Study On The Estimation Methods Of Unified Vehicle Speed In The Vehicle Stability Control System

As technology progresses and the improving of the people lives, more and more attention is paid to the automobile safety by the consumers, how to improve the safety is one of the important research topics in modern automobile area. Automobile safety include two aspects,one is active safty,and the other is passive safty. Active safty is how to reduce or avoid traffic accident with automobile's design; passive safty is to minish the passenger's hurt when the accident happened.As micro-electronics technique and control technique developing,more and more eleconic control equipment are used in automobile manufacture,which making active safty improving a lot. Improving the active safty using control technique is the research emphases all the while.Anti-skid brake system and acceleration slip regulation can't guarantee the flank stability directly,and guarantee the flank stability by the way of restricting the vertical slip to improve the vertical tyre adhering force.So this two systems can't guarantee the automobile's stability in many complex running condition.So the electronic stability program was brought forward.This system can avoid the sideslip which was brought out when the car running in bad weather. Certainly the accurate confidence of the vehicle state is the key of the high precision of the stability control system.So the vehicle state is important .As vehicle speed is one of the main state of the automobile,so it is the important action thereunder of the stability control system .How to obtain the accurate car speed is the hot research point.This text is written under this great environment,making a primery research on the estimate methods in this text.Main research contents the following of the paper:Firstly,establish the mathematics model of the automobile which will be used in stability control simulation.Due to the automobile stability control usually takeing place under the extreme work condition, therefore, this model can simulate theautomobile under not only the normal work condition but also the extreme work condition.This chapter establish a unsteady and nonlinear mechanics tyre model which can simulate under all work condition first.Then build up the whole vehicle model on the basis of the tyre model.verify the model's accuracy through the real vehicle examination and the simulation under especial work condition..This precise and eight freedom degrees automobile model can provide a good data foundation for the appearance estimation.Secondly,in order to building up the experiment set of the stability control system, in this text I researched the wheel speed handling circle and design one.The wheel speed is a important parameter of the vehicle appearance estimation, so the data which is got by the sensor can't be directly used.before using,the data need to be handled by the wheel handling circuit.The stability control experiment is the basis of our keeping on.Thirdly,bring out the arithmetic of the vehicle speed estimation and programe that using Matlab.On the basis of the grand old man's result,get adaptive kalman filter algorithm and the extended kalman filter algorithm.Thereinto the key of adaptive kalman filter algorithm is the renewal of the measuring error in spots.The extended kalman filter algorithm base on the eight free degrees vehicale model. Get the state equation of the extended kalman filter algorithm from the vehicale dynamics model.Fourthly, the algorithm's simulation and validation.Make vehicale speed estimation simulation in Matlab with adaptive kalman filter algorithm and the extended kalman filter algorithm.From the simulation experiment,we find that adaptive kalman filter algorithm can get a good result,but it can only work in one condition,it can't research the ESP's demand.The extended kalman filter algorithm can work in any condition,but the simulation result's error is a little great in some work condition,it also can't satisfy the ESP's precision.The estimation methods of unified vehicle speed in my text are based on the grand old man's algorithm.Of course there is some innovation,that is usingnumerical calculation method in the estimation methods. Thereinto the key of adaptive kalman filter algorithm is the renewal of the measuring error in spots, which making the estimation precision improving a lot. In the extended kalman filter algorithm,four rank Runge-Kutta method is used.When calculation the mean value of the state variable and the covariance matrix,we use four rank Runge-Kutta method.The study on the estimation methods of unified vehicle speed is primary in this taxt.Because of the time,the choosing of the initial value is not successful.So the simulation result of the estimation algorithm is not famous.The following work is to choose the right initial value and make the simulation excellent. Simultaneity,we should try to make out some new estimation algorithm and compare with each method.Find the best estimation algorithm and make experiment on the real car.The research results propose provide bases to the project which is financially supported by "985 Project" of Jilin University named"active safty synthesis control technology of the vehicle underpan".and have important function to further research.