E-Clutch Torque Control Including Compensation of Thermal Expansion Effects

The E-clutch considered is a dry clutch automated by means of a hydrostatic actuator, whose master cylinder is driven by an electric servomotor through a spindle drive. The paper deals with design of E-clutch open-loop torque control strategy which includes compensation of clutch thermal expansion effects. A series of experiments have been conducted by using a custom-designed E-clutch test rig, in order to characterize influence of thermal effects on clutch control performance. A comprehensive analysis of test data reveal a strong correlation of clutch torque reduction and E-clutch slave cylinder (CSC) position increase caused by clutch pack thermal expansion. The determined dependence, where CSC position measurement serves for quantification of thermal effects, is incorporated within the clutch torque control strategy for the sake of thermal effects compensation. Furthermore, it is found out that the CSC position can be effectively estimated based on clutch temperature inputs, thus implying that the CSC position sensor can be omitted, while still keeping the possibility of effective thermal expansion compensation. The proposed clutch control strategy is examined based on experimental data acquired for two clutch friction plates/materials.