Optimal Braking Force Allocation For Vehicles With The Brake-by-wire System During A Braking-in-turn Maneuver

The braking system of vehicle is an important component to ensure its safe.With the continuous advancement of vehicle electronization process,a more efficient and energy-saving brake-by-wire system appeared,which realized the independent control of the braking force of the four wheels of the vehicle and has a broad research space.It is a kind of complicated working condition for a vehicle to apply braking during a turn maneuver.It is easy to cause traffic accidents because of the unreasonable distribution of braking force.At present,there are few researches on the braking force distribution control strategy for vehicles with the BBW system during a braking-inturn maneuver.The research on the braking-in-turn condition of the vehicle with BBW system is carried out.The details are as follows:For four-wheel normal braking conditions in braking-in-turn maneuver an optimal braking force distribution control strategy is proposed.The vehicle dynamics model and two-degree-of-freedom vehicle reference model are established.The structure of hierarchical control is adopted and the instability state identification method is designed based on the phase plane method.The upper controller uses the sliding mode control theory to design a yaw moment weighting controller that considers the yaw rate and the centroid side yaw angle.Then the total braking force setting module is designed.The lower braking force distributor is designed with a multi-objective optimal distribution strategy for braking force.That is to optimize the vehicle tire utilization rate under normal working conditions.In the extreme conditions,the goal is to maximize the vehicle braking force.A joint simulation model of optimal braking force distribution strategy for four-wheel normal braking in curved road is established by using Matlab/Simulink and Carsim.The simulation experiments were carried out under different conditions of initial braking speed,braking strength,road adhesion coefficient and turning radius.The results show that the optimal braking force distribution strategy proposed in this paper can not only ensure the braking performance of the vehicle during a braking-inturn maneuver,but also effectively improve the stability of the vehicle.The vehicle dynamic model of wheel braking failure in different positions of the vehicle during a braking-in-turn maneuver is established.Taking the left-turn condition as an example to analyze the impact of single-wheel braking failure on vehicle performance.The braking force control allocation algorithm is reconstructed for the single-wheel braking failure condition of the braking-in-turn maneuver.Carsim and Matlab/Simulink are combined to carry out simulation verification.The results show that the reconstructed braking force control distribution algorithm reduces the yaw rate of the faulty vehicle under different braking conditions,and ensures the stability and braking safety of the single-wheel braking failure vehicle.