Numerical Simulation of a Floater in a Broken-Ice Field: Part II — Comparative Study of Physics Engines

2012 ◽  
Author(s):  
Ivan Metrikin ◽  
Andrey Borzov ◽  
Raed Lubbad ◽  
Sveinung Løset
Keyword(s):  
Numerical Simulation ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Contact Forces ◽  
Limited Attention ◽  
Detection Accuracy ◽  
Documentation Quality ◽  
Physics Engine ◽  
Broken Ice ◽  
Ice Floes

Numerical simulation of a floater in ice-infested waters can be performed using a physics engine. This software can dynamically detect contacts and calculate the contact forces in a three-dimensional space among various irregularly shaped bodies, e.g. the floater and the ice floes. Previously, various physics engines were successfully applied to simulate floaters in ice. However, limited attention was paid to the criteria for selecting a particular engine for the simulation of a floater in broken-ice conditions. In this paper, four publicly available physics engines (AgX Multiphysics, Open Dynamics Engine, PhysX and Vortex) are compared in terms of integration performance and contact detection accuracy. These two aspects are assumed to be the most important for simulating a floater in broken ice. Furthermore, the access to code, documentation quality and the level of technical support are evaluated and discussed. The main conclusion is that each physics engine has its own strength and weaknesses and none of the engines is perfect. These strength and weaknesses are revealed and discussed in the paper.

Numerical Simulation of a Floater in a Broken-Ice Field: Part I — Model Description

2012 ◽  
Author(s):  
Ivan Metrikin ◽  
Wenjun Lu ◽  
Raed Lubbad ◽  
Sveinung Løset ◽  
Marat Kashafutdinov
Keyword(s):  
Dimensional Space ◽  
Rigid Bodies ◽  
Interaction Process ◽  
Contact Forces ◽  
Model Description ◽  
Physics Engine ◽  
Broken Ice ◽  
Ice Floes ◽  
Rigid Multibody ◽  
Ice Model

This paper presents a novel concept for simulating the ice-floater interaction process. The concept is based on a mathematical model which emphasizes the station-keeping scenario, i.e. when the relative velocity between the floater and the ice is comparatively small. This means that the model is geared towards such applications as dynamic positioning in ice and ice management. The concept is based on coupling the rigid multibody simulations with the Finite Element Method (FEM) simulations. The rigid multibody simulation is implemented through a physics engine which is used to model the dynamic behaviour of rigid bodies which undergo large translational and rotational displacements (the floater and the ice floes). The FEM is used to simulate the material behaviour of the ice and the fluid, i.e. the ice breaking and the hydrodynamics of the ice floes. Within this framework, the physics engine is responsible for dynamically detecting the contacts between the objects in the calculation domain, and the FEM software is responsible for calculating the contact forces. The concept is applicable for simulations in a three-dimensional space (3D). The model described in this paper is divided into two main parts: the mathematical ice model and the mathematical floater model. The mathematical ice model allows modelling both intact level ice and discontinuous ice within a single framework. However, the primary focus of this paper is placed on modelling the broken ice conditions. A floater is modelled as a rigid body with 6 degrees of freedom, i.e. no deformations of the floater’s hull are allowed. Nevertheless, the hydrodynamics of the floater and the ice is considered within the outlined model. The presented approach allows implementing realistic, high fidelity 3D simulations of the ice-fluid-structure interaction process.

Robust contact force estimation for robot manipulators in three-dimensional space

2006 ◽  
Vol 220 (9) ◽  
pp. 1317-1327 ◽  
Author(s):  
J Jung ◽  
J Lee ◽  
K Huh
Keyword(s):  
Contact Force ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Contact Forces ◽  
Robust Estimator ◽  
Force Sensors ◽  
Force Estimation ◽  
Estimation Algorithms

Information on contact forces in robot manipulators is indispensable for fast and accurate force control. Instead of expensive force sensors, estimation algorithms for contact forces have been widely developed. However, it is not easy to obtain the accurate values due to uncertainties. In this article, a new robust estimator is proposed to estimate three-dimensional contact forces acting on a three-link robot manipulator. The estimator is based on the extended Kalman filter (EKF) structure combined with a Lyapunov-based adaptation law for estimating the contact force. In contrast to the conventional EKF the new estimator is designed such that it is robust to the deterministic uncertainties such as the modelling error and the sensing bias. The performance of the proposed estimator is evaluated through simulations of a robot manipulator and demonstrates robustness in estimating the contact force. The estimation results show that it can be potentially used to replace the expensive force sensors in robot applications.

Quaternion-Based Control of Acrobatic Quadrotor With Trajectory Following

2020 ◽  
Author(s):  
Haowen Liu ◽  
Bingen Yang
Keyword(s):  
Numerical Simulation ◽  
Mathematical Model ◽  
Control Method ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Path Following ◽  
Differential Flatness ◽  
Reference Trajectory ◽  
Control Approach ◽  
Trajectory Following

Abstract For an unmanned aerial vehicle (UAV), its navigation in terrains can be quite challenging. To reach the destination within the required time, the maneuver of the quadrotor must behave aggressively. During this aggressive maneuvering, the quadrotor can experience singularities in the yaw-direction rotation. Thus, it is essentially important to develop a mathematical model and control method that can avoid singularities while enabling such an aggressive maneuver. In our previous effort, we demonstrated a vertical loop aggressive maneuver performed by a quadrotor UAV, which utilizes the controlled loop path following (CLPF) method. As found in this work, conventional modeling and tracking control method may not be good enough if specific requirements, such as fast coasting speed and sharp turns, are imposed. The numerical simulation by singularity-free modeling and the CLPF method enables a quadrotor to be operated in aggressive maneuverability with features like automatic flipping and precise trajectory following. The current research extends the maneuverability of a quadrotor by using a different and more capable control approach. More complex trajectories are used to test this new control method. In this paper, a quadrotor is used to demonstrate the capability of the proposed control method in delivering an aggressive and singularity-free maneuver. A quaternion-based mathematical model of the quadrotor is derived to avoid the singularities of rotation during the aggressive maneuvers. At the same time, a new control method, namely the full quaternion differential flatness (FQDF) method, is developed for quadrotors to combat the requirement of a fast maneuver in three-dimensional space. The FQDF method, which makes use of full quaternion modeling and differential flatness, enables the quadrotor to react to the reference trajectory timely and to exhibit aggressive rotation without any singularity. Also, the singularities resulting from the heading direction can be resolved by a new algorithm. The FQDF method is compared with the reference literature’s methods and is tested in different trajectories from the ones in the previous studies. The numerical simulation demonstrates the aggressive maneuverability and computational efficiency of the proposed control method.

Optimal Contact Force Distribution for Multi-Limbed Robots

2005 ◽  
Vol 128 (3) ◽  
pp. 566-573 ◽  
Author(s):  
Dennis W. Hong ◽  
Raymond J. Cipra
Keyword(s):  
Contact Force ◽  
Dimensional Space ◽  
Contact Point ◽  
Three Dimensional ◽  
Optimal Solution ◽  
Solution Space ◽  
Contact Forces ◽  
Force Distribution ◽  
New Strategy ◽  
Contact Force Distribution

One of the inherent problems of multi-limbed mobile robotic systems is the problem of multi-contact force distribution; the contact forces and moments at the feet required to support it and those required by its tasks are indeterminate. A new strategy for choosing an optimal solution for the contact force distribution of multi-limbed robots with three feet in contact with the environment in three-dimensional space is presented. The incremental strategy of opening up the friction cones is aided by using the “force space graph” which indicates where the solution is positioned in the solution space to give insight into the quality of the chosen solution and to provide robustness against disturbances. The “margin against slip with contact point priority” approach is also presented which finds an optimal solution with different priorities given to each foot contact point. Examples are presented to illustrate certain aspects of the method and ideas for other optimization criteria are discussed.

Visualization of the Contact Force Solution Space for Multi-Limbed Robots

2005 ◽  
Vol 128 (1) ◽  
pp. 295-302 ◽  
Author(s):  
Dennis W. Hong ◽  
Raymond J. Cipra
Keyword(s):  
Contact Force ◽  
Dimensional Space ◽  
Contact Point ◽  
Three Dimensional ◽  
Solution Space ◽  
Entire Solution ◽  
Contact Forces ◽  
Static Equilibrium ◽  
Equilibrium Equations ◽  
Force Components

A new analytical method for determining, describing, and visualizing the solution space for the contact force distribution of multi-limbed robots with three feet in contact with the environment in three-dimensional space is presented. The foot contact forces are first resolved into strategically defined foot contact force components to decouple them, and then the static equilibrium equations are applied. Using the friction cone equation at each foot contact point, the problem is then transformed into a geometrical one. Using geometric properties of the friction cones and by simple manipulation of their conic sections, the entire solution space which satisfies the static equilibrium and friction constraints at each contact point can be found. Two representation schemes, the “force space graph” and the “solution volume representation,” are developed for describing and visualizing the solution space which gives an intuitive visual map of how well the solution space is formed for the given conditions of the system.

scholarly journals Numerical Simulation of Laser-Induced Bubble and Metal-Free Water Cannon

2021 ◽  
Vol 25 (1) ◽  
pp. 50-55
Author(s):  
Tomomasa Ohkubo ◽  
Ei-ichi Matsunaga ◽  
Yuji Sato ◽  
◽  
Keyword(s):  
Numerical Simulation ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Free Water ◽  
Qualitative Behavior ◽  
Simulation Code ◽  
Metal Free ◽  
Laser Propulsion ◽  
Three Dimensional Space ◽  
Metallic Target

Laser propulsion is expected to be the next-generation propulsion mechanism. In particular, metal-free water cannon realizes propulsion without a metallic target. In this study, we develop a numerical simulation code using the C-CUP (CIP and Combined, Unified Procedure) method to simulate a laser-induced bubble and a metal-free water cannon. We successfully reproduced the qualitative behavior of spouting water in a three-dimensional space when the metal-free water cannon is irradiated by laser. Furthermore, the calculated results for the time development of displacement of the metal-free water cannon agree qualitatively with the experimental results. We simulate the behavior of the laser-induced bubble and discovered that the bubble inhales the water once spouted out, and the target moves backward owing to the pressure difference generated by the bubble expansion as well as collapsing and inhaling actions. Furthermore, the laser-induced bubble repeats the expansion and collapse, and the target moves forward while it oscillates.

Numerical Simulation of Particle Motion in a Jig Separator

2007 ◽  
Author(s):  
Kuniomi Asakura ◽  
Minoru Nagao ◽  
Midori Mizuno ◽  
Shusaku Harada
Keyword(s):  
Numerical Simulation ◽  
Particle Motion ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Type Equation ◽  
Added Mass ◽  
Contact Forces ◽  
Three Dimensional Flow ◽  
Drag Forces ◽  
Different Diameters

The motion of particles in a jig separator is investigated numerically. The motion of particles is expressed by the BBO-type equation. Three-dimensional flow is simulated by the SIMPLE algorithm. The contact forces among particles are calculated by a discrete element method (DEM) extended to particles of different sizes. The results of simulation show that particles with the same settling velocities and different diameters can also be separated. To analyze the motion of particles in the jig, an equation for the response time of a particle that included added mass, gravity, and drag forces is derived.

scholarly journals Numerical Simulation of Ship Oil Spill in Arctic Icy Waters

2020 ◽  
Vol 10 (4) ◽  
pp. 1394
Author(s):  
Wei Li ◽  
Xiao Liang ◽  
Jianguo Lin ◽  
Ping Guo ◽  
Qiang Ma ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Oil Spill ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Oil Film ◽  
Six Degrees Of Freedom ◽  
Oil Dispersant ◽  
Surface Method ◽  
Water Conditions ◽  
Ice Floes

This paper presents a three-dimensional numerical simulation model of an oil spill for application in emergency treatment methods under icy water conditions. The combined effects of wind, wave, current and ice implemented in our model correspond to Arctic Ocean conditions. A discrete element method combined with an overset grid was adopted to track the trajectory movements of oil film with medium-density ice floes and simulate the flow field of moving ice of large displacement in six degrees of freedom (6DOF). The probability of oil spill area extensions were estimated by a response surface method (RSM). Results showed reduced risk of pollution in icy water conditions and greater drift action of oil film. Accordingly, the spraying location and quantity of oil-dispersant could be rapidly specified.

Three Dimensional structure and organization of diploid chromosomes by optical section microscopy

1987 ◽  
Vol 45 ◽  
pp. 633-635
Author(s):  
David A. Agard ◽  
Yasushi Hiraoka ◽  
John W. Sedat
Keyword(s):  
Dimensional Space ◽  
Three Dimensional ◽  
Developmental State ◽  
Mitotic Cell ◽  
Biological Properties ◽  
Dimensional Structure ◽  
Specific Gene ◽  
Three Dimensional Structure ◽  
Complementary Techniques ◽  
Dynamic Structures

In an effort to understand the complex relationship between structure and biological function within the nucleus, we have embarked on a program to examine the three-dimensional structure and organization of Drosophila melanogaster embryonic chromosomes. Our overall goal is to determine how DNA and proteins are organized into complex and highly dynamic structures (chromosomes) and how these chromosomes are arranged in three dimensional space within the cell nucleus. Futher, we hope to be able to correlate structual data with such fundamental biological properties as stage in the mitotic cell cycle, developmental state and transcription at specific gene loci.Towards this end, we have been developing methodologies for the three-dimensional analysis of non-crystalline biological specimens using optical and electron microscopy. We feel that the combination of these two complementary techniques allows an unprecedented look at the structural organization of cellular components ranging in size from 100A to 100 microns.

Diffraction contrast of dislocations in icosahedral quasicrystals

1990 ◽  
Vol 48 (4) ◽  
pp. 454-455
Author(s):  
K. Urban ◽  
Z. Zhang ◽  
M. Wollgarten ◽  
D. Gratias
Keyword(s):  
Dimensional Space ◽  
Three Dimensional ◽  
Complete Characterization ◽  
Extinction Condition ◽  
Burgers Vector ◽  
Diffraction Contrast ◽  
Lattice Geometry ◽  
Reference Space ◽  
Icosahedral Quasicrystals ◽  
The One

Recently dislocations have been observed by electron microscopy in the icosahedral quasicrystalline (IQ) phase of Al65Cu20Fe15. These dislocations exhibit diffraction contrast similar to that known for dislocations in conventional crystals. The contrast becomes extinct for certain diffraction vectors g. In the following the basis of electron diffraction contrast of dislocations in the IQ phase is described. Taking account of the six-dimensional nature of the Burgers vector a “strong” and a “weak” extinction condition are found.Dislocations in quasicrystals canot be described on the basis of simple shear or insertion of a lattice plane only. In order to achieve a complete characterization of these dislocations it is advantageous to make use of the one to one correspondence of the lattice geometry in our three-dimensional space (R3) and that in the six-dimensional reference space (R6) where full periodicity is recovered . Therefore the contrast extinction condition has to be written as gpbp + gobo = 0 (1). The diffraction vector g and the Burgers vector b decompose into two vectors gp, bp and go, bo in, respectively, the physical and the orthogonal three-dimensional sub-spaces of R6.

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