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Measurement And Control Of Slip In a Continuously Variable Transmission

B. Bonsen, T.W.G.L. Klaassen, K.G.O. van de Meerakker

M. Steinbuch, P.A. Veenhuizen

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CVT• Infinite number of ratios within a range• Shifting while engaged• Optimal use of IC engine

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CVT

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Slip

• Friction drive

• Slip between belt and pulley

• Wear

• Clamping force

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Efficiency

• Actuation losses

• Friction in Belt

• Bearing losses

• Lubrication

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Project goals

• Optimize CVT transmission efficiency by:

– using alternative actuation system

– lowering clamping force

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Lowering clamping force

• Advantage:– Less friction losses in the belt– Less actuation power – Less friction in the bearings– More torque on the wheels

• Disadvantage:– Increased risk of damage due to slip

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Measurement of slip

• Definition of slip

• Measurement of

• Calculation of

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Testrig

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Slip & Efficiency

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Slip & Friction

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Linearizing

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Variator model

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Nonlinear model

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Linearized model

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Eigenfrequencies

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Control

• Clamping force

• Ratio

• Speed

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Slip feedback

Fp

s

rg

re f+

-

Td

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Clamping force

• Safety

• Actuation bandwidth

• Slip measurement

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Stability using slip feedback

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Experimental Results

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Conclusions

• Stable control of slip

• Robustness for torque peaks up to 30Nm

• Lower clamping force (-30%)

• Higher variator efficiency (+4%)