ThesisPDF Available

DEVELOPMENT OF A GRIP & THERMODYNAMICS SENSITIVE TYRE / ROAD INTERACTION FORCES ESTIMATION PROCEDURE EMPLOYED IN HIGH-PERFORMANCE VEHICLES SIMULATION

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The target of the activities described in the PhD thesis, fixed in collaboration with a motorsport racing team, with a high performance vehicle manufacturing company and with a tyre research and development technical centre is the development of a procedure able to estimate tyre interaction characteristics, reproducing them in simulation environments taking into account the fundamental friction and thermal phenomena concerning with tyre/road interaction. A first tool, called TRICK, has been developed with the aim to process data acquired from experimental test sessions, estimating tyre interaction forces and slip indices. Once characterized the vehicle, filtering and sensors output correction techniques have been employed on the available data, creating a robust procedure able to generate as an output a "virtual telemetry" and, following a specifically defined track driving routine, to provide tyre interaction experimental curves. TRICK virtual telemetry can be employed as an input for the second tool, TRIP-ID, developed with the aim to identify the parameters of a Pacejka Magic Formula tyre model. The advantage of this kind of procedure is the possibility to simulate the behaviour of a tyre without the bench characterizations provided by tyremakers, with the further benefit to reproduce the real interactions with road and the phenomena involved with it, commonly neglected in bench data. Among such phenomena, one of the most important is surely the effect that temperature induces on tyre performances, especially in racing applications. For this reason a specific model, called TRT, has been realized and characterized by means of proper thermodynamic tests, becoming a fundamental instrument for the simulation of a tyre behaviour as close to reality as possible. One of the most useful features provided by the model is the prediction of the so called "bulk temperature", recognized as directly linked with the tyre frictional performances. With the aim to analyse and understand the complex phenomena concerning with local contact between viscoelastic materials and rough surfaces, GrETA grip model has been developed. The main advantage to which the employment of the grip model conducts is constituted by the possibility to predict the variations induced by different tread compounds or soils on vehicle dynamics, leading to the definition of a setup able to optimise performances as a function of tyre the working conditions. The described models and procedures can cooperate, generating a many-sided and powerful instrument of analysis and simulation; the main features of the available employment solutions can be summarised as follows:  full geometric, thermodynamic, viscoelastic and structural characterization of tyres on which the analyses are focused;  estimation of the tyre interaction characteristic curves from experimental outdoor test data;  definition of a standard track driving procedure that employs tyres in multiple dynamic and thermal conditions;  identification of Pacejka Magic Formula tyre models parameters on the basis of the estimated tyre interaction characteristic curves;  estimation of surface, bulk and inner liner tyre temperatures for variable working conditions and real-time reproduction of tyre thermodynamic behaviour in simulation applications;  correlation of tyre thermal conditions with friction phenomena observable at the interface with road;  prediction of tyre frictional behaviour at tread compound and soil roughness variations;  modelling of tyre interaction by means of MF innovative formulations able to take into account grip and thermodynamic effects on vehicle dynamics;  definition of the optimal wheels and vehicle setup in order to provide the maximum possible performances improvement.
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... The tire dynamic behavior has to be considered from an early design stage as stability, comfort, handling, and noise, vibration, and harshness (NVH) performances depend on it. [1][2][3] On the other side, the characterization of the tire behavior is one of the toughest things because to provide a complete and precise insight on the tire entire working range, the tire should be tested with the measurement accuracy obtainable only in laboratory-controlled conditions and on the vehicle moving on the real road surface by means of an expensive instrumentation. 2,4 above parameters of the vehicle dynamics itself, as the sliding speed of the compound upon road granularity varying the excitation frequency of the stress distribution within the rubber viscoelastic material. ...
... [1][2][3] On the other side, the characterization of the tire behavior is one of the toughest things because to provide a complete and precise insight on the tire entire working range, the tire should be tested with the measurement accuracy obtainable only in laboratory-controlled conditions and on the vehicle moving on the real road surface by means of an expensive instrumentation. 2,4 above parameters of the vehicle dynamics itself, as the sliding speed of the compound upon road granularity varying the excitation frequency of the stress distribution within the rubber viscoelastic material. 6,7 It is worth to highlight that the majority of the test rigs analyze the tires on smooth surfaces and in steadystate conditions. ...
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A tire is an extremely integrated and multi-physical system. From only a mechanical point of view, tires are represented by highly composite multi-layered structures, consisting of a multitude of different materials, synthesized in peculiar rubber matrices, to optimize both the performance and the life cycle. During the tire motion, due to the multi-material thermodynamic interaction within the viscoelastic tire rubber matrix, the dynamic characteristics of a tire may alter considerably. In the following paper, the multibody research comfort and handling tire model is presented. The main purpose of the research comfort and handling tire is to constitute a completely physical carcass infrastructure to correctly transmit the generalized forces and torques from the wheel spindle to the contact patch. The physical model structure is represented by a three-dimensional array of interconnected nodes by means of tension and rotational stiffness and damper elements, attached to the rim modeled as a rigid body. Research comfort and handling tire model purpose is to constitute a structural physical infrastructure for the co-implementation of additional physical modules taking into account the modification of the tire structural properties with temperature, tread viscoelastic compound characteristics, and wear degradation. At the stage, the research comfort and handling tire discrete model has been validated through both static and dynamic shaker test procedures. Static test procedure adopts contact sensitive films for the contact patch estimation at different load and internal pressure conditions, meanwhile the specifically developed sel test regards the tire dynamic characterization purpose at the current stage. The validation of the tire normal interaction in both static and dynamic conditions provided constitutes a necessary development step to the integration of the tangential brush interaction model for studying the handling dynamics and to the analysis of the model response on the uneven surfaces.
... operating and boundary conditions concerning kinematics, dynamics, temperature, pressure, road roughness, etc.) [8,9]. In such a scenario, tyre-road interaction models cover a fundamental role in the modelling of the vehicle system [10,11], due to the tyre's composite structure and intrinsic non-linearity linked to inter-connected multiphysical phenomena [12][13][14], which must guarantee very strict computational constraints to allow the employment in even more severe real-time environments concerning onboard estimation and control logics [15,16]. An overview of modelling approaches and research activities addressing the complexity concerning an accurate mathematical representation of the highly non-linear tyre behaviour has been described in [17,18], highlighting that the biggest challenge is to ensure the trade-off condition between the necessary level of accuracy and the low computational load. ...
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To cite this article: Aleksandr Sakhnevych (2021): Multiphysical MF-based tyre modelling and parametrisation for vehicle setup and control strategies optimisation, Vehicle System Dynamics, ABSTRACT Starting from the earliest phases of design of the vehicle and its control systems, the understanding of tyres is of fundamental importance to govern the overall vehicle dynamics. A properly charac-terised tyre-road interaction model is essential to achieve a reliable vehicle dynamics model on which more design variations can be studied directly in simulation environment optimising both cost and time. The possibility to count on computationally efficient and reliable formulations represents nowadays a great advantage, and the multiphysical Pacejka's Magic Formula (MF-evo) tyre model presented is one of the best trade-off solutions to meet the strict real-time requirements and to reproduce multiphysical variations of the tyre dynamic behaviour towards temperature, pressure and wear effects. A specific methodology has been developed to characterise and to identify the MF-evo parameters with a high grade of accuracy and reliability directly from experimental data. The proposed technique is based on a pre-processing procedure to remove non-physical outliers and to cluster the data, which allows to optimise the multidimensional parameterisation process. To the purpose of validation of the parametrisation routine, data from a motorsport case, exceptionally difficult to reproduce in simulation due particularly significant variations of the tyre dynamics during a single test, have been employed demonstrating the MF-evo model potential and robustness. ARTICLE HISTORY
... In a second step the force characteristics of the tire road contact are parametrized. As this is very much dependent on surface and environmental conditions like ambient and track temperature, an optimization approach is used here, an example can be found in [10]. The result is an adaption of tire stiffness and grip properties to match the measured vehicle motion states vehicle side slip angle, yaw rate and longitudinal acceleration. ...
Chapter
Racecar operation typically takes place in the near-limit range of the vehicle’s tires. Drivers attempt to exploit all of a vehicles potential to achieve the minimum possible laptime around a given circuit. As the vehicles will run on racetracks with varying characteristics and environmental conditions, racing cars are designed to offer a broad range of adjustability with respect to handling properties. Suspension parameters such and camber and toe, as well as aerodynamic parameters such as wing position are examples of commonly adjusted parameters on a racing vehicle. Since development time schedules are tight and ontrack testing time is limited, a virtual tuning process for vehicle parameters is required to remain competitive. Laptime Simulations are widely used to provide laptime prediction as well as insight into the sensitivity of lap time to vehicle parameters. For this reason, lap time simulation procedures for setup optimization are of special interest [1]. Due to the fact that these methods are purely virtual with no involvement of a human driver, it is likely that there are discrepancies between the predicted theoretical laptime and the laptime which is achieved by the driver-vehicle system in reality. The discrepancies between simulated and actual lap time can be attributed to many details, for example inaccurate component modelling or insufficient consideration of handling characteristics. The research found in this article will focus on the latter example.
... Furthermore, the dependence of the interaction between the tyre and the road on the tyre temperature can be described for extreme conditions using, for example, the tool TRICK (the name of which is derived from tyre-road interaction characterization and knowledge). 14,15 The method using the vehicle model does not allow separate characteristics to be obtained for the left tyres and the right tyres. The characteristics describe the lateral force acting on the axle (the sum of the forces acting on both wheels of the axle) as a function of not only the side-slip angle but also the dynamics of the curvilinear vehicle motion. ...
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This paper presents a method of identifying the dynamic characteristics of tyres for non-steady-state conditions on the basis of road measurements on a vehicle. The side force acting on the tyre is presented as a function of not only the slip angle but also the slip angle derivative (i.e. the velocity of the change in the slip angle). Hence, the influence of the manoeuvre dynamics on the tyre characteristics and the difference between the characteristics obtained for steady-state conditions and the characteristics for non-steady-state conditions are shown. Also the results of computer simulations prepared for different types of tyre characteristics are presented in this paper. It is evident from the presented graphs that applying dynamic non-linear tyre characteristics for computer simulations instead of steady-state characteristics enables us to describe the real motion of a vehicle better.
... The input signal for these controllers is the error magnitude, while the output signal is the action which has to be carried out in order to minimize the error itself. In the tyre subsystem, an essential part of the whole vehicle model, an evolved MF set of equations [31] able to simulate the wheel behaviour has been introduced. In this subsystem it is possible to determine the tyres actual grip at any single time and to calculate the longitudinal and lateral interaction forces the tyre is able to perform. ...
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... To express the center of gravity's acceleration vector ‫ܩ‬ with respect to the LTP enu reference system it is necessary to implement a coordinate transformation, so all the calculations are performed in the absolute reference system. A crucial importance is assumed by the Euler Angles used since these highly affect the obtained accelerations in the ‫}ݖݕݔܩ{‬ reference system, and in turn the resulting velocities and sideslip angle [21]. ...
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