Minimizing Stopping Distance on Split Friction via Steering and Individual Wheel Braking Optimization

Preprint, 2023

Braking hard on a split friction road generates asymmetric brake forces, creating a yaw moment disturbance. For most drivers, it is challenging to counteract the disturbance using steering, which could make the vehicle deviate from the lane and potentially into a dangerous situation. A straightforward way to keep a vehicle in its lane is to apply equal brake force to all wheels based on the lowest level of road friction. Unfortunately, this method has the downside of significantly reducing the vehicle's braking capacity, resulting in an increased stopping distance. Hence, the braking capabilities can be noticeably improved by incorporating automated steering compensation. This paper suggests a solution for optimizing steering jointly with individual wheel braking. The proposed approach determines the upper deceleration limit while ensuring the vehicle stays on its intended path. The upper deceleration limit depends on the friction asymmetry between the vehicle's low and high friction sides.
In cases of low friction asymmetry, steering is an effective means of maximizing braking at each wheel. However, in high friction asymmetry, steering compensation saturates, rendering it impossible to attain maximum braking at each wheel. Also, the vehicle must drift to maintain a straight path during braking.