Off-road Tire Research Articles

Experimental and Numerical Investigations of Tractive Performance of Off-Road Tires on Gravel Terrain

In this work, an indoor soil-bin is designed to investigate the tire–terrain interaction mechanisms for the off-road tires rolling on the gravel terrain. The soil-bin test is carried out by the indoor soil-bin experimental device and the three-dimensional (3D) finite element (FE) and discrete element (DE) coupling method under the same particles conditions, respectively. First, with the indoor soil-bin measurement system, the repeatability of the soil-bin experiments is employed to validate the experimental device and the numerical models. Moreover, the tractive performance experiments of the off-road tires with two tread patterns, smooth and grooved interacting with gravel terrain, are performed at the slip of 10%, 20% and 30%, respectively, to obtain the tractive force and the rim sinkage. Second, the corresponding numerical models are also established, and simulated by the FE–DE coupling method, where the FEM and the DEM are used to describe the off-road tires and the gravel terrain, respectively. The tractive mechanisms of the off-road tires in interaction with the gravel terrain such as the tractive force and the rim sinkage are investigated numerically. Meanwhile, The dynamics and discontinuity of the gravel assembly are described by the presented approach. Besides, both the results of the simulations and experiments indicate that tread patterns and slip conditions have great influence on the tire tractive performance. Finally, the numerical simulations and the experimental results qualitatively show good agreements, which certifies the effectiveness of the FE–DE coupling method in the tractive performance analysis of tire–gravel terrain interactions.

In-Plane Flexible Beam on Elastic Foundation With Combined Sidewall Stiffness Tire Model for Heavy-Loaded Off-Road Tire

Combining the flexible carcass beam and the radial sidewall element, flexible beam on elastic foundation with combined sidewall stiffness tire model is proposed for heavy-loaded off-road tire with a large section ratio. The circumferential vibration of flexible carcass is modeled as Euler beam and the influence of inflation pressure on the circumferential vibration of flexible carcass is investigated with the modal experiment and theoretical modeling. The structural stiffness caused by the sidewall curvature and pretension stiffness caused by the inflation pressure is combined for the radial sidewall element. The influence of the sidewall structural parameters on the combined stiffness of sidewall and modal resonant frequency is researched and discussed. The nonlinear combined stiffness of sidewall is investigated with respect to the radial sidewall deformation. Experimental and theoretical results show that: (1) the combined stiffness of sidewall can character the pretension stiffness caused by inflation pressure and the structural stiffness led by the sidewall curvature and material properties and (2) the combined stiffness of sidewall is nonlinear with respect to the radial sidewall deformation, which is prominent with high inflation pressure. Taking the flexibility characteristic of tire carcass and the nonlinear stiffness of sidewall into consideration, flexible beam on elastic foundation with combined sidewall stiffness tire model is suitable for the heavy-loaded off-road tire with a large section ratio or tires under impulsive loading and large deformation.

Development and validation of an off-road rigid ring truck tyre model

A rigid ring tyre model is developed using MATLAB/Simulink to predict the in-plane and out-of-plane rigid tyre model characteristics of a truck tyre running over different terrains. The in-plane and out-of-plane tyre characteristics include traction, cornering and vertical stiffness. The terrains used include hard surface, flooded surface, snow, and several soils such as dry and moist sand. The MATLAB/Simulink tyre model is validated against previously computed and published tyre-terrain interaction results performed using advanced simulations technique. The rigid ring tyre model is further implemented into a full vehicle model to evaluate the full vehicle response under several operating conditions.

Characterization of machine learning algorithms for slippage estimation in planetary exploration rovers

This paper presents a comprehensive comparison of well-known machine learning algorithms for estimating discrete slip events associated with individual wheels in planetary exploration rovers. This analysis is performed with various tuning configurations for each algorithm (55 setups). This research also shows the key role that environment plays in the performance of the learning algorithms: rover speed (0.05–0.25 [m/s]), type of terrain (gravel vs. sand), and tire type (off-road tires vs. smooth tires). These contributions are validated by using a broad data set collected using a planetary rover equipped with proprioceptive sensing. This work not only identifies the best algorithm to be deployed for discrete slip estimation, but it also helps with the selection and the mounting position of the sensing systems to be employed in future robotic planetary missions.

FE-DEM with interchangeable modeling for off-road tire traction analysis

This study examines a new finite element/discrete element method (FE-DEM) with interchangeable modeling between FEM and DEM for tire traction analysis. In the method, named iFE-DEM, the soil in a soil bin is modeled initially by FEM except for the region under or near the tire, which is modeled using DEM. When the FEM tire model starts to travel over DEM soil elements, the updated tire location will activate new conversion of modeling from FEM to DEM so that the zone of influence around the contact interface between tire and soil can be analyzed continuously using DEM. Those mobilized DEM elements rearward of the tire might be converted again to FEM elements by assuming that the effect of the stress state in DEM generated by tire travel might be negligible. The computational time for two-dimensional iFE-DEM analysis of a slip of 40% using the smallest region of initial DEM under the tire could be reduced to 23% of that obtained using DEM only soil modeling.

Development of a discrete roughness index for longitudinal road profiles

Engineers of off-road equipment, on-road vehicles, pavement and tyres must assess the roughness of a terrain surface for the design of their products. A ubiquitous roughness index is the International Roughness Index (IRI), which quantifies the roughness of a section of road based on the average suspension travel for a particular vehicle at a prescribed speed. The Discrete Roughness Index (DRI) developed in this work addresses a fundamental limitation of the IRI. Specifically, the DRI is calculated for each discretely measured location along a terrain surface; furthermore, the DRI is applicable to vehicles travelling at varying speeds and parameters other than the Golden Quarter-Car on which the IRI is based. The development begins with a consistent discretisation of the terrain surface, vehicle response and the IRI. The Fractional Response Coefficient is then developed which serves a fundamental role in the development of the DRI. Finally, the DRI is developed and its properties are discussed through theory and simulation of the ASTM E1926-08 Profile. One important property of the average DRI is that it converges to the IRI as the distance between sampled points becomes smaller, for the particular case when the Golden Quarter-Car model is simulated at 80 kph. The DRI is a more general solution of the roughness estimation problem than the IRI; therefore, the IRI is a proper subset of the DRI in which the DRI is averaged over a section of road.

Vehicle tyres and road accidents

A research team from Texas A&M University at Qatar (TAMUQ) and Texas A&M Transportation Institute (TTI) conducted during the past three years a study that focused on traffic safety situation in Qatar, tyre properties, and the influence of tyre properties on driving safety. The presentation will compare and contrast the specifications of the Gulf Standardization Organization (GSO) and other specifications used in Europe and United States. Consequently, the presentation will discuss recommendation for changes in GSO tyre specifications in order to better reflect climatic conditions in the region. One of the road safety issues in Qatar is the routine use of some drivers of off-road tyres on paved roads. The research team conducted comprehensive testing of off-road tyres and standard tyres that are used in a typical large SUV. In addition, the team developed computer models and conducted finite element analysis to simulate the driving and manoeuvring conditions of the different types of tyres. The experimental measurements and computer simulations revealed valuable information about performance of off-road tyres and risks associated of using them on roads in Qatar. The results will be very useful for the policy makers and the driving public regarding the development of regulations that control the use of off-road tyres.

Parameterisation and modelling of large off-road tyres for on-road handling analyses

Very few off-road vehicles are used exclusively under off-road conditions. Good off-road mobility dictates large high aspect ratio tyres with aggressive tread, low inflation pressures, soft suspension for good comfort as well as other vehicle parameters including large ground clearance and the related high centre of mass. This results in less-than-satisfactory vehicle handling and high rollover propensity on hard terrains at higher speeds. In order to simulate vehicle handling and roll over propensities, on non-deformable terrain, tyre characteristics in the form of side-force versus slip-angle curves, as well as suitable tyre models are required. For large off-road tyres these characteristics are not readily available. Tyre manufacturers either do not have these characteristics, or do not openly publish them. Similarly, the majority of tyre models have been developed and validated for passenger car tyres and their applicability to large tyres are unknown. The purpose of this study is to measure side-force versus slip-angle characteristics for a Michelin 16.00R20 XZL tyre – typically used on off-road trucks. The data is used to parameterise Fiala, UA (University of Arizona), Pacejka89 and FTire models. Simulation results are compared to both steady state and dynamic handling test results to determine the accuracy of these models.

Finite element modelling of off-road tyres for radial tyre model parameterization

This paper investigates the possibility of using a coarse finite element model with bulk material properties, to model the vertical force–displacement characteristics of a tyre, for the purpose of tyre model parameterization. The paper proves the approach on an off-road tyre of a light truck. The practical application is intended, however, for very large tyres where physical testing is not feasible. The paper indicates that it is feasible to obtain bulk material properties from tensile tests on specimens cut from different positions on a tyre and to use these test results to parameterize suitable non-linear anisotropic material models. The non-linear elements defined in the neo-Hookean model and the Ogden model, as well as the elements with different linear orthogonal stiffnesses, are combined with each other to simulate the global material properties of the tread and the sidewall of the tyre. The global behaviour of the finite element model is analysed by comparing experimental results and simulation data on a flat surface as well as various lateral and longitudinal cleats. The results confirm that the finite element model can predict with acceptable accuracy the vertical force–displacement characteristics, as well as the sidewall deformation of the tyre under static loading conditions on a flat surface and also on various different cleats, by using equivalent (global) material properties. The approach is sufficiently accurate to be used in the parameterization of various tyre models.

Side slip angle prediction model of an off-road tire on different terrains

In this paper, two mathematical models were developed to predict side slip angle for driven wheels of a prototype tractor. The independent variables involved moisture content, cone index, normal load, inflation pressure, angular velocity, and steer angle with three levels. Response Surface Method (RSM) was used to extract models and to analyze results. The tractor was driven in circular paths to the left side to apply all experimental treatments. Among different mathematical models, the linear models with coefficient of determination of 0.8978 and 0.8983 were chosen to predict side slip angle of the left and right wheels, respectively. The mathematical models analysis of variance showed that all factors had significant effect on tire side slip angle. In all experiments the inner wheel side slip angle was lower than that of the outer. An inverse effect for cone index and wheel normal load was observed while other factors effects were found to be direct. Also, the angular velocity had the highest impact on side slip angle for both rear wheels.

Parameterization and modelling of large off-road tyres for ride analyses: Part 2 – Parameterization and validation of tyre models

Every mathematical model used in a simulation is an idealization and simplification of reality. Vehicle dynamic simulations that go beyond the fundamental investigations require complex multi-body simulation models. The tyre–road interaction presents one of the biggest challenges in creating an accurate vehicle model. Many tyre models have been proposed and developed but proper validation studies are less accessible. These models were mostly developed and validated for passenger car tyres for application on relatively smooth roads. The improvement of ride comfort, safety and structural integrity of large off-road vehicles, over rough terrain, has become more significant in the development process of heavy vehicles. This paper investigates whether existing tyre models can be used to accurately describe the vertical behaviour of large off road tyres while driving over uneven terrain. [1] Presented an extensive set of experimentally determined parameterization and validation data for a large off-road tyre. Both laboratory and field test are performed for various loads, inflation pressures and terrain inputs. The parameterization process of four tyre models or contact models are discussed in detail. The parameterized models are then validated against test results on various hard but rough off-road terrain and the results are discussed.

Parameterization and modelling of large off-road tyres for ride analyses: Part 1 – Obtaining parameterization data

Multi-body vehicle dynamic simulations play a significant role in the design and development process of off-road vehicles. These simulations require tyre models to describe the forces and moments, which are generated in the tyre-road contact patch. All external forces acting on the vehicle are either generated in the tyre–road interface or are due to aerodynamic effects, which can be neglected at typical off-road driving speeds. The accuracy of the tyre model describing the forces in the tyre–road interface is thus of exceptional importance. The parameterization of most tyre models relies on some experimental test data that is used to extract the necessary information to fit model parameters. Acquiring the test data, with sufficient accuracy, is often the biggest challenge in the parameterization process. Published data for large off-road tyres is virtually non-existent. This paper describes different methods to acquire the required parameterization data. Experimental measurements are conducted on a 16.00R20 Michelin XZL tyre. Laboratory tests, as well as field tests, over discrete obstacles and uneven hard surfaces were conducted. The paper presents an extensive set of parameterization and validation test data on a large off-road tyre that can be used by researchers to develop and validate tyre models.

Development of a 3-D quasi-steady state tyre model for on-road and off-road vehicle dynamics simulations: Part III - off-road flexible tyre model

Development of a 3-D quasi-steady state tyre model for on-road and off-road vehicle dynamics simulations: Part III - off-road flexible tyre model

Development of a 3-D quasi-static tyre model for on-road and off-road vehicle dynamics simulations: Part I - on-road flexible tyre model

The research conducted in this study deals with the development of a simplified brush-based tyre model for on-road simulation, together with a simplified off-road wheel/tyre model. The on-road tyre model is developed based on data collected by NHTSA throughout the years, while the off-road tyre model is developed based on observations of experimental data and photographic evidence collected by various terramechanics researchers within the last few decades. The principle behind the model revolves around the integration of the stresses at the contact interface and has its basis in terramechanics. The model was parameterised from test data to acquire static and dynamic friction coefficients, cornering and longitudinal stiffness, as well as camber stiffness. The results are compared with test data and show good correlation. This paper is the first of a series of three papers on the modelling tyres for both on- and off-road operations.

Development of a 3-D quasi-steady-state tyre model for on-road and off-road vehicle dynamics simulations: Part II - off-road rigid wheel model

This study presents the development of a simplified brush-based tyre model for on-road simulation, together with a simplified off-road wheel/tyre model that has the capability to revert back to on-road trend of behaviour on firmer soils. The on-road tyre model is developed based on empirical data collected by NHSTA, while the off-road tyre model is developed based on observations of experimental data and photographic evidence collected by various terramechanics researchers within the last few decades. Using theoretical analysis and empirical data, the tyre deformation geometry is determined to establish the tractive forces in off-road operation. The first step of any off-road vehicle is to model the condition where the soil is much more deformable than the tyre, where the tyre can be modelled as a rigid wheel. This study explores the development of the rigid wheel mode of the model, using dry sandy terrain, an example of extremely deformable soil. This paper is the second of three papers on the modelling of tyres for both on and off-road operations.

Multi-Wheeled Combat Vehicle Tire Modeling on Rigid and Soft Terrain

Multi-wheeled off-road vehicles performance depends not only on the total engine power but also on its distribution among the drive axles/wheels. In turn, this distribution is largely regulated by the drivetrain layout and its torque distribution which is constrained by the interaction between the wheels and the terrain (rigid or soft soil). In this paper three-dimensional, non-linear Finite Element Analysis (FEA) off-road tire models on rigid and soft terrain were developed using PAM-CRASH and the general trends of vertical load-deflection, cornering characteristics and aligning moment on rigid terrains are compared with published measured data of a similar tire for validation purposes. Non-linear tire look-up tables for rigid and soft terrain were developed based on FEA off-road tire simulation results and used for vehicle simulation using the multi-body dynamics code TruckSim. The predictions of vehicle handling characteristics and transient response during lane change test on rigid road at different vehicle speeds were compared with simulation results for same vehicle configuration using real experimental tire data. Simulation results are compared on the basis of vehicle steering, yaw rates and accelerations. The published US Army validation criteria has been used to validate simulation results.

Off-road tire modeling and the multi-pass effect for vehicle dynamics simulation

Off-road operations are critical in many fields and the complexity of the tire-terrain interaction deeply affects vehicle performance. In this paper, a semi-empirical off-road tire model is discussed. The efforts of several researchers are brought together into a single model able to predict the main features of a tire operating in off-road scenarios by computing drawbar pull, driving torque, lateral force, slip-sinkage phenomenon and the multi-pass behavior. The approach is principally based on works by Wong, Reece, Chan, and Sandu and it is extended in order to catch into a single model the fundamental features of a tire running on soft soil. A thorough discussion of the methodology is conducted in order to highlight strengths and weakness of different implementations. The study considers rigid wheels and flexible tires and analyzes the longitudinal and the lateral dynamics. Being computationally inexpensive a semi-empirical model is attractive for real time vehicle dynamics simulations. To the best knowledge of the authors, current vehicle dynamics codes poorly account for off-road operations where tire-terrain interaction dominates vehicle performance. In this paper two soils are considered: a loose sandy terrain and a firmer loam. Results show that the model realistically predicts longitudinal and lateral forces providing at the same time good estimates of the slip-sinkage behavior and tire parameters sensitivity.

Off-road tyre model for rollover mitigation strategies

This paper presents an off-road tyre model for use in rollover mitigation strategies for a vehicle driven on off-road terrain. A baseline tyre model was first developed through rolling road testing. Off-road tyre testing was then performed on dirt and gravel driving surfaces to develop scaling factors for extending the baseline tyre model to off-road conditions. A yaw and roll stability control algorithm was then developed and implemented in a vehicle simulation environment. The results show that the proposed control algorithm enhances vehicle roll stability and prevents vehicle rollover for the studied emergency manoeuvres on dry asphalt, dirt and gravel.

Experimental Analysis of Tread Pattern Effects on Tire Tractive Performance on Sand using an Indoor Traction Measurement System with Forced-slip Mechanism

An indoor traction measurement system was redesigned to improve the measurement of tractive performance for off-road tires and to compare experimental tire traction results with those of a tire performance simulation. The system comprises a soil bin, a mixing and compaction device, and a single wheel tester with a forced-slip mechanism. The range of available slip is further extensible than that of a conventional system. Tractive performance of four automotive tires with smooth, lug, rib and block tread patterns was tested on sand. Experimental results show that the tire with lug pattern or block pattern exhibited higher drawbar pull than other tread patterned tires for slip greater than 17.8%.

Experimental analysis of the contact pressure distribution in an off-road tyre

This paper presents the results of an extended method of measurement on a tyre for an off-road vehicle 175/82 R16, inserting Prescale paper at the contact with the ground. The experimental analysis of the pressures is carried out, in a cross-sectional direction, in five zones corresponding to the middle of the single dowels that constitute the tread. The results are analysed by means of suitable software so as to refer easily to the value of the pressure. The obtained results are critically analysed and the results are compared with those obtained by the formulae of Rowland and MacLaurin, and by the nominal pressure at the ground, concluding that the expression of MMP for vehicles on wheels is simply to consider a pointer of the performances, in comparison with other vehicles or wheels, rather than a real prediction of the pressure on the ground. Furthermore, a good agreement is found between the tyre deflection calculated and measured experimentally.