The Optimization Of Braking Force Distribution Control Strategy For ESP System

ESP (Electronic Stability Program) is German Bosch and MERCEDES-BENZ co-developed, integrated full functionality of Anti-lock Braking System and Acceleration Slip Control System. According to the intention of the driver, road conditions and vehicle state of moment, control the movement of vehicles in a few milliseconds to identify trends for automobile driving instability, to prevent dangerous situation, inhibit understeering or oversteering, thus more effectively and more significantly improve the handling stability and driving safety of vehicle.ESP is also a kind of intelligent active safety system, which monitor the state of vehicle through the sensor of high sensitivity and through the calculation and analysis to determine whether the direction deviate from the intent of the driver's operation, identify hazardous conditions and advance rule out a feasible intervention measure to award and back to stable operation state. So, ESP system can reduce traffic accidents, greatly improve the car's active safety. Conquering ESP design theory and key technologies for improving the ability of independent development of domestic car and shorten the gap with the developed countries have important and practical significance.This paper mainly studies optimization problem of braking force distribution control strategy for ESP system in the process of oversteer and understeer control. Starting from the car driving dynamics, establish linear reference model of two degrees of freedom, brake torque distribution model, vehicle dynamic model of eight degrees of freedom including tires and body model, and based on fuzzy logic, design fuzzy logic controller that considered vehicle yaw rate and sideslip angle as control variable. On this basis, because the braking force distribution strategy has significant influence on control effect of ESP, combine with the fuzzy controller and focus on the effect of braking force distribution strategy, under different road conditions, give research process and analysis result on detail under three kinds of braking force distribution control strategy for five typical operating conditions by adjusting the yaw moment control vehicle yaw rate and sideslip angle, and further shows the optimization strategy of braking distribution mode, and the same time, verify the effectiveness of design by simulation results.The main contents of this paper is how to control the stability of vehicle that get use of the longitudinal slip-cornering joint working condition and differential braking control theory. Specific wheel by braking, can be very effective in changing the car's yaw moment to adjust the car's athletic stance. At last, research and analysis are done under three different braking force distribution control strategy and five typical working conditions. Paper is divided into five chapters.In chapter one, an introduction is given about ESP. The background and significance of ESP research are introduced; the development history and application research situation,structure and working principle of ESP are also described.In chapter two, establish vehicle dynamic model for ESP control system including eight degrees of freedom vehicle model and two degrees of freedom vehicle reference model. Among them, the vehicle model including body model and tire model.In chapter three, mainly design ESP control system. (1) Analyze the stability of vehicle, including the reasons of vehicle instability, two important parameter that affects auto stability. (2) Introduce the stability control mode, determine to select differential braking control method, and puts forward the braking torque distribution formula between shaft. (3) Simply introduce the basic principle of fuzzy control, based on the fuzzy controller design steps and establish two-dimensional fuzzy controller model in which yaw rate and sideslip angle as input variables and compensatory yaw moment as the output variables. (4) Use MATLAB/SIMULINK software, the vehicle dynamics model, such as body model, tire model, reference model and so on, into the SIMULINK graphical simulation model; combines with vehicle dynamic mathematical models and differential braking theory, establishes braking force distribution model with compensatory yaw moment, vehicle vertical load as input, braking torque as output.In chapter four, conduct research and analysis on the platform which automobile ESP stability control system, simulink simulation model, three braking force distribution control strategy, five kinds of typical working conditions. Finally receive the conclusion that the optimal braking force distribution control strategy which is determined by the road condition.Chapter five is summary and outlook of full text. This paper theoretically studies the automotive electronic stability control principle. Secondly, based on MATLAB/Simulink software, including the establishment of the vehicle reference model of two degrees of freedom and the brake torque distribution model, vehicle dynamics model of eight degrees of freedom, including tires and body model, and with the combination of the fuzzy controller, research and analyze braking force distribution with three control strategies under five typical working conditions, and finally come to the conclusion that optimal allocation strategy is determined by road condition. Although it is only by means of simulation, does not pass real vehicle tests, provides certain theoretical basis and feasibility of the design for the future improvement of ESP products.