Design And Control Strategy Research Of Automobile Electro-mechanical Braking System

In recent years,driving safety has become a hot topic.Vehicle is used for transportation.In addition,more and more customers begin to seek overall experience with safety,maneuverability and economy,and integrated control-by-wire chassis is an effective way to achieve the requirement.Electro-mechanical braking system uses transmission of electronic information to replace mechanical and hydraulic connections,which has the advantage of simple structure,energy conservation,environmental protection and quick respond.Based on detailed analysis both domestic and international research results of EMB,this thesis is attempting to optimize layout scenario of actuator.Design and selection of key components,especially actuators are completed firstly.Single and double wheel dynamic model include tyre and braking actuators are established by MATLAB/SIMULINK software.On the basis of three-dimensional modeling and common dry,wet and ice pavement,the influences of different tire-road friction coefficient on braking effect is well analyzed.The result shows that the lower friction coefficient and faster initial velocity are much easier to cause traffic accident.What's more,brake force distribution coefficients are studied to reach a conclusion that brake force distribution coefficient should be appropriately increased during the design process to prevent rear wheel from locking first and further causing dangerous working conditions such as braking flick.It is the same as design process,analysis software with high level of visualization for dynamic model has been developed based on GUI toolbox in MATLAB to greatly improve efficiency for analysis.In the master of control principle,PID control model based on ideal slip rate tracing is built,and effects of different parameters such as proportional parameters,integration parameters and derivative parameters on control performances are analyzed.The effects on anti-lock control performance with different braking force distribution coefficients have also been studied.Mathematical model for PID parameters optimization is built with the mean square root of slip rate error as the objectivefunction.The control parameters of PID control are optimized by use of genetic algorithm.The results show that PID control whose parameters are optimized with genetic algorithm can trace the target slip rate well,and improve brake effectiveness and the directional stability when braking.Related theories of the chassis integrated control technology for X-by-wire are introduced at the end of the thesis.“Driver-vehicle-road” closed-loop seven degrees of freedom dynamic model for chassis control-by-wire has been established based on MATLAB/SIMULINK.Effects on dynamic characteristics of the tire are analyzed with the examples of braking and steering joint conditions.