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Oliver M. O’Reilly

Bio: Oliver M. O’Reilly is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Rigid body & Equations of motion. The author has an hindex of 26, co-authored 142 publications receiving 2882 citations. Previous affiliations of Oliver M. O’Reilly include University of California & Cornell University.


Papers
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Journal ArticleDOI
TL;DR: A comprehensive review and bibliography of works on disc brake squeal is provided in this paper, where background sections on vibrations, contact and disc brake systems are also included, in an effort to make this review accessible to a large audience.

712 citations

Journal ArticleDOI
TL;DR: A new musculoskeletal model for the lumbar spine that includes the abilities to predict joint reactions, muscle forces, and muscle activation patterns is described in this paper and can be integrated with existing OpenSim models to build more comprehensive models of the human body.
Abstract: A new musculoskeletal model for the lumbar spine is described in this paper. This model features a rigid pelvis and sacrum, the five lumbar vertebrae, and a rigid torso consisting of a lumped thoracic spine and ribcage. The motion of the individual lumbar vertebrae was defined as a fraction of the net lumbar movement about the three rotational degrees of freedom: flexion–extension lateral bending, and axial rotation. Additionally, the eight main muscle groups of the lumbar spine were incorporated using 238 muscle fascicles with prescriptions for the parameters in the Hill-type muscle models obtained with the help of an extensive literature survey. The features of the model include the abilities to predict joint reactions, muscle forces, and muscle activation patterns. To illustrate the capabilities of the model and validate its physiological similarity, the model’s predictions for the moment arms of the muscles are shown for a range of flexion–extension motions of the lower back. The model uses the OpenSim platform and is freely available on https://www.simtk.org/home/lumbarspine to other spinal researchers interested in analyzing the kinematics of the spine. The model can also be integrated with existing OpenSim models to build more comprehensive models of the human body.

257 citations

Journal ArticleDOI
TL;DR: In this article, the authors consider a class of reversible, two-degree of freedom Hamiltonian systems possessing homoclinic orbits to a saddle-center, and construct a two-parameter unfolding and show that there is a countable infinity of bifurcations in any neighborhood of the original system.
Abstract: We consider a class of reversible, two-degree of freedom Hamiltonian systems possessing homoclinic orbits to a saddle-center: an equilibrium having two non-zero real and two nonzero imaginary eigenvalues. Under mild nondegeneracy conditions, we construct a two-parameter unfolding and show that there is a countable infinity of “secondary” homoclinic bifurcations in any neighborhood of the original system. We also demonstrate the existence of families of periodic orbits and of shifts on two symbols (horseshoes). The lack of hyperbolicity and the presence of conserved quantities make the analysis somewhat delicate. We discuss specific examples for which the nondegeneracy conditions can be explicitly checked but indicate that this is not always possible. We illustrate our results with numerical work.

121 citations

MonographDOI
01 Aug 2008
TL;DR: Part I Dynamics of a Single Particle: 1 Kinematics of a particle 2 Kinetics of a rigid body 3 Lagrange's equations of motion for a single particle 4 Dynamics of System of Particles: 5 Dynamics of systems of particles 6 Rotation tensors as mentioned in this paper.
Abstract: Part I Dynamics of a Single Particle: 1 Kinematics of a particle 2 Kinetics of a particle 3 Lagrange's equations of motion for a single particle Part II Dynamics of a System of Particles: 4 The equations of motion for a system of particles 5 Dynamics of systems of particles Part III Dynamics of a Single Rigid Body: 6 Rotation tensors 7 Kinematics of rigid bodies 8 Constraints on and potentials for rigid bodies 9 Kinetics of a rigid body 10 Lagrange's equations of motion for a single rigid body Part IV Systems of Rigid Bodies: 11 Introduction to multibody systems Appendix 1 Background on tensors Bibliography Index

93 citations


Cited by
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01 Jan 1978
TL;DR: This ebook is the first authorized digital version of Kernighan and Ritchie's 1988 classic, The C Programming Language (2nd Ed.), and is a "must-have" reference for every serious programmer's digital library.
Abstract: This ebook is the first authorized digital version of Kernighan and Ritchie's 1988 classic, The C Programming Language (2nd Ed.). One of the best-selling programming books published in the last fifty years, "K&R" has been called everything from the "bible" to "a landmark in computer science" and it has influenced generations of programmers. Available now for all leading ebook platforms, this concise and beautifully written text is a "must-have" reference for every serious programmers digital library. As modestly described by the authors in the Preface to the First Edition, this "is not an introductory programming manual; it assumes some familiarity with basic programming concepts like variables, assignment statements, loops, and functions. Nonetheless, a novice programmer should be able to read along and pick up the language, although access to a more knowledgeable colleague will help."

2,120 citations

Journal ArticleDOI
TL;DR: In this article, the authors developed the geometry and dynamics of nonholonomic systems using an Ehresmann connection to model the constraints, and showed how the curvature of this connection entered into Lagrange's equations.
Abstract: This work develops the geometry and dynamics of mechanical systems with nonholonomic constraints and symmetry from the perspective of Lagrangian mechanics and with a view to control theoretical applications. The basic methodology is that of geometric mechanics applied to the formulation of Lagrange d'Alembert, generalizing the use of connections and momentum maps associated with a given symmetry group to this case. We begin by formulating the mechanics of nonholonomic systems using an Ehresmann connection to model the constraints, and show how the curvature of this connection enters into Lagrange's equations. Unlike the situation with standard configuration space constraints, the presence of symmetries in the nonholonomic case may or may not lead to conservation laws. However, the momentum map determined by the symmetry group still satisfies a useful differential equation that decouples from the group variables. This momentum equation, which plays an important role in control problems, involves parallel transport operators and is computed explicitly in coordinates. An alternative description using a ``body reference frame'' relates part of the momentum equation to the components of the Euler-Poincar\'{e} equations along those symmetry directions consistent with the constraints. One of the purposes of this paper is to derive this evolution equation for the momentum and to distinguish geometrically and mechanically the cases where it is conserved and those where it is not. An example of the former is a ball or vertical disk rolling on a flat plane and an example of the latter is the snakeboard, a modified version of the skateboard which uses momentum coupling for locomotion generation. We construct a synthesis of the mechanical connection and the Ehresmann connection defining the constraints, obtaining an important new object we call the nonholonomic connection. When the nonholonomic connection is a principal connection for the given symmetry group, we show how to perform Lagrangian reduction in the presence of nonholonomic constraints, generalizing previous results which only held in special cases. Several detailed examples are given to illustrate the theory. September 1994 Revised, March 1995 Revised, June 1995

763 citations

Journal ArticleDOI
TL;DR: A comprehensive review and bibliography of works on disc brake squeal is provided in this paper, where background sections on vibrations, contact and disc brake systems are also included, in an effort to make this review accessible to a large audience.

712 citations