A regenerative brake system significantly improves the energy efficiency of electric vehicles, but road gradient can adversely affect fuel economy and vehicle control. This study seeks to explore the effects of road gradient on the regenerative brake system on the basis of driving information collected by global positioning systems (GPS) and inertial sensors, including road gradient and vehicle speed. Then optimization is made of conventional parallel control strategy, serial control strategy with fixed front–rear brake force allocation, and serial control strategy with optimal energy recovery. By calculating the contribution ratio to energy consumption reduction in each of the three strategies based on a model of pure electric vehicle’s energy flow, the roles that road gradient plays are carefully investigated. Simulation results show that our proposal for taking road gradient into account helps to design more efficient strategies of regenerative braking systems.

No abstract