FTire Model Documentation - cosin

1 FTire - Flexible Structure Tire ModelModelization and Parameter SpecificationDocument Revision: 2018-3-r17933iContents1 Legal Notices12 Aims and Scope of FTire23 FTire Implementation and Interfaces34 FTire Mechanical Model .. Thermal Model .. Thermal Model Structure.. Heat Generation and Heat Transfer Model .. Determination of Heat Transfer Coefficients on Basis ofSteady-State Temperatures. Determination of Heat Capacities on Basis of Heating Time Constants.. Tread Wear Model .. Air Volume Vibration Model .. Flexible and Viscoplastic Rim Model .. 105 FTire Data Files.. Parameterization Process.. Preparation of the Identification Process.. Identification/Validation of Footprint Images.. Identification/Validation of Static Properties.. Identification/Validation of Steady-State Rolling Properties.. Identification/Validation of Friction Characteristics.. Identification/Validation of Dynamic Cleat Tests.. 146 FTire Parameter Scheme of tables.

2 Size, Geometry, Tire Specification, and Tread Pattern.. Mass, Moments of Inertia, Inflation Pressure, and Volume.. Structural Stiffness, Damping, and Hysteresis.. Tread Geometry, Stiffness, Damping, and Friction.. Temperature and Wear.. Imperfections.. Misuse Data.. Rim Data.. TPMS Sensor Data.. Numerical Settings.. 467 Operating Conditions498 Additional Runtime and Output Control519 Undocumented Data Items6010 TYDEX-Conform Output Signals6211 Model Changes Log and Compatibility Mode63 Index69ii1 Legal NoticesThis Documentation is intended for qualified users who will exercise sound engineering judgment and expertisein the use of the FTire software. The FTire software is inherently complex, and the explanations in thisdocumentation are not intended to be exhaustive or to apply to any particular situation. Users are cautionedto satisfy themselves as to the accuracy and results of scientific software shall not be responsible for the accuracy or usefulness of any analysis performed usingthe FTire software or the explanations in this Documentation .

3 cosin scientific software shall not be responsiblefor the consequences of any errors or omissions that may appear in this FTire software is available under license from cosin scientific software and may be used or reproducedonly in accordance with the terms of such license. This Documentation is subject to the terms and conditionsof the then current software license agreement to which the Documentation Documentation and the software described in this Documentation are subject to change without part of this Documentation may be reproduced or distributed in any form without prior written permissionof cosin scientific FTire software is a product of cosin scientific software,Muenchen, Aims and Scope of FTireFTire (Flexible StructureTireModel) is a full 3D nonlinear in-plane and out-of-plane tiresimulation Model . Itis used by engineers in the vehicle and tire industry worldwide. Sophisticated 2D and 3D rigid and flexible roadsurface description models and evaluation methods, and powerful toolboxes for tire and road data processingmake FTire the most comprehensive software package for tiredynamics simulation on the is designed for vehicle comfort simulations and prediction of road loads on road irregularities even withextremely short wave-lengths.

4 It can also be used as a structural dynamics based, highly nonlinear and dynamictire Model for handling studies without modifications of input explains most of the complex tire phenomena on a mechanical, thermodynamical, and tribological basis,with very good correlation to measurements: structural dynamics based, spatial nonlinear in-plane and out-of-plane tire Model for simulation of beltdynamics, local contact patch pressure distribution, rolling resistance, side-wall contact, large camberangles and misuse scenarios; suitable for a frequency range up to 200 Hz, excited by shortsurface wavelengths, mass imbalance,non-uniformity of tire and/or rim, air cavity vibrations, or irregular tread patterns; very fast and flexible, up to real-time capability. Orders of magnitude faster than explicit FE models; simulation of imbalances by inhomogeneous mass and stiffness distribution, radius variation, and localtread wear; belt temperature distribution Model ; air volume vibration Model ; capability of tire slipping on rim for very large drive or brake torques; integrated flexible and/or viscoplastic rim Model ; support for user-defined wear, temperature distribution,and rim flexibility models; full integration of cosin /road digital road library with support for complex rigid time-invariant and time-variant road surfaces; full integration of cosin /soil digital road library with support for flexible and deformable road surfaces; advanced online animation with belt deformation animation, tire temperature distribution animation,pressure distribution plots, road surface visualization and movie export; robust, multi-core system enabled solver engine; parameter editing and validation tools.

5 Tailored parameter fitting tool ( FTire /fit).23 FTire Implementation and InterfacesThe FTire core library can be connected to all important simulation environments, by using cosin s tire interface(CTI), a C/C++ API. CTI provides atime-discrete generalized interfaceand reduces the implementationeffort of FTire to a minimum. CTI is used by the FTire implementations in Adams (all variants), MotionSolve,SIMPACK, Abaqus, VI-CarRealTime, Matlab/Simulink, dSPACE-ASM, CarSim/TruckSim/BikeSim, IPG Car-maker/Truckmaker, CASCaDE, cosin /mbs, DAFUL, Dymola/Modelica, FEDEM, Mesa Verde, PAM-Crash,RecurDyn, veDyna, Motion, and Matlab/Simulink anS-function layer is available ( FTire /link). ThisS-function is completed by a respectiveSimulink interfaces are designed to run an arbitrarily large number of tire instances either case, the coupling to the vehicle or suspension Model of the calling program is done by therigidbody state variablesof the rim, that is: positionof the rim center in the inertial frame; translational velocity vectorof the rim center; angular orientationof the rim, defined by the transformation matrix from the rim-fixed frame to theinertial frame.

6 Euler angles, Cardan angles, or Euler parameters of the rim can be passed by an alternativeAPI call. So the user can pass coordinates in the native reference frame of the calling application; rotational velocity vectorof the returns forces and torques acting on the rim center, represented in the global coordinate , FTire can be used to simultaneously integrate the rim rotation with respect to the this use mode, not the rigid-body states of the rim, but rather those of the wheel-carrier are the inputs,together with the driving and the maximum absolute braking torque. The output torque vector then does notcontain the share in the direction of the wheel rotation. FTire eventually modulates the braking torque, if thewheel is blocked, in order to maintain this blocking as long as it is FTire Mechanical ModelFTire is based on a structural dynamics based tire modeling this core mechanical Model , the tire belt is described as an extensible and flexible ring, carrying bendingstiffnesses, elastically founded on the rim by distributed,partially dynamic stiffnesses in radial, tangential, andlateral direction.

7 The degrees of freedom of this ring are such that belt in-plane, as well as out-of-plane,motions are possible. The ring is numerically approximatedby a finite number of belt elements . These beltelements are coupled with their direct neighbors by stiff springs and by bending stiffnesses both in-plane stiffnesses, bending stiffnesses, and damping factors are calculated during pre-processing, fitting the pre-scribed modal and static properties (cf. list of data below).To every belt element, a number (typically 5 to 50) of mass-less tread blocks are associated. These blocks carrynonlinear stiffness and damping properties in radial, tangential, and lateral direction. The radial deflectionsof the blocks depend on the road profile, locus, and orientation of the associated belt elements. Tangentialand lateral deflections are determined by the sliding velocity on the ground and the local values of the slidingcoefficient. The latter depends on ground pressure and sliding velocity. Radial , tangential , and lateral isto be understood relatively to the orientation of the belt element, whereas sliding velocity is the block endpoint velocity, projected onto the road profile tangent plane.

8 By polynomial interpolation, certain precautionshave been taken not to let the ground pressure distribution mirror the in-plane polygonal shape of the beltchain .To approximate reactions to out-of-plane excitations moreaccurately, every belt element has several additionaldegrees of freedom. These degrees of freedom describe the element s longitudinal rotation angle relative tothe rim, and the element s bending in the lateral rotation angles are coupled by rotationalstiffnesses, located between two adjacent belt elements, aswell as rotational stiffness for each belt element,located between the belt elements and rim. At the same time, the coupling between the lateral displacementof a belt element and its torsion angle is taken into account by an appropriate coupling tread blocks, as mentioned above, are located along several parallel lines, such that both longitudinal andlateral resolution of the road surface is unloaded condition, the belt elements are curvilinear inlateral direction.

9 The actual curvature, however, isnot only determined by these geometrical values (which are defined by cross-section spline data), but at thesame time by the belt lateral bending degrees of freedom. Thebelt elements bending values, in turn, aredetermined by the respective bending moments which are functions of the vertical forces of the belt elements tread 6 components of tire forces and torques acting on the rim are calculated by integrating the forces in theelastic foundation of the resulting overall tire Model is accurate up to high frequencies, in both longitudinal and lateral are few restrictions in the applicability longitudinal, lateral, and vertical vehicle dynamics deals with large and/or short-waved obstacles. It works out of, and up to, complete stand still, withnoadditional computing effort andwithoutany Model switch. Finally, it is applicable and accurate in moredelicate simulations such as ABS breaking on extremely uneven road surfaces, , FTire can take into account tire non-uniformity, which is a harmonic or more general variation ofthe radial or tangential stiffness, as well as static and dynamic of the FTire implementation is an implicit integration algorithm that calculates the belt shape.

10 By usingthis specialized implicit BDF integrator, the belt extensibility may be chosen to be extremely small. FTire thusalso allows the simulation of an in-extensible belt withoutany numerical Thermal ModelFTire provides an optionaldetailed thermal Model , the foundations of which are described in this Model is of special interest in case of strongly temperature-dependent friction properties. Activation anddeactivation is described in Thermal Model StructureThe FTire thermal Model consists of the following components: thethermo-dynamical computation of the actual inflation pressureas function of air (or fillinggas) mass, cold tire inflation pressure , tire temperature, and actual interior volume. The tire filling gasis considered to be ideal. aheat generation and transfer Model , introducing state variables for the temperature of the tirestructure (including filling gas), and the individual temperature of each tread contact element. Heatgeneration and transfer is driven by the power loss distribution due to structural damping and dry frictionon the road surface.