Analysis of a Continuously Variable Transmission Based on a Twin Epicyclic, Power Split Device

This research paper is focused on a novel transmission which provides a continuously variable gearbox based on two epicyclic gear sets plus two electric motor/generator units. This design scheme offers potential efficiency benefits over its competitors. It is referred to as a four branch transmission [1], because it has four independent power input and output, namely the engine, two motor/generators and the output shaft of the transmission. A key advantage of the design, when it is used on a hybrid electric vehicle, is that the electrical machines, namely the two motor/generators, and can be downsized compared with the more common, single epicyclic, 3 branch arrangement. A matrix method for the analysis of planetary transmissions [2] is used; the performance and control strategy of the new system is presented.