Energy Optimality in Electric Vehicles Along Uphill-Downhill Roads

In this paper, an energy optimal controller is designed with torque, speed and battery constraints, and detailed sensitivity analyses are performed. The design is tested on the gross motion mathematical model of the vehicle moving on a variable-slope road in scenarios including uphill and downhill road sections of various slopes and lengths. The tests are repeated along roads with icy slopes, and the superiority of the energy optimal controller is verified for roads with low friction coefficients. A skidding compensation logic is proposed, and it is observed that the energy optimal solution is insensitive to such compensation methods. Further sensitivity analyses are performed, and it is shown that as a representative of different passenger seating arrangements, the sensitivity of the energy optimal controller to the changes in mass and its distribution is small in magnitude. The tests with different initial state-of-charge of the battery demonstrate that the superiority of the energy optimal controller becomes significant especially when battery characteristics limit the charging capability during regenerative braking.