Passenger Car Research On Controlling And Estimating Algorithm For Wheel Cylinder Pressure Of Stability Control System On Car

Sedan electronic stability control system is a kind of active safety control systems based on Anti-lock Braking System and Acceleration Slip Regulation and active yaw moment control. This system, by precisely controlling wheel cylinder brake pressure, exerts certain yaw moment on a vehicle to restrain the motion trend of understeer and oversteer, so the vehicle running stability is improved. As a part of sedan stability control algorithm the controlling and estimating for wheel pressure, located between the master control algorithm and the bottom floor hardware actuation, is used in further analyzing the master control algorithm and transmitting instructions to the bottom floor hardware actuation, is important component of the entire stability control algorithm.At present the overseas company like Germany Bosh and Continental, American TRW Automotive and Delphi, Japanese DENSO CORPORATION and Korean MANDO and so on has applied this technical achievement in the passenger vehicle's electronic stability control system product. There is no deep research on this technology at home, this already had become one of the technical bottlenecks of electronic stability control system development.Carrying on this research has significant meanings for breaking the overseas technical monopoly and enhancing the independent innovation ability. This article unifying national and the province departmental level project carried out main contents as follows:1,Theoretical analysis on ESC hydraulic brake system. It mainly includes the analysis on structure mechanism and operating mechanism of the hydraulic control unit; the analysis on on-off mechanism and control mechanism of high speed switch valve; the analysis on motion mechanism and control mechanism of electric hydraulic pump; the analysis on pressure establishment mechanism of the ESC hydraulic brake system; The above researches provide important theory basis for research on controling and the estimating algorithm for wheel cylinder pressure.2,Experimental analysis on ESC hydraulic brake system. It mainly includes the electrical response characteristic test of electric hydraulic pump, inlet valve and delivery valve; the hydraulic response characteristic test of electric hydraulic pump, inlet valve and delivery valve; the P_V characteristic test is needed for the ESC hydraulic brake system. The above researches provide important experimental basis for controlling and the estimating algorithm for wheel cylinder pressure.3,The determination for key parameters of controlling and estimating for wheel cylinder pressure of ESC system.It mainly includes the research on estimating algorithm of initial wheel cylinder pressure of wheel cylinder pressure control and estimate model; The fuzzy controller design based on the deviation between the desired wheel cylinder pressure and actual wheel cylinder pressure as well as the rate of change of the deviation is designed to determine the desired rate of change of wheel cylinder pressure; the revision principle of the desired rate of change of wheel cylinder pressure is proposed unifying the adhesion jump of road surface. The above researches provide external variables needed by controlling and estimating for wheel cylinder pressure.4,The research on controlling and estimating algorithm for wheel cylinder pressure of ESC system. According to the characteristic curves and key parameters of electromagnetic valve, electric hydraulic pump and ESC hydraulic brake system acquired from test, the experiential and semiexperiential control algorithm of wheel cylinder pressure control and estimate, based on unifying theory and experimental study, is proposed combining the working status and pressure demand of current various parts.5,Hardware in loop experimental verification of ESC hydraulic brake system. The comprehensive test platform based on Matlab/Simulink/xPC Target is established, and the experimental verification to established model under different desired pressure is conducted.The following conclusions can be obtained through above researches:1,Taking opening "the black box" as goal, the research to various factors influencing fast and steady establishment of wheel cylinder pressure is conducted using the unifying way of the theory and the experimental study, and these factors are organically combined to carry experimental study on electromagnetic valve, electric hydraulic pump as well as the P_V characteristics of ESC hydraulic brake system. The research indicates that this method can factually gain the ESC hydraulic brake system's pressure control characteristic.2,Based on the theory of pressure medium coefficient of volume compression, improving relationship between brake pressure and volume of brake fluid (namely P_V characteristic) is adopted, the influence of brake line and brake wheel cylinder's elastic deformation as well as on-way pressure loss and local pressure loss etc. can be flexibly treated. This has laid the foundation for the model of wheel cylinder pressure control and estimate.3,The optimum PWM control signal cycle and PWM control signal duty ratio are obtained by analyzing test data. This applies reference database for PWM control signal duty ratio under certain actual pressure to meet desired rate of change of wheel cylinder pressure. 4,The pressure control principle of alterable rate of change of wheel cylinder pressure, based on wheel pressure status and referring road surface adhesion status, combines pressure estimate principle of electromagnetic valve flow characteristic and hydraulic brake system P_V characteristic to control wheel cylinder pressure so that wheel cylinder pressure can fast and steadily establish.