Shoichi Sasaki


Shoichi Sasaki
Shoichi Sasaki
Associated organizations
University Graduate School of System Design and Management
Fields of study
IEEE Medal for Environmental and Safety Technologies


The combined contributions of Takehisa Yaegashi, Shoichi Sasaki and Shinichi Abe enabled the development and commercialization of hybrid electric vehicles (HEVs) that have revolutionized the automotive industry. They created the “Toyota Hybrid System” (THS), resulting in the 1997 Toyota Prius and impacting future versions of HEV technology. The world’s first mass-produced HEV, the Prius obtained revolutionary fuel efficiency using the THS. Dr. Yaegashi directed the establishment of the integrated vehicle energy management system. He then improved the first-generation technology to create THS II, featured in the 2004 Prius, which significantly improved fuel efficiency, performance and cost reduction. Professor Sasaki developed a unified control algorithm that achieved optimal fuel efficiency and control of the engine, motor and battery. His algorithm has been applied to all Toyota hybrid vehicles. Mr. Abe was responsible for ensuring low emissions and drivability of the vehicle. He implemented a variable valve-timing mechanism to reduce the shock that was instrumental in THS and THS II system efficiency exceeding that of hydrogen fuel-cell hybrids at that time as well as of conventional ICE vehicles.

Mr. Sasaki is an IEEE Member and in 2011 received the institute's Medal for Environmental and Safety Technologies. He is currently a Professor at Keio University Graduate School of System Design and Management, Yokohama, Japan.