Belt-pulley friction estimation for the Continuously Variable Transmission

This study describes an approach to estimate the maximum friction between the pushbelt and pulley set in a mass-produced Continuously Variable Transmission. Up-to-date friction knowledge is useful to accurately determine the maximum transmittable torque and to monitor the variator condition. Besides standard sensors, torque signals are assumed to be available. An adaptive estimator is presented based on the Kalman filter, which estimates friction-related parameters to find the maximum friction. The filter requires no a priori knowledge of the maximum friction and needs no detailed friction model. Experiments show that this method can be used for both an undamaged and damaged pushbelt.