CDTire: State-of-the-Art Tire Models For Full Vehicle Simulation
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Tire modeling is critical for full vehicle simulations because all road excitations pass through the tires to the vehicle. The accurate representation of roads and tires and their interactions is one of the central challenges in full vehicle simulation. CDTire is a family of sophisticated tire models capable of accurately representing the dynamic behavior of tires and the road-tire interaction. This presentation gives an overview of tire modeling methods developed at Fraunhofer and made available through CDTire. The presentation covers three topics: (a) Tire and road models that are commercially available today and where they can be used (b) New developments in tire and road modeling technology (c) Fraunhofer’s special relationship with Altair to make this technology available to you and how CDTire works with MotionSolve
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CDTire: State-of-the-Art Tire Models For Full Vehicle Simulation
- 1. CDTire: State-of-the-art Tire Models for Full Vehicle Simulation 2012 Americas HyperWorks Technology Conference Dr. Manfred Bäcker, Axel Gallrein © Fraunhofer ITWM 1
- 2. Fraunhofer Society Itzehoe Rostock Fraunhofer Society 2010 Lübeck Bremerhaven Non-profit Bremen 60 institutes Berlin Hannover 18 000 employees Braunschweig Potsdam Teltow 1.65 bill. Euro Paderborn Magdeburg Oberhausen Dortmund Cottbus Halle Leipzig Duisburg Schmallenberg Schkopau Fraunhofer ITWM Sankt Augustin Dresden Erfurt 220 employees Aachen Jena Ilmenau Chemnitz Euskirchen 18 mill. Euro Darmstadt Transport, fluid and Würzburg Erlangen material simulation St. Ingbert Kaiserslautern Fürth Dynamics and durability Saarbrücken Nürnberg Karlsruhe Pfinztal Image processing Stuttgart Optimization Freising Freiburg München Finance Oberpfaffenhofen Efringen- High performance computing Kirchen Holzkirchen © Fraunhofer ITWM 2
- 3. Agenda Overview CDTire Model Family Parameterization How CDTire works with MotionSolve Introducing new models CDTire 30/HPS CDTire 50 On-going developments CDTire NVH Tire / soil interaction © Fraunhofer ITWM 3
- 4. Tire Simulation in Vehicle Development Driver model Vehicle model Tire model Road model Open loop MBD model MBD model Rigid surface Closed loop FEA model FEA model Soil Optimal control Subsystems Linearization Multi pass © Fraunhofer ITWM 4
- 5. MBD Tire Models - - - - vs. - - - Application Fields DOFs REPs 100 Handling 103 Empirical Typical number of simulations Typical computational effort 101 NVH Frequency-based Active safety 102 102 Rigid ring Emperical contact Ride/Comfort 103 Flexible belt 101 Brush-type contact Durability 104 FEA 105 Crash 100 © Fraunhofer ITWM 5
- 6. MBD Tire Model Family CDTire DOFs REPs 100 Handling 103 Empirical Typical number of simulations Typical computational effort 101 NVH Frequency-based Active safety 102 102 Rigid ring CDTire 20 Emperical contact Ride/Comfort 103 Flexible belt CDTire 30 101 Brush-type contact CDTire 40 CDTire MC Durability 104 FEA 105 TireTool Crash 100 © Fraunhofer ITWM 6
- 7. MBD Tire Model Family CDTire Model 20 Adaptive models Rigid ring (automatic switching) Physical tangential Model 2030 contact formulation Model 2040 Model 30 Flexible ring Brush type contact Model 40 Flexible Belt Independent sidewalls Model MC Large belt curvature Large inclination angles © Fraunhofer ITWM 7
- 8. CDTire 20 Model details Rigid ring Physical tangential contact formulation Road surfaces Arbitrary 3D Long wavelength Typical applications Handling (Durability) Lateral direction Belt point Active safety Belt velocity Shear deformation cY Tread Real-time factor height Surface point cX 3-6 Longitudinal direction © Fraunhofer ITWM 8
- 9. CDTire 20: Application Scenario Handling Publication Yang, X., Medepalli, S.: Comfort and Durability Tire Model Validation, Tire Science and Technology, TSTCA, Vol. 37, No. 4, October – December 2009, pp. 302-322. © Fraunhofer ITWM 9
- 10. CDTire 30 p Model details Flexible ring Brush type contact formulation Accumulated sidewall Road surfaces Trackwise 2D Arbitrary wavelength Typical applications Ride & Comfort Durability Real-time factor 10 - 30 © Fraunhofer ITWM 10
- 11. CDTire 30: Application Scenario Durability Publication Sawa, N., Nimiya, Y., Kubota, Y., Itsubo, Full vehicle rough road run T. et al., "Fatigue Life Prediction on Rough Road Using Full Vehicle Co- simulation Model with Suspension Control," SAE Technical Paper 2010-01- 0952, 2010, doi:10.4271/2010-01-0952. Full vehicle cleat run © Fraunhofer ITWM 11
- 12. CDTire 40 Model details 3D structure Brush type contact formulation Independent sidewalls Road surfaces Arbitrary 3D Typical applications Ride & Comfort Durability Real-time factor 40 - 100 © Fraunhofer ITWM 12
- 13. CDTire 40: Application Scenario Special Events Publication Baecker, M., Gallrein, A., and Haga, H., "A Tire Model for Very Large Tire Deformations and its Application in Very Severe Events," SAE Int. J. Mater. Manuf. 3(1):142-151, 2010, doi:10.4271/2010-01- 0373. © Fraunhofer ITWM 13
- 14. CDTirePI: Parameterization via Measurements Measurements Geometry (cross section, foot print) Modal analysis Static (stiffness’s, on cleat) Steady-state (long. + lateral slip) Transient (90°+45° cleat runs) Optimization schemes Local Fuzzy (expert knowledge build into rule sets) © Fraunhofer ITWM 14
- 15. TireTool: Parameterization via FEA tire model Layer 1: Material Modal Analyze Stiffness Cleats Exp. Data Geometry Footprints Ground-out Virtual measurement Layer 2: Parameter Local structure Identification properties Layer 3: Application Misuse Special Events Handling Crash NVH Durability © Fraunhofer ITWM 15
- 16. TireTool: Parameterization via FEA tire model Cross section 2D model 3D model Virtual measurements Cross section scan CT-Scan cords Modes and Cleat runs Contour Tire weight frequencies Ground-out measurement Shore A Static stiffness’s … Fine tune © Fraunhofer ITWM 16
- 17. TireTool: Parameterization via FEA tire model Measurements Geometry (cross section, foot print) Modal analysis Static (vertical stiffness) Material CT Output is Abaqus model © Fraunhofer ITWM 17
- 18. Tire-Tool: Parameterization via FEA tire model 90° cleat run 40x40mm, 11 km/h, CDT40 validation Longitudinal Force LDE test rig 4000 @ Fraunhofer 3000 Measurement 2000 Simulation Kistler P530 hub 1000 Max. 12 km/h Force [N] 0 -1000 -2000 Max. Fz 30 kN -3000 -4000 Up to rim contact -5000 5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 Time [s] Vertical Force 30000 Measurement 25000 Simulation 20000 Force [N] 15000 10000 5000 0 5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 Time [s] © Fraunhofer ITWM 18
- 19. Tire-Tool: Parameterization via FEA tire model 90° cleat run 40x40mm, 11 km/h (FEA validation), 30 and 40 km/h (prediction) © Fraunhofer ITWM 19
- 20. TireTool: Parameterization via FEA tire model Reissner-Mindlin 3D continuum hypothesis 2D shell FEM FEM (CDTire 50) Reduction of degrees-of-freedom (dofs) Proper orthogonal decomposition (POD) BMBF joint project „Multi-disciplinary Simulation and Non-linrear Model Reduction (SNiMoRed) © Fraunhofer ITWM 20
- 21. How CDTire works with MotionSolve Cooperation Altair / Fraunhofer Road models Altair is exclusive reseller for RSM1000 (parametric obstacles) CDTire4MotionSolve RSM1002 (drum model) Distributed with HyperWorks 11.0 RSM2000 (large digital data) Integrated visual support in RSM3000 (OpenCRG) development RSM1100 (User API) Tire models Full .adm compatibility 20 / 30 / 40 / 2030 / 2040 Full CDTire.ini support (parallelization) © Fraunhofer ITWM 21
- 22. Introducing new models New developments Model 20 Model 30/HPS Rigid ring C/C++ High Performance Solver Physical tangential Real-time capable contact formulation Model 50 Model 30 Materialized sidewalls Flexible ring Geometrical non-linear Brush type contact elastic shell discretization Model 40 Model NVH Flexible Belt Flexible rim Independent sidewalls Cavity mode Model MC Large belt curvature Large inclination angles © Fraunhofer ITWM 22
- 23. Introducing new models Application scenarions New developments Model 30/HPS Model 30/HPS MIL / SIL / HIL cascade C/C++ High Performance Solver Vehicle performance Real-time capable optimization Model 50 Model 50 Materialized sidewalls Large deformation, ground-out Geometrical non-linear Handling on rough road elastic shell discretization Model NVH Model NVH Up to 300 Hz Flexible rim Cavity mode © Fraunhofer ITWM 23
- 24. CDTire 30/HPS Master integrator (typically larger time steps) Iteration scheme Step size control Slave integrator (typically smaller time steps) Iteration schemes (HPS: PECE, Newmark) Master step size control Tunable controls: Dt = MBS step size new time step to be Secured time step calculated by MBS-solver Master iteration Slave iteration time t t+Dt Slave step size dt = minor step of tire model dt Integrates tire states from t -> t+Dt using integrator much smaller minor steps dt Estimated Tire forces MBS-solver rim states Tire model solver at t+Dt at t+Dt © Fraunhofer ITWM 24
- 25. CDTire 30/HPS Scenario: 4 cleats (20x20mm), 40 km/h, 3 sec C/C++ High Performance Solver Efficient memory storage and access Efficient implicit Newmark with special projector in Newton-Iteration Choice of deterministic integrator settings (fixed step, fixed iterations) Parallelizable incl. road surface models (OpenCrg, RSM2000, RSM1000) New CDT30 model. 100 MP 10000 5000 Fx, N CDT30 (explicit integrator) 0 Real time factor = 1.8 -5000 CDT30/HPS (explicit integrator) 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 Real time factor = 1.1 9000 CDT30/HPS (implicit integrator, var. step) 8000 Real time factor = 0.6 Fz, N 7000 CDT30/HPS (implicit integrator, determ.) 6000 Real time factor = 0.8 5000 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 Time, s © Fraunhofer ITWM 25
- 26. CDTire 30/HPS: Application Scenario Test Rig Scenario MIL / SIL / HIL: Implementation used as component on real test rigs Road profile and driving rule can be used as excitation of the test rig No test track measurement needed (usually used as target for iteration process) © Fraunhofer ITWM 26
- 27. CDTire 30/HPS: Application Scenario Drive Simul. Scenario MIL / SIL / HIL: Component in Drive Simulator VAR-Simulator (Versatile Augmented Reality) Fraunhofer ITWM Fraunhofer IGD & ITWM Fraunhofer FIRST Fraunhofer ITWM Graphics cluster Warping, edge Spherical screen 10m with scene blending, color & diameter graph contrast calibration 300° * 110° FOV Vehicle CAD data 18 synchronal WUXGA projectors 3D scenery HMI data 3D terrain data robot states Real-time Motion tracking PC © Fraunhofer ITWM 27
- 28. CDTire 50 Functional element modeling Element stacking in pre-processing FD shell discretization Belt Sidewall Rim © Fraunhofer ITWM 28
- 29. CDTire 50 Scenario: 18 cleats (10x10,…,20x20mm), 40 km/h, 10 sec C/C++ High Performance Solver Efficient memory storage and access Efficient implicit Newmark with special projector in Newton-Iteration Choice of deterministic integrator settings (fixed step, fixed iterations) Parallelizable incl. road surface models (OpenCrg, RSM2000, RSM1000) CDT50 (explicit integrator) 50 cross sections 12 segments Real time factor = 49 © Fraunhofer ITWM 29
- 30. CDTire NVH Method NVH – FEA tire Internal Fraunhofer research project (MEF) Steady state transport analysis Cavity possible (relative kinematic ALE description) Flexible rim possible Rim and road (footprint) excitation Condensation of road excitation: Track-wise time delay as phase shift apply vertical load on inflated tire Z ODB: 03_tire_loading.odb Abaqus/Standard 6.10−EF2 Fri Jul 08 10:49:32 CEST 2011 Y Step: Loading−0 X Increment 22: Step Time = 0.9650 Deformed Var: U Deformation Scale Factor: +1.000e+00 © Fraunhofer ITWM 30
- 31. CDTire NVH Internal Fraunhofer research project (MEF) Linearization around Solver independence Stationary rolling state Linearization and Transient Transient Equations of motion Add Gyroscopic forces Linear State space equation Laplace Transform Condensation of Road excitation © Fraunhofer ITWM 31
- 32. CDTire NVH Residual force Switch to „eulerian“ description by adding gyroscopic forces Leads to frequency split for rotating tires Example is free hanging tire, but rotating © Fraunhofer ITWM 32
- 33. CDTire NVH Simulated experimental modal analysis Counter Inphase Spacial acceleration measurement Free rim, constant rot. velocity w = 85 rad/s © Fraunhofer ITWM 33
- 34. Tire / Soil interaction No deformation Rigid surface Local deformation, decoupled Terrain response Local deformation, coupled Bulldozing effect Terrain compaction Multipass Tangential mass transport Slip sinkage Diskrete Element Method DEM © Fraunhofer ITWM 34
- 35. Tire / Soil interaction Simple pressure-sinkage relations Bekker: p(z) = (kc/b + kΦ)∙zn Reece: p(z) = (c κc + γs b κΦ)∙(z/b)n (kc,kΦ,κc,κΦ,n: pressure-sinkage parameters, γs: weight density, c: cohesion of terrain) Instantaneous soil deformation No sinkage “propagation” Localized parameter, i.e. k = k(x,y), n = n(x,y) Tangential frictional contact Implementation in C/C++ Python interface for rapid evaluation of alternative sinkage models © Fraunhofer ITWM 35
- 36. Spreading the Application Range DOFs REPs 100 Handling 103 Empirical Typical number of simulations Typical computational effort 101 CDTire NVH NVH Frequency-based CDTire 20 Active safety 102 102 Rigid ring Emperical contact CDTire 30 Ride/Comfort 103 CDTire 40 Flexible belt CDTire MC 101 Brush-type contact CDTire HPS Durability 104 CDTire 50 FEA 105 TireTool Crash 100 © Fraunhofer ITWM 36
- 37. CDTire: State-of-the-art Tire Models for Full Vehicle Simulation 2012 Americas HyperWorks Technology Conference Dr. Manfred Bäcker, Axel Gallrein manfred.baecker@itwm.fraunhofer.de axel.gallrein@itwm.fraunhofer.de Thank you for your attention ! © Fraunhofer ITWM 37