An Electric Gearshift With Ultracapacitors for the Power Train of an Electric Vehicle With a Directly Driven Wheel Motor

A novel electric gearshift with ultracapacitors is designed for the power train of a directly driven electric vehicle. The power train consists of two major subsystems: electric propulsion and energy source. The electric propulsion subsystem is composed of a dedicated wheel motor and its drive; the energy source subsystem is equipped with a stack of lead–acid batteries and ultracapacitor cells. This electric gearshift combines different parallel and serial connections of batteries, motor windings, and ultracapacitors to accommodate various driving patterns in the permissible range of speed and torque. A control core, which is realized by a field-programmable gate array, is employed to manage the energy source and direct optimal propulsion to extend the speed range of constant power, and thereby improve vehicle performance in terms of efficiency, acceleration, and driving range.