Research On Braking Control Strategy Of Pure Electric Vehicle Under Multiple Braking Conditions

Due to the rapid development of society,energy shortage and environmental problems are standing out increasingly.The traditional fuel vehicle as the main consumable of fossil fuel and the main emissions of harmful gas,its development has been limited.Governments of many countries have issued relevant policies to ban the sale of fuel oil vehicles and vigorously support new energy vehicles,so that the new energy vehicles ushered in a period of vigorous development.Pure electric vehicles as a new energy vehicles,it has the advantages of simple structure,zero emission and low noise and so on.According to the 12 th five-year plan and related policies,pure electric vehicle will be one of the important strategic directions of China's automobile industry in the future.Compared with petrol vehicles and other new energy models,pure electric vehicles have a prominent shortcoming in driving range.Besides developing battery technology,developing brake energy recovery control strategy is an effective way to solve this problem.The strategy controls the motor to provide negative torque when braking to participate in braking and serve as a generator to power the power battery,improved the utilization of battery power.The research object of the thesis is the pure electric vehicle with front engined front wheel drive,the parameters of power battery and drive motor are matched and the vehicle model is established to lay a foundation for strategy customization;According to brake correlation curves,such as I curve,f line,ECE regulation line,etc and through the fuzzy controller based on ANFIS training optimization to identify the driver's braking intention,on the premise of braking safety,the allocation strategy of total braking force of front and rear axles under different braking conditions is established;According to the real-time information of the vehicle,the strategy determine the running state of the vehicle,such as normal running,crawling,braking,stopping,sliding and other states,according to different operating conditions,in order to achieve the goal of maximum recovery of braking energy,complete the distribution of electric mechanism force and hydraulic brake braking force,besides,only the motor participates in braking when the vehicle is coasting,and the optimal braking torque at different speeds is established by genetic algorithm;Finally using the MATLAB/Simulink/Stateflow complete the above control strategy and established the joint simulation with AVL CRUISE,the vehicle NEDC driving range,and initial speed braking conditions with different strength are simulated respectively.The results show that this strategy can effectively extend the driving range of NEDC and reduce the power consumption of 100km;The driving range contribution of recovered energy was 12.90%;Its also show that the energy recovery rate is higher under the condition of small brake strength,And the value decreases gradually with the increase of brake strength,the braking energy recovery rate was 72.76% when the braking strength was 0.1.In addition,the sliding condition and braking safety are simulated and verified,it shows the rationality of the strategy;The strategy is compared with that in the original vehicle,taking the initial vehicle speed of 100km/h as an example,the braking energy recovery under the control of this strategy is 71.65%,the results show that this strategy can give back more braking energy;Finally,the braking force distribution points under different braking states are counted to show the braking safety of this strategy.