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In this paper, a three dimensional numerical model of the human spine, specialized for vibrational investigations, is presented. The model has been built using multibody dynamics techniques and includes the entire set of vertebrae, considered as rigid bodies. The interaction between vertebrae has been simulated using six component bushings, without the need of any kinematic constraint. This methodology allows a very relevant flexibility, and the fully three-dimensional deformation modes of the spine may be studied. The investigation has been focused on the assessment of the vibration modes and the computation of the transmissibility functions buttocks-to-head for acceleration inputs along three main directions. It has been observed that the first torsional modes with a relevant mass participation factors are present at very low frequencies. Most of the relevant modes, which involve the deformation of the spine with relevant participation factor, are within the range $0{\div}5\ \mbox{Hz}$ . These peaks are also visible in the transmissibility functions. Results have been also compared to those of other experimental and numerical studies.

In this paper the authors present a control strategy for tendon driven mechanisms. The aim of the control system is to find the correct torques which the motors have to exert to make the end effector describe a specific trajectory. In robotic assemblies this problem is often solved with closed loop algorithm, but here a simpler method, based on a open loop strategy, is developed. The difficulties in the actuation are in keeping the belt tight during all working conditions. So an innovative solution of this problem is presented here. This methodology can be easily applied in real time monitoring or very fast operations. For this reason several virtual reality simulations, developed using codes written in Virtual Reality Markup Language, are also presented. This approach is very efficient because it requires a very low cpu computation time, small size files, and the manipulator can be easily put into different simulated scenarios.

The paper illustrates the application of a systematic technique for thededuction of dynamic equations of epicyclic gear trains. The use of theproposed method is particularly amenable in conjuction with proceduresfor the computerized enumeration of geared kinematic chains. Thediscussed examples illustrate how the presented approach can be extendedfor computing the equivalent inertia of an epicyclic gear train or forthe stability analysis of 2 d.o.f. gear trains.