Research On Vehicle Manoeuvre Stability Control Integrating Vehicle State Observation,Prediction And Intellectual Braking Distribution

In order to improve the manoeuvre stability of high-speed vehicles,this thesis proposes an innovative hierarchical direct yaw-moment control strategy consisting of upper,middle and lower controllers.In the upper layer,a linear quadratic regulator metric based on current side-slip angle and predicted yaw rate is established to generate the controlled yaw moment.The mid-layer determines the actuating forces and allocates the required longitudinal forces for each according to the current-road contact condition.Furthermore,the desired longitudinal slip ratios for each are calculated in the middle layer.Finally,suitable brake pressure is achieved by the sliding mode controller in the lower layer.The simulation results of sine with dwell and double lane change verify the effectiveness of the proposed method.Compared to a traditional direct yaw-moment control strategy that preferentially brakes the priority wheel,the proposed novel strategy is able to keep the longitudinal force of working in linear region and has better robustness response when-road contact condition encounters sudden change.Specifically,the main research work and innovations of this thesis are as follows:(1)A vehicle observer based on Kalman filter(KF)algorithm is proposed.Compared with the nonlinear side-slip angle observers designed according to the extended and unscented Kalman filter algorithms,this dissertation linearizes the nonlinear magic model based on Takagi-Sugeno fuzzy theory,and then solves the side-slip angle Estimation issue under large front wheel steering angle by Kalman filter algorithm,which avoids the operation of Tylor expansion or unscented transform.(2)The expressions of the maximum longitudinal force and stiffness of the magic tyre under comprehensive conditions is proposed.Due to the limitation of the tyre friction ellipse,the maximum longitudinal force of the tyre is not only affected by the wheel vertical load,but also by the tyre side-slip angle.Consequently,the polynomial expression between the maximum longitudinal force and the load as well as side-slip angle is fitted.(3)A new direct yaw moment hierarchical control method based on vehicle state observation and prediction as well as intellectual braking torque distribution strategy is proposed.The upper layer,which is based on real-time side-slip angle and predicted yaw rate,is responsible for calculating the corrective yaw moment,which is advance in the time domain.This partially compensates for the delay in system,such as hydraulic braking.On this basis,a one-side two-wheel intellectual braking torque distribution strategy is proposed to make full use of tyre adhesion in middle controller.Finally,the sliding mode lower controller is applied to calculate the required braking pressure.