Søren Tørholm Christensen

Analysis of Musculoskeletal Systems in the AnyBody Modeling System

This paper reviews the simulation software the AnyBody Modeling System, which was originally developed by the authors. AnyBody is capable of analyzing the musculoskeletal system of humans or other creatures as rigid-body systems. The paper introduces the main features of the system; in particular, the inverse dynamic analysis that resolves the fundamental indeterminacy of the muscle configuration. In addition to the musculoskeletal system, a model can comprise external objects, loads, and motion specifications, thereby providing a complete set of the boundary conditions for a given task. The paper also describes the basic ideas of structured model development in AnyBody. 2006 Elsevier B.V. All rights reserved.

On analysis and optimization in structural acoustics - Part I: Problem formulation and solution techniques

This paper is devoted to problems of structuralacoustic coupling with emphasis on analysis, design sensitivity analysis and optimization. The paper is divided into two parts, and it is the aim of Part I to (i) give a brief survey of recent developments in sensitivity analysis and sound emission and NVH (Noise, Vibration and Harshness) design of acoustically loaded structures, and (ii) discuss alternative objective functions and optimization formulations for structural acoustics. The aims of Part II are to (i) present consistent numerical techniques commonly used for treatment of coupled structural and acoustic dynamics, (ii) use the structural optimization tool ODESSY for solution of several coupled problems, and (iii) compare the numerical efficiency of alternative techniques and the relevance of selected objective functions.

Computational method for muscle-path representation in musculoskeletal models.

Abstract. This paper presents a new and efficient method to calculate the line-of-action of a muscle as it wraps over bones and other tissues on its way from origin to insertion. The muscle is assumed to be a one-dimensional, massless, taut string, and the surfaces of bones that the muscle may wrap around are approximated by cross-sectional boundaries obtained by slicing geometrical models of bones. Each cross-sectional boundary is approximated by a series of connected line segments. Thus, the muscle path to be calculated is piecewise linear with vertices being the contact points on the cross-sectional boundaries of the bones. Any level of geometric accuracy can be obtained by increasing the number of cross sections and the number of line segments in each cross section. The algorithm is computationally efficient even for large numbers of cross sections.

On analysis and optimization in structural acoustics — Part II: Exemplifications for axisymmetric structures

This two-part paper is devoted to problems of structural-acoustic coupling with emphasis on analysis, design sensitivity analysis and optimization. Part II of the paper aims to (i) present consistent numerical techniques commonly used for treatment of coupled structural and acoustic dynamics, (ii) use the structural optimization tool ODESSY for solution of several coupled problems, and (iii) compare the numerical efficiency of alternative techniques and the relevance of selected objective functions.

Low-frequency breakdown of boundary element formulation for closed cavities in excitation conditions with a ‘breathing’-type component

Solution of interior problems of structural acoustics by the boundary element method at low frequencies may be inaccurate due to the absence of a quasi-static component in the computed acoustic pressure. This part of the acoustic pressure is generated by uniform displacements of the fluid–structure interface (volume change). The contribution of this component to the overall acoustic pressure decays with frequency growth and at a certain frequency the accuracy of the solution is recovered. A simple approach is suggested to estimate this threshold value and its validity is illustrated by two examples. Copyright