Modeling Simulation Andmulti-objective Optimization Of EHB System

Now,as the economy develops rapidly,the demand for cars keeps increasing,and the environmental problems that caused by the increase of cars are becoming more and more serious.Use the pure electric vehicle instead of traditional automobile can solve the environmental problems that caused by the automobile exhaust,but the mileage and the safety of pure electric vehicle are still big puzzles for the consumer.Aiming at the problem of stability and braking energy recovery of pure electric vehicle,the structure and working principle of the brake system of electric vehicle were analyzed.A new distribution strategy of brake system was designed,and the multi-objective optimization of regenerative braking system for pure electric vehicle was adopted.The research object was the pure electric vehicle which equipped with four permanent magnet brushless DC hub motors and the ultracapacitor-lithium hybrid battery.First of all,the principle and the character of brushless DC motor and hybrid battery were analyzed and then their mathematical model were established,The electric-hydraulic braking system and regenerative braking recovery process were analyzed,and do some researches on the ideal brake force distribution curve and the electric-hydraulic braking force distribution strategy.Then a new brake distribution strategy was designed that suitable for different braking conditions.The strategy was simulated by Matlab/simulink software,the results show that the braking force distribution is helpful to improve vehicle stability and braking energy recovery efficiency.Then,was optimized.First of all,obtained the ideal centroid of side-slip angle and ideal side-slip angle by establishing the two degree of freedom model,and compared them with the actual data to know the state of the car.If the car was in instability state.By increasing front and rear wheel drive power,to force the car runs in the desired path.Firstly,the optimization model of body stability controller was established.Select the torque controlled by the body stability controller as the optimized object,and analyzed the torque to obtain the range.And then analyzed each management system and vehicle safety and regulation,to obtain constraint conditions of braking process.The vehicle stability and the braking energy recovery efficiency were set as optimal object.By using the genetic algorithm,we could get the optimalsteering angle under various road conditions.Established the vehicle model,brake master cylinder model,vacuum booster model,motor model and battery model with the AMEsim software and connected it with the braking force distribution model and body stability control model that established by the Matlab/simulink software.The optimal date was substituted into the simulation,and the simulation result shows that the optimized braking force not only improves the braking stability of the car,but also improves the braking energy recovery efficiency.