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This paper deals with numerical models developed in order to simulate the vibrational and postural comfort of car occupants. The proposed models have been based on different mathematical approaches: the first is a multibody dynamics model and the second is a finite elements model. Both models have been validated by means of static and dynamic experimental tests on vehicles using appropriate test rigs. The authors focus on the advantages and disadvantages of each model in order to have useful information about which approach has to be used to predict objectively the comfort of driver and passengers.

The formulation of the dynamic equations of motion proposed by Udwadia-Kalaba is discussed from the point of view of numerical efficiency. Since this formulation requires the computation of a pseudoinverse matrix, it is investigated the influence of the method of pseudoinverse computation on the dynamic simulation of an overconstrained linkage. Finally, it has been proposed a new 1 dynamic equation which explicitly computes accelerations also in the case of mathematical models with rank deficient Jacobian and mass matrices.

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SUMMARYTolerance allocation influences production costs in a big way. For this reason it is very important to have an accurate study about the effects of manufacturing errors on the functioning and performances of linkages. In this paper, the authors present a computer-aided methodology based on a 3D geometrical approach using the dual-algebra fundamentals. The purpose is to give an useful tool which can be integrated into CAD software in order to evaluate the performances of spatial mechanisms with mechanical errors. The proposed methodology has been validated by means of experimental tests on a Cardan joint mechanism with clearances, misalignments and dimensional errors.

This investigation concerns with the mechanical efficiency of Cardan joints. The model includes also the effects due to manufacturing and mounting errors and the influence of rotation speed on the efficiency. The joint has been modeled as an RCCC spatial linkage and the full dynamic analysis performed by means of dual vectors algebra.

The number of multibody dynamics courses offered in the university is increasing. Often the instructor has the necessity to go through the steps of an algorithm by working out a simple example. This gives the student a better understand of the basic theory. This paper provides a tutorial on the numerical integration of differential-algebraic equations (DAE) arising from the dynamic modeling of multibody mechanical systems. In particular, some algorithms based on the orthogonalization of the Jacobian matrix are herein discussed. All the computational steps involved are explained in detail and by working out a simple example. It is also reported a brief description and an application of the multibody code NumDyn3D which uses the Singular Value Decomposition (SVD) approach. ß