Chrono: A Parallel Physics Library for Rigid-Body, Flexible-Body, and Fluid Dynamics

2013 ◽  
Author(s):  
Toby Heyn ◽  
Hammad Mazhar ◽  
Arman Pazouki ◽  
Daniel Melanz ◽  
Andrew Seidl ◽  
...  
Keyword(s):  
Parallel Computing ◽  
Rigid Body ◽  
Degrees Of Freedom ◽  
Large Scale ◽  
Gpu Computing ◽  
Rigid Bodies ◽  
Flexible Body ◽  
Simulation Engine ◽  
Physics Simulation ◽  
Flexible Body Dynamics

This contribution discusses a multi-physics simulation engine, called Chrono, that relies heavily on parallel computing. Chrono aims at simulating the dynamics of systems containing rigid bodies, flexible (compliant) bodies, and fluid-rigid body interaction. To this end, it relies on five modules: equation formulation (modeling), equation solution (simulation), collision detection support, domain decomposition for parallel computing, and post-processing analysis with emphasis on high quality rendering/visualization. For each component we point out how parallel CPU and/or GPU computing have been leveraged to allow for the simulation of applications with millions of degrees of freedom such as rover dynamics on granular terrain, fluid-structure interaction problems, or large-scale flexible body dynamics with friction and contact for applications in polymer analysis.

Contact-space resolution model for a physically consistent view of simultaneous collisions in articulated-body systems: theory and experimental results

2020 ◽  
Vol 39 (10-11) ◽  
pp. 1239-1258
Author(s):  
Shameek Ganguly ◽  
Oussama Khatib
Keyword(s):  
System Dynamics ◽  
Rigid Body ◽  
Degrees Of Freedom ◽  
Null Space ◽  
Rigid Bodies ◽  
Computationally Efficient ◽  
Space Resolution ◽  
Resolution Model ◽  
Space Dynamics ◽  
Contact Space

Multi-surface interactions occur frequently in articulated-rigid-body systems such as robotic manipulators. Real-time prediction of contact-interaction forces is challenging for systems with many degrees of freedom (DOFs) because joint and contact constraints must be enforced simultaneously. While several contact models exist for systems of free rigid bodies, fewer models are available for articulated-body systems. In this paper, we extend the method of Ruspini and Khatib and develop the contact-space resolution (CSR) model by applying the operational space theory of robot manipulation. Through a proper choice of contact-space coordinates, the projected dynamics of the system in the contact space is obtained. We show that the projection into the dynamically consistent null space preserves linear and angular momentum in a subspace of the system dynamics complementary to the joint and contact constraints. Furthermore, we illustrate that a simultaneous collision event between two articulated bodies can be resolved as an equivalent simultaneous collision between two non-articulated rigid bodies through the projected contact-space dynamics. Solving this reduced-dimensional problem is computationally efficient, but determining its accuracy requires physical experimentation. To gain further insights into the theoretical model predictions, we devised an apparatus consisting of colliding 1-, 2-, and 3-DOF articulated bodies where joint motion is recorded with high precision. Results validate that the CSR model accurately predicts the post-collision system state. Moreover, for the first time, we show that the projection of system dynamics into the mutually complementary contact space and null space is a physically verifiable phenomenon in articulated-rigid-body systems.

Joint reactions in rigid or flexible body mechanisms with redundant constraints

2012 ◽  
Vol 60 (3) ◽  
pp. 617-626 ◽  
Author(s):  
M. Wojtyra ◽  
J. Frączek
Keyword(s):  
Rigid Body ◽  
Degrees Of Freedom ◽  
Flexible Body ◽  
Flexible Bodies ◽  
Redundant Constraints ◽  
Constraint Equations ◽  
Body Model ◽  
Rigid Body Model ◽  
Flexible Models

Abstract The problem of joint reactions indeterminacy, in engineering simulations of rigid body mechanisms is most often caused by redundant constraints which are defined as constraints that can be removed without changing the kinematics of the system. In order to find a unique set of all joint reactions in an overconstrained system, it is necessary to reject the assumption that all bodies are rigid. Flexible bodies introduce additional degrees of freedom to the mechanism, which usually makes the constraint equations independent. Quite often only selected bodies are modelled as the flexible ones, whereas the other remain rigid. In this contribution it is shown that taking into account flexibility of selected mechanism bodies does not guarantee that unique joint reactions can be found. Problems typical for redundant constraints existence are encountered in partially flexible models, which are not overconstrained. A case study of a redundantly constrained spatial mechanism is presented. Different approaches to the mechanism modelling, ranging from a purely rigid body model to a fully flexible one, are investigated and the obtained results are compared and discussed.

Instantaneous Properties of Multi-Degrees-of-Freedom Motions—Line Trajectories

1987 ◽  
Vol 109 (1) ◽  
pp. 116-124 ◽  
Author(s):  
Ashitava Ghosal ◽  
Bernard Roth
Keyword(s):  
Rigid Body ◽  
General Framework ◽  
Degrees Of Freedom ◽  
Rigid Bodies ◽  
Two Degrees Of Freedom ◽  
Global Properties ◽  
New Concepts ◽  
Line Trajectory

A general framework is presented for the study of the properties of trajectories generated by lines embedded in rigid bodies undergoing multi-degrees-of-freedom motions. Several new concepts, such as a line’s angular and linear velocities and accelerations, are introduced and used to (1) characterize the differences between line trajectories generated by different mechanisms; (2) distinguish trajectories generated by different lines in the same rigid body; (3) distinguish properties at different positions in the same trajectory. Line trajectories are classified according to the number of degrees of freedom of the motion, and local and global properties are discussed. These techniques are illustrated in an example of a line trajectory generated by a two-degrees-of-freedom manipulator.

scholarly journals Rigid Body Interaction for Large-Scale Real-Time Water Simulation

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Timo Kellomäki
Keyword(s):  
Rigid Body ◽  
Real Time ◽  
Traditional Method ◽  
Large Scale ◽  
Rigid Bodies ◽  
Floating Bodies ◽  
Water Effects ◽  
Flow Through ◽  
Single Method ◽  
Water Simulation

Simulating large amounts of water in real time is often achieved using heightfield methods. Allowing the water to interact with rigid bodies is essential for applications such as games, but traditional heightfield interaction methods concentrate on water-to-body effects by letting water flow through the bodies. We instead take an approach where the bodies block water. Our earlier method is improved in several ways, taking steps toward a single method to create both water-to-body and body-to-water effects. The new method is also visually compared to a traditional method by Thürey et al. A drawback of our method is that it has some grid aliasing artifacts that appear especially when the method is used for floating bodies. However, our method is demonstrated to work together with the Thürey method, which allows us to get the best of both worlds to simulate both floating and blocking bodies in a single scene. The method runs in real time for large areas of water even with a very limited GPU budget.

Rigid body refinements in GSAS/EXPGUI

2011 ◽  
Vol 26 (S1) ◽  
pp. S13-S21 ◽  
Author(s):  
Charles H. Lake ◽  
Brian H. Toby
Keyword(s):  
Rigid Body ◽  
Software Package ◽  
Degrees Of Freedom ◽  
Rigid Bodies ◽  
Atomic Motion ◽  
Bond Lengths

Rigid bodies provide a way to simplify the model used in a crystallographic refinement by removing parameters that describe degrees of freedom that are unlikely to change based on chemical experience. The GSAS software package provides a powerful implementation of rigid bodies that allows for refinement of classes of bond lengths, grouping of bodies to further reduce parameterization and where atomic motion can be described from group displacement parameters (TLS) representation. However, use of rigid bodies in GSAS is complex to learn and time-consuming to perform. This paper describes how the rigid body definition process has been simplified and extended through implementation in the EXPGUI interface to GSAS.

scholarly journals CHRONO: a parallel multi-physics library for rigid-body, flexible-body, and fluid dynamics

2013 ◽  
Vol 4 (1) ◽  
pp. 49-64 ◽  
Author(s):  
H. Mazhar ◽  
T. Heyn ◽  
A. Pazouki ◽  
D. Melanz ◽  
A. Seidl ◽  
...  
Keyword(s):  
Parallel Computing ◽  
Large Scale ◽  
Flexible Structures ◽  
Particulate Flows ◽  
Loosely Coupled ◽  
Processing Power ◽  
Select Group ◽  
Physics Simulation ◽  
Physics Modeling ◽  
Many Core

Abstract. The last decade witnessed a manifest shift in the microprocessor industry towards chip designs that promote parallel computing. Until recently the privilege of a select group of large research centers, Teraflop computing is becoming a commodity owing to inexpensive GPU cards and multi to many-core x86 processors. This paradigm shift towards large scale parallel computing has been leveraged in CHRONO, a freely available C++ multi-physics simulation package. CHRONO is made up of a collection of loosely coupled components that facilitate different aspects of multi-physics modeling, simulation, and visualization. This contribution provides an overview of CHRONO::Engine, CHRONO::Flex, CHRONO::Fluid, and CHRONO::Render, which are modules that can capitalize on the processing power of hundreds of parallel processors. Problems that can be tackled in CHRONO include but are not limited to granular material dynamics, tangled large flexible structures with self contact, particulate flows, and tracked vehicle mobility. The paper presents an overview of each of these modules and illustrates through several examples the potential of this multi-physics library.

A Virtual Body and Joint for Constrained Flexible Multibody Dynamics

1999 ◽  
Author(s):  
D. S. Bae ◽  
J. M. Han ◽  
J. H. Choi
Keyword(s):  
Rigid Body ◽  
Multibody Dynamics ◽  
Reference Frames ◽  
Flexible Multibody Dynamics ◽  
General Purpose ◽  
Rigid Body Dynamics ◽  
Flexible Body ◽  
Body Dynamics ◽  
Flexible Multibody ◽  
Flexible Body Dynamics

Abstract A convenient implementation method for constrained flexible multibody dynamics is presented by introducing virtual rigid body and joint. The general purpose program for rigid and flexible multibody dynamics consists of three major parts of a set of inertia modules, a set of force modules, and a set of joint modules. Whenever a new force or joint module is added to the general purpose program, the modules for the rigid body dynamics are not reusable for the flexible body dynamics. Consequently, the corresponding modules for the flexible body dynamics must be formulated and programmed again. Since the flexible body dynamics handles more degrees of freedom than the rigid body dynamics does, implementation of the module is generally complicated and prone to coding mistakes. In order to overcome these difficulties, a virtual rigid body is introduced at every joint and force reference frames. New kinematic admissibility conditions are imposed on two body reference frames of the virtual and original bodies by introducing a virtual flexible body joint. There are some computational overheads due to the additional bodies and joints. However, since computation time is mainly depended on the frequency of flexible body dynamics, the computational overhead of the presented method could not be a critical problem, while implementation convenience is dramatically improved.

Topology Synthesis of a 1-Translational and 3-Rotational Parallel Manipulator With an Articulated Traveling Plate

2015 ◽  
Vol 7 (3) ◽  
Author(s):  
Tao Sun ◽  
Yimin Song ◽  
Hao Gao ◽  
Yang Qi
Keyword(s):  
Rigid Body ◽  
Parallel Manipulator ◽  
Degrees Of Freedom ◽  
Large Scale ◽  
Open Loop ◽  
Synthesis Procedure ◽  
The Relationship

Driven by the increasing demands of the aircraft assemblage for the pose-adjustment equipment in the large-scale component docking, this paper carries out the topology synthesis of a 1-translational and 3-rotational (1T3R) four degrees of freedom (DoF) parallel manipulator with an articulated traveling plate. First, the articulated traveling plate is defined as that includes more than one rigid body articulated by one or more kinematic joints. Then, the relationship among the DoFs of the parallel manipulator and the articulated traveling plate and the number of the in-parts are proposed. According to the agreement of the arrangement way between the open-loop limbs and the in-parts, the topology synthesis procedure of the 1T3R 4-DoF parallel manipulator with an articulated traveling plate is proposed. Finally, their topology structures are obtained by discussing those of four types in terms of 1D-H, 1D-V type with opposite layout and 1D-H, 1D-V type with adjacent layout, in which the topology structures exist only for 1D-H and 1D-V type with opposite layout

Dynamic Analysis and Parametric Excitation of a Multi-Span Beam Structure Coupled With a Sequence of Moving Rigid Bodies

2018 ◽  
Author(s):  
Hao Gao ◽  
Bingen Yang
Keyword(s):  
Rigid Body ◽  
Dynamic Analysis ◽  
Parametric Resonance ◽  
Degrees Of Freedom ◽  
Coupled System ◽  
Rigid Bodies ◽  
Time Varying ◽  
Beam Structure ◽  
Assumed Mode Method ◽  
Mode Method

Dynamic analysis of a multi-span beam structure carrying moving rigid bodies is essentially important in various engineering applications. With many rigid bodies having different speeds and varying inter-distances, number of degrees of freedom of the coupled beam-moving rigid body system is time-varying and the beam-rigid body interaction is thus complicated. Developed in this paper is a method of extended solution domain (ESD) that resolves the issue of time-varying number of degrees and delivers a consistent mathematical model for the coupled system. The governing equation of the coupled system is derived with generalized assumed mode method through use of exact eigenfunctions and solved via numerical integration. Numerical simulation shows the accuracy and efficiency of the proposed method. Moreover, a preliminary study on parametric resonance on a beam structure with 10 rigid bodies provides guidance for future development of conditions on parametric resonance induced by moving rigid bodies, which can be useful for operation of certain coupled structure systems.

scholarly journals Multi-Camera-Based Universal Measurement Method for 6-DOF of Rigid Bodies in World Coordinate System

Sensors ◽  
2020 ◽  
Vol 20 (19) ◽  
pp. 5547 ◽  
Author(s):  
Zuoxi Zhao ◽  
Yuchang Zhu ◽  
Yuanhong Li ◽  
Zhi Qiu ◽  
Yangfan Luo ◽  
...  
Keyword(s):  
Rigid Body ◽  
Coordinate System ◽  
High Speed ◽  
Measurement Method ◽  
Degrees Of Freedom ◽  
Rigid Bodies ◽  
Least Square ◽  
Matrix Analysis ◽  
Average Error ◽  
World Coordinate System

The measurement of six-degrees-of-freedom (6-DOF) of rigid bodies plays an important role in many industries, but it often requires the use of professional instruments and software, or has limitations on the shape of measured objects. In this paper, a 6-DOF measurement method based on multi-camera is proposed, which is accomplished using at least two ordinary cameras and is made available for most morphological rigid bodies. First, multi-camera calibration based on Zhang Zhengyou’s calibration method is introduced. In addition to the intrinsic and extrinsic parameters of cameras, the pose relationship between the camera coordinate system and the world coordinate system can also be obtained. Secondly, the 6-DOF calculation model of proposed method is gradually analyzed by the matrix analysis method. With the help of control points arranged on the rigid body, the 6-DOF of the rigid body can be calculated by the least square method. Finally, the Phantom 3D high-speed photogrammetry system (P3HPS) with an accuracy of 0.1 mm/m was used to evaluate this method. The experiment results show that the average error of the rotational degrees of freedom (DOF) measurement is less than 1.1 deg, and the average error of the movement DOF measurement is less than 0.007 m. In conclusion, the accuracy of the proposed method meets the requirements.

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