Tire Behavior Research Articles

Ranking Tires for Heavy Truck Steering Feel Performance Using a Simulation Model

Abstract The effects of seven different tire sets on heavy truck steering feel characteristics were demonstrated from objective testing. Also, the steering behavior and vehicle dynamics were modeled in order to determine how well the resulting simulations could rank the steering performance of the tire sets relative to the objective results. The objective testing was performed using a 6×4 tractor with a two-axle flatbed semi-trailer. Measured data included steering wheel torque, steering wheel angle, and lateral acceleration behavior resulting from on-center-type steering tests. In addition, the hydraulic pressure from the power steering system was also measured. The tests consisted of multiple cycles at 0.2 Hz and ±0.2 g. Steering-related performance metrics were selected and calculated based on the interaction between measured parameters. The same test procedure was also applied using an analytical model of a steering system. The input was steering wheel torque, and outputs included the road wheel angles at the steer axle, which were then fed into a commercial vehicle dynamics model providing the vehicle dynamics behavior along with feedback required for the steering model (e.g., king pin moments). Tire loads and slip angles were also provided by the vehicle dynamics model and used as input to a tire model predicting tire force and moment behavior. The related metrics were subsequently computed and compared to the measured results. Effects of the different tire sets on steering characteristics were seen from both the objective and simulation tests. Seven performance metrics were applied in a ranking comparison between measured and modeled results. Correlation of the modeled to measured metrics ranged from R2 values of 0.40 to 0.99 for the seven metrics considered.

An optical tire contact pressure test bench

An optical tire contact pressure test bench developed by the IMMa group is described. The measurement system is based on the frustration of total internal reflection (FTIR) of light. The test bench allows performing normal pressure distribution and patch contact shape measurements on passenger car tires. The system is based on the use of a laterally illuminated glass on which the tire leans. Between them a plastic interphase is located that will cause the FTIR of light. A video camera catches the formed shining image through the glass. The brightness level in each pixel of the image can be related to the existing normal pressure. The study of the contact patch provided by the bench makes it possible to characterize tire behaviour under different loading states, inflation pressure, tire defects and toe and camber angles. The bench incorporates a computerized load and control system of the tire operation parameters, an image acquisition module and a data acquisition system that allow monitoring and acting on the experimental variables of interest in the tests such as load on the tire and environmental conditions. A supporting mechanical system incorporated to the bench allows providing the tire with variable toe and camber angles. From the images obtained with this system, the maximum normal pressure points, total force, size and shape of the patch can be determined, which are related to the tire-use conditions. As an application example, results that show the patch size and shape under different load and tire inflation pressures are presented. A further application, which is the use of the system for the detection and study of defective tires is also presented.

Scaled vehicle tire characteristics: dimensionless analysis

This article demonstrates the use of dimensional analysis for scaled vehicle tires. The motivation for this approach is the understanding of realistic nonlinear tire behavior in scaled vehicle control studies. By examining the behavior of vehicle tires within a dimensionless framework, several key tire parameters are developed that allow for an appropriate relationship between full-sized tires and scaled tires. Introducing these scalings into vehicle dynamics studies allows for the development of scaled vehicles that have a high degree of dynamic similitude with full-sized vehicles, but are safer and more economical testbeds on which to develop experimental control strategies. Experimental data are used to compare the nonlinear characteristics for sets of scaled and full-sized tires. Finally, design of a scaled vehicle based on tire characteristics is demonstrated.

A SELF-TUNING ABS CONTROL FOR ELECTROMECHANICAL BRAKING SYSTEMS

One of the main issues of any control strategy for braking systems is to face the many uncertainties due to the strong spread of the system's parameters: road conditions, actuator dynamics, tire behaviour, etc. This paper proposes a self-tuning control for an electromechanical braking system. Electromechanical brake system is a promising replacement for hydraulic brakes in the automotive industry. The proposed control can be seen as a minimum seek algorithm in a highly uncertain situation. Only the measure of the wheel angular speed and a rough measure (or estimate) of the actuator force on the brake pads are required. The proposed control is tested by simulation studies.

Investigation on integrated vehicle chassis control based on vertical and lateral tyre behaviour correlativity

In this article, the integration of vehicle vertical and lateral motion control is investigated via control coordination between active suspension and four wheel steering. With respect to the different treatments of nonlinear tyre vertical and lateral behaviour correlativity, two control approaches based on linear optimal H ∞ synthesis and nonlinear sliding mode control are proposed and studied, respectively. For the former approach, the integrated control benefits have been examined through the overall performance improvement under the influence of external disturbance, such as road unevenness. For the latter approach, the potential of using tyre vertical load influence on lateral behaviour to improve vehicle critical handling performance has been investigated. Simulations and analysis indicate that both the above two approaches exhibit promising effects of vehicle chassis control integration.

Modelling of tire overturning moment and loaded radius

For evaluation of vehicle handling, subjective assessment is currently almost the only criterion. For the purpose of reducing cycle time and avoiding error of subjective assessment, the close-loop objective evaluation system through computer simulations has become an inevitable choice [Gwanghun, G.I.M. and Yongchul, C.H.O.I., 2001, Role of tire modeling on the design process of a tire and vehicle system. ITEC ASIA 2001, Busan, Korea, September 18–20; Guo, K., Ding, H., Zhang, J., Lu, J. and Wang, R., 2003, Development of longitudinal and lateral driver model for autonomous vehicle control. International Journal of Vehicle Design, 36(1), 50–65]. For this reason, the more accurate models of vehicle, tire and driver are necessary. Since structure and operating conditions of tires are very complicated, many researchers have paid more attention to the modeling of tire properties and varieties of tire model have been done to describe the tire behaviour of longitudinal, lateral forces and aligning moment [Pacejka, H.B., 2002, Tyre and Vehicle Dynamics. Butterworth-Heinemann, an imprint of Elsevier Science, ISBN 0-7506-5141-5]. However, there are few studies for the tire overturning moment (TOM), especially under large slip angle and camber angle. For the simulation of vehicle rollover, the expression accuracy of TOM is rather important. In addition, the difference of the loaded radius of left and right tires yields tire roll angle and that also affects vehicle roll behavior. In this paper, the modeling of TOM and loaded radius are presented first, and then the modeling results are compared with tire test data.

Transient Analysis of Tyre Friction Generation Using a Brush Model with Interconnected Viscoelastic Bristles

An analysis of the mechanism of tyre contact force generation under transient conditions is presented. For this purpose, two different versions of a brush model are used, both with inertial and viscoelastic properties. The first model consists of independent bristles, while the second, with a more realistic scenario, introduces viscoelastic circumferential connections between the sequential bristles, which affect the lateral degrees of freedom. Friction between the tyre and the ground follows an experimentally verified stick-slip law. For the model with independent bristles, the state of each bristle at any instant of time depends only on the state of the same bristle at a previous time step. In the second model, the instantaneous state depends on the state of the same bristle at the preceding time step, as well as on the state of the two adjacent bristles at the same time. Simulation results reveal the differences between the two models and most importantly show how transient friction force generation may differ substantially from steady state predictions. The findings suggest that transient tyre behaviour should not be attributed solely to the contributions of the flexible belt and carcass. On the contrary, the observed transience in the neighbourhood of the contact patch should also be taken into account.

Predicting the compressibility behaviour of tire shred samples for landfill applications

Tire shreds have been used as an alternative to crushed stones (gravel) as drainage media in landfill leachate collection systems. The highly compressible nature of tire shreds (25–47% axial strain on vertical stress applications of 20–700 kPa) may reduce the thickness of the tire shred drainage layer to less than 300 mm (minimum design requirement) during the life of the municipal solid waste landfill. There hence exists a need to predict axial strains of tire shred samples in response to vertical stress applications so that the initial thickness of the tire shred drainage layer can be corrected for compression. The present study performs one-dimensional compressibility tests on four tire shred samples and compares the results with stress/strain curves from other studies. The stress/strain curves are developed into charts for choosing the correct initial thickness of tire shred layers that maintain the minimum thickness of 300 mm throughout the life of the landfill. The charts are developed for a range of vertical stresses based on the design height of municipal waste cell and bulk unit weight of municipal waste. Experimental results also showed that despite experiencing large axial strains, the average permeability of the tire shred sample consistently remained two to three orders of magnitude higher than the design performance criterion of 0.01 cm/s for landfill drainage layers. Laboratory experiments, however, need to verify whether long-term chemical and bio-chemical reactions between landfill leachate and the tire shred layer will deteriorate their mechanical functions (hydraulic conductivity, compressibility, strength) beyond permissible limits for geotechnical applications.

Analysis of the transient handling properties of a tyre, based on the coupling of a flexible carcass—belt model with a separate tread incorporating transient viscoelastic frictional properties

The behaviour of tyres under transient handling manoeuvres is studied with the aid of a newly developed model. The model consists of a discretized flexible belt with damping and inertia, connected to the rim by viscoelastic elements representing the carcass. In the neighbourhood of the contact patch, the belt is connected to a separate discretized viscoelastic tread with inertia. A separate algorithm taking into account the radial deflection of the carcass elements is used for the calculation of the contact pressure distribution along the contact patch. Friction follows a stick—slip law taking into consideration the velocity of tread elements, the normal force and the unequal coefficients of friction in the lateral and longitudinal directions. The model seems capable of generating transient forces and moments including the phase lags observed under time-varying kinematic excitations.

Experience with the IMMa tyre test bench for the determination of tyre model parameters using genetic techniques

The study of tyre behaviour is an interesting area in vehicle dynamics research. There are a great number of researchers working in this area. So knowledge of the tyre properties is necessary to design vehicle components and advance control systems properly. For that purpose, mathematical models of the tyre are used in vehicle simulation models. Semiempirical models can be used for this. These kinds of tyre model use a certain number of parameters that define them. Semiempirical models need to fit measurement data to the tyre properties that they define. The determination of these sets of parameters and the measurement data obtained are dealt with in this paper. A new method based on genetic techniques is used to determine these parameters. The main advantages of the method are its simplicity of implementation and its fast convergence to an optimal solution, with no need for an extensive knowledge of the searching space. So, to start the search, it is not necessary to know a set of starting values of the parameters that define the tyre model. A set of measurements that define several tyre properties are obtained on the IMMa tyre test bench. These measurement data are used to compare with results from the method proposed, and a new mutation procedure has been developed.

Vehicle dynamics analysis tasks and related tyre simulation challenges

During the past 20 years, enormous progress has been made in chassis engineering and driveability. Today's vehicles are significantly safer and at the same time more comfortable than their predecessors. Among the reasons are the variety of electronic control systems on offer today, but also the fact that engineers have succeeded in making suspension and chassis design and tuning more precisely and significantly by using modern analysis and simulation methods. This allows product maturity to be assured and intensified, despite wider model ranges and shorter development times. In this context, the significance of modelling and simulation of the tyre behaviour becomes increasingly important. As the link between the vehicle and the road, the tyre ultimately determines the driving properties that can be realized, any latent safety reserves that can be activated, and the vehicle vibration comfort, at least in as far as road-surface-induced excitations are concerned.

Rolling contact between agricultural tire and deformable ground

AbstractWhile external tire mechanics deals with the effect of tires on vehicle behaviour, internal tire mechanics is focused on computation of stress‐strain and heat states in a tire. Analytical and numerical analysis of different level tire substructure is a pre‐condition for a better understanding of tire behaviour and for a suitable choice of practical calculation schemes. The tire is described geometrically non‐linear as a multi‐layered anisotropic torus shell with low transfer shear stiffness. The strains are assumed to be small, however, the cross‐sections of the tire shell will exhibit moderate rotations. In order to reflect energy losses the visco‐elastic behaviour of tire rubber‐cord‐composite is taken into account. Results are used for the determination and improvement of stiffness parameters for external tire models and for Böhm's mass points approach for transient loading of a rolling tire on rigid and deformable ground. This model is modified to the real structure of an agricultural tire with lugs. The soil under the tire is described by different rheological laws of ground surface behaviour in normal and tangential direction. The numerical results of contact calculation are compared with experimental data gained by mechanical multi‐point measurement technique in order to determine the displacements in the inner of a rolling tire. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Finite element simulation of the tyre burst test

The use of predictive finite element (FE) models in tyre design and analysis has become widely popular in recent times. This is largely due to the introduction of high-performance computers in addition to the enhancement in the capabilities of existing proprietary finite element software, thus enabling the efficient use of such tyre models in solving the challenging problems of pneumatic tyre behaviour as an alternative to experimental tests routinely carried out on tyre prototypes. This present work investigates tyre burst behaviour when the tyre is inflated well beyond the manufacturer's recommended maximum pressure. This will help to predict the extent to which a tyre can be loaded before failing catastrophically, thus simulating one of the mandatory tyre qualification tests. Consequently, an axisymmetric finite element tyre model has been developed using the improved capabilities in ABAQUS FE code, which allows the modelling of the tyre burst phenomenon, based on the ultimate strengths of the constituent reinforcement materials. A summary of the results obtained from this model for a passenger car tyre P195/65R15 H91 is presented together with a study of the effect of some tyre design parameters on the tyre burst pressure. Also some recommendations are made for enhancing the functionality of the model.

Behaviour of tire shred – sand mixtures

Tire shreds and tire shred – soil mixtures can be used as alternative backfill material in many geotechnical applications. The reuse of tire shreds may not only address growing environmental and economic concerns, but also help solve geotechnical problems associated with low soil shear strength. In this study, an experimental testing program was undertaken using a large-scale triaxial apparatus with the goal of evaluating the optimum dosage and aspect ratio of tire shreds within granular fills. The effects on shear strength of varying confining pressure and sand matrix relative density were also evaluated. The tire shred content and tire shred aspect ratio were found to influence the stress–strain and volumetric strain behaviour of the mixture. The axial strain at failure was found to increase with increasing tire shred content. Except for specimens of pure tire shreds and with comparatively high tire shred content, the test results showed a dilatant behaviour and a well-defined peak shear strength. The optimum tire shred content (i.e., the one leading to the maximum shear strength) was approximately 35%. For a given tire shred content, increasing the tire shred aspect ratio led to increasing overall shear strength, at least for the range of tire shred aspect ratios considered in this study. The shear strength improvement induced by tire shred inclusions was found to be sensitive to the applied confining pressure, with larger shear strength gains obtained under comparatively low confinement.Key words: tire shreds, shear strength, reinforcement, triaxial testing, stress–strain behaviour.

Cornering Stiffness Adaptation for Improved Side Slip Angle Observation

The vehicle body side slip angle (VBSSA) represents a key variable in vehicle dynamics. It allows to assess vehicle stability in critical driving situations. As it cannot directly be measured with standard sensors it ha to be determined using a vehicle model including an observer. This paper describes a method to increase the accuracy of VBSS A-estimation using adaptation of the cornering stiffnesses. The adaptation bases on a simple but efficient nonlinear approximation equation of the lateral wheel force. It is capable to describe the tire behavior up to the stability limit by means of two independent parameters.

A Modelling Approach to Tire-Obstacle Interaction

In order to improve the behavior of heavy off-road vehicles,the use of numerical simulation has become an absolutely necessarystage. The main difficulty resides in the validity of the tire-groundinteraction model, for a large range of obstacles and test courses, andat all acceptable speeds. In this paper, a new obstacle-tireinteraction model has been presented. Starting from the simple fact thatvertical tire behavior depends essentially on the air contained in thetire, this approach is based on the tire air volume optimisation. Thismodel has been investigated in the case of tire statical deflection, andgood correlation has been obtained with experimental results.

DETERMINATION OF MAGIC TYRE MODEL PARAMETERS

Abstract Tyre behaviour plays an important role in vehicle dynamics studies. The Magic Formula Tyre Model is a semi-empirical tyre model which can describe tyre behaviour quite accurately. A set of Magic Formula parameters constitutes the basis of the model. The determination of these parameters out of tyre measurement data produced by the Delft tyre measurement trailer is dealt with in this paper. Problems that may occur during the "fitting process' are indicated as well. The comparison between the latest version and the 'Monte Carlo version' of the tyre model shows that the latest version results in better fitting results especially for camber influences and (even more important) in an improvement on the fitting process.

タイヤの動的モデルと数値シミュレーションに関する研究(OS.8 動解析の新展開-マルチボディ,モード解析,最適設計-)

タイヤの動的モデルと数値シミュレーションに関する研究(OS.8 動解析の新展開-マルチボディ,モード解析,最適設計-)

Transient Finite Element Analysis of Tire Dynamic Behavior

Abstract Dynamic behavior of a pneumatic tire is simulated by use of an explicit finite element (FE) code. Different parts of the tire and their corresponding material properties are taken into account in the FE model because they play a significant role in tire dynamics. The work presented in this study discusses simulation of cornering behavior, braking behavior, and combined cornering-cum-braking behavior. The effects of camber angle and grooved tread on tire cornering behavior are discussed. ABAQUS/Explicit, a general non-linear FE code, was used for these simulations. To predict the Magic Formula characteristics over a complete range, various simulations are performed at different normal loads and operating conditions. Predicted Magic Formula curves from the simulation results for various dynamic conditions closely follow the experimental data curves. Even though these simulations demand huge computational resources, the predicted Magic Formula curves can be directly used as input in the complete study of vehicle dynamics. Thus, this proposed approach minimizes the costly experiments needed to determine the Magic Formula characteristics and thereby forms a viable tool in the design and the development of tires.

Characterisation of the contact patch behaviour of an automobile tyre by physical testing

This paper describes an experimental investigation into the contact patch behaviour of an automobile tyre. The investigation aims to enhance understanding of tyre behaviour in the contact region with reference to the authors' need to validate advanced finite element simulations. Physical tests were carried out with an experimental rolling tyre on flat bed and rolling drum machines, each instrumented with a tri-axial stress transducer. Many plots giving the normal pressure and shear stress distributions under free-rolling and cornering (slip and camber angle) conditions are presented for a high friction surface. A comparison is made between the contact patch behaviour when the tyre is rolled on the horizontal (at 0.18 km/h) and drum (10 to 50 km/h) surfaces. The characteristics of the stress distributions are discussed and related to the actual physical behaviour of the tyre.