Designing a Super-Fast Prius: Systematic Design of Multispeed eCVT via Virtual Design Space

Abstract

Despite its excellent fuel economy (FE), the Toyota Prius has a poor acceleration performance (AP). Its performance is improved using bigger propulsion components and a multispeed transmission for sports utility vehicles (SUVs) and high-performance models. Nevertheless, this performance improvement is limited as the input-split architecture cannot use its small motor/generator (MG) for motoring. To overcome this shortcoming, this article suggests adding fixed gear (FG) modes to the Prius system. FG modes can boost the AP, thanks to the power amplification resulting from using both MGs as motors. With a focus on the architectural design of FG modes, all potential placements of clutches (CLs) and gears are enumerated. The analysis of candidate physical FG modes revealed a redundancy as one transmission ratio (omega(E)/omega(O)) can be created by different CL and gear pairs. To omit this redundancy, this article conducts the architecture search within the concise virtual design space. The virtual design space consists of all different combinations of candidate input-split and virtual FG architectures. The performance is evaluated within the virtual design space, and virtual designs with good FE and AP and feasible gradeability are selected. An optimal virtual design that is drastically faster (67.82% faster) than the single-mode Prius and with a better FE (5.56% higher) is selected and converted into 50 physical multispeed architectures.