the Hunt and Crossley model, which employs a nonlinear damping term to model the energy dissipation during contact, with the damping coefficient related to the coefficient of restitution. This model prompted several investigations on how to evaluate the damping coefficient, in turn resulting in several variations on the original Hunt-Crossley model. In this paper, the authors aim to experimentally validate the Hunt-Crossley type of nonlinear contact force models and furthermore, to compare the experimental results to the model predictions obtained with different values of the damping coefficient. The paper reports our findings from the sphere to plate impact experiments, conducted for a range of initial impacting velocities, with measurements of impact forces and accelerations. The experimental forces are compared to those predicted from the contact dynamics simulation of the experimental scenario. The experiments, in addition to generating novel impact measurements, provide a number of insights into both the study of impact and the impact response.

scholarly journals Efficient n-to-n Collision Detection for Space Debris using 4D AABB Trees

10.29007/5pl1 ◽  
2019 ◽  
Author(s):  
Stanley Bak ◽  
Kerianne Hobbs
Keyword(s):  
Collision Detection ◽  
Space Debris ◽  
Dynamics Simulation ◽  
Video Gaming ◽  
Time Dimension ◽  
Detection Algorithms ◽  
Space Objects ◽  
Tree Data ◽  
Tree Data Structure ◽  
Three Space

Collision detection algorithms are used in aerospace, swarm robotics, automotive, video gaming, dynamics simulation and other domains. As many applications of collision detection run online, timing requirements are imposed on the algorithm runtime: algorithms must, at a minimum, keep up with the passage of time. Even offline reachability computation can be slowed down by the process of safety checking when n is large and the specification is n-to-n collision avoidance. In practice, this places a limit on the number of objects, n, that can be concurrently tracked or verified. In this paper, we present an improved method for efficient object tracking and collision detection, based on a modified version of the axis-aligned bounding-box (AABB) tree data structure. We consider 4D AABB Trees, where a time dimension is added to the usual three space dimensions, in order to enable per-object time steps when checking for collisions in space-time. We evaluate the approach on a space debris collision benchmark, demonstrating efficient checking beyond the full catalog of n = 16848 space objects made public by the U.S. Strategic Command on www.space-track.org.

scholarly journals A Molecular Dynamics Study on Rotational Nanofluid and Its Application to Desalination

Membranes ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 117
Author(s):  
Qingsong Tu ◽  
Wice Ibrahimi ◽  
Steven Ren ◽  
James Wu ◽  
Shaofan Li
Keyword(s):  
Molecular Dynamics ◽  
Angular Velocity ◽  
Large Scale ◽  
Salt Water ◽  
Dynamics Simulation ◽  
Dynamics Modeling ◽  
Molecular Dynamics Modeling ◽  
Desalination Technology ◽  
Nanofluidic Device ◽  
Fluid Hydrodynamics

In this work, we systematically study a rotational nanofluidic device for reverse osmosis (RO) desalination by using large scale molecular dynamics modeling and simulation. Moreover, we have compared Molecular Dynamics simulation with fluid mechanics modeling. We have found that the pressure generated by the centrifugal motion of nanofluids can counterbalance the osmosis pressure developed from the concentration gradient, and hence provide a driving force to filtrate fresh water from salt water. Molecular Dynamics modeling of two different types of designs are performed and compared. Results indicate that this novel nanofluidic device is not only able to alleviate the fouling problem significantly, but it is also capable of maintaining high membrane permeability and energy efficiency. The angular velocity of the nanofluids within the device is investigated, and the critical angular velocity needed for the fluids to overcome the osmotic pressure is derived. Meanwhile, a maximal angular velocity value is also identified to avoid Taylor-Couette instability. The MD simulation results agree well with continuum modeling results obtained from fluid hydrodynamics theory, which provides a theoretical foundation for scaling up the proposed rotational osmosis device. Successful fabrication of such rotational RO membrane centrifuge may potentially revolutionize the membrane desalination technology by providing a fundamental solution to the water resource problem.

Systems dynamics model of a transition firm

2005 ◽  
Vol 31 (3) ◽  
pp. 67-80
Author(s):  
David L. Olson ◽  
Paraskeva Dimitrova‐Davidova ◽  
Ivan Stoykov
Keyword(s):  
System Dynamics ◽  
Multiple Criteria ◽  
Dynamics Simulation ◽  
Economic Systems ◽  
Eastern European ◽  
Dynamics Modeling ◽  
Dynamics Model ◽  
Pedagogical Tool ◽  
Modeling Process ◽  
Eastern European Countries

Eastern European countries are undergoing a transition from centralized economic planning to more open economic systems. A team of Bulgarian and U.S. researchers have collaborated to study this problem, using a real Bulgarian winery as the focus of their research. System dynamics modeling was selected as a tool to provide better understanding of management issues. A framework for future objective research, and as a pedagogical tool. This system dynamics model generates output on a number of measures. This paper presents initial output from the model, reporting profit ability, risk, and market share measures. These multiple measures create the need for multiple criteria analysis. Three multiple criteria techniques are demonstrated, and their value in the system dynamics simulation modeling process is discussed.

scholarly journals TheαβTCR mechanosensor exploits dynamic ectodomain allostery to optimize its ligand recognition site

2020 ◽  
Vol 117 (35) ◽  
pp. 21336-21345 ◽  
Author(s):  
Wonmuk Hwang ◽  
Robert J. Mallis ◽  
Matthew J. Lang ◽  
Ellis L. Reinherz
Keyword(s):  
T Cell ◽  
Cellular Response ◽  
Complex Molecule ◽  
Immune Surveillance ◽  
Major Histocompatibility Complex Molecule ◽  
Contact Dynamics ◽  
Fine Tuning ◽  
Dynamics Simulation ◽  
Cell Repertoire ◽  
Catch Bond

EachαβT cell receptor (TCR) functions as a mechanosensor. The TCR is comprised of a clonotypic TCRαβligand-binding heterodimer and the noncovalently associated CD3 signaling subunits. When bound by ligand, an antigenic peptide arrayed by a major histocompatibility complex molecule (pMHC), the TCRαβhas a longer bond lifetime under piconewton-level loads. The atomistic mechanism of this “catch bond” behavior is unknown. Here, we perform molecular dynamics simulation of a TCRαβ-pMHC complex and its variants under physiologic loads to identify this mechanism and any attendant TCRαβdomain allostery. The TCRαβ-pMHC interface is dynamically maintained by contacts with a spectrum of occupancies, introducing a level of control via relative motion between Vα and Vβ variable domains containing the pMHC-binding complementarity-determining region (CDR) loops. Without adequate load, the interfacial contacts are unstable, whereas applying sufficient load suppresses Vα-Vβ motion, stabilizing the interface. A second level of control is exerted by Cα and Cβ constant domains, especially Cβ and its protruding FG-loop, that create mismatching interfaces among the four TCRαβdomains and with a pMHC ligand. Applied load enhances fit through deformation of the TCRαβmolecule. Thus, the catch bond involves the entire TCRαβconformation, interdomain motion, and interfacial contact dynamics, collectively. This multilayered architecture of the machinery fosters fine-tuning of cellular response to load and pMHC recognition. Since the germline-derived TCRαβectodomain is structurally conserved, the proposed mechanism can be universally adopted to operate under load during immune surveillance by diverseαβTCRs constituting the T cell repertoire.

Linearization and Model Reduction of Contact Dynamics Simulation

2011 ◽  
Author(s):  
Jianxun Liang ◽  
Ou Ma ◽  
Caishan Liu
Keyword(s):  
Model Reduction ◽  
Multibody Systems ◽  
Reduction Method ◽  
Contact Dynamics ◽  
Dynamics Simulation ◽  
Dynamics Model ◽  
Time Step ◽  
Reduction Techniques ◽  
Proposed Model ◽  
Simulation Time

Finite element methods are widely used for simulations of contact dynamics of flexible multibody systems. Such a simulation is computationally very inefficient because the system’s dimension is usually very large and the simulation time step has to be very small in order to ensure numerical stability. A potential solution to the problem is to apply a model reduction method in the simulation. Although many model reduction techniques have been developed, most of them cannot be readily applied due to the high nonlinearity of the involved contact dynamics model. This paper presents a solution to the problem. The approach is based on a modified Lyapunov balanced truncation method. A numerical example is presented to demonstrate that, by applying the proposed model reduction method, the simulation process can be significantly speeded up while the resulting error caused by the model reduction is still within an acceptable level.

scholarly journals Implementation of A Geometric Constraint Regularization For Multibody System Models

2014 ◽  
Vol 61 (2) ◽  
pp. 365-383 ◽  
Author(s):  
Andreas Müller
Keyword(s):  
Multibody System ◽  
Time Integration ◽  
Simulation Method ◽  
Dynamics Simulation ◽  
Computational Performance ◽  
Kinematic Loops ◽  
Computationally Expensive ◽  
Technical Systems ◽  
Loop Constraints

Abstract Redundant constraints in MBS models severely deteriorate the computational performance and accuracy of any numerical MBS dynamics simulation method. Classically this problem has been addressed by means of numerical decompositions of the constraint Jacobian within numerical integration steps. Such decompositions are computationally expensive. In this paper an elimination method is discussed that only requires a single numerical decomposition within the model preprocessing step rather than during the time integration. It is based on the determination of motion spaces making use of Lie group concepts. The method is able to reduce the set of loop constraints for a large class of technical systems. In any case it always retains a sufficient number of constraints. It is derived for single kinematic loops.

Compliant Force Modelling for Impact Analysis

2004 ◽  
Author(s):  
Yuning Zhang ◽  
Inna Sharf
Keyword(s):  
Contact Force ◽  
Impact Analysis ◽  
Nonlinear Damping ◽  
Simple Expression ◽  
Contact Dynamics ◽  
Damping Coefficient ◽  
Force Model ◽  
Dynamics Modeling ◽  
Contact Phase ◽  
New Research

Contact dynamics modeling remains an intensive area of research with new applications emerging in robotics, biomechanics and multibody dynamics areas. Many formulations for contact dynamics problem have been proposed. The two most prominent categories include the discrete approach, which employs the impulse-momentum relations, and the continuous approach, which requires integration of dynamics equations through the contact phase. A number of methods in the latter category are based on an explicit compliant model for the contact force. One such model was developed by Hunt and Crossley three decades ago who introduced a nonlinear damping term of the form λxnx˙ into the contact force model. In addition to proposing the general form of this damping component of the contact force, Hunt and Crossley derived a simple expression for relating the damping coefficient λ to the coefficient of restitution e. This model gained considerable popularity due to its simplicity and realistic physics. It also spurred new research in the area, specifically on how to evaluate the damping coefficient λ. Subsequently, several authors put forward different approximations for λ, however, without clearly revealing the range of validity of their simplifying assumptions or the accuracy limitations of the resulting contact force models. The authors of this paper analyze the various approaches employed to derive the damping coefficient. We also evaluate and compare performance of the corresponding models by using a meaningful measure for their accuracy. A new derivation is proposed to calculate more precisely the damping coefficient for the nonlinear complaint contact model. Numerical results comparing all models are presented for a sphere dropping on a stationary surface.

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