Experimental analysis of a contact patch form of a rolling tire: influence of speed, wheel load, camber and slip angle Dipl.-Ing. Pavel Sarkisov Prof. Dr.-Ing. Günther Prokop Dipl.-Ing. Steffen Drossel Technische Universität Dresden Dr.-Ing. Sergey Popov Bauman Moscow State Technical University 2 nd IAVSD Workshop on Dynamics of Road Vehicles Berlin, 30.03.2017
Motivation Road traffic safety Driver Assistance Systems Wheel forces Tire behavior ABS / ESP / ASR Torque vectoring Rear axle steering To use as much grip as possible To simulate complex tire behavior To use tire as a sensor Active Rollover Prevention Emergency Steering Assist Stuttgart, 14.03.2017 2
Tire as a sensor? Pressure loss To inform driver Tire-mounted sensor Stuttgart, 14.03.2017 3
Tire as a sensor? Pressure loss Wear level To inform driver Slip angle Friction potential Aquaplaning Longitudinal/lateral slip Road conditions To improve ADAS control To share further via Car2X Stuttgart, Sources: Audi 14.03.2017 AG Presskit 08/15; www.kaltire.com; www.dunlop.eu 4
A method of friction potential estimation A. Niskanen, A. Tuononen: Tire-road contact condition measurements by an intelligent tire (2017) Grip region Slip region 0 % slip 4 % slip 7 % slip * - notes Acceleration sensor is able to capture grip and slip region lengths Stuttgart, 14.03.2017 5
A method of friction potential estimation Slip region Grip region ll gg ll ss Utilized friction potential: Kinematic difference Real: UUUUUU rr = FF xx 2 + FF yy 2 μμff zz Maximum tread deflection Shear deformation Sliding distance Estimated: ll gg UUUUUU ee = 1 2 ll ss + ll gg Intensive braking: 0.5 UUUUUU rr 1 0.5 UUUUUU ee 1 Stuttgart, 14.03.2017 6
A method of friction potential estimation Grip region ll gg Slip region ll ss Utilized friction potential: Kinematic difference Real: UUUUUU rr = FF xx 2 + FF yy 2 μμff zz Maximum tread deflection Shear deformation Sliding distance Estimated: ll gg UUUUUU ee = 1 2 ll ss + ll gg Intensive braking: 0 UUUUUU rr < 0.5 UUUUUU ee 0.5 Stuttgart, 14.03.2017 7
Mission statement Straight run Normal cornering Severe cornering Contact patch shape changes with rolling parameters Sensor notices vibration independently upon slip direction Source: Gim, G. & Choi, Y., 2001 Source: Michelin: Der Reifen: Haftung. 2005. 1 How many sensors are required for estimation? 2 Can this method be applied for cornering tire? Stuttgart, 14.03.2017 8
Mission statement 1 2 How many sensors are required for estimation? Can this method be applied for cornering tire? - To observe contact patch shape depending upon wheel load, speed, camber, slip angle - To develop a simulation model for strain analysis - To analyze method feasibility for lateral slip Stuttgart, 14.03.2017 9
Experimental analysis Stuttgart, 14.03.2017 10
Measurement method Setup: Measurement: Observation: Seven acceleration sensors in a rolling tire Radial acceleration Contact patch length and position Radial acceleration zz Contact patch length A B C D E F G Contact patch position Contact patch length Stuttgart, 14.03.2017 11
Variation of rolling speed A B C D E F G Stuttgart, 14.03.2017 12
Variation of rolling speed Stuttgart, 14.03.2017 13
Variation of camber angle Stuttgart, 14.03.2017 14
Contact patch shape of cambered tire Sensor B 7 kn B Change of patch length up to 25 % per 1 Linear dependence upon camber angle Symmetric patch shape Stuttgart, 14.03.2017 15
Variation of slip angle Stuttgart, 14.03.2017 16
Contact patch shape of cornering tire Sensor B 73 5 kn B Change of patch length up to 15 % per 1 Nonlinear dependence upon the slip angle Asymmetric patch shape Stuttgart, 14.03.2017 17
Model development Picture: www.dewetron.com Stuttgart, 14.03.2017 18
Model development Approach: Focus: Method: To describe physical background of tire behavior Transient handling: Lateral force and aligning torque Decoupling of physical effects Stuttgart, 14.03.2017 19
Model validation Lateral force [kn] Y [m] Aligning torque [Nm] Time [s] X [m] Time [s] Measurement Simulation Stuttgart, 14.03.2017 20
Model-based analysis Picture: Audi AG, Presskit 08/15 Stuttgart, 14.03.2017 21
Feasibility analysis Top view on contact patch Tire excitation: Brake slip, slip angle Utilized friction potential: Real: Estimated: FF 2 2 xx + FF yy μμff zz ll gg 1 2 ll ss + ll gg ll ss ll gg Stuttgart, 14.03.2017 22
Feasibility analysis: braking with camber Estimated Real Real potential: FF xx 2 + FF yy 2 μμff zz Estimated potential: ll gg 1 2 ll ss + ll gg Stuttgart, 14.03.2017 23
Feasibility analysis: cornering and braking Estimated Real One sensor in the middle of tire provides error of 5 % Length-based estimation for cornering tire is feasible Stuttgart, 14.03.2017 24
Sliding speed analysis Sliding speed of cornering tire (3 ) corresponds to sliding speed of braking one (5 %) Stuttgart, 14.03.2017 25
Summary 1 2 3 Contact patch shape changes with: - camber symmetric shape, linear relation - slip angle asymmetric shape, nonlinear relation Implementation of estimation method: - One acceleration sensor, mounted in the middle plane of the tire, is enough for 5 % estimation error Enhancement of estimation method: - Cornering tire features similar slip region length and sliding speed as braking tire Stuttgart, 14.03.2017 26
Thank you for your attention! pavel.sarkisov@mailbox.tu-dresden.de Supported by TU Dresden Graduate Academy Dresden, 26.10.2016 27