Hoić, M.

Modeling of Dry Dual Clutch Dynamics

Doctoral thesis (in Croatian), Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Croatia, 2015.
The thesis deals with modeling and experimental characterization of dry dual clutch characteristics with the goal of forming the clutch dynamical model as well as a set of experimental procedures and test rigs required for experimental identification and validation of the model. The development of a multi-physical model of a dry dual clutch is conducted as an extension of a previous research during which a dynamical model of a related electromechanical actuator and basic clutch axial dynamics model were was developed and experimentally validated with the emphasis on expansion of the existent axial dynamics model by various effects (e.g. thermal expansion due to temperature increase). Together, these two models (actuator model and clutch model) enable the prediction of clutch torque characteristics as a function of actuator motor for a wide range of operating parameters including temperature change and clutch wear. Model is structured as a series of masses, springs and levers in-between which a transfer of forces and heat as well as dry friction occurs. Structure of the model is obtained by consideration of clutch structure while individual model parameters were experimentally identified (including masses, heat capacities, dimensions and spring characteristics) using the developed and upgraded test rigs. Apart from the mechanism for generation of clutch normal force, the model also incorporates a thermal model which enables the prediction of clutch components temperatures based on other operating parameters as well as experimentally identified friction material characteristics. Friction material experimental characterization includes two characterizes build into the model: (i) coefficient of friction as a function of three operating parameters: temperature, slip speed and normal force as well as friction material wear as function of dissipated energy and temperature. Additionally, (iii) friction material tendency towards shudder was investigated both on small sample and the entire clutch including as well as (iv) the effect of wear depth on friction material coefficient of friction and tendency towards shudder. New axial dynamics model is proposed with the goal of a further improvement of precision of torque prediction as well as the positions of individual clutch components. The validation of the new model show increased precision related to modeling of individual effects with respect to the existing model.