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1.
The impact dynamics of a flexible multibody system is investigated. By using a partition method, the system is divided into two parts, the local impact region and the region away from the impact. The two parts are connected by specific boundary conditions, and the system after partition is equivalent to the original system. According to the rigid-flexible coupling dynamic theory of multibody system, system's rigid-flexible coupling dynamic equations without impact are derived. A local impulse method for establishing the initial impact conditions is proposed. It satisfies the compatibility con- ditions for contact constraints and the actual physical situation of the impact process of flexible bodies. Based on the contact constraint method, system's impact dynamic equa- tions are derived in a differential-algebraic form. The contact/separation criterion and the algorithm are given. An impact dynamic simulation is given. The results show that system's dynamic behaviors including the energy, the deformations, the displacements, and the impact force during the impact process change dramatically. The impact makes great effects on the global dynamics of the system during and after impact. 相似文献
2.
Hierarchical modeling in multibody dynamics 总被引:1,自引:0,他引:1
Summary In this paper a hierarchical approach using several mechanical models with different complexities and modeling depths to
describe a single engineering system is presented. The mechanical models are derived from (but not limited to) multibody dynamics. The computer
power available and improvements in theoretical understanding allow today not only to perform analyses but also to attack
the problem of multimodel synthesis. Therefore, hierarchical modeling is used as a basis to analyze simultaneously models
with different complexities and different excitations, and to optimize the performance with the most appropriate model for
an investigated mechanical effect.
Since only one single engineering system is investigated, its different models must be coupled by shared parameters, and the
different criteria have to be combined with multicriteria optimization algorithms in order to obtain a single feasible design.
An example taken from vehicle dynamics demonstrates the application of the approach.
Received 14 January 1997; accepted for publication 11 September 1997 相似文献
3.
Impact dynamics of multibody systems with frictional contact using joint coordinates and canonical equations of motion 总被引:2,自引:0,他引:2
This paper presents a methodology in computational dynamics for the analysis of mechanical systems that undergo intermittent motion. A canonical form of the equations of motion is derived with a minimal set of coordinates. These equations are used in a procedure for balancing the momenta of the system over the period of impact, calculating the jump in the body momentum, velocity discontinuities and rebounds. The effect of dry friction is discussed and a contact law is proposed. The present formulation is extended to open and closed-loop mechanical systems where the jumps in the constraints' momenta are also solved. The application of this methodology is illustrated with the study of impact of open-loop and closed-loop examples. 相似文献
4.
IntroductionThedynamicequationsofmotionofmultibodysystemswithconstraintsarethefollowingdifferential/algebraicequations,i.e.,E... 相似文献
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Recursive formulations have significantly helped in achieving real-time computations and model-based control laws. The recursive dynamics simulator (ReDySim) is a MATLAB-based recursive solver for dynamic analysis of multibody systems. ReDySim delves upon the decoupled natural orthogonal complement approach originally developed for serial-chain manipulators. In comparison to the commercially available software, dynamic analyses in ReDySim can be performed without creating solid model. The input parameters are specified in MATLAB environment. ReDySim has the capability to incorporate any control algorithm with utmost ease. In this work, the capabilities of ReDySim for solving open-loop and closed-loop systems are shown by examples of robotic gripper, KUKA KR5 industrial manipulator and four-bar mechanism. ReDySim can be downloaded for free from http://www.redysim.co.nr and can be used almost instantly. 相似文献
8.
The prediction accuracy of a simulation method is limited by its theoretical background. This fact can lead to disadvantages regarding the simulation quality when investigating systems of high complexity, e.g. containing components showing a fairly different behavior. To overcome this limitation, co-simulation approaches are used more and more, combining the advantages of different simulation disciplines. That is why we propose a new strategy for the dynamic simulation of cutting processes. The method couples Lagrangian particle methods, such as the smoothed particle hydrodynamics (SPH) method, and multibody system (MBS) tools using co-simulations. We demonstrate the capability of the new approach by providing simulation results of an orthogonal cutting process and comparing them with experimental data. 相似文献
9.
Hardware in the loop simulation (HILS) has been investigated in the field of the multibody dynamics (MBD), which combined the MBD simulation with the actual mechanical system. The fast simulation is necessary for the HILS system in order to require the real time simulation. This paper presents a fast simulation technique using the domain decomposition method with the iteration in the flexible multibody system in which flexible linkage system and electro-hydraulic drive system are coupled with each other. 相似文献
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This paper presents stability and convergence results on a novel approach for imposing holonomic constraints for a class of multibody system dynamics. As opposed to some recent techniques that employ a penalty functional to approximate the Lagrange multipliers, the method herein defines a penalized dynamical system using penalty-augmented kinetic and potential energies, as well as a penalty dependent constraint violation dissipation function. In as much as the governing equations are not typically cocreive, the usual convergence criteria for linear variational boundary value problems are not directly applicable. Still numerical simulations by various researchers suggest that the method is convergent and stable. Despite the fact that the governing equations are nonlinear, the theoretical convergence of the formulation is guaranteed if the multibody system is natural and conservative. Likewise, stability and asymptotic stability results for the penalty formulation are derived from well-known stability results available from classical mechanics. Unfortunately, the convergence theorem is not directly applicable to dissipative multibody systems, such as those encountered in control applications. However, it is shown that the approximate solutions of a typical dissipative system converge to a nearby collection of trajectories that can be characterized precisely using a Lyapunov/Invariance Principle analysis. In short, the approach has many advantages as an alternative to other computational techniques:
Just as importantly, these results for nonlinear systems can be sharpened considerably for linear systems:
相似文献
(1) | Explicit constraint violation bounds can be derived for a large class of nonlinear multibody dynamics problems |
(2) | Sufficient conditions for the Lyapunov stability, and asymptotic stability, of the penalty formulation are derived for a large class of multibody systems |
(3) | The method can be shown to be relatively insensitive to singular configurations by selecting the penalty parameters to dissipate constraint violation energy |
(4) | The Invariance Principle can be employed in the method, in certain cases, to derive the asymptotic behavior of the constraint violation for dissipative multibody systems by identifying constraint violation limit cycles |
(5) | Explicit spectral error estimates can be obtained for substructure synthesis |
(6) | The penalty equations can be shown to be optimal in the sense that the terms represent feedback that minimizes a measure of the constraint violation |
12.
平面柔性多体系统正碰撞动力学建模理论研究 总被引:3,自引:1,他引:2
针对目前柔性多体系统碰撞动力学建模方法存在的不足,对影响碰撞动力学仿真的主要因素如柔性体建模和碰撞初始条件进行分析,建立起基于变约束的柔性体碰撞动力学方程。首先,为了解决子结构法在处理碰撞界面搜索时面临的难题,引入多体系统柔性体有限元描述方法,推导出凸形柔性体接触点间法向位移约束的二阶导数形式。其次,从碰撞引起的接触界面速度不连续机理出发,结合连续介质力学间断面理论,给出碰撞瞬时由物体本身物理性质决定的接触位置处速度跳跃公式。最后对两弹性圆盘低速碰撞问题进行数值仿真。结果表明本文提出的改进方法符合力学基本原理,仿真结果满足收敛性要求。 相似文献
13.
Edward J. Haug 《基于设计的结构力学与机械力学》2018,46(3):347-375
A formulation for modeling and simulation of friction effects in spatial multibody systems is presented. Constraint reaction forces on rigid bodies that are connected by joints that support friction are derived as functions of Lagrange multipliers, using D’Alembert’s principle. Friction forces acting on bodies are calculated as a function of joint geometry, constraint reaction forces that are functions of Lagrange multipliers, and relative velocities at constraint contact points that are determined by system kinematics. Friction forces are implemented in index 0 differential-algebraic equations of motion that are solved numerically using explicit and implicit numerical integration methods. Spatial examples are presented, yielding accurate results and demonstrating that the systems are not stiff, even in the presence of friction and stiction. 相似文献
14.
Liu Yanzhu 《Acta Mechanica Sinica》1988,4(2):165-174
In the present paper the concept of screw in classical mechanics is expressed in matrix form, in order to formulate the dynamical
equations of the multibody systems. The mentioned method can retain the advantages of the screw theory and avoid the shortcomings
of the dual number notation. Combining the screw-matrix method with the tool of graph theory in Roberson/Wittenberg formalism.
We can expand the application of the screw theory to the general case of multibody systems. For a tree system, the dynamical
equations for eachj-th subsystem, composed of all the outboard bodies connected byj-th joint can be formulated without the constraint reaction forces in the joints. For a nontree system, the dynamical equations
of subsystems and the kinematical consistency conditions of the joints can be derived using the loop matrix. The whole process
of calculation is unified in matrix form. A three-segment manipulator is discussed as an example.
This work is supported by the National Natural Science Fund. 相似文献
15.
Based on the deformation theory of elastic beams, the coupling effect between the coupling displacements of a point on the
middle line of beam and large overall motion is presented. The “coupling matrix library” and Jourdain's variation principle
and single direction recursive formulation method are used to establish the general coupling dynamical equations of flexible
multibody system. Two typical examples show the coupling effect between coupling displacements and large overall motion on
the dynamics of flexible multibody system consisting of beams.
The project supported by the National Natural Science Foundation of China (No. 19832040). 相似文献
16.
Xiangqiao Yan 《Acta Mechanica Sinica》2006,22(1):62-67
Advanced fiber reinforced polymer composites have been increasingly applied to various structural components. One of the important
processes to fabricate high performance laminated composites is an autoclave assisted prepreg lay-up. Since the quality of
laminated composites is largely affected by the cure cycle, selection of an appropriate cure cycle for each application is
important and must be optimized. Thus, some fundamental model of the consolidation and cure processes is necessary for selecting
suitable parameters for a specific application. This article is concerned with the ``flow-compaction' model during the autoclave
processing of composite materials. By using a weighted residual method, two-dimensional finite element formulation for the
consolidation process of thick thermosetting composites is presented and the corresponding finite element code is developed.
Numerical examples, including comparison of the present numerical results with one-dimensional and two-dimensional analytical
solutions, are given to illustrate the accuracy and effectiveness of the proposed finite element formulation. In addition,
a consolidation simulation of AS4/3501-6 graphite/epoxy laminate is carried out and compared with the experimental results
available in the literature.
The project supported by the National Natural Science Foundation of China (10272037)
The English text was polished by Yunming Chen. 相似文献
17.
In the analysis of multibody dynamics, we are often required to deal with singularity problems where the constraint Jacobian matrix may become less than full rank at some instantancous configurations. This creates numerical instability which will affect the performance of the mechanical system. A modification procedure of the constraints when they vanish or become linearly dependent is proposed to regularize the dynamics of the system. A distinction between the asymptotic stability due to the representation of the constraints (at the velocity and acceleration level), and the one due to the singularity is discussed in full in this paper. It is shown that Baumgarte technique could be extended to accommodate the representation of the constraints in the neighborhood of singularity. A two link planar manipulator undergoing large motion and passing through a singular configuration is used to illustrate the proposed stability technique. 相似文献
18.
Yabo Guan Farhang Pourboghrat Frdric Barlat 《International Journal of Plasticity》2006,22(12):2366-2393
Finite element modeling of tube hydroforming requires information about the anisotropy of the extruded aluminum tube. Unlike sheet metals, the complex geometry of extruded tubes makes it difficult, except in extrusion direction, to directly measure material properties. Therefore, polycrystalline models provide a good alternative for calculating the anisotropy of the tube in all directions and under various loading conditions. Using a rate-independent single crystal yield surface and rigid plasticity, a Taylor-type polycrystalline model was developed and implemented into ABAQUS/Explicit finite element (FE) code using VUMAT. The constitutive model was then used to calculate the crystallographic texture evolution during the hydroforming of an extruded aluminum tube. Initial crystallographic texture measured using orientation imaging microscopy (OIM) and uniaxial tensile test data obtained along the extrusion direction were input to this FEA model. In order to efficiently and practically simulate the tube hydroforming process using the polycrystalline model, sensitivity to the number of grain orientation, total simulation time, and number of finite elements were studied. Predicted results agreed very well with experimentally measured strain obtained from tube hydroforming process. 相似文献
19.
L. Pei J.F. Molinari Mark O. Robbins 《Journal of the mechanics and physics of solids》2005,53(11):2385-2409
This paper presents a finite element calculation of frictionless, non-adhesive, contact between a rigid plane and an elasto-plastic solid with a self-affine fractal surface. The calculations are conducted within an explicit dynamic Lagrangian framework. The elasto-plastic response of the material is described by a J2 isotropic plasticity law. Parametric studies are used to establish general relations between contact properties and key material parameters. In all cases, the contact area A rises linearly with the applied load. The rate of increase grows as the yield stress σy decreases, scaling as a power of σy over the range typical of real materials. Results for A from different plasticity laws and surface morphologies can all be described by a simple scaling formula. Plasticity produces qualitative changes in the distributions of local pressures in the contact and of the size of connected contact regions. The probability of large local pressures is decreased, while large clusters become more likely. Loading-unloading cycles are considered and the total plastic work is found to be nearly constant over a wide range of yield stresses. 相似文献
20.
Continuous contact force models for impact analysis in multibody systems 总被引:14,自引:0,他引:14
One method for predicting the impact response of a multibody system is based on the assumption that the impacting bodies undergo local deformations and the contact forces are continuous. In a continuous analysis, the integration of the system equations of motion is carried out during the period of contact; therefore, a model for evaluating the contact forces is required. In this paper, two such contact force models are presented, both Hertzian in nature and based upon the direct-central impact of two solid particles.At low impact velocities, the energy dissipation during impact can be represented by material damping. A model is constructed based on the general trend of the Hertz contact law in conjuction with a hysteresis damping function. The unknown parameters are determined in terms of a given coefficient of restitution and the impact velocity. When local plasticity effects are the dominant factor accounting for the dissipation of energy at high impact velocities, a Hertzian contact force model with permanent indentation is constructed. Utilizing energy and momentum considerations, the unknown parameters in the model are again evaluated. The two particle models are generalized to an impact analysis between two bodies of a multibody system. 相似文献