Optimal Design To Pressure Control Strategy For Master Cylinder In Hydraulic Brake By Wire System

In recent years,due to the continuous progress of science and technology,the new development trends of electrification,intelligence,networking and sharing which the automotive industry develop toward is more and more clear.Under the promotion of the new development trends of electrification and intelligence,the part-systems in automobile are undergoing a new change,which is mainly reflected in the fact that the new chassis layout with rich topology and the widely used wire control technology have become the core competitiveness of the latest generation automobile.For the braking system in automobile,a kind of electro-hydraulic compound braking system with the topology of electric control and hydraulic driving,named hydraulic brake by wire system,has become a hot spot of theoretical research and prototype trial production in automobile braking field.Based on Jiangxi Science and Technology Innovation High-end Talents Project(Jiangxi Youth Thousand Talents Plan): "Research on key technology of intelligent electric vehicle brake by wire"(subject number:jxsq20192019201119),this paper analyzes and optimizes the design of hydraulic pressure control of hydraulic brake by wire system.(1)Aiming at the current problems of hydraulic pressure control in hydraulic brake by wire system,a simplified simulation model of hydraulic brake by wire system is built in AMESim.Then the parameters of the brake system simulation model are designed,and the system its static working characteristics is tested.In order to use the control model established in MATLAB/Simulink to control the simulation model of hydraulic brake by wire system established in AMESim,the co-simulation platform of AMESim and MATLAB/Simulink is established and tested in this paper.(2)In order to study the simulation model and optimal control strategy of the hydraulic brake by wire system designed in this paper,a vehicle co-simulation model including drive motor,power battery,vehicle and driver model are built in AMESim.Then,the speed condition with the maximum speed of 120/(km/h)is designed,and verified in this paper.(3)In order to optimize the hydraulic pressure control of the hydraulic brake by wire system,some simulation researches based on the two classical hydraulic pressure control methods including the hydraulic pressure closed-loop control in the brake master cylinder,and the piston push rod displacement closed-loop control in the brake master cylinder,are carried out in this paper.According to the results of simulation tests,a double closed-loop switching control strategy based on the hydraulic pressure closed-loop control in the brake master cylinder,and the piston push rod displacement closed-loop control in the brake master cylinder,is put forward in this paper,and its model in MATLAB/Simulink is established and improved further.(4)In order to verify the effectiveness of the hydraulic pressure double closed-loop switching control strategy designed in this paper further,a step brake cycle and a sine brake cycle are designed,and the standardized driving cycles including CLTC-P and WLTC are referred.Under the four cycles,the whole vehicle integration simulation trials are carried out.The trial results show that the hydraulic pressure double closed-loop switching control strategy designed in this paper can control the vehicle speed error within ±3/(km/h)in the vehicle cycle simulation,and effectively identify the braking direction.And,in the low target hydraulic pressure control range,the hydraulic pressure control error is controlled within±2/(bar),and under the ultimate braking load of the system,the impact between piston and master cylinder wall does not occurs.