Fabian Duvigneau

An effective vibration reduction concept for automotive applications based on granular-filled cavities

The acoustic behavior of a combustion engine is primarily dominated by the sound radiation of the oil pan. Therefore, the vibration behavior of the oil pan as the prominent noise emission source is investigated in this paper. The aim of this study is to present a new vibration reduction concept, which is based on the property of high damping possessed by granular materials. The efficiency of this concept is proven by measurements via a scanning laser vibrometer. Finally, it is shown that it is possible to create a lighter oil pan which shows much lower vibration amplitudes than the original one.

NOISE CONTROL OF VEHICLE DRIVE SYSTEMS

The paper presents an overall simulation approach to control the noise emission of car engines at a very early stage of the design process where no real prototypes are available. The suggested approach combines different physical models and couples different software tools such as multi-body analysis, fluid dynamics, structural mechanics, magneto-electrodynamics, thermodynamics, acoustics and control as well. The general overall simulation methodology is presented first. Then, this methodology is applied to a combustion engine in order to improve its acoustical behavior by passive means, such as changing the stiffness and the use of damping materials to build acoustic and thermal encapsulations. The active control by applying piezoelectric patch actuators at the oil sump as the noisiest part of the engine is discussed as well. The sound emission is evaluated by hearing tests and a mathematical prediction model of the human perception. Finally, it is shown that the presented approach can be extended to electric engines, which is demonstrated at a newly developed electric wheel hub motor.

A Numerical Study on the Potential of Acoustic Metamaterials

In the present contribution we are going to investigate a special class of acoustic metamaterials, i.e. synthetic foams with spherical inclusions. This study is motivated by the need for an improved acoustical behavior of engines and vehicles which is one important criterion for the automotive industry. In this context, innovative materials offering a high damping efficiency over a wide frequency range are becoming more and more important. Since there is an innumerable selection of different absorbing materials with an equally large range of properties numerical studies are inevitable for their assessment. In the paper at hand, we look at a special class of such materials in which the influence of the inclusions on the acoustical behavior is examined in detail. To this end, we vary the size, mass density, number and position of spherical inclusions. Here, the main goal is to improve the damping properties in comparison to conventional materials which can be bought off the shelf. In that regard, the lower frequency range is of special interest to us. The results show that a random distribution of the inclusions should be favored while for the other parameters values that are centered within the investigated interval are recommended.

Vibration Analysis of an Electric Wheel Hub Motor at Stationary Operating Points

In the context of environmentally friendliness and challenging pollution limits the electrification of passenger cars becomes more and more important. In this contribution an innovative electrical drive for automobiles is presented and its vibration behavior is analyzed experimentally. In special, the vibrations of an electric wheel hub motor are studied in detail. For this purpose, a laser scanning vibrometer is used. To be able to measure the vibrations at the running engine a derotator is needed additionally to the laser scanning vibrometer. The electric wheel hub motor is investigated on a test bench at different stationary operating points which differ in the rotational speed as well as in the torque that is applied by an electric brake. Analyzing the vibroacoustic behavior of this special electric machine is of utmost importance as its sound radiation is directed straight to the passers-by of the car. The sound radiation of conventional cars drives is normally shielded and attenuated by the vehicle body and for this reason less critical. Moreover, the application of damping materials is more difficult if the engine is placed within a wheel. In the paper at hand different prototype stages of the electric wheel hub motor are presented. The working principle of this special engine is also explained. For the numerical simulations a holistic simulation workflow has been developed which takes into account the electromagnetic field as the most important vibration excitation as well as the structural vibrations coupled with an air volume around the engine to calculate the sound pressure. First, the electromagnetic forces are calculated which are then applied to excite the structural vibrations of the engine. Finally, the calculated surface velocity is used to excite the surrounding air volume under free field conditions to determine the radiated sound pressure level. In all three steps of the holistic methodology, the finite element method (FEM) is used for the numerical simulations. Beside identifying weak points of the engine prototype as well as obtaining a general understanding of such an electrical machine, the experimental data are used to validate a numerical model of the electric wheel hub motor. With the help of both the validated model and the gained experimental experiences the design of the wheel hub motor is improved. However, this contribution focusses on the experimental analysis of the structural vibrations of the running wheel hub motor.

Dynamic modeling with feedforward/feedback control design for a three degree of freedom piezoelectric nanopositioning platform:

This article presents the dynamic modeling of a three degree of freedom nanopositioning platform driven by three parallel piezoelectric actuators. The dynamics of the platform are formulated through the equations of rigid body motion, and then the stiffness of the actuators is included to form the full equations of motion. From a control perspective, the location of the sensors is important as they affect the output equation of the system. Hence, three different cases are analyzed with respect to their input–output characteristics in terms of their Bode plots. Finally, the H∞ loop shaping feedforward/feedback control design is shown and demonstrated via simulation for tracking a step signal.