Range Extension of Electric Vehicles with Independently Driven Front and Rear PMSM Drives by Optimal Driving and Braking Torque Distribution

The paper proposes a real time optimal driving torque distribution strategy for an electric vehicle (EV) with independently driven front and rear wheels. The proposed optimal torque distribution strategy among the front and rear wheels, improves the overall energy efficiency of the vehicle, there by increasing the driving range achievable per charge cycle of the EV. The torque is optimized with the objective of minimizing the energy consumption during driving as well as maximizing the regenerative energy recuperation during the braking. This is realized by minimizing the losses during traction and regeneration by expressing the losses as a function of torque and optimized using Particle swarm optimization (PSO). Here, a real time torque distribution control system is proposed which can realize optimal distribution of driving-braking torque corresponding to the driving commands, for constant speed driving, acceleration, braking and grade climbing driving modes. The optimal torque distribution ensures minimal energy consumption, thus improving the energy efficiency of the EV. By reducing the energy consumed the driving range achievable per charge cycle is improved, realizing range extension of EV. The proposed method is designed for a test vehicle driven by two PMSM drives one each on front and rear wheel axles and the performance is verified with simulation studies. The results obtained shows significant improvement in the energy efficiency of the vehicle and thereby range extension.