Interactions between rigid-body and flexible-body motions in maneuvering spacecraft

1990 ◽  
Vol 13 (1) ◽  
pp. 73-81 ◽  
Author(s):  
Larry M. Silverberg ◽  
Sungtae Park
Keyword(s):  
Rigid Body ◽  
Flexible Body ◽  
Maneuvering Spacecraft

Impacted Object Kinematic

2016 ◽  
Vol 827 ◽  
pp. 11-14
Author(s):  
Lubomír Pešík ◽  
Ondřej Kohl
Keyword(s):  
Rigid Body ◽  
Fundamental Problem ◽  
The Other ◽  
Flexible Body ◽  
Main Task ◽  
Dynamic Parameters ◽  
Acceleration Sensor ◽  
Acceleration Sensors ◽  
Time Courses

By destructive car tests are used acceleration sensors for the determination of a time courses of kinematic variables. The main task is to determine the velocity of measured points of selected objects. The fundamental problem in the solution of this problem is the fact that the acceleration sensor simultaneously record two mechanical movements. One of them is the movement of the object as a rigid body and the other is damped vibration of the object itself as a flexible body which is characterized by its dynamic parameters.

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.

Rigid and Flexible Body Modeling for a Triaxial Shaker Control System

1995 ◽  
Author(s):  
John J. Dougherty ◽  
Hossny El-Sherief ◽  
Thanh Nguyen
Keyword(s):  
Computer Simulation ◽  
Control System ◽  
Rigid Body ◽  
Test Data ◽  
Flexible Body

Abstract The modeling of a triaxial shaker system is discussed. The shaker system has eight inputs and six outputs. The models have been implemented in a computer simulation; both the rigid body and flexible body effects have been simulated. Results from the simulation have been compared to test data.

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.

Input Shaping Vibration Control for Nonminimum Phase Systems

2010 ◽  
Author(s):  
Jiping Tang ◽  
Gordon Parker
Keyword(s):  
Rigid Body ◽  
Body Motion ◽  
Flexible Body ◽  
Input Shaping ◽  
Minimum Phase ◽  
Residual Vibration ◽  
Nonminimum Phase ◽  
Nonminimum Phase Systems ◽  
System Input ◽  
Phase Systems

Many systems exist that contain coupled rigid body and flexible body dynamics. Rigid body repositioning of these systems can be problematic due to unwanted residual vibration of the flexible body degrees of freedom. Input shaping is a method for generating system commands creating desired rigid body motion where the flexible body motion being quiescent at the end of the maneuver. Either operator-in-the-loop or batch commands are convolved with a carefully designed input shaping filter to produce the eventual system input. Systems with minimum phase zeros are easily accommodated using input shaping filters designed for the system without zeros, and then using a secondary pole-zero cancellation filter. This approach cannot be practically applied to nonminimum phase systems since the resulting system input may become unbounded. This paper considers input shaping methods for generating residual vibration-free input time histories for non-minimum phase, oscillatory systems using bounded inputs. An example is presented where the system is an undamped oscillator with a single right plant zero.

Comparative Simulation Research between Rigid Body and Flexible Body for Double-Gear Parallel Driving Systems

2012 ◽  
Vol 157-158 ◽  
pp. 214-219
Author(s):  
Qi Wang ◽  
Hua Deng ◽  
Zhen Xu
Keyword(s):  
Angular Velocity ◽  
Load Balancing ◽  
Rigid Body ◽  
Dynamic Simulation ◽  
Step Function ◽  
Transmission System ◽  
Flexible Body ◽  
Simulation Research ◽  
Driving System ◽  
Forging Manipulator

In this paper , on the platform of Adams ,the model neutral files(MNF) of the double-gear parallel driving system for the forging manipulator were created by utilizing the FEA technology，and its virtual prototype of rigid body and flexible body were established.Through defined same motion and load by step function，dynamic simulation was analyzed.Comparing the results such as angular velocity and gear meshing force of each other，studies suggest that: to treat the transmission system as rigid body can fully meet the research requirement for load balancing.

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.

A Virtual Body and Joint for Constrained Flexible Multibody Dynamics: A Generalized Recursive Formulation

1999 ◽  
Author(s):  
D. S. Bae ◽  
J. M. Han ◽  
J. H. Choi
Keyword(s):  
Rigid Body ◽  
Reference Frames ◽  
Equations Of Motion ◽  
Recursive Formula ◽  
General Purpose ◽  
Rigid Body Dynamics ◽  
Flexible Body ◽  
Relative Coordinate ◽  
Body Dynamics ◽  
Flexible Body Dynamics

Abstract This research extends the generalized recursive formulas for the rigid body dynamics to the flexible body dynamics using the backward difference formula (BDF) and the relative generalized coordinate. When a new force or joint module is added to a general purpose program in the relative coordinate formulations, the modules for the rigid bodies are not reusable for the flexible bodies. Since the flexible body dynamics handles more degrees of freedom than the rigid body dynamics does, implementation of the flexible dynamics module is generally complicated and prone to coding mistakes. In order to overcome the implementation difficulties, a virtual rigid body is introduced at every joint and force reference frames. A virtual flexible body joint is introduced between two body reference frames of the virtual and original bodies. Since the multibody system dynamics are formulated by highly nonlinear algebraic and differential equations and there are many different types of joints, a tremendous amount of computer implementation is required to develop a general purpose dynamic analysis program using the relative coordinate formulation. The implementation burden is relieved by the generalized recursive formulas. The notationally compact velocity transformation method is used to derive the equations of motion in the joint space. The terms in the equations of motion which are related to the transformation matrix are classified into several categories each of which recursive formula is developed. Whenever one category of the terms is encountered, the corresponding recursive formula is invoked. Since computation time in a relative coordinate formulation is approximately proportional to the number of the relative coordinates, computational overhead due to the additional virtual bodies and joints is minor. Meanwhile, implementation convenience is dramatically improved.

Development of a New Multi-Flexible Body Dynamics (MFBD) Platform: A Relative Nodal Displacement Method for Finite Element Analysis

2005 ◽  
Author(s):  
Dae Sung Bae
Keyword(s):  
Rigid Body ◽  
Reference Frame ◽  
Large Deformations ◽  
Shape Function ◽  
Rigid Body Motion ◽  
Body Motion ◽  
Flexible Body ◽  
Element Analysis ◽  
Body Dynamics ◽  
Flexible Body Dynamics

Recently the analysis of multi flexible body dynamics has been a hot issue in the area of the computational dynamics research. There have been two main streams of research. One is the extension of conventional FEA theory for the multi flexible body systems, using either the total Lagrangian or updated Lagrangian method. The other is the extension of the multi body dynamics theory. The latter is the topic of this research. One essential requirement of a shape function in FEA theory is ability to represent the rigid body motion. This research proposes to use the moving reference frame to represent the rigid body motion. Therefore, the shape function does not need to have ability to represent the rigid body motion. The moving reference frame covers the rigid body. Since the nodal displacements are measured relative to its adjacent moving nodal reference frame, they are still small for a truss structure undergoing large deformations if the element sizes are small. As a consequence, many element formulations developed under small deformation assumptions are still valid for structures undergoing large deformations, which significantly simplifies the equations of equilibrium. Several numerical examples are analyzed to demonstrate the efficiency and validity of the proposed method.

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