Pier Paolo Valentini

A Review of Formulas for the Mechanical Efficiency Analysis of Two Degrees-of-Freedom Epicyclic Gear Trains

This paper after a rigorous proof of the formulas originally proposed by Rodzimovsky, demonstrates the numerical equivalence of the different approaches available for computing the mechanical efficiency of two degrees-of-freedom (d.o.f.) epicyclic gear trains. The paper includes also a discussion on the redundancy of data required by some formulas.

Comfort analysis of car occupants: comparison between multibody and finite element models

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.

An application of the Udwadia-Kalaba dynamic formulation to flexible multibody systems

Abstract For the transient response analysis of a flexible slider-crank mechanism, the coordinate partitioning scheme and the Udwadia–Kalaba formulation are herein compared. The flexibility of the coupler has been modelled by means of a single Timoshenko beam element. The present analytical treatment can be viewed as an extension of the model discussed by Shabana in his textbook.

Linear Dual Algebra Algorithms and their Application to Kinematics

Summary. Mathematical and mechanical entities such as line vectors, screws and wrenches can be conveniently represented within the framework of dual algebra. Despite the applications received by this type of algebra, less developed appear the numerical linear algebra algorithms within the field of dual numbers. In this paper will be summarized different basic algorithms for handling vectors and matrices of dual numbers. It will be proposed an original application to finite and infinitesimal rigid body motion analysis.

Dynamic Analysis of Epicyclic Gear Trains by Means of Computer Algebra

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.

DYNAMIC, MECHANICAL EFFICIENCY, AND FATIGUE ANALYSIS OF THE DOUBLE CARDAN HOMOKINETIC JOINT.

Cardan and double Cardan homokinetic joints have a wide spectrum of application in vehicle design. This paper proposes mathematical models for mechanical efficiency and torque analysis. The problem of fatigue analysis has been adressed. In particular, it has been investigated the influence of working parameters on the life expectancy of the joint. Design charts have been prepared for a ready use of the proposed models.

Dynamic Simulation of a Metal Belt CVT Under Transient Conditions

Most of the technical literature on CVT consider steady-state conditions. Very few analyze the behavior of CVT under transient conditions (Kanehara et al., 1999; Ide et al., 1995; Carbone et al., 2002) and none of them include the effects of pulley deformation. This paper is an attempt to fill the gap. It is herein presented a mathematical model of a V-belt metal CVT, valid also under transient conditions, where the pulley deformation has been included. The model, implemented in a numerical code, combines Gerbert’s theory of V belts and the contributions of (Sattler, 1999a; Sattler, 1999b) on pulley deformation. An innovative algorithm for the simulation of dynamic effects during shifting is proposed. Inertia effects as well as deformation of pulleys are taken into account. Two type of working conditions have been experimentally monitored and numerically simulated. Finally, the paper contains a description of the experimental apparatus used for the validation of the model herein presented.© 2002 ASME

Comparison between low-cost marker-less and high-end marker-based motion capture systems for the computer-aided assessment of working ergonomics

The paper deals with the comparison between a high-end marker-based acquisition system and a low-cost marker-less methodology for the assessment of the human posture during working tasks. The low-cost methodology is based on the use of a single Microsoft Kinect V1 device. The high-end acquisition system is the BTS SMART that requires the use of reflective markers to be placed on the subjects body. Three practical working activities involving object lifting and displacement have been investigated. The operational risk has been evaluated according to the lifting equation proposed by the American National Institute for Occupational Safety and Health. The results of the study show that the risk multipliers computed from the two acquisition methodologies are very close for all the analysed activities. In agreement to this outcome, the marker-less methodology based on the Microsoft Kinect V1 device seems very promising to promote the dissemination of computer-aided assessment of ergonomics while maintaining good accuracy and affordable costs. Practitioners Summary: The study is motivated by the increasing interest for on-site working ergonomics assessment. We compared a low-cost marker-less methodology with a high-end marker-based system. We tested them on three different working tasks, assessing the working risk of lifting loads. The two methodologies showed comparable precision in all the investigations.

Virtual dummy with spine model for automotive vibrational comfort analysis

In this paper, the author presents a methodology for implementing a three-dimensional virtual dummy for human vibration investigations. The model is based on a multibody dynamics approach and includes a detailed spine submodel for accurate assessment of seated body vibration. The model has been used to compute vibrational modes and transmissibility functions. The response to vibrational inputs has been compared with previous experimental and numerical studies. The discussed model can be applied for the assessment of vibration dose value (VDV) and design optimisation of human-vehicle interface according to international standards.

Accurate geometrical constraints for the computer aided modelling of the human upper limb

For medical and surgical applications, human modelling and simulation have to be very accurate and realistic. This means that both geometries and movements have to be reproduced precisely, investigating both physiological properties and anatomical shapes. This paper deals with the description of geometrical constraints to mimic the movement of the upper limb segments subjected to physical joints. Anatomical studies show that relative motion cannot be approximated with basic constraints such as revolute or spherical joints, but requires the definition of specific geometrical and kinematic pairs. For this purpose, for each joint the authors deduce a set of equations which can be embedded into a virtual environment in order to simulate the relative motion among body segments in a detailed way.