Tire-road Interface Research Articles

Transient Tire Slip Losses Using the Brush Theory

ABSTRACT Tire slip losses have been shown to have a significant impact on vehicle performance in terms of energy efficiency, thus requiring accurate studies. In this paper, the transient dissipation mechanisms connected to the presence of micro-sliding phenomena occurring at the tire–road interface are investigated analytically. The influence of a two-dimensional velocity field inside the contact patch is also considered in light of the new brush theory recently developed by the authors. Theoretical results align with findings already known from literature but suggest that the camber and turn spins contribute differently to the slip losses and should be regarded as separate entities when the camber angle is sufficiently large. The present work shows that an additional amount of power which relates to the initial sliding conditions is generated or lost during the unsteady-state maneuvers. A simple example is presented to illustrate the discrepancy between the microscopic and macroscopic approaches during a transient maneuver.

A Study on the Contact Characteristics of Tires-Roads Based on Pressure-Sensitive Film Technology.

Tire-road characteristics are a critical focus of research in the automotive and transportation industries. On the one hand, the research can help optimize tires' structural design; on the other hand, it can analyze the mechanical response of the pavement structure under the vehicle load. In addition, the non-uniformity distribution of the tire ground stress will also have a direct impact on the skid resistance, which determines the driving safety. Due to the limitation of testing technology, the measurement of tire ground pressure was mainly carried out on a flat test platform, ignoring the roughness of the actual pavement surface texture. The tire-road contact characteristics research on the macro-texture and micro-texture of asphalt pavement needs to be broken through. A high-precision pressure-sensitive film measurement system is utilized to examine the actual contact characteristics between two types of automobile tires and three types of asphalt pavement in this paper. The influence law of pavement texture and patterned tires on the contact area and stress was explored, and the concentration effect of tire-road contact stress was evaluated. The results indicate that the contact area of grounding tires exhibits a nearly linear relationship with tire inflation pressure and load. Notably, the change in load has a more significant influence on the contact area than tire inflation pressure. On asphalt pavement, the contact reduction rate decreases by approximately 5-10% for block pattern tires and 10-15% for longitudinal pattern tires. Furthermore, as the texture depth of the pavement increases, the contact area between tires and the pavement texture decreases. The actual tire-road interface experiences significant stress concentration due to the embedding and meshing effects between the tire and road surface. Even on a flat steel surface, the peak stress at the edge of the tread block exceeds the 0.7 MPa design load, which is about 2.5-3 times higher than the design uniform load. The peak stress between the tire and asphalt pavement reaches 4-10 times the design uniform load, with a rising trend as the pavement texture depth increases. This study can provide relevant experimental technical support for tire design and functional design of asphalt pavement.

Robust Discrete-Time Lateral Control of Racecars by Unknown Input Observers

This brief addresses the robust lateral control problem for self-driving racecars. It proposes a discrete-time estimation and control solution consisting of a delayed unknown input-state observer (UIO) and a robust tracking controller. Based on a nominal vehicle model, describing its motion with respect to a generic desired trajectory and requiring no information about the surrounding environment, the observer reconstructs the total force disturbance signal, resulting from imperfect knowledge of the time-varying tire-road interface characteristics, presence of other vehicles nearby, wind gusts, and other model uncertainty. Then, the controller actively compensates the estimated force and asymptotically steers the tracking error to zero. The brief also presents a closed-loop stability proof of the method, ensuring perfect asymptotic estimation and tracking by the controlled vehicle. The proposed solution advantageously needs no a-priori information about the total disturbance boundedness, additional variables to model uncertainty, or observer parameters to be tuned. Its effectiveness and superiority to existing methods are studied in theory and shown in simulations where a full racecar model, based on the vehicle dynamics blockset, is required to track aggressive maneuvers. Through a faster and more accurate disturbance estimation, the solution robustly ensures better dynamic responses even with measurement noise.

Model Predictive Control of a Multi-Mode Suspension System Using Preview Information and Weight Optimization

Abstract This study examines the effectiveness of a model predictive controller (MPC) on the multimode active suspension concept to reduce driver absorbed power. A multimode suspension uses additional degrees-of-freedom beyond a traditional active suspension. This allows the suspension to address disturbances with multiple frequencies when coupled with a noncausal control scheme such as MPC. A half-car model is developed by placing both active and passive components in series to mitigate high and low frequency disturbances at the tire-road interface. A stepwise MPC with preview information is applied to the model to measure an incoming disturbance. The model includes noise in state feedback and preview information. A Kalman filter addresses process and measurement noise while the preview information is filtered using an exponential moving average. Process and Measurement noise are considered to be known. Four disturbance profiles are examined: step, two-mode, three-mode, and an ISO8608 Class D profile. Weights used for the MPC process are optimized for each profile according to an objective function based on driver absorbed power. For each profile the response for uncontrolled, controlled, and controlled with preview is examined to assess effectiveness of the multimode suspension. Results demonstrate the utility of the multimode suspension supplemented with MPC for each profile. Driver absorbed power decreases by 68%, 99%, 73%, and 89% for the step, two-mode, three-mode, and ISO8608 Class D profile, respectively. Examination of the natural, disturbance, and forcing frequencies suggests that the MPC accounts for the damped natural frequencies of the system in response to incoming disturbances. The system shows potential to improve performance of vehicles traversing extreme terrain or maintaining a stable chassis for a variety of applications. Future work includes examination of the relationship between the damped natural frequencies, the disturbance, and the resulting control law.

Estimation of the Friction Behaviour of Rubber on Wet Rough Road, and Its Application to Tyre Wet Skid Resistance, Using Numerical Simulation

Tyre wet skid resistance greatly affects vehicle safety, and it is dependent on the frictional behaviour at the tyre–road interface; however, the currently available numerical models, using the finite element method, either neglect the road roughness or obtain the rightness using expensive computed tomography scans, rendering them inefficient and complex. This study aims to present an estimation method of rubber slides on a rough road, to study tyre wet skid resistance. A three-dimensional rough road model was established, using the harmonic superposition method; the sealing effect of the water film on a wet road was modelled in terms of the pseudo-hydrodynamic bearing effect; the contact pressure, hysteresis friction, and water film hydrodynamic lift force were calculated. Subsequently, a friction model was established that accounted for the road surface morphology, tyre properties, sliding speed, and contact pressure. The accuracy of the friction model was experimentally validated, using the published experimental results. The friction model was then adopted, to conduct a study of the wet skid resistance of a 205/55R16 tyre with two different tread patterns. The simulation results were consistent with the experimental results of braking distance on a wet road. Finally, the effects of road roughness, tread rubber, load, and inflation pressure on wet skid resistance were carried out and analysed. The works in this paper have important significance and practical value for the development of high-performance tyres.

An extended LuGre-brush tyre model for large camber angles and turning speeds

ABSTRACT This paper presents a novel tyre model which combines the LuGre formulation with the exact brush theory recently developed by the authors, and which accounts for large camber angles and turning speeds. Closed-form solutions for the frictional state at the tyre-road interface are provided for the case of constant slip inputs, considering rectangular and elliptical contact patches. The steady-state tyre characteristics resulting from the proposed approach are compared to those obtained by employing the standard formulation of the LuGre-brush tyre models and the exact brush theory for large camber angles. Then, to cope with the general situation of time-varying slips and spins, two approximated lumped models are developed that describe the aggregate dynamics of the tyre forces and moment. In particular, it is found that the transient evolution of the tangential forces may be approximated by a system of two coupled ordinary differential equations (ODEs), whilst the dynamics of the self-aligning moment may be described by combining two systems of two coupled ODEs. Given its stability properties and ease of implementation, the lumped one may be effectively employed for vehicle state estimation and control purposes.

Deep reinforcement learning-based antilock braking algorithm

Tires play an important role in the performance of vehicular safety systems. Antilock braking system is one of the most important active safety systems that interacts with the tires. Unlike a variety of existing algorithms which are tuned to a specific tire, this research proposes a model-free reinforcement learning-based control algorithm which can adapt to changing tire characteristics and there by effectively utilising the available grip at tire–road interface. The simulation model, consisting of brake actuator dynamics, transportation delays, tire relaxation behaviour, vehicular longitudinal and pitch dynamics, is trained using more than 350,000 random tires. To reduce training time, a parallelisation architecture has been proposed which distributes learning and simulation tasks to different CPU cores. Finally, a conditional variance-based sensitivity analysis with over twelve thousand tires indicate improved grip utilisation at tire–road interface and decreased sensitivity of stopping distance on tire nonlinearity compared to literature version of Bosch algorithm.

Experimental Research on Kinematic Features of Agricultural Tractor Movement on Asphalt Pavement

Experimental research on agricultural tractor movement, acquisition and archiving of kinematic features is an important issue in the analysis of braking and acceleration processes. The obtained traffic parameters depend on the environmental conditions, condition and type of pavement, load, tire pressure and the area of tire-pavement cooperation. The acceleration factor, and in particular the braking process, is determined by the coefficient of friction enabling the assessment of forces and moments acting at the tire-road interface. The kinematic features known as a result of measurements can be used to assess the extent of road safety. The article describes experimental research aimed at understanding the kinematic features of agricultural tractor movement without a trailer on a homogeneous asphalt surface at three pressures in drive tires.

Robustness Analysis for Adaptive Model Predictive and Sliding Mode Controllers Regulating Longitudinal Tire Slip Ratio

This study aims to evaluate the robustness of Adaptive Model Prediction Controllers (AMPC) and First Order Sliding Mode Controllers (FOSMC) facing modelling uncertainties or external disturbances when used to track longitudinal tire slip ratio. Changing road conditions create uncertainties in the friction coefficient of the tire-road interface, and the uncertainty of mass is caused by over/under loads on the nominal mass of the vehicle. the external perturbations are generally linked to the angle of inclination of the road. The efficiency of the controllers, in terms of ensuring the minimum braking time in the face of uncertainties and perturbations, is evaluated by numerical simulation and detailed comparison.

Review of Factors Controlling Skid Resistance at Tire-Pavement Interface

Road safety is of prime importance for pavement engineers and maintenance authorities. Pavement resistance to skidding of the vehicle has long been recognized as one of the leading parameters governing road safety and driving comfort, especially in wet weather conditions. The knowledge of skid resistance offered by pavement surface is very valuable information for road safety enhancements. Skid resistance is defined as the force developed when a tire that is prevented from rotation slides along the pavement surface. Evaluation of skid resistance over time and estimation of factors influencing it are important for pavement maintenance and rehabilitation planning. This paper presents a state-of-the-art review of various research works carried out for assessing critical parameters like surface texture, tire tread, rain intensity, temperature, loading condition, tire inflation pressure, and pavement type which control skid resistance of asphalt pavement at tire-road interface significantly. First, a brief overview of skid resistance and its importance in asphalt pavement is provided. Then, critical parameters influencing skid resistance are identified and reviewed more elaborately. Furthermore, the key relationship between skid resistance and various controlling parameters is reviewed and presented for a better understanding of skid variation analysis. Finally, a general discussion on skid resistance governing factors, their relative importance in maintaining safety and pavement performance, the complexity involved in computation, and established relationships with skid resistance is briefly summarized.

A Novel Nondestructive Procedure for Tire Tread Viscoelastic Characterization

ABSTRACT Vehicle dynamics is largely influenced by the phenomena occurring in the tire-road interface, and a great portion of these phenomena is mainly conditioned by the viscoelastic properties of the tire tread compound. It is not surprising that the possibility of obtaining the viscoelastic response of a compound by means of a nondestructive procedure is a growing research topic that affects application fields ranging from monitoring of the material performance during its entire life cycle to the quantitative analysis of product quality and repeatability of production processes. In this article, a novel nondestructive procedure for the viscoelastic characterization of tire tread compound is proposed. A portable instrument, based on instrumented indentation, was designed and prototyped with the aim to allow a real-time assessment of moduli directly on site. The testing procedure adopted to perform the test on three different compounds was described. A signal-processing procedure was developed for the identification of compound stiffness and damping parameters from which viscoelastic moduli were estimated. The results were also compared with the Dynamic Mechanical Analysis characterization showing the same relative ranking between the compounds with a different trend in temperature due to the amount of the tests' indentation depth.

An anti-lock braking system algorithm using real-time wheel reference slip estimation and control

Knowledge of the tyre-road interface traction limit during braking of a road vehicle can drastically improve safety and ensure stable braking on varied road conditions. This study proposes an optimal reference slip algorithm that determines the road surface while the vehicle is braking, by implicitly tracking the traction limit. It presents wheel slip variance regulation as a potential approach towards reference wheel slip estimation for wheel slip regulation (WSR). The variance regulation approach computes reference wheel slip using past wheel slip estimates and regulates wheel slip variation at a set point. This variance regulation problem was solved using least-squares estimation, yielding reference slip dynamics. A 3-staged nested control architecture was developed with reference slip dynamics to yield an anti-lock braking system (ABS) algorithm consisting of a brake controller, WSR algorithm and reference slip estimation. The algorithm was experimentally corroborated in a Hardware-in-Loop setup consisting of the pneumatic brake system of a heavy commercial road vehicle, and IPG TruckMaker®, a vehicle dynamics simulation software. The proposed ABS algorithm was tested on straight roads with homogeneous surfaces, split friction surfaces, and transition friction surfaces. It ensured stable braking in all road cases, with a 7%–18% reduction in braking distance on homogeneous road surfaces compared to the same vehicle without ABS. The vehicle directional stability was retained on a split-friction surface, and the ABS algorithm was observed to adapt to sudden transitions in the road surface.

A 3-phase combined wheel slip and acceleration threshold algorithm for anti-lock braking in heavy commercial road vehicles

This research presents a rule-based Anti-lock Braking System (ABS) algorithm towards active vehicle safety in Heavy Commercial Road Vehicles (HCRVs). Wheel Slip Regulation (WSR) algorithms, that are constituents of an ABS, are typically either model-based or rule-based. Model-Based Algorithms (MBAs) utilise mathematical models that characterise vehicle dynamics and are intensive in their demand for real-time information. On the other hand, Rule-Based Algorithms (RBAs) operate on set rules with pre-defined thresholds and utilise data from sensors that are typically available on the vehicle. A great deal of advancement has been reported in literature related to MBAs. However, most commercially available RBAs are proprietary in nature and the finer details are seldom revealed. Hence, this work proposes an RBA, which is a combined Slip and Wheel Acceleration Threshold Algorithm (SWATA), including a framework for identifying the importance of thresholds and their magnitudes. SWATA was tested on a Hardware-in-Loop (HiL) setup across varying road and loading conditions, and it provided a maximum of 36% braking distance improvement compared to a case where it was inactive. An adaptive version – ASWATA – is also proposed that can adapt the thresholds according to the particular tyre-road interface. Additionally, a quantitative comparison of the proposed RBA with a Sliding Mode Control (SMC) based MBA, which was developed and tested on the same HiL setup, is presented. It was observed that the performance of the RBA was on par with that of the MBA for most test cases, but with minimal data requirements.

Enhancement of Anti-locking Brake System Performance by using Intelligent Control Technique with Different Road Conditions

Recently, the vehicle brake system equipped with anti-lock braking systems (ABS) is considered one of the most important effective safety systems. The importance of ABS, to get maintains the safety of vehicles on roads during emergency braking and it enables reliable stopping whilst maintaining the vehicle stability and ease steer-ability. Therefore, the aim of this research is to investigate the vehicle braking performance of controlled brake ABS that is designed with three types of controller and compares them, they are bang-bang, Proportional Integral Derivative (PID) and Fuzzy Logic Control (FLC) on rough dry and wet roads to control longitudinal slip. The main obstacles of controller design in automobile systems are concerned to high non-linearities of the mathematical model. 2DOF longitudinal quarter vehicle model with taking into account the rational motion of the tire is used to examine the braking performance. The tire-road interface model and braking system model are included in vehicle model. By reviewing the results, it was found that FLC method has an effective and better effect compared to two methods on the performance of brake system equipped with ABS system. It was found that vehicle stopping distance was reduced by 21.77m and 10.3m with dry and wet asphalt roads respectively compared to braking without ABS for fuzzy control at velocity 100 km/hr.

Tyre rubber friction on a rough road

One of the most challenging aspects of vehicle dynamics is accurate modelling of the tyre-road interface. Forces between the tyre and road need to be accurately represented in simulation. This is challenging over rough roads since the friction changes along the road due to large surface asperities.The Heinrich/Klüppel friction coefficient estimation model has been implemented on smooth roads in the past. However, this study investigates the applicability of using this model over a rough but hard terrain, such as Belgian paving or cobblestones. The model is based on physical properties that can be determined mathematically or experimentally. The study includes detailed terrain topography and the difference between the top and bottom topography is used to determine the radially averaged PSD. Emphasis is placed on finding and implementing the flash temperature in a practical manner that could also be used in further studies.An experimental setup is built to validate the model. The experimental friction coefficient is compared to the friction coefficient calculated using the Heinrich/Klüppel model. The relative percentage error difference between experimental and friction model results is found to be less than 10% on a smooth concrete road and 20% on a rough road (concrete Belgian paving).

Skid resistance: understanding the role of road texture scales using a signal decomposition technique and a friction model

ABSTRACT Skid resistance markedly depends upon road surface texture. That texture is composed of a range of scales each of which contributes differently to the generation of friction at the tire-road interface. This work aims to contribute to understanding the role of these different scales. The method adopted deploys a signal processing technique, termed Empirical Mode Decomposition, to decompose the texture into a set of component profiles of different wavelengths. The Dynamic Friction Model, a computational friction model already validated on real road surfaces, is then used to determine the relative effect of partially recomposed profiles with their components on skid resistance. The results demonstrate the importance of not only ‘small-scale' and ‘large-scale' textures but also their spatial arrangement and shape. Indeed, on wet road surfaces, ‘small-scale-texture' was found to be key to achieving good skid resistance at low speeds, whilst ‘large-scale-texture' was found to be crucial to maintaining it with increasing speed. But furthermore, the distribution of the summits of the large-scale-textures was established as being able to compensate for a lack of small-scale-texture. Conversely, the reverse was established as also being true, with the small sharp local summits of small-scale-texture being found to compensate for a lack of large-scale-texture.

Yaw Angle Control of Heavy Commercial Road Vehicle with Faulty Brake

Faults in an air brake system affect the performance of Heavy Commercial Road Vehicles (HCRVs). One of the major faults in the air brake system is the “out-of-adjustment”of pushrod due to excessive brake wear, which may cause a significant yaw angle deviation from the current path and an increase in stopping distance. Hence, this paper aims to design a controller that would maintain the vehicle’s directional stability under brake fault scenario. In order to design such a controller, knowledge of vehicle side slip angle is essential, but this is not a measurable quantity. Hence, an Artificial Neural Network (ANN) based estimation scheme for side slip angle prediction is also proposed. As an output regulator problem, Sliding Mode Control (SMC) was used for correction of yaw angle under brake fault scenario through appropriate steering angle input. This controller provided a percentage correction of yaw angle of 93.4 % and 99.8 % respectively for fully laden and fully unladen vehicle on a high friction tire road interface surface, and the same corresponding to a low friction tire road interface was 99.8 % and 98.9 % respectively.

Mechatronic Systems to the Braking Mechanisms

With the evolution of technology, the construction and geometry of the piston, together with the materials from which it is made, as well as the related manufacturing technologies, have been continuously improved. Thus, modern engines have become less polluting, working at higher temperatures and pressures. Body aerodynamics have been improved, leading to lower resistance forces from the air. Also, the internal losses of the engines, generated by friction, as well as those at the level of the tire-road interface were diminished. All these improvements to motor vehicles have led to a proportional decrease in native braking capacity. Moreover, this decrease is evident in tonnage vehicles, which are disadvantaged in terms of the small contact area of the friction elements in conventional braking systems. For these reasons as well as due to the attempts to coordinate the platoon of cars, the decrease of the fuel consumption, the increase of the safe speed of movement resulted in the necessity of the development of new auxiliary braking systems, or the improvement of the already existing ones.

Friction on road surfaces contaminated by fine particles: Some new experimental evidences

Accidents increase during the first rain after a long dry period due to the accumulation of fine particles, which contaminates the road surface and induces a friction loss. This paper presents new experimental evidences that help to understand how the particulate contaminants lubricate the tire–road interface. A laboratory test method is developed to reproduce the deposit of contaminant particles on the road surface and measure the friction coefficient on dry and wet contaminated surfaces. Test protocol is described with respect to the contaminant collection, the spreading of contaminant particles on the road specimen and their compaction to simulate the effect of the traffic, the wetting of the test surface to simulate precipitations, and the friction measurement. Friction tests are conducted in dry and wet conditions (by adding successive known quantities of water). Results show that dry particles can induce friction loss and the friction coefficient of dry contaminated surfaces is always lower than that of a dry and clean surface. The dry lubrication mechanism is attributed to shearing and sliding of the particle layer. Water induces first a significant friction drop, attributed to the viscosity of the particles–water mixture, then a friction increase due to a washing effect. Weight analysis shows a tight relationship between the friction coefficient and the mass of contaminants (particles in dry condition and particles–water mixture in wet conditions). There is a minimum in the friction versus water weight variation. Interpretation is made by considering fine particles as a wet granular material. Discussions are made with respect to the influence of particle concentrations and surface texture.

A planar quasi-static constraint mode tyre model

The fast-paced, iterative, vehicle design environment demands efficiency when simulating suspension loads. Towards that end, a computationally efficient, linear, planar, quasi-static tyre model is developed in this work that accurately predicts a tyre's lower frequency, reasonably large amplitude, nonlinear stiffness relationship. The axisymmetric, circumferentially isotropic, stiffness equation is discretised into segments, then parameterised by a single stiffness parameter and two shape parameters. The tyre's deformed shape is independent of the overall tyre stiffness and the forces acting on the tyre. Constraint modes capture enveloping and bridging properties and a recursive method yields the set of active constraints at the tyre–road interface. The nonlinear stiffness of a tyre is captured by enforcing unidirectional geometric boundary conditions. The model parameters are identified semi-empirically; simulated cleat test loads match experiments within 7% including nonlinear stiffness when simulating a flat plate test and a discontinuous stiffness when simulating a cleat test.