An analytic foundation for the Two-mode hybrid transmission with a comparison to other hybrid vehicle power split transmissions

The new hybrid system developed by General Motor, Daimler-Chrysler and BMW recently is called Two-mode hybrid transmission, named as “Technology of the year” for 2007 by Automobile Magazine. The Two-mode hybrid transmission, contains two electric machines, three planetary gear units and four electrically controlled clutches, allows six different operation modes: two electrically variable transmission modes and four fixed-gear modes. The purpose of this present paper is to explain the basics of Two-mode hybrid transmissions, input-split and compound-split modes, and the addition of fixed-gear ratios, thereby presenting an analytic foundation for its operation. And the same time, the dynamic equations of the new system is derived, which can be use in modeling the Two-mode hybrid transmission for developing control strategy. Other hybrid vehicle power split transmissions being considered by auto companies, such as Toyota hybrid system-II, are also discussed, in order to make a comparison with Two-mode hybrid transmission.