Research On MPC-based Electro-Mechanical Hybrid Braking Torques Distribution For Electrical Vehicle

With the rapid development of the global automobile industry and the explosive growth of car ownership,the energy consumption and environmental pollution of conventional cars become more and more serious.In order to deal with the increasingly serious crises of energy and environment,the new energy vehicles,which mainly includes hybrid electric vehicle,electric vehicle and fuel cell vehicle,have attracted more and more attention from the public.The regenerative braking system of electric vehicle has become a hot spot of global research and development because of its energy conservation and non-pollution.Compared with the hydraulic braking system,the regenerative braking system of electric vehicle can not only achieve vehicle braking and recovery braking energy,but also has the characteristics of rapid response.Because of the regenerative braking system can not produce large enough braking torque and is easily influenced by many constraints,the regenerative braking system can not achieve the vehicle braking alone when high strength braking.Therefore,the combination of regenerative braking and hydraulic braking is necessary.Through a reasonable control method,the composite braking can not only achieve a high performance of braking,but also can recover more braking energies.In this paper,a rear-wheel-drive electric vehicle is took as the research object.In order to improve the recovery of braking energy and brake pedal comfort when the emergency braking is applied,systematic study of the electro-mechanical braking system has been made in this paper,and a coordination control between the regenerative braking system and hydraulic braking system has been designed.At last,system simulation proves a perfect braking performance.The main contents of this paper are as follows:(1)In order to achieve good braking performance on various roads,according to the relationship between slip ratio and friction coefficient under five road adhesion coefficients,a real-time estimation system of road adhesion coefficient is designed,and the optimal slip ratio of current road adhesion coefficient is determined.(2)For the sake of the safety of braking and high energy recovery efficiency,a MPC-based electro-mechanical braking control system has been proposed in this paper.This system makes full use of the characteristics of rolling horizon optimization of model predictive control(MPC),makes the real slip ratios of wheels track the optimal slip ratio,ensures the stable of braking and prevents anti-lock braking of the vehicle.This system can calculate the optimal braking torque of each wheel,and complete the first distribution of braking torque.(3)To obtain much more braking energy or enjoy a good brake pedal feel,two strategies has been designed to distribute regenerative braking torque and hydraulic braking torque.(4)According to the requirements of electro-mechanical braking system and its control strategy,the whole vehicle model and control strategy model based on Matlab/Simulink are established,and the simulation analysis is completed under different pavement conditions.