engleski

Computational Multibody Dynamics - Dynamic Simulation of Human Movement

In spite of recent notable advances in multibody dynamics, there are still disagreements among analysists which methods are the best for specific application and for computational efficiency. The best method for obtaining governing dynamical equations for redundant and constrained multibody system is still in dispute. Methods for solving the systems of differential-algebraic equations are yet to be examined in the light of particular dynamical problems treatment. In addition, there are still disagreements how global algorithms are to be tailored to optimally fit the purposes of the specific applications (Huston, 1991). All these aspects are reflected on dynamic simulation of 3D human movement which is very demanding numerical task. Due to the inherent non-repeatability and discontinuity of analysed motion patterns, highly irregular input functions and highly non-linear differential-algebraic equation of motion, all the questions stated above have to be considered very carefully when accurate and stable algorithm for such simulations has to be shaped. Commercially available general purpose software packages (Schiehlen, 1990) very often are not flexible enough to adapt their integration routines to such immoderate conditions (some of the shortcomings of packages DADS and ADAMS are reported by Soest et al. (1992)). Other peculiarities of biodynamic systems, like the non-rigidity of the human body segments (segments skin and other deformations) which complicates kinematic data determination and aggravates results interpretation, make the procedure of 3D human movement simulation even more formidable (Yeadon, 1990). Having all this in mind, the objective of the paper is to describe mathematical model for an accurate and stable numerical procedure, compatible with ODE most frequently used integrators, for dynamic simulation of 3D human movement. The movement of upper trunk and arm of subject performing tennis stroke has been chosen as an example of a complex motion (Terze and Muftic, 1998), upon which proposed method is based. With the aim of obtaining simulation procedure input parameters, kinematic and dynamic analysis of analysed movement have also been performed. The described approach is founded on the recent multibody formulations and numerical algorithms for solving differential-algebraic system of equations as well as on the values of the characteristic kinematic data of analysed movement, obtained by measuring (Terze and Muftic, 1997).

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