Torque Distribution Strategies for Energy-Efficient Electric Vehicles with Multiple Drivetrains

The paper discusses novel computationally efficient torque distribution strategies for electric vehicles with individually controlled drivetrains, aimed at minimising the overall power losses while providing the required level of wheel torque and yaw moment. Analytical solutions of the torque control allocation problem are derived and effects of load transfers due to moderate driving/braking and cornering conditions are studied and discussed in detail. Influences of different drivetrain characteristics on the front and rear axles are described. The analytical solution of the control allocation problem is experimentally validated along multiple driving cycles on an electric vehicle with four identical drivetrains. The results of the analytically-derived algorithm are contrasted with those from two other control allocation strategies, based on the off-line numerical solution of more detailed formulations of the control allocation problem (i.e., a multi-parametric non-linear programming problem). The experiments show that the computationally efficient analytical solution represents a very good compromise between energy efficiency, drivability and controller complexity.