The Estimation Of Tractor-semitrailer State And Road Friction Coefficient Based On Unscented Kalman Filter

With the rapid development of Chinese economy,the highway will continuously extends,At the same time,the role of tractor-semitrailer in transportation is increasingly strengthened.However,It is more likely for tractor-semitrailer to occur traffic accident because of high center of mass,large load and complex structure and so on.The application of active safety control system used in tractor-semitrailer is to reduce the number of traffic accidents,one of the most critical problem is the estimation of road friction coefficient.This thesis focuses on the road friction coefficient estimation based on Unscented Kalman Filter and processes simulation verification at different conditions on the basis of analysis of the research status and development trend of road friction coefficient identification methods at home and abroad.The results show that the algorithm of road friction coefficient estimation has good accuracy and robustness.The main research work of this paper is as follows:(1)The theory and algorithms of Kalman FilterThe theory and algorithm of Kalamn Filter have been studied in depth,and unbiased estimation of recursive filtering method using the signal system on the use of state variables and parameters variables have been summarized.Compared to traditional theory and algorithm of Kalman Filter and its advantages and disadvantages,analyzing the superiority of Unscented Kalman Filter theory,as well as the specific algorithm flow of optimal estimation of the state variables of the nonlinear system,it lays a theoretical foundation for the latter road friction coefficient estimation.(2)The algorithm research of vehicle state estimation based on UKFBased on the nonlinear 3-DOF vehicle dynamic model,estimation algorithm of vehicles movement state on the using of vehicle senor information have been studied and the Unscented Kalman state observer has been designed.The lateral speed of tractor,yaw rate of tractor,hitch articulation,hitch articulation rate can be estimated online.Vehicle state estimation algorithm in Matlab/Simulink has been achieved,and to verify the validity of the algorithm by compared with the results of simulation analysis software TruckSim.The results show that the state estimation algorithm based on UKF can estimate vehicle state information accurately and lay a reliable foundation of the research of road friction coefficient estimation algorithm for the next chapter.(3)The estimation algorithm of road friction coefficient based on UKFThrough the comparison and analysis of magic formula tire,the unitire model and Dugoff tire model,Dugoff tire model has been determined to apply into the research of road friction coefficient estimation algorithm.At the same time,a simulation verification of the tire characteristics of the Dugoff tire model has been made using the simulation softwarc TruckSim8.0.The vehicle dynamics model of a tractor-semitrailer with six wheels has been constructed,the esti:mation algorithm of road friction coefficient based on UKF has been researched and achieved in Matlab/Simulink.(4)simulation verificationThe simulation verification of road friction coefficient estimation algorithm at different road condition and driving cycles has been completed by using of simulation software TruckSim.Compare the estimated values of road friction coefficient based on UKF with the results of TruckSim at the same working condition,the accuracy and feasibility of the algorithm have been verified.This paper has researched the tractor-semitrailer's state estimation and road friction coefficient estimation algorithm based on UKF theory.At the same time,the two kinds of estimation have been verified through simulation and the result is satisfactory,what's more,providing a certain reference value for the research of tractor-semitrailer active safety control system.