Abstract
There have been efforts to enhance the performances of the conventional power split hybrid electric vehicles by combining two different power split devices. The twomode planetary gear hybrid powertrains take advantages of each mode operation. For example, GM Allison´s AHS-2 is designed to achieve high fuel efficiency over the entire velocity range by using the input split mode at low vehicle velocity and the compound split mode at high velocity.
To investigate the performances and characteristics of the two-mode planetary gear hybrid powertrain, the backward-facing simulation was carried out based on the equivalent fuel consumption and quasi-static motion. By the results, the characteristics that the transmission efficiency highly depends on the speed ratio could be understood. Slightly lower fuel economy was expected when compared to the corresponding one-mode planetary gear hybrid powertrain. However, the top velocity and acceleration to 100 kph were expected to be better. Each mode operation complemented another and this brought improvement in the dynamic performances. Additionally, other anticipated merits of the transmission were discussed and suggestions for further researches were made.
Keywords:hybrid electric vehicle, two-mode, power split, planetary gear, fuel economy