Influence Of Sideslip Angle On Lateral Stability Of The Bus Under Extreme Turning And Its Adjusting

Bus is one of the major transporter of people's collective travel.It has the characteristics of large capacity,big weight,high gravity and often travels on the highway,approach bridge and mountain road where accidents are more likely to happen.Therefore,it is of great significance to intensively study the dynamic mechanism of bus,analysis of its instability form and the definition of instability and improve the driving stability control method.This thesis makes bus under extreme turning as the research object.Lateral instability form of bus and relationship between lateral stability and sideslip angle were analyzed.Estimation method and correction method of sideslip angle were investigated to provide theoretical reference for bus active safety technology.The main contents of this thesis are as follows:(1)Based on the concept of extreme turning condition,calculation model of lateral force and longitudinal force was established.On the basis of Lagrange dynamic equation,bus dynamic equation including longitudinal motion,lateral motion,yaw motion,roll motion and rotation of the four wheels was deduced.Furthermore,simulation model was established through Simulink.Data of bus motion state were sampled by using multi-functional on-board sensor(OxTS-RT2500),and simulation results were compared with the data to verify correctness of the model.(2)Form of instability of bus under extreme turning was analyzed.Based on bus dynamic model,sideslip angle responses under different speeds,different steering wheel angles and different road surface adhesion coefficients were simulated.The relationship between sideslip angle and lateral force and yaw moment under the conditions of uniform steering,braking steering and different road adhesion coefficient was analyzed by adopting?method.Effects of sideslip angle on the lateral stability of bus were analyzed further.(3)On the basis of the theory of energy phase plane,method named instability boundary circle was presented.The energy phase diagram of bus under critical state of instability was derived.Maximum distance from point on phase locus to origin was defined as R_u and the circle whose radius is R_u was defined as instability boundary circle.Safety factor C_s was introduced and it divided the plane into different regions to determine the lateral stability of bus.(4)Considering the difficulties of sideslip angle measurement,estimation method of sideslip angle which is suitable for the mixed condition of straight driving and steering was designed.Simulink/TruckMaker was used to verify the estimation algorithm.Based on direct yaw moment control,sideslip angle adjusting algorithm was deduced.The adjusting model was simulated on Matlab/Simulink platform and verified by the HIL of bus handling stability.The results of this thesis will enrich the theory of bus active safety control and provide theoretical reference for improving the stability of bus and promoting the development of bus control technology.