Optical measurement of tire pressure

Optical measurement of tire pressure Research in automotive production at the WZL at RWTH Aachen University Prof. Dr.-Ing. Rainer Müller R.Mueller@wzl.rwth-aachen.de Stuttgart, 18.05.11

Content 1 Production technology in Aachen 2 Optical measurement of tire pressure 3 Application in a chassis geometry stand for busses and trucks 4 Acknowledgement of partners and fundation & seminar announcement Seite 2

RWTH Aachen and raunhofer-gesellschaft raunhofer-gesellschaft More than 80 institutes und facilities at 40 locations in Germany 18,000 employees approx. 1.65 billion research funds per year, 1.4 billion through research contracts 3 institutes in Aachen RWTH Aachen Unversity ounded in 1870 33,000 students aculty of Mechanical Engineering 8,700 students (incl. 1,800 first year students) 54 professors 2,600 employees 140 doctorate degrees per year Seite 3

Production Technology in Aachen Laboratory for Machine Tools and Production Engineering (WZL) RWTH Aachen University institute ounded in 1906 600 employees (160 scientific staff) 10,000 m² offices and laboratories raunhofer Institute for Production Technology IPT raunhofer-gesellschaft institute ounded in 1980 450 employees (95 scientific staff) 3,000 m² offices and laboratories Certified to DIN EN ISO 9001:2000 Partner in Boston/USA: raunhofer Center for Manufacturing Innovation CMI WZL orum Professional education, conferences and seminars (e.g. Executive MBA) Seite 4

Production technology chairs at RWTH Aachen University and divisions at IPT Prof. C. Brecher Prof.. Klocke Prof. R. Schmitt Prof. G. Schuh Prof. A. Kampker Prof. R. Müller Chair of Machine Tools Chair of Manufacturing Technology Chair of Metrology and Quality Management Chair of Production Engineering Chair of Production Management Chair of Assembly Systems Production Machines Process Technology Production Quality and Metrology Technology Management Seite 5

Research areas at the chair of assembly systems Assembly Systems Technology Robotics and Handling Technologies Tolerance Management Assembly process planning Automation of assembly processes Processes and technologies for adjustment, parameter setting and testing Modularization of assembly systems Reconfigurable robot systems Control and path planning Cooperating robots Tolerance management in the process planning phase Tolerance analysis and compensation of deviations in individual processes; process feedback Parameter identification and adaptation image source: Dürr Seite 6

Joint research project for the reduction of fuel consumption and tire wear of commercial vehicles wheel alignment for trucks Industry Research Development of a chassis geometry test stand for busses and trucks easibility study for tire pressure measurement wheel alignment in car production image source: Dürr, Josam Prototype installation at a trucking company Simulation of fuel consumption busses and trucks Potential savings through correct wheel geometry alignment Seite 7

Transfer of non-contact measuring techniques in a chassis geometry test stand for busses and trucks wheel alignment stand in automotive production chassis geometry test stand for busses and trucks wheel geometry measurement system wheel geometry measurement system floating plates pit pit guide rails image source: Dürr Seite 8

Non-contact measuring method in car production Non-contact laser measurement x-3dprofile Stereophotogrammetry: Measuring principle & data processing (x r,y r,-f) f b x y z f (x l,y l,-f) P(x,y,z) optical axis laser beam cameras laser arrays optical axis camera 1 camera 2 image sources: Jiang, Bunke, Dürr Wheel geometry (camber, toe, ) Seite 9

Motivation for non-contact tire pressure measurement Axle misalignment Axle misalignment coefficient of rolling friction c R Sources: Daimler, Goodyear, Josam, ahrwerkhandbuch, MAN A A A: frontal area Tire condition and pressure tire pressure wheel load Z,W Tire pressure Air resistance Rolling resistance Tire wear Studies indicate: Reduction of tire service life through insufficient pressure Tire pressure 1bar below specification increases fuel consumption by 5% Seite 10

Development of innovative measuring methods for non-contact tire pressure measurement Chassis geometry test stand for busses and trucks mobile test stand for trucks and busses chassis geometry measurement Single wheel test stand wheel load unit for a single wheel (substitute system) optical tire pressure measurement image source: Dürr Development of new measurement methods in a test stand environment Seite 12

easibility study on optical tire pressure measurement Development objective wheel load Optical tire pressure measurement Integration into a mobile wheel alignment stand Tire-form/ -position Research objective Tire pressure p Wheel load Optical measurand (tire form/ -position) Seite 13

Test bench environment Single wheel load wheel load unit max = 1 ton tire inflator wheel load test stand computer x-line (software) LabView (load cell) load measurement system piezoelectric load cell Measurement system x-3dprofile Seite 14

Correlation of optical measurands and the wheel load Vertical deflection Virtual camber Radial expansion λ f virtual camber Ø D unloaded Ø D unloaded wheel load p 1 > p 2 wheel load p 1 > p 2 wheel load p 1 > p 2 vertical deflection f virtual camber radial expansion λ Seite 15

unctional correlation for tire pressure determination Universal model for all radial tires (e.g. by Rhyne & Padula) Tire specific characteristic diagram wheel load p 2 p 1 wheel load p 2 > p 1 data point approximation: linear correlation optical measurand optical measurand = (C1 tire geometry * p + C2 ) * optical measurand C1= constant, tire geometry (width, Ø, ) C2= empirically determined constant formula applies for all radial tires in dependence on tire geometry insufficient precision source: Rhyne, Tire Science and Technology p = unction (, optical measurand) = wheel load p = tire pressure tire s unique characteristic diagram needs to be determined sufficient precision Seite 16

Determination of tire pressure using specific tire characteristic diagrams two optical measurands 1.) vertical deflection f wheel load [kn] 8 6 4 2 tire pressure 0,9306 1,2992 f e = p 3,6021 4,5 bar 0 0 4 8 12 16 20 24 f 4,0 bar 3,5 bar 3,0 bar = 5 kn f = 18 mm p = 3,5 bar vertical indentation f [mm] 2.) virtual camber wheel load [kn] 7 5 3 tire pressure 5,0 bar 3,5 bar 3,0 bar 1 0 γ 0 20 40 60 80 100 virtual camber γ [ ] Tire pressure via characteristic diagram = 5 kn γ =56 p = 3,5 bar Seite 17

Applicable measurement method via measuring tire diameter while considering radial expansion Single Prüfstand wheel test stand vertical deflection it for practise measurement method f λ φ=0 φ Ø D unloaded variable 1 D/2 + λ variable 2 D/2 - f Reference: unloaded condition new measurand = variable 1 variable 2 = λ + f vertical deflection is difficult to measure in P (, f ) P (, λ) practical application tire diameter unknown for the unloaded p 1 p 2 p 1 p 2 condition + = = wheel load p = tire pressure f = vertical deflection λ = radial expansion f λ P (, λ + f ) p 1 p 2 Linear correlation λ+f Seite 18

Practical application of the optical measurement method in a test stand for busses and trucks Wheel geometry measuring system 1.) vertical indentation f image source: Dürr 2.) virtual camber γ OR optical measurand wheel load scale wheel load Tire pressure via characteristic diagram Seite 20

Cooperation of industry and university research in a joint project Partners of the cooperative research project Industry Research This project has been funded by the ederal Ministry of Economics and Technology based on a decision of the German Bundestag. image source: Dürr Seite 22

Seminar Commisioning processes in Automotive inal Assembly at Aachen on September 27, 2011 topics: overview on vehicle commissioning processes noise vibration harshness test (NVH) wheel alignment, headlamp aiming & commisioning of driver assistant systems roll, brake, function test stands and procedures E/E-commissioning innovations in vehicle commissioning starting points and goals: goals: vendor independent understanding of processes and operating equipment establishing a close collaboration between plant suppliers and OEMs to advanced technological competence establishing a systematic approach for the optimisation of technologies applied in EOL definition of technological requirements moderated discussion on the topic of vehicle commissioning with manufacturers, planning staff and operators of EOL applications Seite 23

Thank you for your attention! Prof. Dr.-Ing. Rainer Müller Chair of Assembly Systems Laboratory for Machine Tools and Production Engineering (WZL) at RWTH Aachen University Tel: +49 (0) 241/80-27733 ax: +49 (0) 241/80-22287 Mail: R.Mueller@wzl.rwth-aachen.de Web: www.wzl.rwth-aachen.de