Analytical method of the front–rear driving and braking force distribution for neutral steering characteristics and maximum lateral acceleration

This paper proposes an analytical method to determine the optimal front–rear longitudinal force distribution that maximises lateral acceleration in electric All-Wheel-Drive (AWD) vehicles equipped with independent front–rear motors. Conventional approaches numerically compute the wheel-locking limits from driver demand, vehicle longitudinal and lateral accelerations, and road friction and then embed the results as lookup maps or perform iterative calculations in real time; these schemes are computationally costly, memory-intensive, and less robust to variations in vehicle specifications and road conditions. The proposed approach analytically derives the optimal force ratio using a vehicle model that captures longitudinal and lateral load transfer and roll stiffness, enabling real-time implementation without map calibration or high computational resources. Vehicle tests on a low-friction surface verified that the derived ratio achieves maximum lateral acceleration while maintaining balanced handling. Robustness was assessed by adding a 300 kg load to the rear axle. At a road friction coefficient of 0.4, the analytical method closely matched theoretical predictions, whereas a conventional map-based method showed a 22% error at a driving acceleration of 1.0 m/s/s.