Simulation of Submerged Slack Tethers and Their Interaction With the Environment

2004 ◽  
Author(s):  
J. A. Carretero ◽  
B. J. Buckham
Keyword(s):  
Dynamic Model ◽  
Three Dimensional ◽  
Separation Distance ◽  
Contact Forces ◽  
Contact Dynamics ◽  
Dynamics Model ◽  
Model Fidelity ◽  
Tethered Systems ◽  
And Training ◽  
Profile Change

Tethered systems, underwater or otherwise, are nowadays used for very diverse tasks. Due to the complexity of such systems, it is necessary to simulate them for design, operation and training purposes. This paper deals with an approach to simulation of tethered systems, in particular underwater remotely operated vehicles (ROVs), by incorporating contact forces acting between the tether and the environment into the dynamic model of the tether. This will ensure model fidelity when the tethered system is operated in a dense environment. In this paper, methods used to compute contact forces are described. In the calculation of contact dynamics, the distance between the tethered system and the environment is of utmost interest. Algorithms to determine the separation distance between the tether and the environment are discussed in the scope of this work. These algorithms are then incorporated into an existing dynamics model of the ROV tether. Finally, this paper concludes with a simple numerical example where a tether is moved in a concave environment. The distance between the tether and the environment is computed as the tether’s location and three-dimensional profile change with time.

Simulation of Nanomanipulation Using Compliance-Based Contact Dynamics Modeling Technique

2007 ◽  
Author(s):  
Ou Ma ◽  
Xiumin Diao ◽  
Mingjun Zhang
Keyword(s):  
Contact Forces ◽  
Contact Dynamics ◽  
Modeling Technique ◽  
Published Data ◽  
Dynamics Modeling ◽  
Dynamics Model ◽  
Friction Forces ◽  
Nano Scale ◽  
Model Fidelity ◽  
Macro Scale

This paper describes dynamics modeling and simulation of AFM-based manipulation of a nano-scale object using the compliance-based contact dynamics modeling technique (also referred to as the penalty method). Such a modeling technique has been well developed and widely applied in macro-scale applications. Its applicability to nano-scale cases is, however, relatively new and thus, requires more investigation. The dynamics model developed in the paper includes the Van der Waals forces, electrostatic forces, contact forces (for modeling repulsion), and friction forces with consideration of contact geometry, stiffness, and friction properties of all the physically interacting objects. The model can simulate the dynamic behavior of interactions between nano-scale objects and its environment. For demonstration, the dynamic simulation results of an AFM-based manipulation process are presented. To provide confidence of the model fidelity, a simulation example which matches some published data is presented.

scholarly journals Multibody Dynamic Analysis of a Wind Turbine Drivetrain in Consideration of the Shaft Bending Effect and a Variable Gear Mesh Including Eccentricity and Nacelle Movement

2021 ◽  
Vol 8 ◽  
Author(s):  
Yonghui Park ◽  
Hyunchul Park ◽  
Zhe Ma ◽  
Jikun You ◽  
Wei Shi
Keyword(s):  
Wind Turbine ◽  
Dynamic Model ◽  
Gear Tooth ◽  
Translational Motion ◽  
Three Dimensional ◽  
Contact Forces ◽  
Dynamic Responses ◽  
Renewable Energy Resources ◽  
Gear Mesh ◽  
Direct Numerical Integration

Due to the energy crisis and global warming issues, the wind energy is becoming one of the most attractive renewable energy resources in the world. The drivetrains in the wind turbine tend to fail more prematurely than those in any other applications. Gearbox is the subsystem that causes the most downtime for the wind turbines. In the previous research, only the torsional flexibility of the shaft was considered in the drivetrain model. However, because the shaft is longer than other parts, and components connected by the shaft affect each other via shaft bending, the flexibility of the shaft cannot be ignored. In this study, a spherical joint that consists of three rotational springs was used to define the shaft bending. This shaft bending will affect the drivetrain rotation, the translational motion and the gear mesh contact force. Additionally, the eccentricity and the nacelle movement are analyzed due to the coupled motion. In this paper, a mathematical model of the drivetrain is proposed, which is a three-dimensional dynamic model that includes flexible bearings, a gear mesh model, shaft flexibility, eccentricity, and nacelle movement. The equation of motion of the drivetrain is derived using Lagrange's equation. The governing equation is solved numerically via direct numerical integration. The dynamic responses of the system and contact forces between the gear tooth in the time and frequency domains are calculated numerically. The study shows that this dynamic model of the drivetrain will be highly useful for subsequent studies on the wind turbine condition monitoring.

scholarly journals Using a 4K three-dimensional exoscope system (Vitom 3D) for mastoid surgery during the coronavirus disease 2019 pandemic

2021 ◽  
pp. 1-3
Author(s):  
M Ally ◽  
P Kullar ◽  
G Mochloulis ◽  
A Vijendren
Keyword(s):  
Residual Disease ◽  
Elective Surgery ◽  
Three Dimensional ◽  
Depth Of Field ◽  
High Definition ◽  
Microscopic Surgery ◽  
Lateral Skull Base ◽  
Mastoid Surgery ◽  
And Training

Abstract Objective Microscopic surgery is currently considered the ‘gold standard’ for middle-ear, mastoid and lateral skull base surgery. The coronavirus disease 2019 pandemic has made microscopic surgery more challenging to perform. This work aimed to demonstrate the feasibility of the Vitom 3D system, which integrates a high-definition (4K) view and three-dimensional technology for ear surgery, within the context of the pandemic. Method Combined approach tympanoplasty and ossiculoplasty were performed for cholesteatoma using the Vitom 3D system exclusively. Results Surgery was performed successfully. The patient made a good recovery, with no evidence of residual disease at follow up. The compact system has excellent depth of field, magnification and colour. It enables ergonomic work, improved work flow, and is ideal for teaching and training. Conclusion The Vitom 3D system is considered a revolutionary alternative to microscope-assisted surgery, particularly in light of coronavirus disease 2019. It allows delivery of safe otological surgery, which may aid in continuing elective surgery.

Multibody Dynamic Model of Web Guiding System With Moving Web

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Lei Yu ◽  
Zhihua Zhao ◽  
Gexue Ren
Keyword(s):  
Dynamic Model ◽  
Lateral Displacement ◽  
Dynamical Behavior ◽  
Contact Forces ◽  
Lagrangian Formulation ◽  
Pi Control ◽  
Control Law ◽  
Reference Surface ◽  
Multibody Dynamic ◽  
Guiding System

In this paper, a multibody dynamic model is established to simulate the dynamics and control of moving web with its guiding system, where the term moving web is used to describe thin materials, which are manufactured and processed in a continuous, flexible strip form. In contrast with available researches based on Eulerian description and beam assumption, webs are described by Lagrangian formulation with the absolute nodal coordinate formulation (ANCF) plate element, which is based on Kirchhoff’s assumptions that material normals to the original reference surface remain straight and normal to the deformed reference surface, and the nonlinear elasticity theory that accounts for large displacement, large rotation, and large deformation. The rollers and guiding mechanism are modeled as rigid bodies. The distributed frictional contact forces between rollers and web are considered by Hertz contact model and are evaluated by Gauss quadrature. The proportional integral (PI) control law for web guiding is also embedded in the multibody model. A series of simulations on a typical web-guide system is carried out using the multibody dynamics approach for web guiding system presented in this study. System dynamical information, for example, lateral displacement, stress distribution, and driving moment for web guiding, are obtained from simulations. Parameter sensitivity analysis illustrates the effect of influence variables and effectiveness of the PI control law for lateral movement control of web that are verified under different gains. The present Lagrangian formulation of web element, i.e., ANCF element, is not only capable of describing the large movement and deformation but also easily adapted to capture the distributed contact forces between web and rollers. The dynamical behavior of the moving web can be accurately described by a small number of ANCF thin plate elements. Simulations carried out in this paper show that the present approach is an effective method to assess the design of web guiding system with easily available desktop computers.

A Nonlinear Rail Vehicle Dynamics Computer Program SAMS/Rail: Part 1—Theory and Formulations

2009 ◽  
Author(s):  
Khaled E. Zaazaa ◽  
Brian Whitten ◽  
Brian Marquis ◽  
Erik Curtis ◽  
Magdy El-Sibaie ◽  
...  
Keyword(s):  
High Speed ◽  
Dynamic Performance ◽  
Three Dimensional ◽  
Contact Element ◽  
Contact Forces ◽  
Simulation Code ◽  
Vehicle Performance ◽  
Normal Contact ◽  
Advantages And Disadvantages ◽  
High Speed Trains

Accurate prediction of railroad vehicle performance requires detailed formulations of wheel-rail contact models. In the past, most dynamic simulation tools used an offline wheel-rail contact element based on look-up tables that are used by the main simulation solver. Nowadays, the use of an online nonlinear three-dimensional wheel-rail contact element is necessary in order to accurately predict the dynamic performance of high speed trains. Recently, the Federal Railroad Administration, Office of Research and Development has sponsored a project to develop a general multibody simulation code that uses an online nonlinear three-dimensional wheel-rail contact element to predict the contact forces between wheel and rail. In this paper, several nonlinear wheel-rail contact formulations are presented, each using the online three-dimensional approach. The methods presented are divided into two contact approaches. In the first Constraint Approach, the wheel is assumed to remain in contact with the rail. In this approach, the normal contact forces are determined by using the technique of Lagrange multipliers. In the second Elastic Approach, wheel/rail separation and penetration are allowed, and the normal contact forces are determined by using Hertz’s Theory. The advantages and disadvantages of each method are presented in this paper. In addition, this paper discusses future developments and improvements for the multibody system code. Some of these improvements are currently being implemented by the University of Illinois at Chicago (UIC). In the accompanying “Part 2” and “Part 3” to this paper, numerical examples are presented in order to demonstrate the results obtained from this research.

scholarly journals A Collision Dynamics Model of a Multi-Level Train

2006 ◽  
Author(s):  
Michelle Priante ◽  
David Tyrell ◽  
Benjamin Perlman
Keyword(s):  
Three Dimensional ◽  
Design Parameters ◽  
Collision Dynamics ◽  
Dynamics Model ◽  
Single Level ◽  
High Speeds ◽  
Front End ◽  
Multi Level ◽  
Low Speeds ◽  
Vertical Accelerations

In train collisions, multi-level rail passenger vehicles can deform in modes that are different from the behavior of single level cars. The deformation in single level cars usually occurs at the front end during a collision. In one particular incident, a cab car buckled laterally near the back end of the car. The buckling of the car caused both lateral and vertical accelerations, which led to unanticipated injuries to the occupants. A three-dimensional collision dynamics model of a multi-level passenger train has been developed to study the influence of multi-level design parameters and possible train configuration variations on the reactions of a multi-level car in a collision. This model can run multiple scenarios of a train collision. This paper investigates two hypotheses that could account for the unexpected mode of deformation. The first hypothesis emphasizes the non-symmetric resistance of a multi-level car to longitudinal loads. The structure is irregular since the stairwells, supports for tanks, and draglinks vary from side to side and end to end. Since one side is less strong, that side can crush more during a collision. The second hypothesis uses characteristics that are nearly symmetric on each side. Initial imperfections in train geometry induce eccentric loads on the vehicles. For both hypotheses, the deformation modes depend on the closing speed of the collision. When the characteristics are non-symmetric, and the load is applied in-line, two modes of deformation are seen. At low speeds, the couplers crush, and the cars saw-tooth buckle. At high speeds, the front end of the cab car crushes, and the cars remain in-line. If an offset load is applied, the back stairwell of the first coach car crushes unevenly, and the cars saw-tooth buckle. For the second hypothesis, the characteristics are symmetric. At low speeds, the couplers crush, and the cars remain in-line. At higher speeds, the front end crushes, and the cars remain in-line. If an offset load is applied to a car with symmetric characteristics, the cars will saw-tooth buckle.

Intergrowth polytypoids as modulated structures: a superspace description of the Sr n (Nb,Ti) n O3n + 2 compound series

2001 ◽  
Vol 57 (4) ◽  
pp. 471-484 ◽  
Author(s):  
L. Elcoro ◽  
J. M. Perez-Mato ◽  
R. L. Withers
Keyword(s):  
Dimensional Space ◽  
Three Dimensional ◽  
Separation Distance ◽  
Space Group ◽  
Space Groups ◽  
Cell Parameters ◽  
Average Structure ◽  
Layer Stacking ◽  
Compound Series ◽  
Three Dimensional Space

A new, unified superspace approach to the structural characterization of the perovskite-related Sr n (Nb,Ti) n O3n + 2 compound series, strontium niobium/titanium oxide, is presented. To a first approximation, the structure of any member of this compound series can be described in terms of the stacking of (110)-bounded perovskite slabs, the number of atomic layers in a single perovskite slab varying systematically with composition. The various composition-dependent layer-stacking sequences can be interpreted in terms of the structural modulation of a common underlying average structure. The average interlayer separation distance is directly related to the average structure periodicity along the layer stacking direction, while an inherent modulation thereof is produced by the presence of different types of layers (particularly vacant layers) along this stacking direction. The fundamental atomic modulation is therefore occupational and can be described by means of crenel (step-like) functions which define occupational atomic domains in the superspace, similarly to what occurs for quasicrystals. While in a standard crystallographic approach, one must describe each structure (in particular the space group and cell parameters) separately for each composition, the proposed superspace model is essentially common to the whole compound series. The superspace symmetry group is unique, while the primary modulation wavevector and the width of some occupation domains vary linearly with composition. For each rational composition, the corresponding conventional three-dimensional space group can be derived from the common superspace group. The resultant possible three-dimensional space groups are in agreement with all the symmetries reported for members of the series. The symmetry-breaking phase transitions with temperature observed in many compounds can be explained in terms of a change in superspace group, again in common for the whole compound series. Inclusion of the incommensurate phases, present in many compounds of the series, lifts the analysis into a five-dimensional superspace. The various four-dimensional superspace groups reported for this incommensurate phase at different compositions are shown to be predictable from a proposed five-dimensional superspace group apparently common to the whole compound series. A comparison with the scarce number of refined structures in this system and the homologous (Nb,Ca)6Ti6O20 compound demonstrates the suitability of the proposed formalism.

scholarly journals Dynamic response analysis for multi-degrees-of-freedom parallel mechanisms with various types of three-dimensional clearance joints

2021 ◽  
Vol 18 (3) ◽  
pp. 172988142110177
Author(s):  
Jia Yonghao ◽  
Chen Xiulong
Keyword(s):  
Dynamic Response ◽  
Multibody Systems ◽  
Parallel Mechanism ◽  
Three Dimensional ◽  
Response Analysis ◽  
Parallel Mechanisms ◽  
Dynamics Model ◽  
Clearance Joints ◽  
Clearance Joint ◽  
Spatial Parallel Mechanism

For spatial multibody systems, the dynamic equations of multibody systems with compound clearance joints have a high level of nonlinearity. The coupling between different types of clearance joints may lead to abundant dynamic behavior. At present, the dynamic response analysis of the spatial parallel mechanism considering the three-dimensional (3D) compound clearance joint has not been reported. This work proposes a modeling method to investigate the influence of the 3D compound clearance joint on the dynamics characteristics of the spatial parallel mechanism. For this purpose, 3D kinematic models of spherical clearance joint and revolute joint with radial and axial clearances are derived. Contact force is described as normal contact and tangential friction and later introduced into the nonlinear dynamics model, which is established by the Lagrange multiplier technique and Jacobian of constraint matrix. The influences of compound clearance joint and initial misalignment of bearing axes on the system are analyzed. Furthermore, validation of dynamics model is evaluated by ADAMS and Newton–Euler method. This work provides an essential theoretical basis for studying the influences of 3D clearance joints on dynamic responses and nonlinear behavior of parallel mechanisms.

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