Automotive ESP Hydraulic Modulator Modeling And Control Logic Analysis

Vehicle Stability Control also means Electronic Stability Program (shortened as ESP), based on braking system to prevent the vehicle from losing stability when oversteered and understeered. When a vehicle is cornering at an excessive speed, the lateral forces on all the four wheels will determine the lateral acceleration and yaw moment, so the tire side forces may easily reach the grip limit; after that the vehicle becomes unstable, especially on a road with a low friction coefficient (lowμ), such as a snow-covered road. At present, ESP has become the international research focus in the vehicle active safety field and it is gradually equipped to the moderate and top cars; while in china, the research in this field has just started. This dissertation focuses on how to develop the vehicle stability control system. Based on the abroad achievements in this field, the modeling of the hydraulic modulator and simulation of vehicle yaw torque control logic are discussed. Altogether there are six chapters.In Chapter One, the function and the construction of the vehicle stability control system are introduced; the history of the vehicle stability and its present status are discussed; the contents of the dissertation are also put forward in this part.In chapter two, introduce the software AMESim in detail the function, for AMESim has various hydraulic components, it provides a big advantage for the HCU research. The HCU working principle and basic configuration are researched.Under the MK60ESP hydraulic schematics, the HCU model is founded with AMESim. The mathematical model of the main HCU model switch solenoid valve,throttle valve,pressure reservoir and pump are in detail analysed. By setting several values of the models, ESP pressure change is simulated. Also, by setting several values with different parameter and comparing the simulation results. In Chapter Three, describes the ESP basic principle of improving vehicle stability, and the main ways to improve it. Also, introduce a unite ESP simulation environment, use software Carsim, AMESim and Simulink. The author introduce AMESim and Simulink interface settings and Carsim and Simulink interface settings. This is full use of the advantages of each software to achieve the best simulation results.In Chapter Four, The ESP control strategies based on the yaw rate and the slip angle are first analyzed. According to it, the author combine the yaw rate and the slip angle to use fuzzy logic to establish another ESP control strategy, the fuzzy logic is three input and one output structure. The author introduce the automobile ESP evaluation test method, and let the combined fuzzy control simulate several typical situations double lane change and single lane change in the unite ESP simulation environment. Theβ?βphase-plane in this simulations are in the stable state, validate the availability of the ESP combine fuzzy control logic. The author also compared the advantages and disadvantages of the combine control strategy with single control strategy under practical effect.In Chapter Five, the author first based the tire friction circle analyse the principle of the longitudinal force and lateral force. And analyse the differential brake in ultimate steer. Based the former chapter educed the desired yaw orque, The author analyse different methods to the yaw torque distribute to the tires.Chapter Six is the conclusion part. In this final chapter, the author summarized the achievement of thesis and forecasted the research prospect.By the simulation analysis under both the single lane change and double lane change of ESP system, we can get the conclusion that the control strategy of this dissertation is correct. The ESP control system can effectively improve the stability of the vehicle under high-speed steering circumstance so as to assist the drivers'steering operation.