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By: John den Engelse Date: 19 – 6 - 2013

Master Thesis at SKF: Lateral force estimation acting at a vehicle wheel using a hub bearing unit equipped with strain gauges and Eddy-current sensors. By: John den Engelse Date: 19 – 6 - 2013. Presentation overview. Introduction Research goals Strain gauge measurements

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By: John den Engelse Date: 19 – 6 - 2013

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  1. Master Thesis at SKF:Lateral force estimation acting at a vehicle wheel using a hub bearing unit equipped with strain gauges and Eddy-current sensors By: John den Engelse Date: 19 – 6 - 2013

  2. Presentation overview • Introduction • Research goals • Strain gauge measurements • Eddy-current sensor measurements • Field- / validation measurements • BETSY calibration method • Conclusions

  3. 1 Introduction

  4. Introduction: LoadSensingBearing (LSB) • Whywould we like to measureforces? • Monitoring the mechanicalloads of a bearing. • Control the activesafetysystems in vehicleslike the ABS • (longitudinalforce) and ESC (lateralforce). • Measure the verticalload in, forinstance, trucks. Introduction – Research goals – Strain gauge measurements – Eddy-current sensors measurements – Field- / validation measurements - …

  5. Introduction: LoadSensingBearing (LSB) • How?  A loadsensinghubbearing unit instrumentedwith: • 6 straingauges: deformation of the bearingouter ring. • 2 Eddy-current sensors: tiltingmovement of the ABS-ring. Introduction – Research goals – Strain gauge measurements – Eddy-current sensors measurements – Field- / validation measurements - …

  6. 2 Research goals

  7. Research goals • Lateralforceestimation, acting at a vehiclewheel, using • straingauges and Eddy-current sensors. • Calibration of the loadsensingbearingusing the • Bearing Test System (BETSY) Introduction – Research goals – Strain gauge measurements – Eddy-current sensors measurements – Field- / validation measurements - …

  8. 3 Straingaugemeasurements

  9. Straingaugemeasurements • The straingaugesmeasure the deformation of the bearingouter ring at sixplacesalong the circumference. • The deformation provides informationabout the loadsactingon the bearing. Introduction – Research goals – Strain gauge measurements – Eddy-current sensors measurements – Field- / validation measurements - …

  10. Straingaugemeasurements • Sowhat happens? Introduction – Research goals – Strain gauge measurements – Eddy-current sensors measurements – Field- / validation measurements - …

  11. Warning The following slide features a mathematical trick performed by a professional and under the supervision of a professional. Accordingly, the TU Delft and the students must insist that no one attempt to recreate of re-enact any trick or activity performed on this slide.

  12. Straingaugemeasurements: MLRA • Multivariate Linear Regression Analysis (MLRA): The output is assumed to be a linear combination of the input and higher order terms of the input. • For one single dimension: • For multi input multi output Introduction – Research goals – Strain gauge measurements – Eddy-current sensors measurements – Field- / validation measurements - …

  13. Straingaugemeasurements: MLRA • Absolute valueproblem • Difference in sensitivityforFy < 0 N and Fy > 0 N • Difference in response for 0 Hz < f < 1 Hz and 1 Hz < f < 10 Hz Introduction – Research goals – Strain gauge measurements – Eddy-current sensors measurements – Field- / validation measurements - …

  14. Straingaugemeasurements: Fyestimationblock diagram Introduction – Research goals – Strain gauge measurements – Eddy-current sensors measurements – Field- / validation measurements - …

  15. 4 Eddy-current sensor measurements

  16. Eddy-current sensor measurement • Why (inductive) Eddy-current sensor measurements? • The straingauges are subject to the absolute valueproblem. • Strainmeasurements are subject to low frequent thermalinfluences. Introduction – Research goals –Strain gauge measurements – Eddy-current sensors measurements – Field- / validation measurements - …

  17. Eddy-current sensor measurement • ABS-ring integrated in the seal of the bearing. 48 holes and • 48 spokes. • The tiltingmovement of the ABS-ringgivesanestimate of the • lateralforceFyactingon the bearing. Introduction – Research goals –Strain gauge measurements – Eddy-current sensors measurements – Field- / validation measurements - …

  18. Eddy-current sensor measurement • TwoEddy-current sensors are mountedinto the knuckle. Introduction – Research goals –Strain gauge measurements – Eddy-current sensors measurements – Field- / validation measurements - …

  19. Eddy-current sensor measurement: Signal • The change in the lowervalues provides the information • aboutFy Introduction – Research goals –Strain gauge measurements – Eddy-current sensors measurements – Field- / validation measurements - …

  20. Eddy-currentmeasurement: Low valuealgorithm • Algorithm to retrieve these lowervalues. • Basedsignalderivative • Maximum change per time sample ∆ymax • Aninitialcondition y0 (the equilibriumvalue) • The wheel speed Discontinious output Continuous output Introduction – Research goals –Strain gauge measurements – Eddy-current sensors measurements – Field- / validation measurements - …

  21. 5 Field measurements

  22. Field measurements • The LSB equipment has been built in a BMW E60 and tests • have been performed at the test track at SKF …– Eddy-current sensors measurements – Field- / validation measurements– BETSY calibrationmethod - Conclusions

  23. Field measurements • Movie: Circle run at 30 km/h …– Eddy-current sensors measurements – Field- / validation measurements– BETSY calibrationmethod - Conclusions

  24. Field measurements • A Kistler VELOS force measuring wheel is used as reference …– Eddy-current sensors measurements – Field- / validation measurements– BETSY calibrationmethod - Conclusions

  25. Field measurements: Tilt vsFy • Eddy-current sensor measurement. • Data is approximatedby a 2nd and a 6th order polynomial: • Accuracyvsextrapolationcharacteristics N N …– Eddy-current sensors measurements – Field- / validation measurements– BETSY calibrationmethod - Conclusions

  26. Field measurements • Strainmeasurement …– Eddy-current sensors measurements – Field- / validation measurements– BETSY calibrationmethod - Conclusions

  27. Field measurements : Fyestimation • Twoforceestimationalgorithms. Both foranin-situcalibration • and a BETSY calibration. • Using 4 MLRA on the straingauges and use the Eddy-current sensors for the determination of the direction. • Usingboth the Eddy-current sensors and the straingaugesfor theforceestimation. …– Eddy-current sensors measurements – Field- / validation measurements– BETSY calibrationmethod - Conclusions

  28. Field measurements : Algorithm 1 • Using 4 MLRA on the straingauges and use the Eddy-current • sensors for the determination of the direction. …– Eddy-current sensors measurements – Field- / validation measurements– BETSY calibrationmethod - Conclusions

  29. Field measurements: Algorithm 2 • Usingboth the Eddy-current sensors and the straingauges • for the forceestimation …– Eddy-current sensors measurements – Field- / validation measurements– BETSY calibrationmethod - Conclusions

  30. Field measurements : Fyestimation, result • Estimatedforcevs time forbothalgorithms. …– Eddy-current sensors measurements – Field- / validation measurements– BETSY calibrationmethod - Conclusions

  31. Field measurements : Fyestimation, result • Estimatedforcevsmeasuredforceforbothalgorithms. …– Eddy-current sensors measurements – Field- / validation measurements– BETSY calibrationmethod - Conclusions

  32. Field measurements : Fyestimation, result • Estimationerrors In-situcalibration …– Eddy-current sensors measurements – Field- / validation measurements– BETSY calibrationmethod - Conclusions

  33. 6 BETSY calibration

  34. Straingaugemeasurements: BETSY • What is BETSY and why do we want to useit? • The Bearing Test System is a 5 Degree of Freedom (DoF) • system, where forces and moments are applied in 5 DoF • by hydraulic actuators. …– Eddy-current sensors measurements – Field- / validation measurements – BETSY calibrationmethod- Conclusions

  35. BETSY calibration: strain εBETSY = c3 ∙ Fy + c4 εvehicle = c1 ∙ Fy + c2

  36. BETSY calibration: Eddy-current sensors Good! 

  37. Field measurements : Fyestimation, result • EstimatedFyvs time forbothalgorithms …– Eddy-current sensors measurements – Field- / validation measurements – BETSY calibrationmethod- Conclusions

  38. Field measurements : Fyestimation, result • EstimatedFyvsmeasuredFyforbothalgorithms. …– Eddy-current sensors measurements – Field- / validation measurements – BETSY calibrationmethod- Conclusions

  39. Field measurements : Fyestimation, result • Estimationerrorsusing a BETSY calibration • So we canuse BETSY forcalibration? …– Eddy-current sensors measurements – Field- / validation measurements – BETSY calibrationmethod- Conclusions

  40. Reproducibility: strain • Reproducibility is necessaryforcalibration of a whole • productionline of LSB Not good!  …– Eddy-current sensors measurements – Field- / validation measurements – BETSY calibrationmethod- Conclusions

  41. Reproducibility: Eddy-current sensors • Reproducibility is necessaryforcalibration of a whole • productionline of LSB 2011 2012 Good!  …– Eddy-current sensors measurements – Field- / validation measurements – BETSY calibrationmethod- Conclusions

  42. 7 Conclusions

  43. Conclusions: lateralforceestimation • In the semi-staticfrequency range the straingauges as well as the • Eddy-current sensors canbeusedforforceestimationwitherrors • rangingfrom 15 % - 20 %. • In the dynamicfrequency range the lateralforce is notcorrelatedwith • the strain and ABS-ringdeflection. • Regarding the Eddy-current sensors BETSY canbeusedforcalibration. • Regarding the straingauges sensors BETSY cannotbeusedfor • calibration. …– Eddy-current sensors measurements – Field- / validation measurements – BETSY calibrationmethod - Conclusions

  44. Questions? Thankyouforyourattention !

  45. Backupslides

  46. Introduction: LoadSensingBearing • Whatforces act on a vehicle? • 3 forces: • Fx = longitudinalforce • Fy = lateralforce • Fz = verticalforce • 3 moments: • Mx = moment around the x-axis • My = moment around the y-axis • Mz = moment around the z-axis

  47. Straingaugemeasurements: Appliedloads • Cycle consisting of 24 load steps. • Load steps with 10 seconds of duration. • Between each load step a 10 seconds interval of running without load is inserted. • Combinations of static and dynamicforces are applied.

  48. Straingaugemeasurements: Signalconditioningprocess • Filtering • Static offset and drift • Inverted signal strain gauge 3 • No-load intervals • Scaling to physical dimensions

  49. BETSY calibration • Field • BETSY • BETSY and field • Some differences are present • How can we compensate for • those differences. …– Eddy-current sensors measurements – Field- / validation measurements – BETSY calibrationmethod- Conclusions

  50. BETSY calibration Bydescribingbothsides of the V-shapeby a 1st order polynomialtwocoefficients, Ca and Cb, canbederivedforbothpositive and negativeFy to transform te one to the other. (So 4 coefficients in total). Εleft,BETSY = c1,left ∙ Fy,left + c2,left εright,BETSY = c1,right ∙ Fy,right + c2,right BETSY Εleft,field = c3,left ∙ Fy,left + c4,left Field εright,Field = c3,right ∙ Fy,right + c4,right

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