Research On The Key Technologies Of The Compact Electro-hydraulic Braking System

With the growing energy and pollution problem and the rising demand for driving safety,electrification and intelligentization of the vehicles have become a prospective trend.Both of them put forward new requirements for the friction braking system.As a brake-by-wire system,the Compact Electro-Hydraulic Brake System("CEHB” hereafter)can meet the above requirements.In addition,it's small-sized,in no need of highly dynamic motor and adopts mature components,bringing it a promising prospect.Therefore,design,trial and control of CEHB are of great importance.CEHB prototype and research environment,precise pressure regulation,scheduling method with multi-wheel pressure regulation and the upper algorithm of pressure regulation are discussed in this thesis.Since CEHB prototype and research environment are the basis of CEHB research,CEHB prototype is designed and trial-produced,while a numerical simulation environment and a test bed are set up.Single-wheel pressure regulation method and multi-wheel pressure scheduling algorithm are carried out based on the research above.Considering the mounting position of the pressure sensor,a nonlinear backstepping hydraulic pressure regulation method based on the real pressure observer of the wheel cylinder is proposed in this paper.This method is well-adapted to different pressure amplitudes and frequencies,and is robust to the perturbation of parameters.By analogy with the process scheduling of the operating system,the scheduling of CEHB pressure control is analyzed.And a time scheduling algorithm based on dynamic priority considering the switching time of pressure increase and decrease is proposed.A priority generation method is adopted considering the deviation of pressure regulation,the possible rate of pressure change,the switching time of pressure increase and decrease and whether the vehicle is under extreme conditions.The scheduling method can take into account both the response speed and the regulation accuracy of the pressure.The upper algorithm of hydraulic pressure regulation is discussed based on the prototype and research environment of CEHB,as well as the four-wheel precious pressure regulation and scheduling method.On the basis of the identified additional displacement of the brake disc,a method of using feedforward control to compensate the brake pressure variation caused by additional brake disc displacement is proposed,which can reduce pressure fluctuation and improve the pressure control performance.A braking intention classification method is proposed,and the purpose of which is to reduce the pressure fluctuation,improve the comfort,the working condition and the life of CEHB.The braking intentions are classified into normal deceleration,pressure following and emergency braking.Braking force control methods are employed accordingly.A multi-sensor data fusion and neural network method is adopted to identify the braking intention online.This method can availably reduce the actuator actions and pressure fluctuation,improving the braking comfort and extend the life of the hydraulic control unit.