Motion Design by Interference Analysis of Multibody Systems

Author(s):  
Deming Wang ◽  
David Beale

Abstract A new computer aided analysis method for frictionless interference impact problems between two bodies in a constrained multibody system is presented in the paper, which can be used to perform interference analysis and motion design of multibody systems. A virtual contact joint concept is used to detect interference between two bodies and calculate the jump in the body momenta, velocity discontinuities, rebounds and system motion after the interference impact analysis. The interference surfaces can be any geometric element, such as point, line segment, are and circle described by the joint coordinates of the virtual contact joint. The method are very useful to predict and determine the interference time, the types and positions of two impact surfaces. System motion after the interference can be controlled by changing some dynamic parameters in the multibody system.

1999 ◽  
Vol 121 (1) ◽  
pp. 128-135 ◽  
Author(s):  
D. Wang ◽  
C. Conti ◽  
D. Beale

A new computer aided analysis method for frictionless impact problems due to interference between two bodies in a constrained multibody system is presented in this paper. A virtual contact joint concept is used to detect interference between two bodies and calculate the jump in the body momenta, velocity discontinuities and rebounds. The interference surfaces can be described by the joint coordinates of the virtual contact joint, which are very useful for determining the impact time, the types and positions of two impact surfaces and impact initial conditions when an interference happens between two bodies.


Author(s):  
W Favre ◽  
S Scavarda

In this paper a bond graph representation of the point contact joint between two bodies with any outline curves and in planar motion is proposed. The body geometry and frames are described, the kinematic constraints attached to the point contact joint are identified and the bond graph junction structure is deduced. The example of an elliptic cam-follower is used to illustrate the bond graph representation. In particular this shows the need for the simulation to add strong damping and very stiff elements to the system.


Author(s):  
Tulga Ersal ◽  
Hosam K. Fathy ◽  
Jeffrey L. Stein

Previous work by the authors developed a junction-inactivity-based structural simplification technique for bondgraph models. The technique is highly sensitive to the orientation of the body coordinate frames in multibody systems: improper alignment of body coordinate frames may prohibit a significant simplification. This paper demonstrates how the Karhunen-Loe`ve expansion can be used to automatically detect the existence of and to find the transformation into body coordinate frames that render the bond-graph of a multibody system more conducive to simplification. The conclusion is that the Karhunen-Loe`ve expansion complements well the junction-inactivity-based structural simplification technique when multibody dynamics are involved in the system.


Author(s):  
Seyed Ali Modarres Najafabadi ◽  
Jo´zsef Ko¨vecses ◽  
Jorge Angeles

This paper presents detailed discussions and a potential grouping of various approaches to the dynamic analysis of the transition phase in multibody contacts. The methods considered are able to address the general case of multiple-point contact. The main grouping principle relies on the fundamental unilateral nature of the contact between two bodies in a multibody system. Based on this, three main classes of modeling techniques are considered.


Author(s):  
Shakil Ahmed ◽  
Hamid M. Lankarani ◽  
Manual F. O. S. Pereira

Abstract Analysis of impact problem in the presence of any tangential component of impact velocity requires a friction model capable of correct detection of the impact modes such as sliding, sticking, and reverse sliding. A survery of literature has shown that studies on the impact analysis of multibody systems have either been limited to the direct impact type with only a normal component of impact velocity (no frictional effect) or the ones that include friction have shown energy gains in the results due to the inherent problem in the use of Newton’s hypothesis. This paper presents a formulation for the analysis of impact problems with friction in constrained multibody mechanical systems. The formulation recognizes the correct mode of impact, i.e., sliding, sticking, and reverse sliding. The Poisson’s hypothesis is used for the definition of the coefficient of restitution, and thus the energy gains inherent with the use of Newton’s hypothesis are avoided. The formulation is developed by using a canonical form of the system equation of motion using joint coordinates and joint momenta. The use of canonical formulation is a natural way of balancing the momenta for impact problems. The joint coordinates reduces the equations of motion to a minimal set, and eliminate the complications arised from the kinematic constraint equations. The canonical form of equations are solved for the change in joint momenta using Routh’s graphical method. The velocity jumps are then calculated balancing the accumulated momenta of the system during the impact process. The impact cases are classified based on the pre-impact positions and velocities, and mass properties of the impacting systems. Analytical expressions for normal and tangential impulse are derived for each impact case. The classical problem of impact of a falling rod with the ground (a single object impact) is solved with the developed formulation, and the results are compared and verified by the solution from other studies. Another classical problem of a double pendulum striking the ground (a multibody impact) is also solved. The results obtained for the double pendulum problem confirms that the energy gain in impact analysis can be avoided by considering the correct mode of impact and using Poisson’s instead of Newton’s hypothesis.


2019 ◽  
Vol 20 (4) ◽  
pp. 267-275
Author(s):  
Yury N. Razoumny ◽  
Sergei A. Kupreev

The controlled motion of a body in a central gravitational field without mass flow is considered. The possibility of moving the body in the radial direction from the center of attraction due to changes in the kinetic moment relative to the center of mass of the body is shown. A scheme for moving the body using a system of flywheels located in the same plane in near-circular orbits with different heights is proposed. The use of the spin of elementary particles is considered as flywheels. It is proved that using the spin of elementary particles with a Compton wavelength exceeding the distance to the attracting center is energetically more profitable than using the momentum of these particles to move the body. The calculation of motion using hypothetical particles (gravitons) is presented. A hypothesis has been put forward about the radiation of bodies during accelerated motion, which finds indirect confirmation in stellar dynamics and in an experiment with the fall of two bodies in a vacuum. The results can be used in experiments to search for elementary particles with low energy, explain cosmic phenomena and to develop transport objects on new physical principles.


Author(s):  
Robert Seifried ◽  
Alexander Held

In many machine and robotic applications energy efficiency is an increasingly crucial issue. In order to achieve energy efficiency lightweight structural designs are necessary. However, undesired elastic deformations might occur due to the light wight design. In order to achieve good system performance the actual dynamic loads must be taken into account in the design of the system’s components. In this paper optimization approaches for lightweight machine designs are employed to improve the tracking behavior the systems. Thereby, fully dynamical simulations of flexible multibody systems are coupled with both shape or topology optimization for the elastic members of the multibody system. It is shown, that by these approaches the end-effector trajectory tracking error of light wight manipulators can be decreased significantly.


2010 ◽  
Vol 79 (3) ◽  
pp. 531-555 ◽  
Author(s):  
Catherine M. Chin

The late ancient body is a historiographical problem. In the combined lights of feminist, Foucaultian, and post-Foucaultian methodologies, much recent scholarship on bodies in late antiquity has focused on bodies as sites on which power relations are enacted and as discourses through which ideologies are materialized. Contemporary concern with definitions and representations of the posthuman, however—for example, in medical technologies that expand the capacities of particular human bodies, in speculative pursuit of the limits of avatars, or in the technological pursuit of artificial intelligence or artificial life—seem both to underline the fundamental lability of the body, and to require a broadening of scholarly focus beyond the traditional visible boundaries of the human organism. At the same time, scholarship on the posthuman emphasizes contemporaneity and futurity to an extent that may seem to preclude engagement with the premodern. I would like to suggest here that doubt about the boundaries of human embodiment is a useful lens through which to reconsider some very traditional questions in the history of Christianity, and that we may begin to think of bodies in Christian premodernity in terms of what we might call their pre-humanity, that is, as fundamentally open to extension, transformation, and multiple instantiation. The figure on whom I focus is Ambrose, the fourth-century bishop of Milan, who, I argue, defined his own body in such a way that he was able to instantiate physically in dozens of living human bodies, at least two dead human bodies, thousands of angelic bodies, and four church buildings. Ambrose's dynamic conception of his episcopal body was formed within a complex political and theological situation, so questions concerning the political ideology of bodies remain very much at issue. I add to these questions a concern for premodern uncertainty about how to recognize a body, both when it is visible and, perhaps more importantly, when it is not.


Author(s):  
Mohammad J. Izadi

A CFD study of a 3 Dimensional flow field around two bodies (Two Canopies of a Parachutes) as two bluff bodies in an incompressible fluid (Air) is modeled here. Formations of these two bodies are top-to-top (One on the top of the other) with respect to the center of each other. One canopy with a constant cross sectional area with a vent of air at its apex, and the other with a variable cross sectional area with no vent is studied here. Vertical distances of these two bodies are varied form zero to half, equal, double and triple radius of the body with a vent on it. The flow condition is considered to be 3-D, unsteady, turbulent, and incompressible. The vertical distances between the bluff bodies, cross sectional area, and also vent ratio of bluff bodies are varied here. The drag forces with static pressures around the two bodies are calculated. From the numerical results, it can be seen that, the drag coefficient is constant on the range of zero to twenty percent of the vent ratio and it decreases for higher vent ratios for when the upper parachute is smaller than the lower one, and it increases for when the upper parachute is larger than the lower one. Both Steady and Unsteady cases gave similar results especially when the distance between the canopies is increased.


Author(s):  
Cody Leeheng Chan ◽  
Kwun-Lon Ting

Abstract According to Camus’ theorem, for a single DOF 3-body system with the three instant centers staying coincident, a point embedded on a body traces a pair of conjugated curves on the other two bodies. This paper discusses a fundamental issue not addressed in Camus’ theorem in the context of higher order curvature theory. Following the Aronhold-Kennedy theorem, in a single degree-of-freedom three-body system, the three instant centers must lie on a straight line. This paper proposes that if the line of the three instant centers is stationary (i.e. slide along itself), on the line of the instant centers a point embedded on a body traces a pair of conjugated curves on the other two bodies. Another case is that if the line of the three instant centers rotate about a stationary point, the stationary point embedded on the body also traces a pair of conjugated curves on the other two bodies. The paper demonstrates the use of instantaneous invariants to synthesize such a three-body system leading to a conjugate curve-pair generation. It is a supplement or extension of the Camus’ theorem. The Camus’ theorem may be regarded as a special singular case, in which all three instant centers are coincident.


Sign in / Sign up

Export Citation Format

Share Document