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An Application of TRIP-ID: MF Identification Tool for an Automobile Tire Interaction Curves Dataset: Proceedings of the Second International Conference of IFToMM Italy
Abstract
One of the most diffused tire/road interaction models, widely employed in simulation applications, is the Pacejka’s Magic Formula (MF) [1, 2]. It is a semi-empirical model able to fit full scale test data, characterized by a large number of coefficients, often called micro-parameters, grouped basing on physical considerations in order to create specific functions, called macro-parameters. MF model coefficients provided by tire manufacturers are generally not fully representative of the behaviour of tires in contact with road. This is due to the testing conditions employed to identify model coefficients: tests are usually performed on a specific rolling bench or on a flat-trac (Tire testing system, commercialised by MTS Systems Corporation. It applies forces and motions to a tire running on a continuous flat belt.), that keep the tire in contact with a steel or an abrasive paper covered belt. The impossibility to test the tires under real working conditions causes unavoidable approximation errors, mainly due to differences in thermal exchanges and wear phenomena [3] between tire/belt and real tire/road contact. Therefore it is commonly necessary to modify the MF coefficients in order to improve the bench data correlation and to be able to validate vehicle models with data coming from experimental tests. The aim of the developed tool, called TRIP-ID (Tire/Road Interaction Parameters IDentification), is to provide an innovative procedure to identify the Pacejka coefficients basing on the experimental tests carried out measuring global vehicle data during outdoor track sessions. In the presented application, the procedure collects and processes the data provided by TRICK tool [4], allowing to eliminate the outlier points, to discriminate wear and thermal phenomena, taking into account the combined slip condition and the effects of vertical load and camber angle on the global grip. The innovative approach proposed can be useful to reproduce in real time simulation applications the feedback that high performances tires give to sport vehicle drivers, whose interest and skills are focused on keeping them in the optimal thermal range. The coupling of a properly modified MF model with a thermal and with a friction model can provide a reliable simulation and analysis instrument for drivers, carmakers and tire producers.
This textbook covers handling and performance of both road and race cars. Mathematical models of vehicles are developed always paying attention to state the relevant assumptions and to provide explanations for each step. This innovative approach provides a deep, yet simple, analysis of the dynamics of vehicles. The reader will soon achieve a clear understanding of the subject, which will be of great help both in dealing with the challenges of designing and testing new vehicles and in tackling new research topics.
The book deals with several relevant topics in vehicle dynamics that are not discussed elsewhere and this new edition includes thoroughly revised chapters, with new developments, and many worked exercises.
Praise for the previous edition:
Great book! It has changed drastically our approach on many topics. We are now using part of its theory on a daily basis to constantly improve ride and handling performances.
--- Antonino Pizzuto, Head of Chassis Development Group at Hyundai Motor Europe Technical Center
Astonishingly good! Everything is described in a very compelling and complete way. Some parts use a different approach than other books.
--- Andrea Quintarelli, Automotive Engineer
Designers and technicians involved in vehicle dynamics face during their daily activities with the need of reliable data regarding tyres and their physical behaviour. The solution is often provided by bench characterizations, rarely able to test tyres in real working conditions as concerns road surface and the consequential thermal and frictional phenomena. The aim of the developed procedure is the determination of the tyre/road interaction curves basing on the data acquired during experimental sessions performed employing the whole vehicle as a sort of moving lab, taking into account effects commonly neglected.
The analysis two-phase flow inside centrifugal pumps is a fundamental issue in several engineering applications. This often represents a bad working condition with respect to single phase one, causing head reduction, efficiency decrease, and higher operational costs in terms of energy and money. The paper reports a numerical analysis of bubbles behavior inside centrifugal pumps. Equations regulating the air bubble motion within the rotor of a centrifugal pump have been solved considering the effects of all forces acting. Coalescence phenomena have been investigated too, in order to identify how gas zone presence in the rotor can lead to anomalous working condition. Results are reported in graphs and diagrams varying bubble dimension and water flow rate. An experimental approach to visualize the two-phase flow field inside the impeller is presented too. Images have been acquired, elaborated, compared with numerical results, and discussed in order to understand the interaction between gas phase and liquid phase and to correlate this behavior with the energy dissipation phenomena for a centrifugal pump.
Book available at HALF PRICE (50% off), shipping included worldwide till MARCH 31, 2016 here
http://www.springer.com/en/book/9789401785327 (Springer website)
THE MORE YOU KNOW VEHICLE DYNAMICS, THE MORE YOU'LL BE SURPRISED
Vehicle dynamics is often perceived as a quite intuitive subject. As a matter of fact, lots of people are able to drive a car. Nevertheless, without a rigorous mathematical formulation it is very difficult to truly understand the physical phenomena involved in the motion of a road vehicle.
In this book, mathematical models of vehicles are developed, always paying attention to state the relevant assumptions and to provide explanations for each step. This approach allows for a deep, yet simple, analysis of the dynamics of vehicles, without having to resort to foggy concepts. The reader will soon achieve a clear understanding of the subject, which will be of great help both in dealing with the challenges of designing and testing new vehicles and in tackling new research topics.
However, there is much more than that. Quite surprisingly, it is shown that several classical concepts, such as the understeer gradient or the roll axis, are either wrong or inadequate and need to be replaced.
The book covers handling and performance of both road and race cars. A new approach, called MAP (Map of Achievable Performance), is presented and thoroughly discussed. It provides a global and intuitive picture of the handling features of a vehicle. Moreover, the book also deals with several relevant topics in vehicle dynamics that have never been discussed before. Even very experienced people should find the book interesting and stimulating.
This new book is not a translation of the Italian Dinamica del Veicolo; by the same author. Actually, in some sense, this new book is totally different, with new topics and with new points of view for the topics covered in the Italian book as well.
In the paper a new physical tyre thermal model is presented. The model, called Thermo Racing Tyre (TRT) was developed in collaboration between the Department of Industrial Engineering of the University of Naples Federico II and a top ranking motorsport team.
The model is three-dimensional and takes into account all the heat flows and the generative terms occurring in a tyre. The cooling to the track and to external air and the heat flows inside the system are modelled.
Regarding the generative terms, in addition to the friction energy developed in the contact patch, the strain
energy loss is evaluated. The model inputs come out from telemetry data, while its thermodynamic parameters come either from literature or from dedicated experimental tests.
The model gives in output the temperature circumferential distribution in the different tyre layers (surface,
bulk, inner liner), as well as all the heat flows.
These information have been used also in interaction models in order to estimate local grip value.
According to the most recent approaches, the friction coefficient arising between tyre rubber and road can be seen as constituted by three components: adhesion, deforming hysteresis and wear.
This paper deals with the estimation of the hysteretic component of friction. This component is due to indentation phenomena regarding contact mechanics of deformable bodies sliding on the asperities of a rough substrate, which exert oscillating forces at the interface, leading to cyclic deformations of the rubber and then to energy "dissipation" via its internal damping. To evaluate this component, a physical model able to calculate energy dissipation of a rubber block indented by a rigid asperity in sliding contact has been built. To this aim the visco-elastic characteristics of the material have been taken into account.
The road profile has been modelled as the sum of two sinusoidal waves characterizing the macro and the micro roughness scales.
The results coming out from the physical model have been validated by means both of FEM models results and of experimental tests carried on a pin on disk tribometer.
The present work represents a first approach for the realization of a methodology for objects location and recognition. The choice objects was the starting point of the study; it has been decided to consider nuts and bolts of various dimensions. Then in order to eliminate the noise added to the images a neural network was designed. Once the desired pictures were obtained, an algorithm, based on the theory of the fuzzy sets, was applied, for detecting the position of each objects. The instruments used were low cost: a digital camera, one stand, equipped with four lamps assuring, for each acquisition, a diffused lighting system, one personal computer.
An algorithm for minimizing a nonlinear function subject to nonlinear inequality constraints is described. It applies sequential
quadratic programming techniques to a sequence of barrier problems, and uses trust regions to ensure the robustness of the
iteration and to allow the direct use of second order derivatives. This framework permits primal and primal-dual steps, but
the paper focuses on the primal version of the new algorithm. An analysis of the convergence properties of this method is
presented.
An interior-point method for nonlinear programming is presented. It enjoys the flexibility of switching between a line search
method that computes steps by factoring the primal-dual equations and a trust region method that uses a conjugate gradient
iteration. Steps computed by direct factorization are always tried first, but if they are deemed ineffective, a trust region
iteration that guarantees progress toward stationarity is invoked. To demonstrate its effectiveness, the algorithm is implemented
in the Knitro [6,28] software package and is extensively tested on a wide selection of test problems.
A bewilderingly large number of statistical quantities have been proposed to study outliers and influence of individual observations in regression analysis. In this article we describe the inter-relationships which exist among the proposed measures. An examination of these relationships leads us to conclude that only three of these measures along with some graphical displays can provide an analyst a complete picture of outliers (major discrepant points) and points which excessively influence the fitted regression equation. Illustrative examples based on real data are presented.
The 3rd edition of The Science and Technology of Rubber provides a broad survey of elastomers with special emphasis on materials with a rubber-like elasticity. As in the 2nd edition, the emphasis remains on a unified treatment of the material; exploring topics from the chemical aspects such as elastomer synthesis and curing, through recent theoretical developments and characterization of equilibrium and dynamic properties, to the final applications of rubber, including tire engineering and manufacturing. Many advances have been made in polymer and elastomers research over the past ten years since the 2nd edition was published. Updated material stresses the continuous relationship between the ongoing research in synthesis, physics, structure and mechanics of rubber technology and industrial applications. Special attention is paid to recent advances in rubber-like elasticity theory and new processing techniques for elastomers. This new edition is comprised of 20% new material, including a new chapter on environmental issues and tire recycling.
The tire and vehicle setup definition, able to optimise grip performance and thermal working conditions, can make the real difference as for motorsport racing teams, used to deal with relevant wear and degradation phenomena, as for tire makers, requesting for design solutions aimed to obtain enduring and stable tread characteristics, as finally for the development of safety systems, conceived in order to maximise road friction, both for worn and unworn tires. The activity discussed in the paper deals with the analysis of the effects that tire wear induces in vehicle performance, in particular as concerns the consequences that tread removal has on thermal and frictional tire behaviour. The physical modelling of complex tire–road interaction phenomena and the employment of specific simulation tools developed by the Vehicle Dynamics UniNa research group allow to predict the tire temperature local distribution by means of TRT model and the adhesive and hysteretic components of friction, thanks to GrETA model. The cooperation between the cited instruments enables the user to study the modifications that a reduced tread thickness, and consequently a decreased SEL (Strain Energy Loss) and dissipative tread volume, cause on the overall vehicle dynamic performance.
In this paper a spray behaviour based on digitalised images is presented for a specific fluid the working range of a spray, the main parameters indicating the spray performances, e.g DeLavan data sheet, cone angle, supply pressure and mass flow rate are defined. Such parameters determine the spray behaviour but they don't give any answer about the main parameter whose variation determines a different pattern of the atomization. To atomize a high viscous fluid and to achieve an efficient lubrication, the drops of the spray jet have to coalesce and form a continuous liquid film in a very short time. To achieve this kind of behaviour the spray has to generate the droplets in a particular range of diameters so, their deformation after the impact, have to minimize the coalescence time. In this paper the behaviour of a pressure swirl spray working with a high viscous fluid its spectra of droplets and a numerical simulation of the internal flow are presented.
The most powerful engine, the most sophisticated aerodynamic devices or the most complex control systems will not improve vehicle performances if the forces exchanged with the road are not optimized by proper employment and knowledge of tires. The vehicle interface with the ground is constituted by the sum of small surfaces, wide about as one of our palms, in which tire/road interaction forces are exchanged. From this it is clear to see how the optimization of tire behavior represents a key-factor in the definition of the best setup of the whole vehicle.Nowadays, people and companies playing a role in automotive sector are looking for the optimal solution to model and understand tire's behavior both in experimental and simulation environments. The studies carried out and the tool developed herein demonstrate a new approach in tire characterization and in vehicle simulation procedures. This enables the reproduction of the dynamic response of a tire through the use of specific track sessions, carried out with the aim to employ the vehicle as a moving lab.The final product, named TRICK tool (Tire/Road Interaction Characterization and Knowledge), comprises of a vehicle model which processes experimental signals acquired from vehicle CAN bus and from sideslip angle estimation additional instrumentation. The output of the tool is several extra "virtual telemetry" channels, based on the time history of the acquired signals and containing force and slip estimations, useful to provide tire interaction characteristics. TRICK results can be integrated with the physical models developed by the Vehicle Dynamics UniNa research group, providing a multitude of working solutions and constituting an ideal instrument for the prediction and the simulation of the real tire dynamics.
An account is given of the latest version 3 of the Magic Formula tyre model. The model provides a set of mathematical formulae from which the forces and moment acting from road to tyre can be calculated at longitudinal, lateral and camber slip conditions, which may occur simultaneously. The model aims at an accurate description of measured steady-state tyre behaviour. The coefficients of the basic formula represent typifying quantities of the tyre characteristic. By selecting proper values, the characteristics for either side force, aligning torque or fore and aft force can be obtained. The new version of the model contains physically based formulations to avoid the introduction of correction factors. Double-sided, possibly non-symmetric pure slip curves are employed as the basis for combined slip calculations. Suggestions are given to estimate the driving part of the longitudinal slip curve and to represent the characteristic at rolling backwards.
Vehicle steering dynamics depends on the tire lateral characteristics. In particular, the relationship between the tire lateral force and the slip angle is a crucial element in the analysis and design of vehicle lateral dynamics and controls. This relationship is generally obtained through laboratory tests, but the laboratory test procedures have two major limitations: (I) the simulated road surface may not represent certain real road conditions; (II) the test environment may not sufficiently mimic the tire characteristics under realistic operating conditions, such as large tire-vehicle interactions under emergency conditions or the changes of suspension and/or steering geometry. It is advantageous to develop an identification approach for tire lateral characteristics using a minimum set of on-board vehicle sensors when the tires are operated in a real configuration and environment. An ideal identification procedure should be insensitive to noise and predict the vehicle lateral behavior accurately. A pointwise updating approach with a Kalman filter using a nonlinear vehicle model is designed to address this problem. The effectiveness of the approach is demonstrated using tires with and without snow chains.