Numerical Simulation of Multibody Systems With Time Dependant Structure

1993 ◽  
Author(s):  
Pierre Joli ◽  
Madeleine Pascal ◽  
René Gibert
Keyword(s):  
Numerical Simulation ◽  
Multibody Systems ◽  
Computational Algorithm ◽  
Rigid Bodies ◽  
Three Dimensions ◽  
Integration Step ◽  
General Systems ◽  
Articulated Systems ◽  
Jump Velocity ◽  
Assembly Tasks

Abstract Current dynamic simulation programs are able to calculate the continuous motions of articulated systems or more general systems of rigid bodies in the absence of contact between members of the system or between the system and its environment. Some are able to simulate the effects of isolated contacts and impacts but none are able to simulate the motion with unrestricted multiple concurrent contacts. However, in special robotic programs such as robots performing assembly tasks or walking, it would be very interesting to simulate appropriate commands before implementing them on the robots. This paper develops intrinsic problems of collision to produce an efficient computational algorithm. This algorithm handles the detection of collision in three dimensions, the reduction of the integration step in order to avoid interpenetration between the bodies before impact, the jump velocity caused by a new collision and indicator magnitudes which determine the addition or deletion of constraints.

Developing a Numerical Simulation Software for 3D Multibody Systems Based on a Unified Computational Modeling Technique

2009 ◽  
Author(s):  
Shahram Shokouhfar ◽  
Sayyid Mahdi Khorsandijou
Keyword(s):  
Numerical Simulation ◽  
Multibody Systems ◽  
Dynamic Models ◽  
Initial Conditions ◽  
Rigid Bodies ◽  
Simulation Software ◽  
Computational Technique ◽  
Main Task ◽  
Algebraic Equations ◽  
Time Step

This article represents the features and capabilities of a newly developed application namely MASS (Mechanisms Analysis and Simulation Software) and the formulation and techniques therein. MASS is a general C++ application program whose main task is to construct and solve the governing algebraic differential motion equations of 3D multibody systems automatically in matrix forms complying with the computational algorithms required for numerical simulation. Newton-Raphson and SVD methods have been used for kinematical assembling and producing consistent initial conditions. Adaptive time-step Runge-Kutta-Fehlberg numerical integration methods might be used for forward dynamics problems. The governing equations perfectly describe the kinematics and dynamics of multibody systems within which 3D kinematical joints and collisions between rigid bodies might be taken into consideration. The unified computational technique for mathematical modeling of kinematical joints is the most important concept on top of which MASS has been implemented. It has occurred due to the existence of thirteen basic kinematical constraint equations. Each kinematical joint might be defined by a set of algebraic equations being selected from the mentioned basic equations. The unified dynamic models for collisions and impulsive loads have been also achieved using the mentioned technique. Simulation results obtained from MASS have been compared with that of the corresponding software of Working Model ver. 6 and a discussion about the coincidences and differences has been exposed.

Dynamics of Multibody Systems With Known Configuration Changes

1991 ◽  
Vol 58 (1) ◽  
pp. 215-221 ◽  
Author(s):  
J. J. McPhee ◽  
R. N. Dubey
Keyword(s):  
Numerical Simulation ◽  
Computer Program ◽  
Multibody Systems ◽  
Equations Of Motion ◽  
Rigid Bodies ◽  
Rotation Vector ◽  
Dynamic Effects ◽  
Physical Systems ◽  
Dynamics Of Multibody Systems ◽  
Configuration Changes

The equations of motion are derived for a system with inertial properties that are varying in time as a result of known relative motions between the rigid bodies comprising the system. This vector-dyadic formulation has been encoded into a computer program, making use of the conformal rotation vector for the representation of rotations. The numerical simulation of two different physical systems is presented in order to illustrate the dynamic effects of the changing inertial properties, and the usefulness of the encoded formulation for modeling these effects.

Shock and Sine Response of Rigid Structures on Nonlinear Mounts

1991 ◽  
Author(s):  
R. Dufour ◽  
J. Der Hagopian ◽  
M. Pompei ◽  
C. Garnier
Keyword(s):  
Numerical Simulation ◽  
Power Spectrum ◽  
Dynamic Behavior ◽  
Dynamic Environment ◽  
Rigid Bodies ◽  
Nonlinear Parameters ◽  
Large Power ◽  
Passive Damper ◽  
Highly Nonlinear

Abstract The dynamic environment of embarqued structures such as radars or more generally electronic equipments consists of impacts, sine and large power spectrum excitations. Under these real conditions and amongst different kinds of isolation, the passive damper with nonlinear parameters can provide good performances. This paper is concerned with the dynamic behavior of rigid bodies on highly nonlinear mounts. The numerical simulation and the experiment carried out, show that the load-deflection behavior of the dampers have to be slightly ajusted with respect to impact vibrations to obtain a well designed behavior.

Numerical simulation of seismic waves in porous media components

2021 ◽  
Vol 9 (1) ◽  
pp. 4-30
Author(s):  
M. Azeredo ◽  
◽  
V. Priimenko ◽  
Keyword(s):  
Numerical Simulation ◽  
Porous Medium ◽  
High Frequency ◽  
Seismic Waves ◽  
Computational Algorithm ◽  
Low Frequency ◽  
Physical Parameters ◽  
Mathematical Algorithm ◽  
Biot Equations ◽  
Attenuation And Dispersion

This work presents a mathematical algorithm for modeling the propagation of poroelastic waves. We have shown how the classical Biot equations can be put into Ursin’s form in a plane-layered 3D porous medium. Using this form, we have derived explicit for- mulas that can be used as the basis of an efficient computational algorithm. To validate the algorithm, numerical simulations were performed using both the poroelastic and equivalent elastic models. The results obtained confirmed the proposed algorithm’s reliability, identify- ing the main wave events in both low-frequency and high-frequency regimes in the reservoir and laboratory scales, respectively. We have also illustrated the influence of some physical parameters on the attenuation and dispersion of the slow wave.

Hydraulic Characteristics of the New Type Bulb Turbine With Micro-Head

2013 ◽  
Author(s):  
Lingyu Li ◽  
Yuan Zheng ◽  
Daqing Zhou ◽  
Zihao Mi
Keyword(s):  
Numerical Simulation ◽  
Cfd Simulation ◽  
Guide Vane ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Three Dimensions ◽  
Guide Vanes ◽  
Runner Blade ◽  
Cfd Method ◽  
Bulb Turbine

The head of low-head hydropower stations is generally higher than 2.5m in the world, while micro-head hydropower resources which head is less than 2.5m are also very rich. In the paper, three-dimensional CFD method has been used to simulate flow passage of the micro-head bulb turbine. The design head and unit flow of the turbine was 1m and 3m3/s respectively. With the numerical simulation, the bulb turbine is researched by analyzing external characteristics of the bulb turbine, flow distribution before the runner, pressure distribution of the runner blade surface, and flow distribution of the outlet conduit under three different schemes. The turbine in second scheme was test by manufactured into a physical model. According to the results of numerical simulation and model test, bulb turbine with no guide vane in second scheme has simpler structure, lower cost, and better flow capacity than first scheme, which has traditional multi-guide vanes. Meanwhile, efficiency of second scheme has just little decrease. The results of three dimensions CFD simulation and test results agree well in second scheme, and higher efficiency is up to 77% which has a wider area with the head of 1m. The curved supports in third scheme are combined guide vanes to the fixed supports based on 2nd scheme. By the water circulations flowing along the curved supports which improve energy transformation ability of the runner, the efficiency of the turbine in third scheme is up to 82.6%. Third scheme, which has simpler structure and best performance, is appropriate for the development and utilization of micro-head hydropower resources in plains and oceans.

scholarly journals Global ionospheric models in three dimensions from GPS measurements: Numerical simulation

2000 ◽  
Vol 39 (1) ◽  
pp. 21-27
Author(s):  
Amali Meza ◽  
Claudio Brunini ◽  
Alfred Kleusberg
Keyword(s):  
Numerical Simulation ◽  
Three Dimensions ◽  
Gps Measurements ◽  
Atmospheric Research ◽  
Ionospheric Models

Gracias a las observaciones GPS en doble - frecuencia de receptores distribuidos uniformemente sobre la superficie terrestre es posible hacer un análisis de la ionosfera como puede verse en los trabajos de Mannucci A. et al., 1993; Beutler G., 1995 y Brunini C. et al., 1997 entre otros. Este análisis consiste básicamente en el modelado de las variaciones del contenido total de electrones en función de 2 coordenadas que bien pueden ser la latitud y la longitud en un sistema sol fijo. Estos modelos asumen que la ionosfera puede representarse por una capa esférica de espesor despreciable, situada a una determinada altura (entre los 300 y 400 km), donde se concentra la totalidad de los electrones libres. Para modelar la distribución espacial de la concentración total de electrones en la delgada capa, se han utilizado series de Taylor en dos dimensiones o armónicos esféricos entre otros. En abril de 1995, gracias al lanzamiento de la misión GPS-MET, se pudo hacer realidad la obtención de observaciones GPS desde un receptor en el espacio. GPS-MET es un experimento dirigido por el UCAR (University Corporation of Atmospheric Research), cuyo objetivo es el sondeo de la atmósfera terrestre mediante observaciones GPS colectadas por un receptor de alto rendimiento situado a bordo del satélite MicroLab I (MLI). Este satélite describe una órbita circular a 730 km de altura (LEO=Low Elevation Orbit), con una inclinación de 60°. Las observaciones colectadas por este receptor están disponibles vía ftp en una base de datos administrada por el UCAR. Este satélite de baja altura con receptor GPS de doble frecuencia nos brinda la posibilidad de contar con señales GPS que atraviesan la ionosfera a diferentes alturas. Este trabajo no apunta a discutir un modelo ionosférico en sí mismo, sino más bien a analizar las posibilidades de utilizar mediciones GPS para extraer información sobre el comportamiento vertical de la densidad electrónica, basadas en un modelo medio y global. En este trabajo emplearemos simulaciones numéricas con el objetivo de analizar si las observaciones del Microlab I son suficientemente sensibles a las variaciones en altura de la ionosfera. Afortunadamente y pese a la limitación en la geometría del problema, ya que sólo contamos con un satélite de órbita fija, se concluye que el receptor espacial nos brinda información fundamental para el modelado en altura de la densidad de electrones.

Utilizing the Effort/Motion Approach in the Simulation of Interconnected Rigid Body Systems

1997 ◽  
Author(s):  
N. Duke Perreira
Keyword(s):  
Numerical Simulation ◽  
Rigid Body ◽  
Multibody Systems ◽  
Invariant Form ◽  
Second Law ◽  
Orthogonal Projections ◽  
Gauge Invariant ◽  
Motion Equations ◽  
Newton's Second Law ◽  
Constraint Surface

Abstract The effort/motion approach has been developed for use in designing, simulating and controlling multibody systems. Some aspects of each of these topics are discussed here. In the effort/motion formulation two sets of equations based on the orthogonal projections of a dimensional gauge invariant form of Newton’s Second Law occur. The projections are onto the normal and tangent directions of a dimensional gauge invariant constraint surface. The paper shows how these equations are obtained for a particular linkage with redundant effort and motion actuation. Two alternative Runga-Kutta based approaches for numerical simulation of the effort/motion equations are developed and applied in simulating the motion and determining the effort generated in the example linkage under various conditions. Oscillation about equilibrium positions, solutions with constant motion and with constant effort are given as examples of the approach.

A Semi-Discrete Approach for the Numerical Simulation of Freestanding Blocks

2016 ◽  
pp. 416-439
Author(s):  
Fernando Peña
Keyword(s):  
Differential Equation ◽  
Numerical Simulation ◽  
Numerical Modeling ◽  
Discrete Model ◽  
Mathematical Formulation ◽  
Equation Of Motion ◽  
Rigid Bodies ◽  
The Body ◽  
Discrete Approach ◽  
Rocking Motion

This chapter addresses the numerical modeling of freestanding rigid blocks by means of a semi-discrete approach. The pure rocking motion of single rigid bodies can be easily studied with the differential equation of motion, which can be solved by numerical integration or by linearization. However, when we deal with sliding and jumping motion of rigid bodies, the mathematical formulation becomes quite complex. In order to overcome this complexity, a Semi-Discrete Model (SMD) is proposed for the study of rocking motion of rigid bodies, in which the rigid body is considered as a mass element supported by springs and dashpots, in the spirit of deformable contacts between rigid blocks. The SMD can detect separation and sliding of the body; however, initial base contacts do not change, keeping a relative continuity between the body and its base. Extensive numerical simulations have been carried out in order to validate the proposed approach.

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