The Impulsive Action Integral for Rigid-Body Mechanical Systems With Impacts

2012 ◽  
Vol 7 (3) ◽  
Author(s):  
Kerim Yunt
Keyword(s):  
Rigid Body ◽  
Regularity Condition ◽  
Mechanical Systems ◽  
Momentum Balance ◽  
Lagrangian System ◽  
Analytical Mechanics ◽  
Impulsive Action ◽  
Action Integral ◽  
Finite Dimensional ◽  
Stationarity Conditions

There is a missing link in analytical mechanics which shows that general impactive processes are obtained by extremizing some sort of action integral for which momentum and energy are not necessarily conserved. In this work, the conditions under which general nonconserving impacts become a part of an extremizing solution for mechanical systems, which are scleronomic (not explicitly time depending) and holonomic, are investigated. The stationarity conditions of an impulsive action integral are investigated and the main theorem is proven. The general momentum balance and the total energy change over a collisional impact for a mechanical scleronomic holonomic finite-dimensional Lagrangian system are obtained in the form of stationarity conditions of a modified action integral under a regularity condition on the impactive transition sets.

An Efficient Method for a Category of Contact/Impact Problems in Multibody Systems: Tree Topologies

2005 ◽  
Author(s):  
Michael J. Sadowski ◽  
Kurt S. Anderson
Keyword(s):  
Rigid Body ◽  
Dynamic Systems ◽  
Equations Of Motion ◽  
Momentum Balance ◽  
Unilateral Constraints ◽  
Constraint Forces ◽  
Rigid Body Dynamic ◽  
Tree Topologies ◽  
Contact Impact ◽  
Impact Problems

This paper presents an algorithm for the efficient numerical analysis and simulation of a category of contact/impact problems in multi-rigid-body dynamic systems with tree topologies. The algorithm can accommodate the jumps in structure which occur in the equations of motion of general multi-rigid-body systems due to a contact/impact event between bodies, or due to the locking of joints as long as the resulting system is a tree topology. The presented method uses a generalized momentum balance approach to determine the velocity jumps which take place across impacts in such multibody dynamic systems where event constraint forces are of the “non-working” category. The presented method does not suffer from the performance (speed) penalty encountered by most other momentum balance methods given its O(n) overall cost, and exact direct embedded consideration of all the constraints. Due to these characteristics, the presented algorithm offers superior computing performance relative to other methods in situations involving both large n and potentially many unilateral constraints.

Dynamics of Mechanical Systems and the Generalized Free-Body Diagram—Part I: General Formulation

2008 ◽  
Vol 75 (6) ◽  
Author(s):  
József Kövecses
Keyword(s):  
Configuration Space ◽  
Dynamic Equilibrium ◽  
Mechanical Systems ◽  
Constrained Systems ◽  
Dynamic Equations ◽  
Analytical Mechanics ◽  
Constrained Motion ◽  
Equilibrium Equations ◽  
Free Body Diagram ◽  
Free Body

In this paper, we generalize the idea of the free-body diagram for analytical mechanics for representations of mechanical systems in configuration space. The configuration space is characterized locally by an Euclidean tangent space. A key element in this work relies on the relaxation of constraint conditions. A new set of steps is proposed to treat constrained systems. According to this, the analysis should be broken down to two levels: (1) the specification of a transformation via the relaxation of the constraints; this defines a subspace, the space of constrained motion; and (2) specification of conditions on the motion in the space of constrained motion. The formulation and analysis associated with the first step can be seen as the generalization of the idea of the free-body diagram. This formulation is worked out in detail in this paper. The complement of the space of constrained motion is the space of admissible motion. The parametrization of this second subspace is generally the task of the analyst. If the two subspaces are orthogonal then useful decoupling can be achieved in the dynamics formulation. Conditions are developed for this orthogonality. Based on this, the dynamic equations are developed for constrained and admissible motions. These are the dynamic equilibrium equations associated with the generalized free-body diagram. They are valid for a broad range of constrained systems, which can include, for example, bilaterally constrained systems, redundantly constrained systems, unilaterally constrained systems, and nonideal constraint realization.

scholarly journals Simulation of Mechanical Systems With Multiple Frictional Contacts

1992 ◽  
Author(s):  
Yin-Tien Wang ◽  
Vijay Kumar
Keyword(s):  
Energy Conservation ◽  
Rigid Body ◽  
Mechanical Systems ◽  
Rigid Body Dynamics ◽  
New Approach ◽  
Frictional Contacts ◽  
Rigid Objects ◽  
Coulomb’S Law ◽  
Body Dynamics ◽  
Coulomb's Law

Abstract There are several applications in robotics and manufacturing in which nominally rigid objects are subject to multiple frictional contacts with other objects. In most previous work, rigid body models have been used to analyze such systems. There are two fundamental problems with such an approach. Firstly, the use of frictional laws, such as Coulomb’s law, introduce inconsistencies and ambiguities when used in conjunction with the principles of rigid body dynamics. Secondly, hypotheses traditionally used to model frictional impacts can lead to solutions which violate principles of energy conservation. In this paper these problems are explained with the help of examples. A new approach to the simulation of mechanical systems with multiple, frictional constraints is proposed which is free of such difficulties.

Perpetual points in natural mechanical systems with viscous damping: A theorem and a remark

2020 ◽  
pp. 095440622093483
Author(s):  
Fotios Georgiades
Keyword(s):  
Rigid Body ◽  
Mechanical Systems ◽  
Dissipative Systems ◽  
Viscous Damping ◽  
Ongoing Research ◽  
Rigid Body Motions ◽  
Gyroscopic Effects ◽  
Nonlinear Mechanical Systems ◽  
Stiffness And Damping ◽  
Perpetual Points

Perpetual points have been defined recently and their role in the dynamics of mechanical systems is ongoing research. In this article, the nature of perpetual points in natural dissipative mechanical systems with viscous damping, but excepting any externally applied load, is examined. In linear dissipative systems, a theorem and its inverse are proven stating that the perpetual points exist if the stiffness and damping matrices are positive semi-definite and they coincide with the rigid body motions. In nonlinear dissipative natural mechanical systems with viscous damping excepting any external load, the existence of perpetual points that are associated with rigid body motions is shown. Also, an additional type of perpetual points due to the added dissipation is shown that exists, and this type of perpetual points, at least in principle can be used for identification of dissipation in nonlinear mechanical systems. Further work is needed to understand the nature of this additional type of perpetual points. In all the examined examples the perpetual points when they exist, they are not just a few points, but they are forming manifolds in state space, the Perpetual Manifolds, and their geometric characteristics worth further investigation. The findings of this article are applied in all mechanical systems with no gyroscopic effects on their motion, e.g. cars, airplanes, trucks, rockets, robots, etc. and can be used as part of the elementary studies for basic design of all mechanical systems. This work paves the way for new design processes targeting stable rigid body motions eliminating any vibrations in mechanical systems.

scholarly journals Exact Augmented Perpetual Manifolds: Corollary about Different Mechanical Systems with Exactly the Same Motions

2021 ◽  
Vol 2021 ◽  
pp. 1-24
Author(s):  
Fotios Georgiades
Keyword(s):  
Differential Equation ◽  
Rigid Body ◽  
Degrees Of Freedom ◽  
Mechanical Engineering ◽  
Initial Conditions ◽  
Mechanical Systems ◽  
Perfect Agreement ◽  
Ongoing Research ◽  
Rigid Body Motions ◽  
Perpetual Points

Perpetual points have been defined in mathematics recently, and they arise by setting accelerations and jerks equal to zero for nonzero velocities. The significance of perpetual points for the dynamics of mechanical systems is ongoing research. In the linear natural, unforced mechanical systems, the perpetual points form the perpetual manifolds and are associated with rigid body motions. Extending the definition of perpetual manifolds, by considering equal accelerations, in a forced mechanical system, but not necessarily zero, the solutions define the augmented perpetual manifolds. If the displacements are equal and the velocities are equal, the state space defines the exact augmented perpetual manifolds obtained under the conditions of a theorem, and a characteristic differential equation defines the solution. As a continuation of the theorem herein, a corollary proved that different mechanical systems, in the exact augmented perpetual manifolds, have the same general solution, and, in case of the same initial conditions, they have the same motion. The characteristic differential equation leads to a solution defining the augmented perpetual submanifolds and the solution of several types of characteristic differential equations derived. The theory in a few mechanical systems with numerical simulations is verified, and they are in perfect agreement. The theory developed herein is supplementing the already-developed theory of augmented perpetual manifolds, which is of high significance in mathematics, mechanics, and mechanical engineering. In mathematics, the framework for specific solutions of many degrees of freedom nonautonomous systems is defined. In mechanics/physics, the wave-particle motions are of significance. In mechanical engineering, some mechanical system’s rigid body motions without any oscillations are the ultimate ones.

Dunkerley-Mikhlin Estimates of Gravest Frequency of a Vibrating System

1976 ◽  
Vol 43 (2) ◽  
pp. 345-348 ◽  
Author(s):  
J. E. Brock
Keyword(s):  
Rigid Body ◽  
Mechanical Systems ◽  
Vibrating System ◽  
Rigid Body Motions

Estimates are made of the smallest nonzero frequency of vibration of undamped linear mechanical systems having lumped and/or distributed mass and permitting rigid body motions. The approximations are smaller than the correct values but remarkable accuracy may be achieved. The procedures are based upon methods of S. Dunkerley and S. G. Mikhlin.

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