Shear compliant cellular structures are being considered for shear band applications due to low hysteretic energy loss and the ability to design the effective properties of the material through geometric modifications.  In this paper, a rectangular shaped cellular shear band for a non-pneumatic tire is introduced which utilizes a tapered bristle geometry.  One challenge in the design of cellular structures is that shear compliance is limited by the maximum stress incurred in the structure during deflection.  As such, the structures should be designed to reduce stress concentrations so that material deformation throughout the structure can be utilized efficiently to achieve high compliance.  The bristle concept developed in this paper utilizes a tapered geometry which results in an even distribution of maximum bending stress along the bristle profile, resulting in increased compliance with high stiffness.  An analytical model is developed for the tapered profile to determine bending stiffness based on a desired amount of deflection and maximum bending stress.  Numerical tests are conducted using Abaqus to validate the analytical model, find the effective properties, the resulting contact pressure and the rolling resistance of the tapered bristle design.

It is well-known that acoustic modes exist in tire cavities.  Previous research on tire cavity modes has focused on the splitting of this mode owing to tire loading and rotation, and on the transmission of structure-borne noise to the vehicle interior due to force that the tire cavity mode exerts on the wheel hub.  In contrast, here the major concern is the identification of the tire surface vibration and the sound radiation from the tire surface that can be attributed to the tire cavity mode.

The tire cavity mode results from the interference of airborne, acoustical waves propagating in opposite directions within the tire cavity.  Those waves drive corresponding waves in the tire carcass.  Here, the surface normal vibration of a point-driven tire has been measured over a complete circumference by using a scanning laser Doppler vibrometer.  When the space-frequency data is transformed to the wavenumber-frequency domain, a clear feature that can be attributed to the tire cavity mode becomes visible.  Wavenumber filtering (to remove the effect of structure-borne waves in the tire carcass), followed by an inverse transform, reveals the spatial pattern of vibration on the tire surface resulting from the tire cavity mode.  Although the magnitude of the surface vibration resulting from the tire cavity mode is small, its radiation efficiency is high owing to the high phase speed of the acoustic waves that create the tire cavity mode.  It has also been found, that, as expected, tire vibration features associated with the tire cavity mode disappear when the tire is filled with fibrous, sound absorbing material.  The splitting of the tire cavity mode into two modes having slightly different frequencies will also be demonstrated, and the degree of the split will be compared with theoretical predictions.  Finally, measurements of sound radiation from a tire driven by a steady-state, point input, and from a tire driven by a uniform impact over the contact patch area will be presented, and the features associated with the tire cavity mode will be highlighted.

The environment inside an automobile tire is typically harsh, with temperature extremes ranging from -25°C to 140°C. Often, these temperature extremes preclude the use of batteries for sensor nodes embedded inside an intelligent tire. The high vibration levels inside a tire have the potential to generate electrical power using vibration based energy harvesting techniques. In this paper, the feasibility of using an inertial vibrating energy harvester unit to power a sensor module being used to monitor the tire road interaction parameters is assessed. To predict the electrical power output of the generator, a generic analytical model based on the transfer of energy within the system has been derived. The vibration measurements taken from the test conducted using accelerometers embedded in the tire have been applied as an excitation to the model to predict the power output for a device of suitable dimensions and to study the feasibility of this concept. The power generator unit is adapted to the tire vibration spectra and the superimposed acceleration signal. The harvester utilizes the radial accelerations, which are impacts resulting from the tire–road contact and are present even at constant vehicle speeds. For the intelligent tire applications, a special compact harvester design has been proposed that is able to withstand large shocks and vibrations. Suitable mathematical models for different harvester configurations have been developed to identify the best configuration suited for use inside a tire. The harvester unit demonstrates power generation over a wide speed range and enables sensor systems to transmit tire information at desired rates. The proposed concept addresses one of the key challenges in the realization of the intelligent tire system concepts, by presenting a battery-less power supply unit which can generate power that is sufficient for a multitude of wireless platforms such as ZigBee and Wi-Fi protocols which are expected to find their way in the next generation intelligent tires. These harvesters designed for the harsh tire environments provide a distinct advantage in cost and flexibility of installation while extending the lifetime of the power supply for sensor data acquisition and communication. Results indicate the viability of the procedure outlined in the paper.

This paper investigates the use of computational and experimental methods to characterize the behavior of an automobile tire. First a 3D finite element model of standard reference test tire (SRTT) was developed to better understand the tire deformation under loading conditions. A parametric study of inflation pressure, normal loading, camber angle and slip angle was carried out to capture the influence of these parameters. A parametric study of the combined case scenario of the effects of the previously mentioned parameters was also performed.

A wireless sensor suite comprising of analog devices (strain, pressure and temperature sensors) was developed to capture the tire deformation under loading conditions similar to the ones used in running the finite element model. This sensor suite formed the basis for experimentally verifying the trends captured by the finite element model on a custom built tire test stand with capabilities of mimicking real-time conditions of a tire in contact with road. Using the results from the experiments and the finite element model an empirical model was developed which demonstrates how the hoop strains measured on the inner surface of the tire could be used to quantify desired parameters such as camber, slip and normal load. This model outlines empirical equations that relate strains to the contact area, slip (including slip angle and slip ratio), camber and normal load.   

KEY WORDS:  camber, 3D FEM, tire deformations, hoop strain, contact area, normal load, empirical model, tire sensors, strain gages, slip ratio, slip angle