Peter Kindt

Analysis of tire/road noise caused by road impact excitations

This paper presents the experimental analysis of tire/road noise and tire vibrations during road impact excitations. The tests are performed on a setup which is based on a tire on tire principle. Radiated noise, vibrations of the tire surface and spindle forces are measured during impact excitations. The influence of driving speed, cleat dimension, inflation pressure, tire temperature and preload are analyzed. Two novel tire measurement techniques are presented for the validation and/or parameterization of tire models. Those techniques include the use of a 6 degree of freedom high frequency CUBE shaker table for the characterization of rotating and non-rotating tires up to 250 Hz.

Damping analysis with respect to rolling speed by analytic solution of a flexible ring model and its frequency response function derivation by modal summation method

In this research, a modal approach has been adopted to analyze the dynamic characteristics of the rolling tire by a ring model. Previously, most of the researchers focused on the changes in natural frequencies with respect to the rotational speed (in global coordinate) only. In this research, the change in the damping has also been taken into account by including a damping term in the ring model equations. The bi-orthogonal property which is used to obtain the Frequency Response Functions (FRFs) of a rotor/bearing system described in Cartesian coordinate has been applied to the ring model described in cylindrical coordinate to obtain the FRFs. The obtained damping values and FRFs from the analytic model are then compared with experimental results. Moreover, the physical meanings of the results are analyzed, based on experimental data of a stationary tire and a rolling tire at 60 km/h and 100 km/h.

Dynamic Behavior of Rolling Tires Under Different Operating Conditions

Although tire/road noise and tire vibration phenomena have been studied for decades, there are still some missing links in the process of accurately predicting and controlling the overall tire/road noise and vibration. An important missing link is represented by the effect of rolling on the dynamic behavior of a tire. Consequently, inside the European seventh framework program, an industry-academia partnership project, named TIRE-DYN, has been founded between KU Leuven, Goodyear and LMS International. By means of experimental and numerical analyses, the effects of rolling on the tire dynamic behavior are quantified.This paper presents the results of vibration measurements on a rotating tire with an embedded accelerometer. Modal parameters of the rolling tire are estimated from an operational modal analysis. In addition, the dispersion curves, which give detailed insight in the wave propagation behavior of a structure, are analyzed for the rolling tire. The goal of these analyses is to deepen the understanding on the influence of rolling on the tire dynamic behavior.Copyright

Reconstruction of the in-plane mode shape of a rotating tire with a continuous scanning measurement using the Hilbert–Huang transform

Generally, the dynamic characteristics (natural frequency, damping, and mode shape) of a structure can be estimated by experimental modal analysis. Among these dynamic characteristics, mode shape requires multiple measurements of the structure at different positions, which increases the experimental cost and time. Recently, the Hilbert-Huang transform (HHT) method has been introduced to extract mode-shape information from a continuous measurement, which requires vibration measurements from one position to another position continuously with a non-contact sensor. In this research study, an effort has been made to estimate the mode shapes of a rolling tire with a single measurement instead of using the conventional experimental setup (i.e., measurement of the vibration of a rolling tire at multiple positions similar to the case of a non-rotating structure), which is used to estimate the dynamic behavior of a rolling tire. For this purpose, HHT, which was used in the continuous measurement of a non-rotating structure in previous research studies, has been used for the case of a rotating system in this study. Ambiguous mode combinations can occur in this rotating system, and therefore, a method to overcome this ambiguity is proposed in this study. In addition, the specific phenomenon for a rotating system is introduced, and the effect of this phenomenon with regard to the obtained results through HHT is investigated.

Analytic Formula Derivation for a Rolling Tire with a Ring Model

This paper analyzes the dynamic characteristics of a rolling tire with a modal approach. A ring model is adopted to model a tire and this model is substituted in a general transfer function and considers the rolling condition to make a transfer function of a rolling tire in the Laplace domain and an corresponding impulse response function in the time domain. From this transfer function it is clearly confirmed that the shifting effect, the so-called Doppler Effect, shifts not only the natural frequencies but also the damping ratios.

Indoor Vibration Testing for High-Frequency Modal Characterization of Tyres

The driver subjective perception of a vehicle is strongly determined by its Noise, Vibration and Harshness (NVH) behavior. Consequently, the NVH performance has become an important design and marketing criterion for vehicle manufacturers. The low-frequency (0–500Hz) noise and vibration perceived by a passenger are mainly determined by the dynamic behavior of rolling tyres. Besides the increasing awareness for the problems associated with road traffic noise has lead to the demand for more quiet tyres and road surfaces. Computer aided engineering tools play an important role for improving the vehicle vibration behavior at the earliest step of the design. In order to carry out precise modeling of the vehicle and its subsystems, an accurate tyre model is a key element in predicting the performance of the vehicle system with respect to ride comfort, NVH, durability, safety (braking manoeuvre) and tyre/road interaction. To obtain the best possible performance from a tyre model, a number of different measurements are required to support the tyre model parameter identification process. Although tyre vibration and noise behavior has been studied for several decades, there are still some missing links in the process of accurately predicting and controlling the overall tyre/road noise and vibration linked to the difficulty of performing modal testing on a tyre when rotating. This paper deals with the main test benches, experimental activities and modal analysis techniques available nowadays for characterizing the dynamic behavior of a static (unloaded tyre on a fixed hub and loaded tyre on a fixed hub) and a rotating tyre under different boundary conditions. The main results arising from modal analysis of a static and dynamic test on a tyre are highlighted and compared. In particular the effect of rolling speed, inflation pressure, preload, temperature and excitation amplitude on the dynamic response of a rolling tyre will be discussed.Copyright

Operational Modal Analysis of a rotating tyre subject to cleat excitation

Structure-borne tyre/road noise is an important component of the perceived noise annoyance of passenger cars. More in particular, it was observed that crossing road surface discontinuities (e.g. concrete road surface joints, railroad crossing, potholes, …) causes a significant increase in instantaneous exterior noise level. In addition, it has an adverse effect on the interior vehicle NVH in the sense that the passengers experience high-amplitude transient noise and vibrations. Therefore, an extensive research programme was established at the Department of Mechanical Engineering, K.U.Leuven, to study structure-borne tyre/road noise due to road surface discontinuities. As part of the research activities, an original test setup for impact tyre/road noise was developed so that rolling tyre vibrations, radiated noise and dynamic spindle forces could be measured at different rolling speeds. The test setup is based on the tyre-on-tyre principle and a cleat is used to reproduce a road surface discontinuity. This paper concentrates on the data processing techniques used to experimentally obtain the modes of a rolling tyre. Since the forces introduced by the cleat cannot me measured, Operational Modal Analysis was selected as processing technique. A major challenge is the requirement to obtain spatial information on the tire from a single-point measurement device. Therefore, a dedicated triggering and time-domain averaging procedure was elaborated. The purpose of averaging is obviously to reduce random noise whereas triggering is required to be able to correlate different tyre locations that have not been measured at the same time (a singlepoint Laser Doppler Vibrometer was used).