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Modelling Slip- and Creep-mode Shift Speed Characteristics of a Pushbelt Type CVT

Modelling Slip- and Creep-mode Shift Speed Characteristics of a Pushbelt Type CVT. Bram Bonsen, Tim Klaassen, Koen van de Meerakker, Bram Veenhuizen, Maarten Steinbuch. Project goal. Optimize a pushbelt-type CVT to maximize efficiency by changing the actuation system. Slip & Efficiency.

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Modelling Slip- and Creep-mode Shift Speed Characteristics of a Pushbelt Type CVT

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  1. Modelling Slip- and Creep-mode Shift Speed Characteristics of a Pushbelt Type CVT Bram Bonsen, Tim Klaassen, Koen van de Meerakker, Bram Veenhuizen, Maarten Steinbuch

  2. Project goal • Optimize a pushbelt-type CVT to maximize efficiency by changing the actuation system

  3. Slip & Efficiency

  4. Slip & Friction

  5. CVT actuation changes • Reduction of actuation losses by: • Lowering clamping force • Using alternative actuation methods

  6. Modeling variator • What is the expected • Efficiency • Needed actuation forces • Transient response

  7. Existing models • Either • Too complex • Did not describe the effects of slip and its influence on the actuation system

  8. Transient models • Ide • Shafai • Simplified

  9. Transient models • Ide • Good description of transient behavior when not in slip-mode • Shafai • Good description of transient behavior when in slip-mode

  10. Combination • Ide when in creep-mode shifting • Shafai when in slip-mode shifting

  11. Friction / Slip • Friction force opposite to slip direction • Tangential slip vs Radial slip Torque transmission vs Shifting

  12. Testrig

  13. Measurements

  14. Measurements

  15. Measurements

  16. Friction model • Coulomb friction model: • Microslip = stiction = creepmode • Macroslip = sliding = slipmode

  17. Microslip shifting mechanism • Shifting and torque transmission not related • Belt only partially slipping • Shifting by elastic deformation of the pulleys • Shifting behavior dependent on primary speed

  18. Macroslip shifting mechanism • Slip in both tangential and radial direction • Shift speed primary speed independent • Shift speed limited by actuation system only

  19. Model • Sliding when force >= friction, • Stick when force < friction

  20. Friction calculation

  21. Friction calculation • Friction • Direction

  22. Identification • Minimize output error • Number of Parameters limited to 4

  23. Identification results • Very high pulley mass found • Oil in pipes • Simplified Ide model used to reduce number of parameters

  24. Results

  25. Results

  26. Conclusions • Combined model is more in agreement with the measurements • Possibility to investigate more efficient actuation system based on slip

  27. Recommendations • Identification on different transmissions • Slip while shifting is incorporated in this model. This can be used to make the actuation more efficient. • Optimize the transmission based on the given parameters. (stiffness, length and thickness of pipes, place of actuators etc)

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