A Mathematical Review and Comparison of Continuously Variable Transmissions

The capability of Continuously Variable Transmissions (CVTs) to provide a continuous speed ratio change and smooth power flow has been widely recognized. These unique characteristics of CVTs make them especially suited for a variety of power transmission needs. Several studies have been accomplished in the past, to understand the power transmission characteristics of individual CVT concepts. However, few general analytical models and comparisons of different CVT concepts have been reported in the literature.

In this work, different CVT concepts have been compared on an equitable basis in a selected operating envelope. Mathematical models of different CVT concepts have been developed from the published literature by normalizing the available information to allow comparison of different CVT concepts on an equitable basis. The models have been used next, to compute the efficiencies of individual CVTs at selected points covering the entire operating envelope. The data have been plotted on nine 2-dimensional plots to facilitate visualization of results. A discussion of results of comparison also has been provided.