Systematic Design of Fixed Gear Modes for Novel Multi-Mode Architectures: A Prius Case Study

Abstract

The Toyota Prius system has an excellent fuel economy (FE), but a mediocre acceleration performance (AP), especially at high speed. In order to enhance its AP while maintaining a good FE, this paper investigates the addition of multi-mode capabilities to this benchmark system with a focus on the incorporation of fixed gear modes, which are able to achieve a good AP at high speed. Firstly, candidate clutches and gears were systematically added to the single-mode Prius system. Secondly, 63 candidate multi-mode architectures were generated through the enumeration of the different clutch combinations, and their AP was evaluated. Then, AP screening criteria aiming to select systems with an outstanding AP and feasible gradeability were applied and a total of 3300 systems were selected. Lastly, the FE was assessed for these selected multi-mode systems and the 'best' systems with good FE and AP were selected. The results revealed that the addition of fixed gear modes significantly enhances the AP of this benchmark system, which is also able to maintain an outstanding FE thanks to its input-split mode.