Simulation Research On Electronic Stability Control Algorithm For Three-axe Vehicle

ESP (Electronic Stability Program), through online vehicle sensor system, in real-time, monitors the intent of driver and driving condition, identifies and assesses the vehicle steering character and the trend of control-losing, through engine torque and wheels brake control, and prevents vehicle from understeering and overstoring. ESP enables vehicle to realize driver's steering intent, and at the same time, improves the controllability and stability of vehicle by restraining the overturning and underturning of vehicle.Firstly, dynamics simulation models of Three-axle vehicle is built ,and the ESP out-line simulation platform was built on Matlab/Simulink environment;Secondly, the research of identification and selection to control- tire of three-axis motor vehicle were carried out ;the research of vehicle longititude speed estimation, slip angle rate estimation, road adhesion coefficient estimation were carried out based on the primary structure of ESP control algorithm;The ESP control algorithm was proposed;The target yaw moment control algorithm was proposed based on integrate control of distribution coefficient yaw rate control by PI and slip angle rate control by PI;The target yaw torque distribution algorithm and the brake torque control algorithm on the base of brake pressure estimation were proposed;The ESP out-line simulation platform was built on Matlab/Simulink environment, and some out-line simulations on different situations were proceeded.1. Vehicle Dynamics Model of Three-axle vehicleAccording to the needs of ESP strategy research, the 15DOF of nonlinear vehicle dynamics model was established .The vehicle model of Three-axle vehicle, including driver model, engine model, power-train model, tire model, wheel dynamics model, brake system model, vehicle body model and other assistant modules, was provided. Using these models,conditions such as acceleration with straight line and steering, the double change steering could be simulated. The program foundations for ESP off-line simulation platform and hardware-in-loop platform were made.2. Study of ESP Control Algorithm to Three-axle vehicleWith request of the project, the study ESP control algorithm has been accomplished:①E SP control algorithm and modular functions of the algorithm program are proposed;②When the car is steering, method of estimation of vehicle velocity,slip angle estimation algorithm and road adhesion coefficient estimation algorithm are proposed;③based on the yaw rate PI control and side angle PI control,the yaw torque control algorithm has been confirmed, and by introducing partition coefficientα, switching between the two controller is implemented;④B ased on the Dugoff tire model target slip rate is confirmed;⑤Based on the dual-PI control algorithm is proposed.3.ESP Off-line Simulation Platform and SimulationESP control algorithm model were built with Matlab/Simulink based on vehicle dynamics model and ESP control algorithm prototype. The offline simulations of double line turning, double line turning on low adhesion road, step turning on alterable adhesion road, sine wave turning a, etc. were carried out on the platform.The simulation results showed:①the offline simulation platform was qualified to the development of ESP algorithm;②the vehicle yaw rate variety was controlled effectively by ESP control algorithm, and the slip angle of center of mass was restricted, so the lateral stability of vehicle was improved effectively.The building of offline simulation platform and the offline simulations established theory foundation for the design and development of HIL test platform and HIL test.The test simulations showed:①The ESP control algorithm could restrain the overturning or underturning of vehicle effectively through brake torque regulation, thus the lateral stability of automotive was improved. The ESP control algorithm was provided with better robust and better adaptation.②The ESP HIL test proved that the HIL platform was qualified to the test.Through the research of the control algorithm of Three-axle vehicle steering stability, we could achieve the following conclusion: 1. The ESP control algorithm could restrain the overturning or underturning of Three-axle vehicle effectively through brake torque regulation, thus the lateral stability of automotive was improved.2. The coupling of yaw rate and slip angle could be resolved by the yaw torque control algorithm based on the distribution coefficient "α". ESP controlled the vehicle by yaw rate PI controller when the slip angle was small and by slip angle PI controller when the slip angle was large.