1,720,981 research outputs found
Numerical Analysis of the Dynamics of Reed Valves Taking into account the Acoustic Coupling with the Fluid. Application to Compressors for Domestic Refrigeration
No full textOptimum Synthesis of Spatial Function Generator Mechanisms
No full textIn this study a numerical method for optimum synthesis of spatial function generator four-bar linkages is presented. The key features of the method are: the embedding of the assembly criterion and of the transmission ratio in the penalty function; the non-derivative minimization procedure; the parametric variation of the first-guess mechanism. The effectiveness of the method is illustrated by means of examples of optimum design. In some examples articulated mechanisms, which can replace cam systems in automatic machinery, are synthesized
Positioning error prediction in boring machines
No full textThis paper focuses the attention on the possibility to describe and predict the positioning
error of the end-effector (or tool-holder) of a Cartesian boring machine. The aim of the
work is i) to build a deterministic expression of the positioning error, starting from
independent measurements of linear and angular errors for each independent axis, and
ii) to investigate the precision enhancement, which may eventually be achieved by
implementing such deterministic error-prediction into the numerical control of the boring
machine.
The six components of the end-effector positioning error are expressed on the basis of a
symbolic analysis of the kinematic linkages, which represents the machine layout. Each
component results as a function of the command position, some environmental
parameters (mainly the ambient temperature), and alignment errors for each axis. In
particular, alignment errors may be expressed as six functions of position for each axis:
three position errors and three angular errors [1,2].
An accurate measurement of these errors (which may take place either on-line or at
regular time schedule as a result of an auto-diagnosis procedure) allows expressing the
end-effector positioning error as a deterministic vector field in the whole machine working
space.
Beside these considerations, the paper investigates the applicability of different
techniques allowing the measurement of axes alignment errors
A SYMBOLIC APPROACH FOR AUTOMATIC GENERATION OF THE EQUATIONS OF MOTION OF MULTIBODY SYSTEMS
No full textThis paper describes a collection of methods and procedures for the automatic generation of the equations of motion of multibody systems using general-purpose Computer Algebra Software. A brief review of existing symbolic multibody systems is given, and advantages and disadvantages of symbolic approaches compared with numerical ones are discussed. Then, a set of methods for symbolic modeling of multibody systems is explained. The first step of the modeling procedure consists of the description of the multibody system, by defining objects (such as points, vectors, rigid bodies, forces and torques, special objects) and the relationships between them (kinematic chains, constraints). The second step is the derivation of the equations of motion, which can be performed in a quasiautomatic way. A further step is the linearization of the equations and the calculation of the system's frequency response functions. By way of example, a dynamic model of the motorcycle is developed, obtaining the nonlinear equations of motion in a dependent coordinates' formulation. Next, the equations of motion are linearized and reduced to an independent formulation, reobtaining the well known Sharp's model of the straight running of the motorcycle. Root loci and frequency response functions are also calculated. This example demonstrates the power of the given symbolic procedures and shows how a model suitable for stability, handling and control analysis can be developed quickly and easily. The procedure described in this paper has been implemented in a Maple package called 'MBSymba', which is available on the web page www.dim.unipd.it/lot/mbsymba.html
An intelligent curve warning system for powered two wheel vehicles
Full text linkThis article illustrates a novel Curve Warning system for motorcycles which has been developed in the SAFERIDER project (www.?saferider-eu.?org) of the 7th EU FP, among other Advanced Rider Assistance Systems. The Curve Warning function (CW) described here follows a holistic approach, which combines road geometry, motorcycle dynamics, rider input and riding styles. The warning strategy is based on the correction of longitudinal dynamics derived from a previewed ideal manoeuvre (reference manoeuvre) continuously computed from the actual state of the vehicle. Under normal driving conditions the reference manoeuvre matches the rider’s and no correction is needed and no warning is given. But if large differences between actual and ideal accelerations are found the rider is warned to decelerate or brake. As soon as the correct value of deceleration is achieved the warning disappears, improving system acceptability. Warnings are given to the rider via an HMI, which uses a haptic accelerator throttle, a vibrating glove and helmet, and a visual display
Non-linear Interaction between In-plane and Out-of-plane Vibrations of Electrostatic Precipitator Plates
No full text
PROCEDIMENTO PER ASSISTERE UN CONDUCENTE A COPRIRE UN PERCORSO, E RELATIVO SISTEMA DI ASSISTENZA NELLA CURVA, MOTOCICLETTA E PRODOTTO INFORMATICO
No full textINTELLIGENT CURVE WARNING FUNCTION IN AN ADVANCE RIDER ASSISTANCE SYSTEM FOR POWERED TWO WHEEL VEHICLES
No full text
- …
