A New Electrified Planetary Gear Set - The Cost- and Fuel-Efficient Alternative to Continuously Variable Transmissions

In order to mitigate the effects of climate change, the global transport sector, one of the largest emitters of CO2, needs to drastically reduce its emissions. Although hybridization and electrification are becoming increasingly popular as a solution for a variety of applications, their use in two- and three-wheelers, as well as in recreational and powersports vehicles, remains limited due to their high costs and complexity compared to conventional drivetrains with continuously variable transmissions (CVTs). Despite their affordability and simplicity, CVTs suffer from low mechanical efficiency, with transmission losses ranging from 20–50 %, highlighting a significant opportunity for improvement. In response to these limitations, this study presents the development and experimental evaluation of an electrified planetary gear set (ePGS) in a lightweight off-road vehicle. It is designed to overcome the efficiency limitations of CVTs while maintaining high driving comfort and low system complexity, and enhancing performance and fuel efficiency. The system design followed a structured approach, beginning with a morphological analysis and multi-criteria evaluation to refine potential drivetrain concepts. The final concept is characterized by its exceptionally compact design, which is achieved despite the use of off-theshelf components. The functionality of the concept was validated through a prototype transmission that is tested in a series of driving scenarios, both on the road and on a chassis dynamometer. The results demonstrated a 17 % enhancement in fuel efficiency relative to the original vehicle that was equipped with a CVT, despite the absence of access to the engine control unit. These findings highlight the potential of the ePGS system as a cost-effective, fuel efficient alternative for conventional CVT powered vehicles.