Transmission Architecture and Topology Design of EVs and HEVs

For electric vehicles (EVs), the motor is used as the power source to drive the vehicle. According to the arrangement of motors, there are four configurations: single-motor driving, dual-motor independent driving, wheel-motor driving, and dual-motor front- and rear-axle independent driving. In general, hybrid EVs can be crudely divided into three types: parallel, series, and split. Among all three types, the power-split type is the most popular. This is mainly because the engine in a power-split hybrid vehicle is decoupled from vehicle speeds and can operate efficiently even when much of the power flows in the mechanical path. In this chapter, a novel and efficient methodology is presented for the design of power-shifting transmissions (PSTs). The keys of the methodology are the degree of freedom model of the PSTs and the basic configurations. An algorithm of mini-max solution for the overdetermined equations is applied to design the gear ratios. Furthermore, the design concept can also be applied to the other fixed gear transmissions, such as automated manual transmissions and dual-clutch transmissions.