Transient-Dynamic Model of a Metal V-Belt CVT for Ratio Shift Control Applications

Abstract

A continuously variable transmission (CVT) enhances the fuel economy and acceleration performance of a vehicle by allowing the engine to operate at or near its best specific fuel consumption rate for variable driving scenarios. A large volume of work has been reported on the dynamic modeling a metal V-belt CVT system. Most of the models mentioned in literature are steady-state quasi-static equilibrium based or multibody-formalism based, thereby being unsuitable for CVT control applications. Since steady state models fail to accurately capture inertial effects and multibody models present a challenge for control applications due to the large number of bodies involved, the focus of the current work has been to develop a simulation model relatively quick and accurate enough to predict the power transmission behavior and inertial dynamics of a metal pushing V-belt CVT at transient states. The objective of this research is to develop a detailed continuous one-dimensional transient-dynamic model of a metal V-belt CVT system for control applications. The model presented in this work is able to capture the dynamic correlation between the required pulley axial forces and the corresponding transmission ratio. In addition to this, it takes into account detailed inertial effects and predicts the slip behavior and torque capacity of the CVT system under both transient and steady-state regimes. The model proposed in this work would serve as a powerful tool to develop fast, reliable, and accurate controllers for a CVT-equipped driveline to meet the objectives of reduced losses, higher torque capacity, higher vehicle fuel economy and better acceleration performance. The results from the present model subsequently discuss in detail the transient performance of a metal V-belt CVT drive for high torque loading conditions. Various control strategies can be readily implemented with this detailed transient-dynamic model of a metal V-belt CVT system to achieve minimum slip loss and maximum fuel economy and torque capacity.