Review of latest technological advancement in electro-mechanical continuously variable transmission

Continuously variable transmission (CVT) is a type of automotive transmission commonly used to achieve minimum fuel consumption. Nevertheless, a conventional CVT applies a hydraulic actuation system, which is powered by the vehicle's engine, to vary its ratio and to clamp the metal pushing V-belt accordingly. As a result, a significant portion of the engine power is diverted for the CVT's operation, making the powertrain system significantly less efficient. To address this challenge, many researchers have proposed the idea of electro-mechanical CVT (EM CVT). This paper provides a review of the latest designs of EM CVT, followed by highlights on the relevant research areas that should be pursued so that the advances made in EM CVT can be brought closer to commercialisation. These areas are: 1) efficiency validation of an EM CVT vs. a conventional CVT; 2) durability of the screw-thread system and the thrust bearing; 3) ratio and belt slip controls; 4) packaging of the actuation system.