As vehicle dynamics research delves deeper into better insights in performance, modeling, and vehicle controls, one area remains of utmost importance: tire and road friction forces. The vehicle???s interaction with the road remains the dominant mean of vehicle control. Ultimately, the tire-road interaction will determine the majority of the vehicle???s capabilities and as the understanding of the interface improves, so too can the performance. With more computationally intensive systems being instrumented into modern vehicle systems, one is able to observe a great deal of important vehicle states directly for the remaining vehicle information; excellent estimation techniques are providing the rest of the insights. This study looks at the possible improvements that can be observed by implementing an adaptive dynamic tire model that is physical and flexible enough to permit time varying tire performance. The tire model selected is the Average Lumped LuGre Friction Tire Model, which was originally developed from physical properties of friction and tire systems. The material presented here examines the possibility of an adaptive tire model, which can be implemented on a real-time vehicle platform. The adaptive tire model is just one section of an entire control strategy that is being developed by General Motors in partnership with the University of Waterloo. The approach allows for estimated and measured vehicle information to provide input excitation for the tire model when driven with real-world conditions that enabling tire estimations. The tire model would then provide the controller information indicating the expected tire capacity and compares it with the instantaneous loading. The adaptive tire model has been tested with flat road experimental cases and the results provided reasonable estimates. The experimentation was performed with a fully instrumented research vehicle that used in-wheel force transducers, and later repeated with a completely different non-instrumented fully electric vehicle. The concepts and investigation presented here has initiated the ground work for a real-time implementation of a full adaptive tire model. Further work is still required to evaluate the influence of a range of operating conditions, tire pressure, and of different tire types. However, the findings indicate that this approach can produce reasonable results for the specified conditions examined.

Sensor-embedded tires, known as intelligent tires, have been widely studied because they are believed to provide reliable and crucial information on tire-road contact characteristics e.g., slip, forces and deformation of tires. Vehicle control systems such as ABS and VSP (Vehicle Stability Program) can be enhanced by leveraging this information since control algorithms can be updated based on directly measured parameters from intelligent tire rather than estimated parameters based on complex vehicle dynamics and on-board sensor measurements. Moreover, it is also expected that intelligent tires can be utilized for the purpose of the analysis of tire characteristics, taking into consideration that the measurements from the sensors inside the tire would contain considerable information on tire behavior in the real driving scenarios. In this study, estimation methods for the tire-road contact features by utilizing intelligent tires are investigated. Also, it was discussed how to identify key tire parameters based on the fusion technology of intelligent tire and tire modeling. To achieve goals, extensive literature reviews on the estimation methods using the intelligent tire system was conducted at first. Strain-based intelligent tires were introduced and tested in the laboratory for this research. Based on the literature review and test results, estimation methods for diverse tire-road contact characteristics such as slippages and contact forces have been proposed. These estimation methods can be grouped into two categories: statistical regressions and model based methods. For statistical regressions, synthetic regressors were proposed for the estimation of contact parameters such as contact lengths, rough contact shapes, test loads and slip angles. In the model-based method, the brush type tire model was incorporated into the estimation process to predict lateral forces. Estimated parameters using suggested methods agreed well with measured values in the laboratory environment. By utilizing sensor measurements from intelligent tires, the tire physical characteristics related to in-plane dynamics of the tire, such as stiffness of the belt and sidewall, contact pressure distribution and internal damping, were identified based on the combination of strain measurements and a flexible ring tire model. The radial deformation of the tread band was directly obtained from strain measurements based on the strain-deformation relationship. Tire parameters were identified by fitting the radial deformations from the flexible ring model to those derived from strain measurements. This approach removed the complex and repeated procedure to satisfy the contact3 constraints between the tread and the road surface in the traditional ring model. For tires with different specifications, identification using the suggested method was conducted and their results are compared with results from conventional methods and tests, which shows good agreements. This approach is available for the tire standing still or rolling at low speeds. For tires rolling at high speeds, advanced tire model was implemented and associated with strain measurements to estimate dynamic stiffness, internal damping effects as well as dynamic pressure distributions. Strains were measured for a specific tire under various test conditions to be used in suggested identification methods. After estimating key tire parameters step by step, dynamic pressure distributions was finally estimated and used to update the estimation algorithm for lateral forces. This updated estimation method predicted lateral forces more accurately than the conventional method. Overall, this research will serve as a stepping stone for developing a new generation of intelligent tire capable of monitoring physical tire characteristics as well as providing parameters for enhanced vehicle controls. / PHD

In any automotive system, the tires play a very crucial role in defining both the safety and performance of the vehicle. The interaction between the tire and the road surface determines the vehicle's ability to accelerate, decelerate and steer. Having information about this interaction in real-time can be very valuable for the on-board advanced active safety systems to mitigate the risks ahead of time and keep the vehicle stable. The crucial information which can be obtained from the tire includes but are not limited to tire-road friction, tire forces (longitudinal, lateral), normal load, road surface characteristics and tire pressure. This information can be acquired through indirect vehicle dynamics based estimation algorithms or through direct measurements using sensors inside the tire. However, the indirect estimations fail to give an accurate measure of the vehicle state in certain conditions (e.g. side winds, road banking, surface change) and require ABS or VSC activation before the estimation begins. Therefore, to improve the performance of these active stability systems, direct measurement based approaches must be explored. This research expands the applications of Intelligent tire and focuses on using the sensor based measurement approach to develop estimation algorithms relating to tire force measurement. A tri-axial accelerometer is attached to the inner liner of the tire (Intelligent Tire) and two of such tires are placed on an instrumented (MSW, VBox, IMU, Encoders) VW Jetta. Different controlled tests are carried out on the instrumented vehicle and the Intelligent tire signal is analyzed to extract features related to the tire forces and pressure. Due to unavailability of direct force measurements at the wheel, a VW Jetta simulation model is developed in CarSim and the extracted features are validated with a good correlation. / Master of Science

Used vulcanized rubber tires have caused serious trouble worldwide. Current disposal and recycling methods all have undesirable side effects, and they generally do not produce maximum benefits. A thermocatalytic process using aluminum chloride as the main catalyst was demonstrated previously from 1992 to 1995 in our laboratory to convert used rubber tire to branched and ringed hydrocarbons. Products fell in the range of C4 to C8. Little to no gaseous products or fuel oil hydrocarbons of lower value were present. This project extended the previous experiments to accumulate laboratory data, and provide fundamental understanding of the thermocatalytic decomposition reaction of the model compounds including styrene-butadiene copolymers (SBR), butyl, and natural rubber. The liquid product yields of SBR and natural rubber consistently represented 20 to 30% of the original feedstock by weight. Generally, approximately 1 to 3% of the feedstock was converted to naphtha, while the remainder was liquefied petroleum gas. The liquid yields for butyl rubber were significantly higher than for SBR and natural rubber, generally ranging from 30 to 40% of the feedstock. Experiments were conducted to separate the catalyst from the residue by evaporation. Temperatures between 400 °C and 500 °C range are required to drive off significant amounts of catalyst. Decomposition of the catalyst also occurred in the recovery process. Reports in the literature and our observations strongly suggest that the AlCl3 forms an organometallic complex with the decomposing hydrocarbons so that it becomes integrated into the residue. Catalyst mixtures also were tested. Both AlCl3/NaCl and AlCl3/KCl mixtures had very small AlCl3 partial pressures at temperatures as high as 250 °C, unlike pure AlCl3 and AlCl3/MgCl2 mixtures. With the AlCl3/NaCl mixtures, decomposition of the rubber was observed at temperatures as low as 150 °C, although the reaction rates were considerably slower at lower temperatures. The amount of naphtha produced by the reaction also increased markedly, as did the yields of aromatics and cyclic paraffin. Recommendations are made for future research to definitively determine the economic and technical feasibility of the proposed thermocatalytic depolymerization process.

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Used vulcanized rubber tires have caused serious trouble worldwide. Current disposal and recycling methods all have undesirable side effects, and they generally do not produce maximum benefits. A thermocatalytic process using aluminum chloride as the main catalyst was demonstrated previously from 1992 to 1995 in our laboratory to convert used rubber tire to branched and ringed hydrocarbons. Products fell in the range of C4 to C8. Little to no gaseous products or fuel oil hydrocarbons of lower value were present. This project extended the previous experiments to accumulate laboratory data, and provide fundamental understanding of the thermocatalytic decomposition reaction of the model compounds including styrene-butadiene copolymers (SBR), butyl, and natural rubber. The liquid product yields of SBR and natural rubber consistently represented 20 to 30% of the original feedstock by weight. Generally, approximately 1 to 3% of the feedstock was converted to naphtha, while the remainder was liquefied petroleum gas. The liquid yields for butyl rubber were significantly higher than for SBR and natural rubber, generally ranging from 30 to 40% of the feedstock. Experiments were conducted to separate the catalyst from the residue by evaporation. Temperatures between 400 °C and 500 °C range are required to drive off significant amounts of catalyst. Decomposition of the catalyst also occurred in the recovery process. Reports in the literature and our observations strongly suggest that the AlCl3 forms an organometallic complex with the decomposing hydrocarbons so that it becomes integrated into the residue. Catalyst mixtures also were tested. Both AlCl3/NaCl and AlCl3/KCl mixtures had very small AlCl3 partial pressures at temperatures as high as 250 °C, unlike pure AlCl3 and AlCl3/MgCl2 mixtures. With the AlCl3/NaCl mixtures, decomposition of the rubber was observed at temperatures as low as 150 °C, although the reaction rates were considerably slower at lower temperatures. The amount of naphtha produced by the reaction also increased markedly, as did the yields of aromatics and cyclic paraffin. Recommendations are made for future research to definitively determine the economic and technical feasibility of the proposed thermocatalytic depolymerization process.

The development work of a race car revolves around numerous goals such as drag reduction, maximizing downforce and side force, and maintaining balance. Commonly, these goals are to be met at the same time thus increasing the level of difficulty to achieve them. The methods for data acquisitions available to a race team during the season is mostly limited to wind tunnel testing and computational fluid dynamics, both of which are being heavily regulated by sanctioning bodies. While these methods enable data collection on a regular basis with repeat-ability they are still only a simulation, and as such they come with some margin of error due to a number of factors. A significant factor for correlation error is the effect of tires on the flow field around the vehicle. This error is a product of a number of deficiencies in the simulations such as inability to capture loaded radius, contact patch deformation in Y direction, sidewall deformation and overall shifts in tire dimensions. These deficiencies are evident in most WT testing yet can be captured in CFD. It is unknown just how much they do affect the aerodynamics performance of the car. That aside, it is very difficult to correlate those findings as most correlation work is done at WT which has been said to be insufficient with regards to tire effect modeling. Some work had been published on the effect of tire deformation on race car aerodynamics, showing a large contribution to performance as the wake from the front tires moves downstream to interact with body components. Yet the work done so far focuses mostly on open wheel race cars where the tire and wheel assembly is completely exposed in all directions, suggesting a large effect on aerodynamics. This study bridges the gap between understanding the effects of tire deformation on race car aerodynamics on open wheel race cars and closed wheel race cars. The vehicle in question is a hybrid of the two, exhibiting flow features that are common to closed wheel race cars due to each tire being fully enclosed from front and top. At the same time the vehicle is presenting the downstream wake effect similar to the one in open wheel race cars as the rear of the wheelhouse is open. This is done by introducing a deformable tire model using FEA commercial code. A methodology for quick and accurate model generation is presented to properly represent true tire dimensions, contact patch size and shape, and deformed dimension, all while maintaining design flexibility as the model allows for different inflation pressures to be simulated. A file system is offered to produce CFD watertight STL files that can easily be imported to a CFD analysis, while the analysis itself presents the forces and flow structures effected by incorporating tire deformation to the model. An inflation pressure sweep is added to the study in order to evaluate the influence of tire stiffness on deformation and how this results in aerodynamic gain or loss. A comparison between wind tunnel correlation domain to a curved domain is done to describe the sensitivity each domain has with regards to tire deformation, as each of them provides a different approach to simulating a cornering condition. The Study suggests introducing tire deformation has a substantial effect on the flow field increasing both drag and downforce.In addition, flow patterns are revealed that can be capitalized by designing for specific cornering condition tire geometry. A deformed tire model offers more stable results under curved and yawed flow. Moreover, the curved domain presents a completely different side force value for both deformed and rigid tires with some downforce distribution sensitivity due to inflation pressure.

The interaction between a tire and road surface is of critical importance as the motion of a car in both transient and steady-state maneuvers is predicated on the friction forces generated at the tire-road interface. A general method for predicting friction coefficients for an arbitrary asphalt pavement surface would be an invaluable engineering tool for designing many vehicle safety and performance features, tire design, and improving asphalt-aggregate mixtures used for pavement surfaces by manipulating texture. General, physics-based methods for predicting friction are incredibly difficult, if not impossible to realize—However, for the specific case of rubber sliding across a rough surface, the primary physical mechanisms responsible for friction, notably rubber hysteresis, can be modeled. The objective of the subsequent research is to investigate one such physics model, referred to as Persson Theory, and implement the constitutive equations into a MatLab® code to be solved numerically. The model uses high-resolution surface measurements, along with some of the physical properties of rubber as inputs and outputs the kinetic friction coefficient. The Persson model was successfully implemented into MatLab® and high resolution measurements (from optical microscopy and imaging software) were obtained for a variety of surfaces. Friction coefficients were calculated for each surface and compared with measured friction values obtained from British Pendulum testing. The accuracy and feasibility of the Persson model are discussed and results are compared with a simpler, semi-empirical indenter model. A brief discussion of the merits and drawbacks of the Persson model are offered along with recommendations for future research based on the information acquired from the present study. / Master of Science

Weftless Bead design has long been in existence and still used in many passenger car, bus, truck and agriculture tractors. The ideal bead design is a high strength flexible cable with minimal cross section and covered by rubberized nylon, rayon or steel wire side wall. The basic tire bead designs are weftless bead with rubberized ribbon of parallel wires of multiple wound layers and a continuous wire wound in sufficient number of loops to give the required strength. Weftless bead failures generally occur within about 5cm from the end of the overlapping parallel wire ribbon. The cause for this failure is generally attributed to the mounting process in which the diameter of the tire bead is changed during the mounting process in the well of the rim. A finite element model of the tire bead was developed and under the known stresses of the mounting and final use conditions. The Weftless bead generally consists of five steel wires in parallel in a continuous rubber tape or ribbons, which loosely secures the wires in a soft insulating rubber. The ribbon is wound into a hoop with four courses resulting in a grommet composed of a stack of wires. This ribbon with ten cut ends forming a splice, with five at the inner cut edge and five at the outer cut edge. A continuous bead formed from a single wire does not have this failure prone splice region. Field data and the finite element calculations show the failure point of the weftless bead is almost always at the under lap or at the starting point of the weftless bead. Continuous wire bead have significant advantages in safety over the Weftless bead still used in tires.

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